New Circuits Page 207
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The basic circuit illuminates up to ten LEDs in sequence, following the rhythm of music or speech picked-up by a small microphone. The expanded version can drive up to ten strips, formed by up to five LEDs each, at 9V supply. IC1A amplifies about 100 times....
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I`ll eventually post an explanation, but in the meantime, here it is. Meanwhile, a slightly refined version (with flashing LEDs to indicate "lock") was posted a few weeks later:..
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Using this simple resistor circuit, you can trick your oscilloscope into displayin..
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Sound or light sensors corniected to J2 produce a voltage that is amplified by ICl-a and ICl-b. A positive trigger voltage that is developed by D1 and 1)3 and amplified by ICl-d, drives 1C2 and 1C1 to trigger SCR1. SCR1 is connected to a strobe. ..
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According to the MSC1210 datasheet, you will perform an external reset by taking RST pin high for two tOSC periods as this stops device operation, crystal oscillation, causes all digitall pins to be pulled high from that point and then followed by taking the....
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This circuit provides either latched switching or timed switching. U1A and UlB provide audio amplification from the ..
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The TPS61040 is a highly integrated, low power, boost converter capable of delivering
output voltages up to 28 V. However, using a coupled inductor enables the TPS61040 to
be used in applications where higher voltages are required. Output voltages up to 75....
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The electronic bagpipe mimics the sound of real instruments. This circuit uses two UJT oscillators and an amplifier (Q3,..
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In the form it appears the theoretical circuit of filter. In first glance we see three different circuits that are mainly manufactured round two operational amplifiers. This circuits constitute mixed, amplifier with variable aid and a variable filter. The....
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This VHF VCO circuit is suitable for 30 to 200 MHz. Q1 can be replaced by a 2N3563 for operation above 100 MHz..
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By using two 8-bit ADC channels for the same signal, the technique in Figure 1 can accommodate both conditions. One channel, which the controller uses for fast motion, reads the input directly and adds four 0 LSBs for a 12-bit result. The second channel....
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The tube headphone amplifier in figure 1 is a high current mu follower, with a 12AU7 cathode follower driven by a 6CG7. Both sections of each tube are paralleled to minimize noise. It's a zero global feedback, OTL design of pretty high quality. I use it and....
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The circuit has a frequency response ranging from 100Hz to 3 MHz; gain is about 30 dB. Field-effect transistor Q1 is configured in the common-source self-biased mode. Optional resistor R1 allows you to set the input impedance to any desired value;....
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The charger"s output voltage is adjustable and regulated, and has an adjustable constant-current charging circuit that makes it easy to use with most NiCad batteries. The charger can charge a single cell or a number of series-conoected cells up to a....
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This circuit is a simple form of the commercial UPS, the circuit provides a constant regulated 5 Volt output and an unregulated 12 Volt supply. In the event of electrical supply line failure the battery takes over, with no spikes on the regulated supply...
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The pitch of the tone is dependent upon the resistance under test. The tester will respond to resistance of hundreds of kilohms, yet it is possible to distinguish differences of just a few tens of ohms in low-resistance circuits. Ql and Q2 form a....
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The current source formed by Ql in conjunction with capacitor Cl set the duration time of the ramp. As the positive dc voltage at the gate is changed, the peak point firing voltage of the PUT is changed, which changes the duration time...
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I decided to make a commercial surface mount PC board using the LED2 sensor concept. It is quite sensitive and can track to a few degrees of accuracy in bright sunlight. If a blocking shadow is used the accuracy is better then 1/4 degree, that`s about as....
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A simple project, within most of homebrewers capabilities. Very simple tuning, a single stage to align, besides VFO frequency adjusting. Easy to find, cheap components. Reduced dimensions and low power requirement, a totally portable rig. It's worth while to....
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The circuit is based on an LM3914N bar graph display driver device (IC1), which can be used to drive up to ten LEDs. This is connected so that with OV12 at the input only the first LED indicator switches on. This simple peak reading VU meter circuit uses six....
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This circuit shows a simple way to add text information to a composite-video signal that might be floating at some indeterminate de level. The text generator and composite-video source must have the same sync signal. The video-input and -output signals....
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The coil on the left is coil#1, and has 17 taps. The other coil is coil #3. The vertical strips are the lath material, screwed to the 1 foot long base. Holes drilled in the ends of the lath hold the dowel rod; it can be removed to change coils. The....
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This is a high quality power supply with a continuously variable stabilised output adjustable at any value between 0 and 30VDC. The circuit also incorporates an electronic output current limiter that effectively controls the output current from a few....
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There`re many, who built the Easy Programmer or C-52 Evaluation Board, asking for the RS232C level converter chip, DS275. Many have changed to MAX232 instead, because of not available in his home. Here is another simple and cheap circuit using small signal....
