New Circuits Page 210
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This circuit determines the cold cranking amps of a battery by first discharging the surface charge, then checking the internal resistance. This gives a more realistic measurement than simply measuring the instantaneous drop in voltage with a load. A....
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Charge redistribution to achieve A/D conversion. In typical applications, as a ratiometric conversion system for a microprocessor, V^p, will be connected to ground and VREF+ will be connected to Vcc.
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The circuit is an VXO with buffered output. It operates on 20-meter amateur radio band with the output voltage about 0.2 Vp-p.
The crystal frequency is pulled by tuning the variable capacitor CV1 about 36Khz with only one crystal (Y1), and 250Khz by using....
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An RF probe is used to directly measure the level of RF voltage present at a particular point and is one of the most useful test instrument in the hands of the home brewer. It is normally used with a digital multi meter to indicate the voltage level as dc....
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The Talking Phone Dial Monitor detects the
tones generated when numbers are dialed
on your touch tone telephone and speaks
the numbers that were dialed. This verifies
that you dialed the correct number and is
especially useful when the keypad is not....
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The 74AC240 stepper driver works by alternately enabling each half of the buffer. Only one half can be enabled at a time.
Let`s assume that the top half of the driver is enabled. U1A & U1B along with R8, C1, and the input protection resistor R7 form....
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This circuit is actuated by an increase in capacitance between a sensing electrode and the ground side of the line. The sensitivity can be adjusted to switch when a human body is within inches of the insulated plate used as the sensing electrode. Thus,....
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This signal tracker and lock detector combine to make a precision tone switch. Filter R3/R4/C2 determines..
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Micro-Cap 9 is an integrated schematic editor and mixed analog/digital simulator that provides an interactive sketch and simulate environment for electronics engineers. Since its original release in 1982, Micro-Cap has been steadily expanded and improved.....
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This thermometer is capable of 0.01°C accuracy over - 50°C to +150°C. A unique trim arrangement eliminates cumbersome trim interactions so that zero gain, and nonlinearity correction can be trimmed in one even trip. Extra op amps provide full Kelvin....
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The LTC10432 switched-capacitor building block provides nonoverlapping complementary drive to the Ql to Q4 power MOSFETs. The MOSFETs are arranged so that Cl and C2 are alternately placed in series and then parallel. During the series phase, the + 12 V....
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A practical, efficient LCD backlight design is a classic
study of compromise in a transduced electronic system.
Every aspect of the design is interrelated, and the physical
embodiment is an integral part of the electrical circuit. The
choice and location....
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The 20-W + 20-W stereo amp consists of two complete, separate 20-W RMS bridge-type amplifiers. The input signal source is brought into the amplifier through the voltage divider network, which is made up of Rl, R2, and PI. Resistor Rl provides a load....
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This circuit will generate a linear sawtooth between 30 Hz and 3 000 Hz. Ql is a constant-current s..
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This power supply circuit is highly stabilized that its output voltage will drop only 0.005% even though the load changes from 0 to 100%. Another excellent capability is that the output voltage will change only by 0.01% if the input voltage fluctuates. The....
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I propose a simple CW decoder wich makes use of a PIC16F84 microprocessor with
a 16x2 chars LCD display. It is equipped with an audio frequency input from your receiver,
an input for a stright key and an audio output locked to the input signal. It....
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Figure 1 shows an efficient and cost-effective frequency counter using an Atmel 89C2051 µC (Reference 1). The design can use any µC of the 8051 family. The circuit counts frequency and sends the count to a PC via the serial port. The signal connects to pin....
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Null detector uses simple LED readout to indicate if test resistor R* is below, equal to, or greater than test resistance Rref. IfR* = Rref, the 741 output sits at midpoint value of 4 volts and LED A lights..
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In the never-ending quest for simplicity even one extra diode is a price I loath to pay and to avoid using extra components it struck me that the the two diodes in SIMD1 V1 were connected like the two junctions in one transistor. Eureka! replace two....
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The GPS interface can be fed in 2 ways: with a stabilized 5V supply or with a 10 to 25V unregulated DC supply. In both cases the power is fed into the RJ45 connector on point 8. Pin 7 is DC ground. The power supply current is first secured with a slow....
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Ql is a phototransistor that is normally illuminated by a beam of light. When the beam is intercoupled, pin ..
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The Tritium circuit was the first (to my knowledge) type 3 SE. As such, it is quite experimental, and should be regarded as a prototype rather than the `state of the art`! Nevertheless, it does function reasonably well, and in some circumstances outperforms....
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This circuit can be used to prevent relay contact arcing for loads up to 50 amperes. There is some delay between the time a relay coil is energized and the time the contacts close. There is also a delay between the time the coil is de-energized and the time....
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This project is finalized, that means it is no longer experimental. This amplifier, altough limited in output power (20W), has been designed to give the best listening pleasure. No compromise has been made during components choice: the 845 output triode is....
