Top Circuits Page 269
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The timer circuit shown gives independent control of the output`s on and off intervals, which can range from 0. 055 seconds to 30 minutes, relatively unaffected by power-line transients. IC1 is a CMOS programmable-timer chip that includes 24 ripple-binary....
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Combination of IF amplifier, audio compressor, tunable audio filter, and audio output system operates from single supply. Compressor and filter each use N5558V dual opamps or equivalent units. Tuning range of filter is about 500 to 2000 Hz. IF input goes....
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This rf detector can locate low-power transmitters (bugs) that are hidden from sight. It can sense the presence of a 1-mW transmitter at 20 feet, which is sensitive enough to detect the tiniest bug. As you bring the rf detector closer to the bug, more and....
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A useful marker oscillator can be made using an NE555 to pulse the oscillator at an audio rate. This makes it easy to find the signal in the presence of interference. The crystal can be any suitable frequency from 1 to 30 MHz. ..
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This application uses the timer connected for astable (free-running) operation, with a modulating signal again applied to the control voltage terminal. The pulse position varies with the modulating signal, since the threshold voltage and the time delay is....
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When the carrier level is adequate to switch the cross-coupled pair of differential amplifiers, the modulation signal, which has been applied to the gate, will be switched at the carrier rate, between the collector loads. When switching occurs, it will....
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The basic current allows no carrier to be present in the output. By adding offsets to the carrier differential pairs, controlled amounts of carrier appear at the output. The amplitude becomes a function of the modulation signal-AM modulation. ..
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A keypad enters a four-digit access code, which is programmed via jumpers on a 24-pin plug-in header and socket. U1 is an LST220, which detects a four-digit sequential data input. When the correct data is entered into the keyboard, pin 13 of U1 goes high,....
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The 4046 PPL is used as the heart of a tunable ultrasonic receiver that can be used to locate unheard ultrasonic sounds. The receiver might also be used, along with a simple ultrasonic generator, to send and receive Morse code. The incoming ultrasonic signal....
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This circuit is a 555 timer IC connected as a square-wave generator. Its base frequency is approximately 45 kHz, as determined by the values of R1, R2, and C1. The 45-kHz carrier is frequency modulated by a modified trapizoidal voltage waveform applied to....
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This circuit uses an SAD 512D (Reticon) chip, which is a 512-stage analog shift register. By varying the clock frequency between 5 and 50 kHz, delay time can be set between 51. 2 and 5. 12 ms. The clock fre-quency must be at least twice the highest audio....
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The circuit will provide a 20 ±0. 1 dB voltage gain from 500 kHz to 50 MHz. The low-frequency response of the amplifter can be extended by increasing the value of the 0. 05- F capacitor connected in series with the input terminal. This circuit will yield an....
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Light onphototransistorQ1 (Radio Shack 276-130) produces voltage change across R2 for amplification by opamp whose output drives array fiveLEDs forming bar graph voltage indicator. Adjust R3 initially for highest sensitivity by tuming off room lights and....
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When S1 is pressed, counter U2 is driven by oscillator U1A/U1B and the count (0 through 6) is read on DISP1. R1 and C1 determine the count rate, which should be fast enough to ensure a "random" count. ..
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3130 CMOS opamp gives required high input impedance for pH probe at low cost. Output of probe, ranging from positive generated DC voltage for low pH to 0 V for pH 7 and negative voltages for high pH values, is amplified in circuit that provides gain....
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This circuit provides a cheap alternative to the LM3915 series LED displays. The meter relies on a square-wave oscillator built around two CMOS analog switches, which alternatively selects the right and left channels for monitoring and display. The selected....
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Simple opamp circuit with one transistor gives reliable hot-wire anemometer for measuring flow of gases or liquids. R2 is heated above ambient temperature in Wheatstone bridge including overheat resistor R1which is calibrated to be 30% larger than cold....
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CA081 and CA3140 BiMOS op amp offer minimal loading on the circuits being measured ‚The wide bandwidth and high slew rate of the CA081 allow the meter to operate up to 0. 5 MHz ..
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A2N3819 FET provides a solid state VOM ‚The 2N3819 acts as a cathodefollowerin a VOM The biasoffset(meter null) is obtained with R14 and R12 sets full scale calibration R2 through R9 should totalabout10 M © R10 is a protective resistor and C2 provides ac....
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This schematic shows a peak-reading diode voltmeter driven by two stages of amplification. A 100- F capacitor provides a fairly large time constant, which results in satisfactory meter damping. The limited differential output voltage coupled with an....
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This FETVM replaces the function of the VTVM and rids the instrument of the usual line cord. In addition, FET drift rates are far superior to vacuum tube circuits, allowing a 0. 5 V full-scale range which is impractical with most vacuum tubes. The low....
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In this circuit, a diode bridge is used as a meter rectifier. The offset voltage is compensated for by the op amp, since the bridge is in the feedback network. ..
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L1, Q1, L2, and L3 compose an RF amp’’fter stage that feeds Ml, a doubly balanced mixer. Q4 is alocal oscillator stage In the 375-MHz range Signals h the 420 ‰to 450-MHz range from Q1 are mixed in M1 and fed through filter L6/L7/C17, where only the 60- to....