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This circuit was designed on request to drive a Light-cluster formed by several LEDs that can be mounted in the vehicle as a tail and brake light. When SW1 is on, the cluster will illuminate at medium brightness. When brakes are operated, SW2 will be closed....
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Just a handful of components builds an 8-pin microcontroller based circuit for temperature logging via a serial port; small, fast, and acceptably accurate...
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This miniature transmitter is easy to construct and it`s transmissions can be picked up on any standard FM receiver. It has a range of up to 1/4 of a mile or more. It is great for room monitoring, baby listening, nature research, etc. L1 is 8 to 10 turns of....
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Figure 1 shows a classic voltage-to-current (V/I) converter. You can select the resistor values such that the output current in the load, RL, varies only with the input voltage, VIN, and is independent of RL. The circuit is widely used in industrial....
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The decoder is intended to be a reference quality prototype with maximum flexibility for experimental use with different speaker layouts. A new improved version has been added at the end. There are two main sections to the instrument. The UHJ decoder board,....
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The output voltage of a thermocouple is converted into frequency measured by a digital frequency meter. The output thermocouple signal is proportional to the temperature difference between the hot junction and the thermostat kept at 0°C, it drives the....
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The Sallen-Key realization of a 5.25-MHz, three-pole Butterworth filter has a gain of 2V/V and can drive 75 back-terminated coax with an overall gain of 1 (Figure 1). Used to reconstruct component-video (Y, Pb, Pr) and RGB signals, this filter has an....
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Six LEDs are arranged to produce a display the same as the dots on a dice. When PBI is depressed, the display is blanked and the oscillator (ICl a, b, c) clocks IC2 at about 1MHz. IC2 counts from zero and resets on seven..
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Two IC rf modulators convert a suitable baseband video and audio signal up to a low VHF modulated carrier-Channel2 through 6 in the U.S., and 1 through 3 in japan-the LM1889 and the LM2889. Both !Cs are identical regarding the rf modulation function,....
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A practical realization of a spread-spectrum technique lowers a µP`s clock-related EMI by approximately 4 dB without the drawbacks associated with modulation (Figure 1). The spread-spectrum technique is a popular method to reduce µP-clock-related EMI....
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Here we use the PIC16711. Rechargeable battery capacity is rated in mAH (milliampere-hours). The total capacity of a battery is defined as "C", that is it can supply C mA for 1 hour, or 2C for 30 minutes etc. Charge rates can vary from trickle charges to....
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This system uses a Microchip's PIC16F877A as a main controller, LM339 as sensor interface, UM3561 as a tone generator and ?PC2002 as a speaker driver (audio amplifier). LM7805, LM7812 and LM317 voltage regulators are used to obtain +5V, +12V and +3V....
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The output of the detector contains a term related to the cosine of the phase angle. Two signals of equal frequency are applied to the inputs. The frequencies are multiplied together, producing the sum and difference frequencies. Equal frequencies cause....
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A microcontroller, by default, can execute only one program at a time. What do you do if, in a given project, you need to perform more than one operation at a time? Add more microcontrollers to the design? In certain cases it`s unnecessary...
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The digital navigation PC board may be configured for a number of navigation functions, see figure 1. It may be made into a simple visual digital compass, or a microcontroller based compass. The microcontroller based compass can be used for mobile robotics....
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The µCurrent is in many cases also able to improve upon your meters current range accuracy by using your meters more accurate mVDC or mVAC voltage ranges instead to display the DC or AC current. With AC the frequency response extends flat up to 10KHz, but....
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The design consists of an amplifier, a double-pole changeover switch and two loudspeakers: one for the master station and..
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This device is a microprocessor controlled waveform generator that can be used for driving a voltage controlled stereo panner for music applications. Panning is simply the movement of a mono audio signal between the left and right channels of a stereo sound....
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Circuit with electronic symmetrical input, with possibility of regulation of the gain from the pontesometer RV1 and the level of signal with the RV2. The quality of pontesometer RV1 (as other material), should be very good, in order to we avoid annoying....
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High quality, noise free, wireless FM transmitter/receiver operates over standard power lines. Complete system is suitable for high-quality transmission of speech or music, and will operate from any ac outlet anywhere on a one-acre home site. Frequency....
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The frequency of this sine-wave oscillator is determined by a direct voltage, U" of 0 to 15 V. The distortion on..
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This circuit utilizes the quasi-complementary output stage of the popular LM380 audio power IC. The device is internally biased so that with no input the output is held midway between the supply rails Rl, which should be initially set to mid-travel, is used....
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The output goes high when the supply falls below a value determined by zener diode Dl. If Dl is a 5.6-V zener, the op..