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This circuit is a simple two transistor (2N2222) FM transmitter. No license is required for this transmitter according to FCC regulations regarding wireless microphones. If powered by a 9 volt battery and used with an antenna no longer than 12 inches, the....
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The circuit is placed parallel with the exit of power amplifier and us gives the level of signal ,from output. Changing resistance R1, in the input circuit, we adapt the indication of power, in the resistance of loudspeaker, that we use.
..
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This control, with zero-voltage load switching, uses a CA3130 BiMOS op amp and a CA3079 zero-voltage switc..
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This wide-range light dimmer circuit uses a unijunction transistor and a pulse transformer to provide phase control for the TRIAC. The circuit operates from a 115 volt, 60 Hz source and can control up to 800 watts of power to incandescent lights. The power....
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A charge pump is a simple means of generating a low-power voltage supply of opposite polarity from the main supply. The 74Cl4 IC is a self-oscillating driver for the MOSFET power switch. It produces a pulse width of 6.5 p,s at a repetition frequency of....
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The lights seem to dance in time with the music. Line-voltage lamps of about 40 to 100 W do nicely. The current for the lamp is from an SCR. When low-level audio is present across Tl, SCR1 is not triggered into conduction. A louder signal, however,....
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A block diagram and a schematic of the receiver are shown in Figures 2 and 3, respectively. In Figure 3, L6 and L7 are spaced 0.6 inch for a loss of about 0.5 dB. Q4 is the first RF amplifier. L9 and L10 are spaced about 0.8 inch with a partial shield....
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Unusual frequency compensation gives this logarithmic converter a 100 µs time constant from 1 mA down to 100 µA, increasing from 200 µe to 200 ms from 10 nA to 10 pA. Optional bias current compensation can give 10 pA resolution from - 55 °C to 100 °C..
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The controller is quite (actually very) simple. An input buffer ensures that the input impedance of the source does not affect the integrator performance, and allows summing of left and right channels without any crosstalk. The output provides a phase....
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The 4047 is configured as a free-running, astable- multivibrator (oscillator) circuit. That configuration, offers three different outputs. The output pulses at the Q and Q output (pins 10 and 11, respectively) are the same as in the previous two....
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This simple circuit uses an incandescent lamp to detect airflow. With the filament exposed to air, a constant current source is used to slightly heat the filament. As it is heated, the resistance increases. As air flows over the filament it cools down, thus....
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A1 amplifies and regulates the signal from the spark coil. A2 converts frequency to voltage so that its output is a voltage proportional to engine rpm. A3 compares the tachometer voltage with the reference voltage and turns on the output transistor at the....
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It's a simple metal detector design that has the quite good characteristics. the principle of operation which one differs from the classic schemes (BFO, transmit-receive known as "two-boxes" metal detector, inductive). The dynamic mode is used to find....
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PulsePar turns a PC into a multi-channel pulse generator utilizing the parallel port. The period, duty and phase of each channel are adjustable so as to be used in PWM systems as well as in testing servo and stepper (stepping) motors. If you have an old PC,....
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Next is the microcontroller or MCU. In previous projects, we used the Atmel AT89C2051. However, the I/O port structure is not quite suitable for this application so we have used the similar Atmel AT90S2313. The main feature influencing this decision is that....
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This design was published in the June 1994 issue of Electronics Australia, and has proven extremely popular. The kit was sold by Jaycar Electronics, but has since been discontinued. It is a simple device that connects between your keyboard and VGA card....
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This application note describes techniques of using a PC based Digital I/O Board to characterize analog-to-digital converters (ADCs). It will look at static DC parameters such as integral nonlinearity (INL), differential nonlinearity (DNL), gain, and offset....
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These two schematics are variations on another PWM circuit that I designed. The diagrams are for 12V operation only and there are high side (common ground) and low side (common +12V) versions. The low side version of the circuit uses an N Channel FET, the....
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The 555 Ic is wired as an astable and the frequency is constant and independent of the duty cycle, as the total resistance (R charge + R discharge, notice the diode) is constant and equal to 22Kohm (givin a frequency of about 1Khz, notice the hum). When the....
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A quad op amp makes up the heart of this function generator. Ul-a generates a square wave, and outputs this to J8. J1 and J2 are pulse outputs obtained by differentiating the square wave. Integrator Ul-b generates a triangle-wave shaper to obtain a sine wave...
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Ul, an FET op amp needs a bipolar voltage atpins 4 and 7 with a common ground for optimum gain. You can calculate the gain by dividing R2 by Rl. Zero-set balance can be had through pins i and 5 through R3. Put a voltmeter between pin 6 and ground and....
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This is the simplest possible design. The local oscillator of the receiver is adjusted slightly so that its second harmonic can be used for mixing. RF leakage from the local oscillator is sufficient to drive this crystal diode mixer, which has an output at....
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The circuit provides accurate full wave rectification. The output impedance is low for both input polarities, and the errors are small at all signal levels. Note that the output will not sink heavy current, except a small amount through the 10K resistors.....