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When the input goes from low to high, a narrow positive pulse is generated at point A. This pulse becomes - 13 V at point B, which cuts off D2. ICC`s V+ voltage becomes zero. The charge on C1 will be absorbed by ICC on in a short time. The time constant of....
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The oscillator based on IC2 is responsible for producing the sound. Its output is connected to the base of TR1, which amplifies it to drive the speaker. Resistor R4 is included in the circuit to limit the current through TR1 to a safe and reasonable level.....
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For normal wailing tone, short D1 and open R2. For fast rise and slow fall in frequency, include D1 and R2. Use of a CD4046B with a diode-RC network as shown produces a siren tone, using a VCO. ..
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The analog display consists of a frequency/voltage converter (IC12) and bar-graph segment drivers IC10 and IC11. R34 is the calibration adjustment and is set so that an engine rpm of 5000 to 7000 rpm lights the first LED (redline value). ..
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This circuit detects the 1050-Hz tone sent by the NOAA (National Oceanic and Atmospheric Adminis-tration) Weather radio stations that operate from 162. 40 to 162. 55 MHz. This tone lasts for several sec-onds. Q1 is an amplifter that feeds tone detector U1,....
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The SCR is wired across the trigger circuit of the flash gun. Normally, the SCR is off, so the flash gun is able to charge to its trigger voltage. Photo transistor Q1 is used to monitor the light level. When a high-intensity flash occurs, Q1 briefly....
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This circuit symmetrically divides an input by virtually any odd number. The circuit contains n+l/2 clocks twice to achieve the desired divisor. By selecting the proper n, which is the decoded output of the 74LS161 counter, you can obtain diisors from 3 to....
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Built around an Intersil 7216 frequency-counter IC, this counter has a basic range of 10 MHz, a 100-MHz prescaler, and an extra frequency divider (IC3). This divider divides `oy an extra factor, as marked on S7 (see schematic), to extend the range of the....
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You can use this circuit in most FM VHF receivers; the hookup is off the FM discriminator. Because every signal transmitted has its own deviation signature, this can be a red plusin hunting jammers ..
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This 4 1/2-digit DVM circuit is built around a Maxim ICL7129ACPL A/D converter and LCD driver. An ICL8069 CCZR 1. 2-V band-gap reference diode is used for a voltage reference. S2a-b-c select one of four ranges up to 200 V (maximum). The meter also has a....
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National LX5700 temperature transducer provides input for code conversion circuit driving 3-digit LED display indicating temperature range from -40ƒ to +100ƒ or -40 °F to +199 °F under control of ganged switch. -"Linear Applications , Vol. 2, " National....
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This circuit mixes H synch. V synch. and actual video. T2 mixes the synch, while T1 serves as an emitter-follower. Bandwidths of up to 25 MHz are typical for this circuit. ..
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An NTSC/RGB decoder is shown here. Using a TDA3330, 1-V input video is broken down into its R, G, B components, and composite synch. U1 is an integrated synch separator (LM1881). This circuit should be useful for interfacing RGB monitors to NTSC video....
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Call letters stored in 8223 PR0M U3 drive 74151 multiplexer/data selector U4 for keying NE555 audio oscillator U5 which feeds transmitter mike input through RA. Timed holdoff keeps identifier from being rekeyed within spedfied time period, with reiden.....
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JFET Pierce oscillator will test any crystal from 50 kHz through 25-MHz upper frequency limit of fundamental-mode crystals without tuning, and drive counter for measuring crystal frequency, Will test overtone VHF crystals on their fundamental frequency. T1....
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This VCO uses an LF356 op amp to produce a linear frequency vs. voltage characteristic using the CMOS HC4046. The frequency range can be changed by changing the capacitor connected between pins 6 and 7 of the HC4046. Using the HC4046`s internal transistor....
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A modified B/W TV flyback transformer is used in this circuit with a voltage multiplier to produce 9- to 14-kV negative voltage. This is connected to a discharge needle to produce negative ions. ..
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The circuit is built around a 555 oscillator (IC1) and an LM386 audio amplifier (IC2). The 555 circuit is an astable oscillator, with the chip output retriggering the circuit. When the key (S1) is pressed, it activates the circuit. The 555 oscillates at a....
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Controls intervals up to 1 h in 1-s increments as programmed by thumb wheel switches S1 and S2. Circuit is basically two-stage programmed counter driven by 1-s clock derived from 60-Hz power line. A1 is connected as divide-by-60 counter triggered by 60-Hz....
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A block diagram of the stereo-TV decoder is shown in A. It shows the overall relationships be-tween the separate sections of the circuit; B through E show the details of each subsection. The de-coder section centers around IC1, a standard 4. 5-MHz audio....
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This circuit depends on the entry of a correct sequence code. An incorrect number that is not part of the code causes the circuit to reset. When the correct code is entered, Q2 operates relay K1 for a short time, depending on C3. ..
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Simple rectifier circuit replaces battery in vacuum-tube voltmeter. Provides good regulation and eliminates need for frequent battery replacement. Remove battery before using supply. AC source can be 6. 3-V secondary of filament transformer or terminals of....
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This counter can measure frequencies from 2 Hz to 1 MHz, time interval, and period, and count random events. A 74C926 and 74C925 are used as the counter, and these will drive a multiplexed LED display. A 2-MHz time base is used, and a divider chain is used....