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A 13.56-MHz, ISM (industrial, scientific, and medical)-band RF-measurement device had the test requirement of a 50-hour, 1-kW burn-in. The device under test needed to be simultaneously stressed at an RF potential and RF current equivalent to 1 kW, but the....
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The device is a dc switch that is normally on via the forward biasing of Ql via R3. Ql now clamps Q2 into a forward state by biasing its complement well into a saturated state via R4. The dc switch is turned off via a negative voltage above that of the zener....
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You often need to know when a telecomm power supply`s output drops below its nominal value. The dropout generally indicates a failure and may dictate replacement of the supply or some other form of system maintenance. The circuit in Figure 1 uses an isolated....
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Anyone who has been to a night club, concert or school dance has probobly seen a colour organ. Colour organs cause lights to blink and flash to music from your TV, stereo, guitar and even your own voice. The colour organ presented here needs no connection to....
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When you`re copying videotapes, it`s sometimes desirable to suppress some passages. Using the pause control of the recorder does not yield satisfactory results. Another method produces better results (Figure 1). The video source connects to the video-in....
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LDR1, a cadmium sulphide (CDS) photoresistive cell is used as the lower leg of a voltage divider between Vcc and ground. The timer terminals 2 and 6 are connected to the junction of the photocell and SENSITIVITY control Rl. The resistance of the....
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This circuit is intended for charging lead-acid batteries with a solar panel. The customary diode that prevents the battery from discharging through the solar panel has been replaced by a FET-comparator combination. The charger will stop charging once a....
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The simple circuit in Figure 1 latches on an LED and an audio sounder when an appropriate new audible e-mail signal occurs. The method replaces the normal e-mail sound.wav file with a .wav file of any valid recorded dual-tone multifrequency (DTMF) sound. The....
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It is the essential continuity of circuits Sel 8 Sources and Up/Down Sel 8 Sources, but can work and autonomously, collaborating with any suitable circuit of control. The Relay 1-8 can be 6-24v DC. For current of collector of transistors Q1-8, bigger the 10....
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Op amp Ul and its associated components comprise the 67-kHz bandpass filter. A twin-T network, comprised of four 1100-12 resistors and four 0.0022- capacitors, is connected in the feedback network of the op amp. That gives some gain at 67 kHz and heavy....
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The Wireless Keylogger consists of two main building blocks: the transmitter, and the receiver. The actual keylogging takes place in the transmitter, which is in fact a PS/2 hardware keylogger, with a built-in 2.4 GHz wireless module. Captured keystroke data....
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This project is a miniature, VHF FM (wideband) Wireless Microphone transmitter of the type that are commonly refered to as BUG's. Note that "BUGS" are illegal but "Wide-Band Frequency Modulation Wireless Microphones" (WBFMWMs) are not, as so many people have....
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The supply voltage should be about +/- 35 Volts at full load, which will let this little guy provide a maximum of 56 Watts (rated minimum output at 25 degrees C). To enable maximum power, it is important to get the lowest possible case to heatsink thermal....
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This circuit has been designed to alert the vehicle driver that he/she has reached the maximum fixed speed limit (i.e. in a motorway). It eliminates the necessity of looking at the tachometer and to be distracted from driving. There is a strict relation....
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This circuit simulates the sound of an American police siren. IC2 is wired as a low frequency astable that has a cycling period of about 6 seconds. The slowly varying ramp waveform on Cl is fed to pnp emitter follower Ql, and is then used to frequency....
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This technique uses digital I/O pins to multiplex analog voltages into an analog input on the microcontroller. The method is most suitable for signals that do not need to be sampled frequently and it may be extended to accommodate a large number of inputs,....
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A speedometer measures a wheel`s rotational speed. Unlike conventional mechanical and moving-magnet designs that use analog moving-pointer displays, the electronic speedometer in this Design Idea features a digital readout and a power-saving device that uses....
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The ignition substitute provides a constant power source for the ignition coil. Its frequency, 0.5-1.0 kHz, is that used by an 8-cylinder engine with an idling speed of 650 RPM, and the unit provides a rapid spark at a 17% duty cycle, while staying within....
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We have developed a powerful yet inexpensive and easy to construct experiment control system. The construction of the system together with the control software is described here. All circuits and software are free to download and use for nonprofit. The....
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An Intersil 7101 31/2-digit A/D converter is used to display the duty cycle of a pulse train as a percentage. The frequ..
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With RFT illuminated, point R goes to 0 volt and LM runs. With LFT illuminated, point R goes to 0 volt and RM runs. With RFT and/or LFT not illuminated, points R/L go to +9 volt; P1 and P2 controls threshold point when RM/LM stop or start running. Remember....