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A simple 120 V: 24 V, center-tapped control transformer and four additional components can do the job. This circuit outputs a clean 200 V pk-pk square wave at 60 Hz and can supply up to 20 W. The circuit is self-starting and free-running. If Q1 is....
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The ATmega8 microcontroller-based Low-Cost Telemetry Device (LTD) is an efficient telemetry keyer. The LTD measures the voltage levels of up to four analog channels via its on-chip 10-bit ADC, converts the measurements to numbers, and then sends the data in....
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CI and LI resonate on the 1750 meter band, with coverage from 150 kHz to 500 kHz. LI can be slug-tuned for 160-to-190 kHz coverage alone or a 2.5 mH choke can be used for LI, if desired, using CI for tuning. A 1N270 germanium diode rectifies the RF signal....
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The DUT"s(Device Under Test) cathode, anode, and gate are connected to the unit"s K, A, and G terminals, respectively. Pressing switch ·Sl feeds a gate current to the D UT, which triggers it on. Resistor Rl limits the gate current to the appropriate....
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In this circuit a non-locking push switch is used to activate a load. The load remains switched on until power is removed from the circuit. The load is represented by R5 and D1, but could be a lamp, a relay or another circuit. S2 breaks power to the circuit....
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A circuit design, based on a C-mos chip to Drive a Car Ignition Coil. This is a Very Simple and Efficient Design for an Electric Fence. It puts out a Very high Voltage Current pulse, yet it draws a very small average Current from the battery or supply. As....
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This spring reverberation unit comprises three identical main sections each of which contains an Accutronics type 9 spring reverb tank with short, medium and long decay times. Controls are provided to adjust the amount of signal arriving at the output from....
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This device uses the second method (which, if you don't already know, requires about 100 times less parts), but adds motion detection to switch cameras. The usual way to detect motion is to store a complete video frame and then look for changes on successive....
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This unit is a single oscillator built around an LF351 JFET-input op amp. Resistors Rl and R2 bias the noninverting input while R3 biases the inverting input from the output. This layout provides lOO% negative feedback, but the decoupling caused by C2....
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This circuit features automatic Exit and Entry delays and a timed Bell Cut-off. It has provision for both normally-closed and normally-open contacts, and a 24-hour Personal Attack/Tamper zone. It is connected permanently to the 12-volt supply and its....
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The circuit described here provides around 180mA current at 5.6V and protects the mobile phone from unexpected voltage fluctuations that develop on the mains line. So the charger can be left ?on? over night to replenish the battery charge. The circuit....
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Creating projects that connect to the phone line can be a real chore without some device like this. It generates the 48 volts DC for the on-hook condition, the 100 volts AC for the ring signal, and the 20 milliamperes DC for the off-hook condition. To use....
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The primary advantage of this circuit, when compared to other comparators, is its ability to latch after the input has reached a predetermined threshold level. When the input exceeds the threshold level, the LM311N output increases. This transition enables....
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This receiver uses an IR-sensitive phototransistor (Clairex, HP, etc.) mounted in a light-tight enclosur..
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Two gates of a 4011 arc used as a comparator. When the resistance of R4 decreases the voltage at pin 1 and 2 increases, producing a logic zero at pin 3, causing pin 4 to go high and activating the LED. R3 is calibrated in light units, or seconds exposure....
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Repell those repugnent insects from your Garden this Summer with this insect repellant circuit. Designed by Graham Maynard the circuitry consists of a phase locked loop (CMOS 4047) wired as a 22KHz oscillator. The output is amplified by a pair of....
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The circuit of Figure 1 provides the termination voltage for both 1.8 and 2.5V memory systems and delivers output current as high as 6A. IC1 includes a step-down controller and two linear-regulator controllers and operates with input voltages of 4.5 to 28V...
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This 115 Vac, electronic circuit breaker uses the low drive power, low on resistance and fast turn off of the TMOS MTM15N50. The trip point is adjustable, LED fault indication is provided and battery power provides complete circuit isolation. The two....
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The output voltage changes approximately linearly up to 20 KV as the input voltage is varied from 0 to 5 V. The oscillator is tuned by a 5-0 potentiometer to peak the output voltage at the frequency of maximum transformer response between 45 and 55 kHz. The....
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This design explains how to use an encoder to set the number shown by a 7-segment display. Turn the knob clockwise to increment the number, turn it counterclockwise to set it back. Encoders are the most practical (and handy) way to set a large number of....
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A simple FM wireless microphone uses a single BC183C transistor as an audio amplifier. A 2N3565 can be substituted. ..
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This circuit design was used to switch on device via a LED photocell arrangement (optocoupler) using components R1, C1, D1 and Q1. It produces a delay on powering up to ensure correct sequencing of certain equipment. A very simple delay timer using a....
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This circuit shows a twin-T network connected to an LMl02 to fonn a high-Q, 60-Hz notch filter. The junction of R3 and C3 which is normally connected to ground, is bootstrapped to the output of the follower. Because the output of the follower is a very low....