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This circuit will produce outputs on TV lines 24 and 257. It was used for a decoder circuit. It uses a CMOS counter and gate logic. Only one pin is used for the output line indicator. ..
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Uses probe containing Clairex 905HN light-dependent resistance element, connected to DC differential amplifier driving meter having specially calibrated scale. Article gives calibration procedure. Switching circuit provides constant check on voltage of 22.....
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Two transistor oscillator generates pulses at about 500 Hz for step-up by 300-mA filament transformer T1 (Radio Shack 273-1384) to charge storage capacitors C2 and C3, which are 250-V electrolytics. Simultaneously, C4 is charged through R2. After allowing....
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Provides timing in seconds to 99 s, and timing in minutes to 99 min, with 2-digit LED indicator showing elapsed time. Desired interval is set with BCD thumbwheel switches. LED readout counts up to preset time, then resets automatically to zero. Switch giving....
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Simple interconnection of RS7490 decade counter RS7447 decoder, and 7-segment digital display for each desired digit makes ideal counter for classroom demonstrations and Sci-ence Fair exhibits, With two additional stages added, display reaches 9999 before....
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Provides full range of brightness control for up to 500w of lamps. Ujt Q1 provides turn. on pulses for scr-L. Stern, "Thyristors Provide New Opportunities for Electronic Applications in the Home, " Motorola Application Note AN-141, Dec. 1965. ..
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This circuit will produce sine, square, and triangle waves from 0. 1 Hz to 1 MHz and has a counter which will read the frequency of the function generator or an external signal of a few volts peak-to-peak that will drive the CMOS counter. ..
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It is possible to build a three-phase sine-wave oscillator using just one UAF42 state variable filter along with some resistors and diodes. Three output nodes are available: high-pass out, bandpass out, and low-pass out. The signals at the bandpass and....
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The circuit is built around an LM317T adjustable voltage regulator. Its output voltage (VOUT) is determined by the formula VOUT= l. 25 (1+R2/R1). I chose a 10-k © resistor for R1 and a 100-k © resistor for R2 to allow for a little wasted current flow (around....
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An adaptable siren generator circuit with a multitude of uses is shown. It is based around a 556 twin-timer chip, IC1. An audio tone is created by one timer section and is directly coupled to the driver transistor, TR1. The other half of the timer is used to....
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Uses surface-barrier transistors in arrangement wherein pattern of four on stages is stepped along ring, per mining maximum number of stages in ring lo be much higher than in conventional rings. -W. Carlson, Ring Counter has Increased Count Capacity,....
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When developing a battery charger, using a real battery might be inconvenient. The battery simulator circuit described here is an alternative. The battery input positive and negative terminals should be connected in place of the battery in the charger....
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Designed to simulate by electronic means thetossing of a coin, the circuit is based upon a 4049 hex inverter IC, two of which are used. IC1a andIC1b are wired as an astable oscillator, which causes two LEDs D1 and D2 ‰ to alternate rapidly, at a frequency....
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Each bistable circuit has two opposite-symmetry germanium transistors, two diodes, and four resistors. Additional transistor Q transfers conducting stage to next position when actuated by transfer pulse. Absence of capacitors gives high-speed operation. No....
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Uses only six components per stage. Combining of counter and indicator functions gives low battery drain. After reset button is re leased, 0. 22-mid capacitor insures that first stage turns on. Current is drown by stage only when lamp is on. Any number of....
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The telephone-line extension bell ringer shown will enable you to add a remote ringer in your garage or some other area where a ringing telephone cannot be heard Up to Four ringers can be used on a single telephone line and a remote bell can be used 100 feet....
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As shown, the circuit is powered by a 9-V battery, B1, but it can easily run off any 7- to 10-Vdc power supply. At the heart of the thermometer is IC1, an LM34 temperature sensor. That device produces a voltage between the Vout and GND terminals that is....
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This circuit is based on the 7240 CMOS programmable timer chip (IC3), which has an accuracy of 0. 5 percent. It contains a time-base generator, the frequency of which is decided by a resistor and a capacitor. The basic time period is RC seconds; so, given....
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Can be used for Touch-Tone decoding as well as for telephone-line and wireless control applications using single audio frequency. Operating center frequency depends on H1 and C1. R1 should be between 2K and 20K. C1 in microfarads is computed from f = 1/R1C1,....
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Provides overload and short-circuit protection for load while isolating malfunctioning circuit from other loads on common supply bus. In normal operation, Q1 is saturated. When load attempts to draw more than this saturation value, base current of Q1 cannot....
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Sections of RS339 quad comparator each drive LED to give indications of four different input voltage levels, While LED 1 is connected to ground for use as zero indicator Resistors shown are for Radio Shack 276-041 red LEDs ›change R6-R9 to 270 ohms and R1 to....
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Timing interval is initiated by applying power, and is determined by RT-CT. At end of interval, unijunction transistor triggers silicon controlled rectifier, to apply essentially full supply voltage to load. Delay range is from 0. 4millisec to 1 minute.....
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Used to delay beginning of crt sweep for expanded display. Provides three ranges: 0 to 5, 60, and 200 miles. Circuit is basically cathode-coupled phantastron, with additional coupling by returning suppressor and screen to same divider. Cathode follower....
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The 0-to 130-V voltmeter and neon "AC PWR" lamp provide an average indication of the ac power. The fuse and metal oxide varistor(MOV)protect the monitor against overvoltage spikes. Four 1N4004 diodes rectify the ac voltage, generating negative-going pulses....
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Pentode is astable phantastron during radar search, and d-c amplifier during lock-on when pentode furnishes direct control of klystron repeller. -NBS, "Handbook Preferred Circuits Navy Aeronautical Electronic Equipment, " Vol. 1, Electron Tube circuits,....
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The circuit uses an IR phototransistor, Q1, to detect a remote control`s IR output signal. A PNP transistor, Q2, then amplifies Q1`s output and lights LED1. That indicates that an infrared signal has been detected by the phototransistor, or in other words,....
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Values shown are for 13-kHz bandwidth 1070 Hz for mark and 1270 Hz for space, using Exar XR-2206 function generator and XR-2211 FSK de-modulator Report gives design procedure Supply can be ‹12 v "Phase-Locked Loop Data Book, "Exar Integrated Systems,....
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Used in digital voltmeters to convert AC waveform to full-waverectified DC equivalent. First 3130 opamp is used as polarity separator, with negative-going signals appearing across upper 10K resistor and positive-going signals across lower 10K resistor.....
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With FET in one leg of Wheatstone bridge, meter has input impedance of over 1 megohm. With no input voltage, adjust R4 so meter reads zero. With 9-V battery, RI can be adjusted for full-scale meter reading of 8 V. With 12-V battery, meter range is 0-10 V.....
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A servo contains a small motor and gear box that rotates a shaft to a precise location and holds it there. This photo shows a typical servo with its top removed. The position of the shaft is based on a digital signal. Most servos rotate through a 180 degree....
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The objective of this controller project is to have automatic block and switch control of five separate engines that run on two completely independent loops of track. Part of each loop is outside (public) and part is inside (hidden from public view). The....
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How the Bug-Eyed Eggliner came to life along with instructions that will help you to make your own. I believe that you can also use many of the concepts presented here in other projects and animations. The honey bee Eggliner already has two large eyes....
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LEDs are available in a number of different sizes and shapes with most being round topped cylinders that are either 3 mm or 5 mm in diameter. These sizes are also commonly referred to as T1 (3 mm) and T1 (5 mm). The body of most LEDs is made of plastic that....
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The last installment in this series ( LEDs 102 - Use On Board Trains ) ended with a few thoughts about turning battery powered LEDs on and off. In this article I would like to explore several options for turning LEDs, and other things on your railroad, on....
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The AD322 is an 8 amp G-Scale DCC decoder. The notes below may be of benefit to owners who wish to understand or repurpose ("hack") the decoder. It has a rather full set of functions that could easily be repurposed for a number of other projects. One....
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The microcontroller board is shown (top left/green board) along with the auxiliary board (bottom left / brown board) and the two geared Hurst stepper motors. In this view of the microcontroller board the programming jumper is in the upper right area. Power....
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The prototype circuit board used an external LCD display that received commands via an RS-232 interface. Although it worked well programming it was cumbersome. For this reason the circuit board was revised so that it would support a directly attached LCD....
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Model railroad turnouts, often called switches, can be controlled in a number of ways. The most basic is a manual control that is thrown by hand. Remote activation is usually accomplished by either pneumatic (air) or electrical means. The project that is the....
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The eyes of the switch control system allow the microcontroller`s "brain" to know where the trains are located on the layout. This insures that only one train is on the main line at a time and that the switches are set so that the train returns to the proper....
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A sensor in garden railway applications. Hall Effect sensors are the electronic equivalent of a reed switch. You can think of them as a cross between a reed switch and a transistor. They are frequently used to determine the rotational speed of a spinning....
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Develop a self contained unit that can automatically control up to four DCC equipped engines, starting and stopping them based on their position on a loop of track The control PIC interacts with the MiniDCC controller through the MiniDCC`s keypad. Six pins....
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The Aristo ART-5474 Accessory Panel is a complete receiver intended to control accessories through the use of the A through E buttons on the Train Engineer transmitter. As the 5474 comes, it will control two turnouts, one constant load such as lights, and....
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The Shay is equipped with flickering ashpan and firebox lights. These are simulated with LEDs. The red and yellow ones both flicker, the red ones stay on about 2/3 of the time and the yellow ones 1/3 of the time. The effect is pretty good while it is going,....
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The Bachmann Big Hauler locomotive has improved greatly over the last few years in appearance, reliability and noise level. However one thing that hasn`t improved is the very basic sound system. The system provides a pretty poor facsimile of an exhaust sound....
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A couple of years ago I decided I would (eventually) need to replace my decades-old Nakamichi stereo with something more suited to a mobile lifestyle. It was immediately pretty obvious that the Class-D and E switching amplifiers I had researched in the `70s....
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Whatever past project these were used in obviously required three cells to be wired in parallel with a rather large (4700 uF) capacitor on a perf board. There were 13 of these board assemblies, for a total of 39 solar cells and 13 capacitors (not to mention....
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The Controller Area Network data rate can be from 10kbit/s to 1Mbit/s giving recommended distances of 40 to 1000metres over two twisted pairs, one for the data, the other to carry power and ground. Up to 110nodes may be connected. 2. Set the DIL switch on....