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The range of this transmitter is about 50 feet with a short whip antenna. The tone generator, is made up of a unijunction transistor, Q1, and R1, R2, R3, and C2. Transistor Q1 pulses on and off at a rate determined by the time constant of R1 and R2,....
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The battery life and operating cost of an electric vehicle is severely affected by overdischarge of the battery. This circuit provides both warning and shutdown. An electronic switch is placed in series with the propulsion motor contactor coil. Three modes....
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A diac is used in the gate circuit to provide work for the signal being applied to the gate. R1 a threshold level for firing the triac. C3 and R4 is selected to limit the maximum charging cur-provide a transient suppression network..
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This circuit uses the 555 timer in the asta-ble or oscillatory mode. The length of time the timer is off is a function of the values of CI, R2, and R3. The potentiometer which controls the amount of "hesitation"..
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Finding out where your microcontroller`s firmware spends most of its time can be a tedious task when you use a conventional in-circuit emulator and breakpoint techniques. Other such tasks include discovering why a state machine doesn`t work as you intended....
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this is a very easy circuit to build - all parts can be found at the local electronics shop...
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Picured in Figure 1 is a miniature magnetic gun. When optimally tuned, it will propel a small slug about 1.5 metres high, or 2.5 metres horizontally.
IC1 is a 555 timer in astable mode, sending approx. 10 ms pulses to decade counter IC2. IC2 is....
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Here, S1 and S2 are normally open , push to close, press button switches. The diodes can be
red or green and are there only to indicate direction. You may need to alter the TIP31 transistors
depending on the motor being used. Remember, running under....
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Linear Technologys LT®3466 is a dual step-up converter
capable of driving up to 20 white LEDs with a programmable
constant current. The device is also capable of
driving asymmetric LED strings with independent dimming
and shutdown control for multipanel....
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The LT®1785 and LT1791 RS485/RS422 transceivers
with ±60V fault tolerance solve a real-world problem of
field failures in typical RS485 interface circuits. Modems
and other computer peripherals use point-to-point RS422
connections to support higher....
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A dual optocoupler is used in a configuration which has the same current throughout as the LEDs. Assuming similar optocoupler features the output voltage must be equal to the non-inverting input voltage. Since the op amp is within a closed loop the output....
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The TDA2616 is a hi-fi stereo amplifier designed for mains fed applications, such as stereo radio and TV. The circuit is optimally designed for symmetrical power supplies, but is also well-suited to asymmetrical power supply systems.
An output power of 2 X....
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Most experienced amateurs know that SSB (single side band) reception requires a receiver fitted with a product detector or BFO (beat frequency oscillator) to reinsert the missing carrier. They also know that such receivers command significantly higher prices....
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Here is a deluxe version of the simple charge rate limiter, using the same idea but with the ability to charge two packs simultaneously from a single wall charger. For circuit description and parts list, see the simple charger page. Since wall chargers....
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The equivalent series resistance (ESR) of a capacitor can be measured using this circuit and an ac voltmeter. Ul fun..
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The circuit includes a low-distortion, 1-kHz oscillator and will measure THD at a user selected voltage level for voltage amplifiers, or for checking amplifiers of power levels to 600 W. It will detect THD levels of .005% (-86 dB). A built-in one-percent....
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Sending Morse on a rig without a sidetone is not impossible, but is not particularly pleasant either. This battery-powered monitor has been designed to provide an audible indication of keying for those whose rigs lack a CW sidetone. Its sensor wire is....
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The water detection time is less than 10 seconds. Since the microcontroller enters a low consumption state between readings to preserve battery life, this state is always 10 seconds long. If water reaches the probes while being in the low power state it will....
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DC Servo Motor Driver kit, designed using MC33030 IC, is the fastest and low cost way of getting your DC Servo Motor up and running...
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Want to add video to your next project? This device uses a PIC16F819 and not much else. Getting 20 characters to a line is possible by using the SPI port to generate video. Neat trick, eh? The character set is limited to upper case and a few punctuation....
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The output cable from my 20 MHz function/sweep generator dangled over the side of the workbench, the alligator clip hovering over the floor. Deeply engrossed in a project, I moved the power strip on the floor a little closer so I could plug in the circuit....
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As the circuit operates, the three sets of diodes with their isolation capacitors, build up an increasing voltage on capacitor ?C1?. The voltage at point ?B? will also increase and be about twelve volts less than the voltage on capacitor ?C1?. Eventually,....
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This is one of my favorites. The LM386 is a low voltage audio power amplifier. It can provide 125mW to 750mW, enough for any project that uses audio. This circuit can work with batteries, requieres minimum external parts and works from 4 to 18 Volts (contact....
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This circuit was designed and manufactured the `80`s. From then it works without problem. It does not present any particular constructional problem, beyond known: the attention in the provided force of power supply - choice suitable heatsink and good....
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"Class A" refers to configuring an amplifier so that its output devices remain turned on all the time. This reduces thermal variation and eliminates crossover distortion, which makes the chip perform better. To bias an op-amp into class A, you simply put a....