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This section covers Compact Flash, Flash-ATA and hard disks. For other media see DATA LOGGING TO RAM CARDS, page274, and DATA LOGGING TO FLASH AND RAM CHIPS, page279, With this module you can quickly build tailor-made data collection systems with removable....
The timer circuit shown gives independent control of the output`s on and off intervals, which can range from 0. 055 seconds to 30 minutes, relatively unaffected by power-line transients. IC1 is a CMOS programmable-timer chip that includes 24 ripple-binary....
Combination of IF amplifier, audio compressor, tunable audio filter, and audio output system operates from single supply. Compressor and filter each use N5558V dual opamps or equivalent units. Tuning range of filter is about 500 to 2000 Hz. IF input goes....
This rf detector can locate low-power transmitters (bugs) that are hidden from sight. It can sense the presence of a 1-mW transmitter at 20 feet, which is sensitive enough to detect the tiniest bug. As you bring the rf detector closer to the bug, more and....
A useful marker oscillator can be made using an NE555 to pulse the oscillator at an audio rate. This makes it easy to find the signal in the presence of interference. The crystal can be any suitable frequency from 1 to 30 MHz. ..
This application uses the timer connected for astable (free-running) operation, with a modulating signal again applied to the control voltage terminal. The pulse position varies with the modulating signal, since the threshold voltage and the time delay is....
When the carrier level is adequate to switch the cross-coupled pair of differential amplifiers, the modulation signal, which has been applied to the gate, will be switched at the carrier rate, between the collector loads. When switching occurs, it will....
The basic current allows no carrier to be present in the output. By adding offsets to the carrier differential pairs, controlled amounts of carrier appear at the output. The amplitude becomes a function of the modulation signal-AM modulation. ..
A keypad enters a four-digit access code, which is programmed via jumpers on a 24-pin plug-in header and socket. U1 is an LST220, which detects a four-digit sequential data input. When the correct data is entered into the keyboard, pin 13 of U1 goes high,....
The 4046 PPL is used as the heart of a tunable ultrasonic receiver that can be used to locate unheard ultrasonic sounds. The receiver might also be used, along with a simple ultrasonic generator, to send and receive Morse code. The incoming ultrasonic signal....
This circuit is a 555 timer IC connected as a square-wave generator. Its base frequency is approximately 45 kHz, as determined by the values of R1, R2, and C1. The 45-kHz carrier is frequency modulated by a modified trapizoidal voltage waveform applied to....
This circuit uses an SAD 512D (Reticon) chip, which is a 512-stage analog shift register. By varying the clock frequency between 5 and 50 kHz, delay time can be set between 51. 2 and 5. 12 ms. The clock fre-quency must be at least twice the highest audio....
The circuit will provide a 20 ±0. 1 dB voltage gain from 500 kHz to 50 MHz. The low-frequency response of the amplifter can be extended by increasing the value of the 0. 05- F capacitor connected in series with the input terminal. This circuit will yield an....
Light onphototransistorQ1 (Radio Shack 276-130) produces voltage change across R2 for amplification by opamp whose output drives array fiveLEDs forming bar graph voltage indicator. Adjust R3 initially for highest sensitivity by tuming off room lights and....
When S1 is pressed, counter U2 is driven by oscillator U1A/U1B and the count (0 through 6) is read on DISP1. R1 and C1 determine the count rate, which should be fast enough to ensure a "random" count. ..
3130 CMOS opamp gives required high input impedance for pH probe at low cost. Output of probe, ranging from positive generated DC voltage for low pH to 0 V for pH 7 and negative voltages for high pH values, is amplified in circuit that provides gain....
This circuit provides a cheap alternative to the LM3915 series LED displays. The meter relies on a square-wave oscillator built around two CMOS analog switches, which alternatively selects the right and left channels for monitoring and display. The selected....
Simple opamp circuit with one transistor gives reliable hot-wire anemometer for measuring flow of gases or liquids. R2 is heated above ambient temperature in Wheatstone bridge including overheat resistor R1which is calibrated to be 30% larger than cold....
CA081 and CA3140 BiMOS op amp offer minimal loading on the circuits being measured ‚The wide bandwidth and high slew rate of the CA081 allow the meter to operate up to 0. 5 MHz ..
A2N3819 FET provides a solid state VOM ‚The 2N3819 acts as a cathodefollowerin a VOM The biasoffset(meter null) is obtained with R14 and R12 sets full scale calibration R2 through R9 should totalabout10 M © R10 is a protective resistor and C2 provides ac....
This schematic shows a peak-reading diode voltmeter driven by two stages of amplification. A 100- F capacitor provides a fairly large time constant, which results in satisfactory meter damping. The limited differential output voltage coupled with an....
This FETVM replaces the function of the VTVM and rids the instrument of the usual line cord. In addition, FET drift rates are far superior to vacuum tube circuits, allowing a 0. 5 V full-scale range which is impractical with most vacuum tubes. The low....
In this circuit, a diode bridge is used as a meter rectifier. The offset voltage is compensated for by the op amp, since the bridge is in the feedback network. ..
L1, Q1, L2, and L3 compose an RF amp’’fter stage that feeds Ml, a doubly balanced mixer. Q4 is alocal oscillator stage In the 375-MHz range Signals h the 420 ‰to 450-MHz range from Q1 are mixed in M1 and fed through filter L6/L7/C17, where only the 60- to....