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This simple add-on capacitance meter has been specially designed to help you identify capacitors from 1p to 10u. There has always been a problem identifying capacitors, due to the enormous variety in size, shape and coding. Most of the time it is impossible....
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Figure A shows the circuit of a direct-trigger timing light. The trigger voltage is -taken from the car's ignition circuit by a direct connection to a spark plug. A circuit using an inductive pickup is shown in Fig. B. A trigger transformer is used to....
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Atmel described a simple programmer based on the AT90S1200 (NOT the AT90S1200A) controller in their application note, AVR910 (a modification to use the AT90S2313 is also given below).The circuit is so small and simple, I was able to put two of them together....
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This text-to-speech converter is built around the SP0256-AL2 speech processor and the Cf6256AL2 text-to-speech converter chips~manufactured by General Instruments. The circuit is set up to receive standard ASCII code from virtually any microcomputer or....
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Its frequency depends on the capacitance of the vary cap diode. The center frequency is changed by varying the biasing voltage of the vary cap through the 47K pot. You can use a 75cm telescopic antenna or simply a length of hook-up wire. Mine worked fine....
This circuit determines the cold cranking amps of a battery by first discharging the surface charge, then checking the internal resistance. This gives a more realistic measurement than simply measuring the instantaneous drop in voltage with a load. A....
Charge redistribution to achieve A/D conversion. In typical applications, as a ratiometric conversion system for a microprocessor, V^p, will be connected to ground and VREF+ will be connected to Vcc. ..
The circuit is an VXO with buffered output. It operates on 20-meter amateur radio band with the output voltage about 0.2 Vp-p. The crystal frequency is pulled by tuning the variable capacitor CV1 about 36Khz with only one crystal (Y1), and 250Khz by using....
An RF probe is used to directly measure the level of RF voltage present at a particular point and is one of the most useful test instrument in the hands of the home brewer. It is normally used with a digital multi meter to indicate the voltage level as dc....
The Talking Phone Dial Monitor detects the tones generated when numbers are dialed on your touch tone telephone and speaks the numbers that were dialed. This verifies that you dialed the correct number and is especially useful when the keypad is not....
The 74AC240 stepper driver works by alternately enabling each half of the buffer. Only one half can be enabled at a time. Let`s assume that the top half of the driver is enabled. U1A & U1B along with R8, C1, and the input protection resistor R7 form....
This circuit is actuated by an increase in capacitance between a sensing electrode and the ground side of the line. The sensitivity can be adjusted to switch when a human body is within inches of the insulated plate used as the sensing electrode. Thus,....
This signal tracker and lock detector combine to make a precision tone switch. Filter R3/R4/C2 determines..
Micro-Cap 9 is an integrated schematic editor and mixed analog/digital simulator that provides an interactive sketch and simulate environment for electronics engineers. Since its original release in 1982, Micro-Cap has been steadily expanded and improved.....
This thermometer is capable of 0.01°C accuracy over - 50°C to +150°C. A unique trim arrangement eliminates cumbersome trim interactions so that zero gain, and nonlinearity correction can be trimmed in one even trip. Extra op amps provide full Kelvin....
The LTC10432 switched-capacitor building block provides nonoverlapping complementary drive to the Ql to Q4 power MOSFETs. The MOSFETs are arranged so that Cl and C2 are alternately placed in series and then parallel. During the series phase, the + 12 V....
A practical, efficient LCD backlight design is a classic study of compromise in a transduced electronic system. Every aspect of the design is interrelated, and the physical embodiment is an integral part of the electrical circuit. The choice and location....
The 20-W + 20-W stereo amp consists of two complete, separate 20-W RMS bridge-type amplifiers. The input signal source is brought into the amplifier through the voltage divider network, which is made up of Rl, R2, and PI. Resistor Rl provides a load....
This circuit will generate a linear sawtooth between 30 Hz and 3 000 Hz. Ql is a constant-current s..
This power supply circuit is highly stabilized that its output voltage will drop only 0.005% even though the load changes from 0 to 100%. Another excellent capability is that the output voltage will change only by 0.01% if the input voltage fluctuates. The....
Null detector uses simple LED readout to indicate if test resistor R* is below, equal to, or greater than test resistance Rref. IfR* = Rref, the 741 output sits at midpoint value of 4 volts and LED A lights..
In the never-ending quest for simplicity even one extra diode is a price I loath to pay and to avoid using extra components it struck me that the the two diodes in SIMD1 V1 were connected like the two junctions in one transistor. Eureka! replace two....
The GPS interface can be fed in 2 ways: with a stabilized 5V supply or with a 10 to 25V unregulated DC supply. In both cases the power is fed into the RJ45 connector on point 8. Pin 7 is DC ground. The power supply current is first secured with a slow....
Ql is a phototransistor that is normally illuminated by a beam of light. When the beam is intercoupled, pin ..