When the input goes from low to high, a narrow positive pulse is generated at point A. This pulse becomes - 13 V at point B, which cuts off D2. ICC`s V+ voltage becomes zero. The charge on C1 will be absorbed by ICC on in a short time. The time constant of....
The oscillator based on IC2 is responsible for producing the sound. Its output is connected to the base of TR1, which amplifies it to drive the speaker. Resistor R4 is included in the circuit to limit the current through TR1 to a safe and reasonable level.....
For normal wailing tone, short D1 and open R2. For fast rise and slow fall in frequency, include D1 and R2. Use of a CD4046B with a diode-RC network as shown produces a siren tone, using a VCO. ..
The analog display consists of a frequency/voltage converter (IC12) and bar-graph segment drivers IC10 and IC11. R34 is the calibration adjustment and is set so that an engine rpm of 5000 to 7000 rpm lights the first LED (redline value). ..
This circuit detects the 1050-Hz tone sent by the NOAA (National Oceanic and Atmospheric Adminis-tration) Weather radio stations that operate from 162. 40 to 162. 55 MHz. This tone lasts for several sec-onds. Q1 is an amplifter that feeds tone detector U1,....
The SCR is wired across the trigger circuit of the flash gun. Normally, the SCR is off, so the flash gun is able to charge to its trigger voltage. Photo transistor Q1 is used to monitor the light level. When a high-intensity flash occurs, Q1 briefly....
This circuit symmetrically divides an input by virtually any odd number. The circuit contains n+l/2 clocks twice to achieve the desired divisor. By selecting the proper n, which is the decoded output of the 74LS161 counter, you can obtain diisors from 3 to....
Built around an Intersil 7216 frequency-counter IC, this counter has a basic range of 10 MHz, a 100-MHz prescaler, and an extra frequency divider (IC3). This divider divides `oy an extra factor, as marked on S7 (see schematic), to extend the range of the....
You can use this circuit in most FM VHF receivers; the hookup is off the FM discriminator. Because every signal transmitted has its own deviation signature, this can be a red plusin hunting jammers ..
This 4 1/2-digit DVM circuit is built around a Maxim ICL7129ACPL A/D converter and LCD driver. An ICL8069 CCZR 1. 2-V band-gap reference diode is used for a voltage reference. S2a-b-c select one of four ranges up to 200 V (maximum). The meter also has a....
National LX5700 temperature transducer provides input for code conversion circuit driving 3-digit LED display indicating temperature range from -40ƒ to +100ƒ or -40 °F to +199 °F under control of ganged switch. -"Linear Applications , Vol. 2, " National....
This circuit mixes H synch. V synch. and actual video. T2 mixes the synch, while T1 serves as an emitter-follower. Bandwidths of up to 25 MHz are typical for this circuit. ..
An NTSC/RGB decoder is shown here. Using a TDA3330, 1-V input video is broken down into its R, G, B components, and composite synch. U1 is an integrated synch separator (LM1881). This circuit should be useful for interfacing RGB monitors to NTSC video....
Call letters stored in 8223 PR0M U3 drive 74151 multiplexer/data selector U4 for keying NE555 audio oscillator U5 which feeds transmitter mike input through RA. Timed holdoff keeps identifier from being rekeyed within spedfied time period, with reiden.....
JFET Pierce oscillator will test any crystal from 50 kHz through 25-MHz upper frequency limit of fundamental-mode crystals without tuning, and drive counter for measuring crystal frequency, Will test overtone VHF crystals on their fundamental frequency. T1....
This VCO uses an LF356 op amp to produce a linear frequency vs. voltage characteristic using the CMOS HC4046. The frequency range can be changed by changing the capacitor connected between pins 6 and 7 of the HC4046. Using the HC4046`s internal transistor....
A modified B/W TV flyback transformer is used in this circuit with a voltage multiplier to produce 9- to 14-kV negative voltage. This is connected to a discharge needle to produce negative ions. ..
The circuit is built around a 555 oscillator (IC1) and an LM386 audio amplifier (IC2). The 555 circuit is an astable oscillator, with the chip output retriggering the circuit. When the key (S1) is pressed, it activates the circuit. The 555 oscillates at a....
Controls intervals up to 1 h in 1-s increments as programmed by thumb wheel switches S1 and S2. Circuit is basically two-stage programmed counter driven by 1-s clock derived from 60-Hz power line. A1 is connected as divide-by-60 counter triggered by 60-Hz....
A block diagram of the stereo-TV decoder is shown in A. It shows the overall relationships be-tween the separate sections of the circuit; B through E show the details of each subsection. The de-coder section centers around IC1, a standard 4. 5-MHz audio....
This circuit depends on the entry of a correct sequence code. An incorrect number that is not part of the code causes the circuit to reset. When the correct code is entered, Q2 operates relay K1 for a short time, depending on C3. ..
Simple rectifier circuit replaces battery in vacuum-tube voltmeter. Provides good regulation and eliminates need for frequent battery replacement. Remove battery before using supply. AC source can be 6. 3-V secondary of filament transformer or terminals of....
This counter can measure frequencies from 2 Hz to 1 MHz, time interval, and period, and count random events. A 74C926 and 74C925 are used as the counter, and these will drive a multiplexed LED display. A 2-MHz time base is used, and a divider chain is used....