The Tritium circuit was the first (to my knowledge) type 3 SE. As such, it is quite experimental, and should be regarded as a prototype rather than the `state of the art`! Nevertheless, it does function reasonably well, and in some circumstances outperforms....
This circuit can be used to prevent relay contact arcing for loads up to 50 amperes. There is some delay between the time a relay coil is energized and the time the contacts close. There is also a delay between the time the coil is de-energized and the time....
This project is finalized, that means it is no longer experimental. This amplifier, altough limited in output power (20W), has been designed to give the best listening pleasure. No compromise has been made during components choice: the 845 output triode is....
This circuit is a simple two transistor (2N2222) FM transmitter. No license is required for this transmitter according to FCC regulations regarding wireless microphones. If powered by a 9 volt battery and used with an antenna no longer than 12 inches, the....
The circuit is placed parallel with the exit of power amplifier and us gives the level of signal ,from output. Changing resistance R1, in the input circuit, we adapt the indication of power, in the resistance of loudspeaker, that we use. ..
This control, with zero-voltage load switching, uses a CA3130 BiMOS op amp and a CA3079 zero-voltage switc..
This wide-range light dimmer circuit uses a unijunction transistor and a pulse transformer to provide phase control for the TRIAC. The circuit operates from a 115 volt, 60 Hz source and can control up to 800 watts of power to incandescent lights. The power....
A charge pump is a simple means of generating a low-power voltage supply of opposite polarity from the main supply. The 74Cl4 IC is a self-oscillating driver for the MOSFET power switch. It produces a pulse width of 6.5 p,s at a repetition frequency of....
The lights seem to dance in time with the music. Line-voltage lamps of about 40 to 100 W do nicely. The current for the lamp is from an SCR. When low-level audio is present across Tl, SCR1 is not triggered into conduction. A louder signal, however,....
A block diagram and a schematic of the receiver are shown in Figures 2 and 3, respectively. In Figure 3, L6 and L7 are spaced 0.6 inch for a loss of about 0.5 dB. Q4 is the first RF amplifier. L9 and L10 are spaced about 0.8 inch with a partial shield....
Unusual frequency compensation gives this logarithmic converter a 100 µs time constant from 1 mA down to 100 µA, increasing from 200 µe to 200 ms from 10 nA to 10 pA. Optional bias current compensation can give 10 pA resolution from - 55 °C to 100 °C..
The controller is quite (actually very) simple. An input buffer ensures that the input impedance of the source does not affect the integrator performance, and allows summing of left and right channels without any crosstalk. The output provides a phase....
The 4047 is configured as a free-running, astable- multivibrator (oscillator) circuit. That configuration, offers three different outputs. The output pulses at the Q and Q output (pins 10 and 11, respectively) are the same as in the previous two....
This simple circuit uses an incandescent lamp to detect airflow. With the filament exposed to air, a constant current source is used to slightly heat the filament. As it is heated, the resistance increases. As air flows over the filament it cools down, thus....
A1 amplifies and regulates the signal from the spark coil. A2 converts frequency to voltage so that its output is a voltage proportional to engine rpm. A3 compares the tachometer voltage with the reference voltage and turns on the output transistor at the....
It's a simple metal detector design that has the quite good characteristics. the principle of operation which one differs from the classic schemes (BFO, transmit-receive known as "two-boxes" metal detector, inductive). The dynamic mode is used to find....
PulsePar turns a PC into a multi-channel pulse generator utilizing the parallel port. The period, duty and phase of each channel are adjustable so as to be used in PWM systems as well as in testing servo and stepper (stepping) motors. If you have an old PC,....
This design was published in the June 1994 issue of Electronics Australia, and has proven extremely popular. The kit was sold by Jaycar Electronics, but has since been discontinued. It is a simple device that connects between your keyboard and VGA card....
These two schematics are variations on another PWM circuit that I designed. The diagrams are for 12V operation only and there are high side (common ground) and low side (common +12V) versions. The low side version of the circuit uses an N Channel FET, the....
The 555 Ic is wired as an astable and the frequency is constant and independent of the duty cycle, as the total resistance (R charge + R discharge, notice the diode) is constant and equal to 22Kohm (givin a frequency of about 1Khz, notice the hum). When the....
A quad op amp makes up the heart of this function generator. Ul-a generates a square wave, and outputs this to J8. J1 and J2 are pulse outputs obtained by differentiating the square wave. Integrator Ul-b generates a triangle-wave shaper to obtain a sine wave...
Ul, an FET op amp needs a bipolar voltage atpins 4 and 7 with a common ground for optimum gain. You can calculate the gain by dividing R2 by Rl. Zero-set balance can be had through pins i and 5 through R3. Put a voltmeter between pin 6 and ground and....
The circuit provides accurate full wave rectification. The output impedance is low for both input polarities, and the errors are small at all signal levels. Note that the output will not sink heavy current, except a small amount through the 10K resistors.....
A simple 120 V: 24 V, center-tapped control transformer and four additional components can do the job. This circuit outputs a clean 200 V pk-pk square wave at 60 Hz and can supply up to 20 W. The circuit is self-starting and free-running. If Q1 is....
The ATmega8 microcontroller-based Low-Cost Telemetry Device (LTD) is an efficient telemetry keyer. The LTD measures the voltage levels of up to four analog channels via its on-chip 10-bit ADC, converts the measurements to numbers, and then sends the data in....
CI and LI resonate on the 1750 meter band, with coverage from 150 kHz to 500 kHz. LI can be slug-tuned for 160-to-190 kHz coverage alone or a 2.5 mH choke can be used for LI, if desired, using CI for tuning. A 1N270 germanium diode rectifies the RF signal....
The DUT"s(Device Under Test) cathode, anode, and gate are connected to the unit"s K, A, and G terminals, respectively. Pressing switch ·Sl feeds a gate current to the D UT, which triggers it on. Resistor Rl limits the gate current to the appropriate....
In this circuit a non-locking push switch is used to activate a load. The load remains switched on until power is removed from the circuit. The load is represented by R5 and D1, but could be a lamp, a relay or another circuit. S2 breaks power to the circuit....
A circuit design, based on a C-mos chip to Drive a Car Ignition Coil. This is a Very Simple and Efficient Design for an Electric Fence. It puts out a Very high Voltage Current pulse, yet it draws a very small average Current from the battery or supply. As....
This spring reverberation unit comprises three identical main sections each of which contains an Accutronics type 9 spring reverb tank with short, medium and long decay times. Controls are provided to adjust the amount of signal arriving at the output from....
This device uses the second method (which, if you don't already know, requires about 100 times less parts), but adds motion detection to switch cameras. The usual way to detect motion is to store a complete video frame and then look for changes on successive....
This unit is a single oscillator built around an LF351 JFET-input op amp. Resistors Rl and R2 bias the noninverting input while R3 biases the inverting input from the output. This layout provides lOO% negative feedback, but the decoupling caused by C2....
This circuit features automatic Exit and Entry delays and a timed Bell Cut-off. It has provision for both normally-closed and normally-open contacts, and a 24-hour Personal Attack/Tamper zone. It is connected permanently to the 12-volt supply and its....
The circuit described here provides around 180mA current at 5.6V and protects the mobile phone from unexpected voltage fluctuations that develop on the mains line. So the charger can be left ?on? over night to replenish the battery charge. The circuit....
Creating projects that connect to the phone line can be a real chore without some device like this. It generates the 48 volts DC for the on-hook condition, the 100 volts AC for the ring signal, and the 20 milliamperes DC for the off-hook condition. To use....
The primary advantage of this circuit, when compared to other comparators, is its ability to latch after the input has reached a predetermined threshold level. When the input exceeds the threshold level, the LM311N output increases. This transition enables....
This receiver uses an IR-sensitive phototransistor (Clairex, HP, etc.) mounted in a light-tight enclosur..
Two gates of a 4011 arc used as a comparator. When the resistance of R4 decreases the voltage at pin 1 and 2 increases, producing a logic zero at pin 3, causing pin 4 to go high and activating the LED. R3 is calibrated in light units, or seconds exposure....
Repell those repugnent insects from your Garden this Summer with this insect repellant circuit. Designed by Graham Maynard the circuitry consists of a phase locked loop (CMOS 4047) wired as a 22KHz oscillator. The output is amplified by a pair of....
This 115 Vac, electronic circuit breaker uses the low drive power, low on resistance and fast turn off of the TMOS MTM15N50. The trip point is adjustable, LED fault indication is provided and battery power provides complete circuit isolation. The two....
The output voltage changes approximately linearly up to 20 KV as the input voltage is varied from 0 to 5 V. The oscillator is tuned by a 5-0 potentiometer to peak the output voltage at the frequency of maximum transformer response between 45 and 55 kHz. The....
This design explains how to use an encoder to set the number shown by a 7-segment display. Turn the knob clockwise to increment the number, turn it counterclockwise to set it back. Encoders are the most practical (and handy) way to set a large number of....
A simple FM wireless microphone uses a single BC183C transistor as an audio amplifier. A 2N3565 can be substituted. ..
This circuit design was used to switch on device via a LED photocell arrangement (optocoupler) using components R1, C1, D1 and Q1. It produces a delay on powering up to ensure correct sequencing of certain equipment. A very simple delay timer using a....
This circuit shows a twin-T network connected to an LMl02 to fonn a high-Q, 60-Hz notch filter. The junction of R3 and C3 which is normally connected to ground, is bootstrapped to the output of the follower. Because the output of the follower is a very low....
The range of this transmitter is about 50 feet with a short whip antenna. The tone generator, is made up of a unijunction transistor, Q1, and R1, R2, R3, and C2. Transistor Q1 pulses on and off at a rate determined by the time constant of R1 and R2,....
The battery life and operating cost of an electric vehicle is severely affected by overdischarge of the battery. This circuit provides both warning and shutdown. An electronic switch is placed in series with the propulsion motor contactor coil. Three modes....