This circuit will produce outputs on TV lines 24 and 257. It was used for a decoder circuit. It uses a CMOS counter and gate logic. Only one pin is used for the output line indicator. ..
Uses probe containing Clairex 905HN light-dependent resistance element, connected to DC differential amplifier driving meter having specially calibrated scale. Article gives calibration procedure. Switching circuit provides constant check on voltage of 22.....
Two transistor oscillator generates pulses at about 500 Hz for step-up by 300-mA filament transformer T1 (Radio Shack 273-1384) to charge storage capacitors C2 and C3, which are 250-V electrolytics. Simultaneously, C4 is charged through R2. After allowing....
Provides timing in seconds to 99 s, and timing in minutes to 99 min, with 2-digit LED indicator showing elapsed time. Desired interval is set with BCD thumbwheel switches. LED readout counts up to preset time, then resets automatically to zero. Switch giving....
Simple interconnection of RS7490 decade counter RS7447 decoder, and 7-segment digital display for each desired digit makes ideal counter for classroom demonstrations and Sci-ence Fair exhibits, With two additional stages added, display reaches 9999 before....
Provides full range of brightness control for up to 500w of lamps. Ujt Q1 provides turn. on pulses for scr-L. Stern, "Thyristors Provide New Opportunities for Electronic Applications in the Home, " Motorola Application Note AN-141, Dec. 1965. ..
This circuit will produce sine, square, and triangle waves from 0. 1 Hz to 1 MHz and has a counter which will read the frequency of the function generator or an external signal of a few volts peak-to-peak that will drive the CMOS counter. ..
It is possible to build a three-phase sine-wave oscillator using just one UAF42 state variable filter along with some resistors and diodes. Three output nodes are available: high-pass out, bandpass out, and low-pass out. The signals at the bandpass and....
The circuit is built around an LM317T adjustable voltage regulator. Its output voltage (VOUT) is determined by the formula VOUT= l. 25 (1+R2/R1). I chose a 10-k © resistor for R1 and a 100-k © resistor for R2 to allow for a little wasted current flow (around....
An adaptable siren generator circuit with a multitude of uses is shown. It is based around a 556 twin-timer chip, IC1. An audio tone is created by one timer section and is directly coupled to the driver transistor, TR1. The other half of the timer is used to....
Uses surface-barrier transistors in arrangement wherein pattern of four on stages is stepped along ring, per mining maximum number of stages in ring lo be much higher than in conventional rings. -W. Carlson, Ring Counter has Increased Count Capacity,....
When developing a battery charger, using a real battery might be inconvenient. The battery simulator circuit described here is an alternative. The battery input positive and negative terminals should be connected in place of the battery in the charger....
Designed to simulate by electronic means thetossing of a coin, the circuit is based upon a 4049 hex inverter IC, two of which are used. IC1a andIC1b are wired as an astable oscillator, which causes two LEDs D1 and D2 ‰ to alternate rapidly, at a frequency....
Each bistable circuit has two opposite-symmetry germanium transistors, two diodes, and four resistors. Additional transistor Q transfers conducting stage to next position when actuated by transfer pulse. Absence of capacitors gives high-speed operation. No....
Uses only six components per stage. Combining of counter and indicator functions gives low battery drain. After reset button is re leased, 0. 22-mid capacitor insures that first stage turns on. Current is drown by stage only when lamp is on. Any number of....
The telephone-line extension bell ringer shown will enable you to add a remote ringer in your garage or some other area where a ringing telephone cannot be heard Up to Four ringers can be used on a single telephone line and a remote bell can be used 100 feet....
As shown, the circuit is powered by a 9-V battery, B1, but it can easily run off any 7- to 10-Vdc power supply. At the heart of the thermometer is IC1, an LM34 temperature sensor. That device produces a voltage between the Vout and GND terminals that is....
This circuit is based on the 7240 CMOS programmable timer chip (IC3), which has an accuracy of 0. 5 percent. It contains a time-base generator, the frequency of which is decided by a resistor and a capacitor. The basic time period is RC seconds; so, given....
Can be used for Touch-Tone decoding as well as for telephone-line and wireless control applications using single audio frequency. Operating center frequency depends on H1 and C1. R1 should be between 2K and 20K. C1 in microfarads is computed from f = 1/R1C1,....
Provides overload and short-circuit protection for load while isolating malfunctioning circuit from other loads on common supply bus. In normal operation, Q1 is saturated. When load attempts to draw more than this saturation value, base current of Q1 cannot....
Sections of RS339 quad comparator each drive LED to give indications of four different input voltage levels, While LED 1 is connected to ground for use as zero indicator Resistors shown are for Radio Shack 276-041 red LEDs ›change R6-R9 to 270 ohms and R1 to....
Timing interval is initiated by applying power, and is determined by RT-CT. At end of interval, unijunction transistor triggers silicon controlled rectifier, to apply essentially full supply voltage to load. Delay range is from 0. 4millisec to 1 minute.....
Used to delay beginning of crt sweep for expanded display. Provides three ranges: 0 to 5, 60, and 200 miles. Circuit is basically cathode-coupled phantastron, with additional coupling by returning suppressor and screen to same divider. Cathode follower....