A diac is used in the gate circuit to provide work for the signal being applied to the gate. R1 a threshold level for firing the triac. C3 and R4 is selected to limit the maximum charging cur-provide a transient suppression network..
This circuit uses the 555 timer in the asta-ble or oscillatory mode. The length of time the timer is off is a function of the values of CI, R2, and R3. The potentiometer which controls the amount of "hesitation"..
this is a very easy circuit to build - all parts can be found at the local electronics shop...
Picured in Figure 1 is a miniature magnetic gun. When optimally tuned, it will propel a small slug about 1.5 metres high, or 2.5 metres horizontally. IC1 is a 555 timer in astable mode, sending approx. 10 ms pulses to decade counter IC2. IC2 is....
Here, S1 and S2 are normally open , push to close, press button switches. The diodes can be red or green and are there only to indicate direction. You may need to alter the TIP31 transistors depending on the motor being used. Remember, running under....
A dual optocoupler is used in a configuration which has the same current throughout as the LEDs. Assuming similar optocoupler features the output voltage must be equal to the non-inverting input voltage. Since the op amp is within a closed loop the output....
The TDA2616 is a hi-fi stereo amplifier designed for mains fed applications, such as stereo radio and TV. The circuit is optimally designed for symmetrical power supplies, but is also well-suited to asymmetrical power supply systems. An output power of 2 X....
Most experienced amateurs know that SSB (single side band) reception requires a receiver fitted with a product detector or BFO (beat frequency oscillator) to reinsert the missing carrier. They also know that such receivers command significantly higher prices....
Here is a deluxe version of the simple charge rate limiter, using the same idea but with the ability to charge two packs simultaneously from a single wall charger. For circuit description and parts list, see the simple charger page. Since wall chargers....
The equivalent series resistance (ESR) of a capacitor can be measured using this circuit and an ac voltmeter. Ul fun..
The circuit includes a low-distortion, 1-kHz oscillator and will measure THD at a user selected voltage level for voltage amplifiers, or for checking amplifiers of power levels to 600 W. It will detect THD levels of .005% (-86 dB). A built-in one-percent....
Sending Morse on a rig without a sidetone is not impossible, but is not particularly pleasant either. This battery-powered monitor has been designed to provide an audible indication of keying for those whose rigs lack a CW sidetone. Its sensor wire is....
The water detection time is less than 10 seconds. Since the microcontroller enters a low consumption state between readings to preserve battery life, this state is always 10 seconds long. If water reaches the probes while being in the low power state it will....
DC Servo Motor Driver kit, designed using MC33030 IC, is the fastest and low cost way of getting your DC Servo Motor up and running...
Want to add video to your next project? This device uses a PIC16F819 and not much else. Getting 20 characters to a line is possible by using the SPI port to generate video. Neat trick, eh? The character set is limited to upper case and a few punctuation....
The output cable from my 20 MHz function/sweep generator dangled over the side of the workbench, the alligator clip hovering over the floor. Deeply engrossed in a project, I moved the power strip on the floor a little closer so I could plug in the circuit....
As the circuit operates, the three sets of diodes with their isolation capacitors, build up an increasing voltage on capacitor ?C1?. The voltage at point ?B? will also increase and be about twelve volts less than the voltage on capacitor ?C1?. Eventually,....
This is one of my favorites. The LM386 is a low voltage audio power amplifier. It can provide 125mW to 750mW, enough for any project that uses audio. This circuit can work with batteries, requieres minimum external parts and works from 4 to 18 Volts (contact....
This circuit was designed and manufactured the `80`s. From then it works without problem. It does not present any particular constructional problem, beyond known: the attention in the provided force of power supply - choice suitable heatsink and good....
"Class A" refers to configuring an amplifier so that its output devices remain turned on all the time. This reduces thermal variation and eliminates crossover distortion, which makes the chip perform better. To bias an op-amp into class A, you simply put a....
This simple add-on capacitance meter has been specially designed to help you identify capacitors from 1p to 10u. There has always been a problem identifying capacitors, due to the enormous variety in size, shape and coding. Most of the time it is impossible....
Figure A shows the circuit of a direct-trigger timing light. The trigger voltage is -taken from the car's ignition circuit by a direct connection to a spark plug. A circuit using an inductive pickup is shown in Fig. B. A trigger transformer is used to....
Atmel described a simple programmer based on the AT90S1200 (NOT the AT90S1200A) controller in their application note, AVR910 (a modification to use the AT90S2313 is also given below).The circuit is so small and simple, I was able to put two of them together....
This text-to-speech converter is built around the SP0256-AL2 speech processor and the Cf6256AL2 text-to-speech converter chips~manufactured by General Instruments. The circuit is set up to receive standard ASCII code from virtually any microcomputer or....
Its frequency depends on the capacitance of the vary cap diode. The center frequency is changed by varying the biasing voltage of the vary cap through the 47K pot. You can use a 75cm telescopic antenna or simply a length of hook-up wire. Mine worked fine....