The 0-to 130-V voltmeter and neon "AC PWR" lamp provide an average indication of the ac power. The fuse and metal oxide varistor(MOV)protect the monitor against overvoltage spikes. Four 1N4004 diodes rectify the ac voltage, generating negative-going pulses....
Pentode is astable phantastron during radar search, and d-c amplifier during lock-on when pentode furnishes direct control of klystron repeller. -NBS, "Handbook Preferred Circuits Navy Aeronautical Electronic Equipment, " Vol. 1, Electron Tube circuits,....
The circuit uses an IR phototransistor, Q1, to detect a remote control`s IR output signal. A PNP transistor, Q2, then amplifies Q1`s output and lights LED1. That indicates that an infrared signal has been detected by the phototransistor, or in other words,....
Values shown are for 13-kHz bandwidth 1070 Hz for mark and 1270 Hz for space, using Exar XR-2206 function generator and XR-2211 FSK de-modulator Report gives design procedure Supply can be ‹12 v "Phase-Locked Loop Data Book, "Exar Integrated Systems,....
Used in digital voltmeters to convert AC waveform to full-waverectified DC equivalent. First 3130 opamp is used as polarity separator, with negative-going signals appearing across upper 10K resistor and positive-going signals across lower 10K resistor.....
With FET in one leg of Wheatstone bridge, meter has input impedance of over 1 megohm. With no input voltage, adjust R4 so meter reads zero. With 9-V battery, RI can be adjusted for full-scale meter reading of 8 V. With 12-V battery, meter range is 0-10 V.....
A servo contains a small motor and gear box that rotates a shaft to a precise location and holds it there. This photo shows a typical servo with its top removed. The position of the shaft is based on a digital signal. Most servos rotate through a 180 degree....
The objective of this controller project is to have automatic block and switch control of five separate engines that run on two completely independent loops of track. Part of each loop is outside (public) and part is inside (hidden from public view). The....
How the Bug-Eyed Eggliner came to life along with instructions that will help you to make your own. I believe that you can also use many of the concepts presented here in other projects and animations. The honey bee Eggliner already has two large eyes....
LEDs are available in a number of different sizes and shapes with most being round topped cylinders that are either 3 mm or 5 mm in diameter. These sizes are also commonly referred to as T1 (3 mm) and T1 (5 mm). The body of most LEDs is made of plastic that....
The last installment in this series ( LEDs 102 - Use On Board Trains ) ended with a few thoughts about turning battery powered LEDs on and off. In this article I would like to explore several options for turning LEDs, and other things on your railroad, on....
The microcontroller board is shown (top left/green board) along with the auxiliary board (bottom left / brown board) and the two geared Hurst stepper motors. In this view of the microcontroller board the programming jumper is in the upper right area. Power....
The prototype circuit board used an external LCD display that received commands via an RS-232 interface. Although it worked well programming it was cumbersome. For this reason the circuit board was revised so that it would support a directly attached LCD....
Model railroad turnouts, often called switches, can be controlled in a number of ways. The most basic is a manual control that is thrown by hand. Remote activation is usually accomplished by either pneumatic (air) or electrical means. The project that is the....
The eyes of the switch control system allow the microcontroller`s "brain" to know where the trains are located on the layout. This insures that only one train is on the main line at a time and that the switches are set so that the train returns to the proper....
A sensor in garden railway applications. Hall Effect sensors are the electronic equivalent of a reed switch. You can think of them as a cross between a reed switch and a transistor. They are frequently used to determine the rotational speed of a spinning....
Develop a self contained unit that can automatically control up to four DCC equipped engines, starting and stopping them based on their position on a loop of track The control PIC interacts with the MiniDCC controller through the MiniDCC`s keypad. Six pins....
The Aristo ART-5474 Accessory Panel is a complete receiver intended to control accessories through the use of the A through E buttons on the Train Engineer transmitter. As the 5474 comes, it will control two turnouts, one constant load such as lights, and....
The Shay is equipped with flickering ashpan and firebox lights. These are simulated with LEDs. The red and yellow ones both flicker, the red ones stay on about 2/3 of the time and the yellow ones 1/3 of the time. The effect is pretty good while it is going,....
The Bachmann Big Hauler locomotive has improved greatly over the last few years in appearance, reliability and noise level. However one thing that hasn`t improved is the very basic sound system. The system provides a pretty poor facsimile of an exhaust sound....
A couple of years ago I decided I would (eventually) need to replace my decades-old Nakamichi stereo with something more suited to a mobile lifestyle. It was immediately pretty obvious that the Class-D and E switching amplifiers I had researched in the `70s....
Whatever past project these were used in obviously required three cells to be wired in parallel with a rather large (4700 uF) capacitor on a perf board. There were 13 of these board assemblies, for a total of 39 solar cells and 13 capacitors (not to mention....
The Controller Area Network data rate can be from 10kbit/s to 1Mbit/s giving recommended distances of 40 to 1000metres over two twisted pairs, one for the data, the other to carry power and ground. Up to 110nodes may be connected. 2. Set the DIL switch on....
This section covers Compact Flash, Flash-ATA and hard disks. For other media see DATA LOGGING TO RAM CARDS, page274, and DATA LOGGING TO FLASH AND RAM CHIPS, page279, With this module you can quickly build tailor-made data collection systems with removable....