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This circuit measures the distance covered during a walk. Hardware is located in a small box slipped in pants` pocket and the display is conceived in the following manner: the leftmost display D2 (the most significant digit) shows 0 to 9 Km. and its dot is....
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The electronic darkroom timer is built around a 555 oscillator/timer, a pair of general-purpose transistors, a buzzer, and an LED. The 555 (Ul) is configured as an astable multivibrator (free-running oscillator). The frequency of the oscillator is....
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A single connection change permits division by any integer between 2 and 10. The RCA CD4017A Johnson decade counter is shown connected as a divide by 7 counter. The resistor is used to hold the reset line low. When the appropriate number is reached, that....
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This wave shaper needs an input saw that goes from Vss to (ideally) Vdd. It works well with the 4069 VCO designed by Ren? Schmitz. Any saw will work as long as the wave is centered halfway between the rails. It works as follows: The upper set of 2 linear....
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The purpose of this circuit is to power a lamp or other appliance for a given time (30 minutes in this case), and then to turn it off. It is useful when reading at bed by night, turning off the bedside lamp automatically in case the reader falls asleep... 30....
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The driver in the package is connected as a Schmitt trigger oscillator (A) where R1 and R2 are used to generate hysteresis. R3 and C are the inverting feedback timing elements and R4 is the pull-down load for the first driver. Because of its current....
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The new 14-bit, 800ksps LTC®1419 enhances new communications, spectral analysis, instrumentation and data acquisition applications by providing an upgrade path to users of 12-bit converters. It provides outstanding 81.5dB SINAD (signal-to-noise and....
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The mixer is the common "virtual earth" mixing amplifier, and there is nothing special about it. Note that it is inverting, which complements the tone controls (also inverting) so the absolute signal polarity is maintained. As shown, the mixer also has a....
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IR detector diode D1 intercepts the IR signal at around 40 kHz and feeds it from U1, a high-gain preamp, to PLL, U2, a 4046 configured to serve as an FM detector. U3 is an audio amplifier that feeds a pair of headphones or a speaker...
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Stabilised tendency of catering: Vcc=9~12V. Frequency of reception: 88~108MHz. Consumption: 100mA. If you know some language of programming as C ++, PASCAL, VISUAL BASIC, DELPHI etc you can write a program which will send in the parallel door (378 I) of PC....
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The direct conversion receiver described consists of only a bandpass filter, mixer IC, VFO and audio filter. With only 22 parts, this simple circuit should take a few hours at the weekend to construct. For extra simplicity, eliminate L1 & C1 and connect C2....
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This small circuit is a Linear amplifier for driving small UHF TV transmitters. Its gain is 7dB and can amplify a signal between 450-800 MHz. You can drive the circuit with 1 to 1,5 Watts signal. Better use double layer PCB with the second layer connected to....
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A simple count-down LED timer that counts in minutes and seconds. Three buttons below the LED provide control of the unit, allowing you set the desired countdown time in minutes and seconds and a start/stop button.
Completion of the countdown is indicated....
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This simple AVR Programmer will allow you to painlessly transfer hex programs to most ATMEL AVR microcontrollers without sacrificing your budget and time. It is more reliable than most other simple AVR programmers available out there and can be built in very....
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Many applications require analog signals to be sensed and digital signals to be controlled. A way to detect these p..
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The bicore is the basis of advanced BEAM! Most intermediate to advanced BEAM robots are built off of the bicore. Uses go all the way from photovores to servo motor drivers to walkers to.... You get the idea. What it is is basically just an oscillator who's....
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The circuit is a microphone amplifier for use with low impedance (~200 ohm) microphones. It will work with stabilized voltages between 9-30VDC. If you don`t build the impedance adapter part with T1, you get a micamp for higher impedance microphones. In this....
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As dusk begins to -fall, the sensor (a cadmium-sulfide light-dependent resistor or LDR) operates a small horn to provide an audible reminder that it's time to turn on your lights. To turn the circuit off—simply turn your headlights on and the noise stops.....
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This converter enables reception of 800 to 1000 MHz on any scanner covering the 400 to 500-MHz range. The converter can be set up to cover either 800 to 900 MHz or by readjustment 900 to 1000 MHz. Sensitivity is very high because of the GASFET front end. ..
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When the comparator`s output changes its state from low to high, the rising edge of the output pulse, differentiated by the Cl/Rl chain, opens Ql. This blocks comparator via its strobing input and sustains its output in the state for a period of time,....
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A low-frequency, op-amp oscillator and a VCO, both configured from a single MC3405 ~dual op amp and dual comparator, are tbe major components in a siren circuit tbat can be made to produce various warbles and wails, or serve as an audio sweep generator. ..
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The purpose of the Kapagen is to suck the free electrons from the Earth. The Earth is a big capacitor which contains free electric charges. If it is possible to create or to find a potential imbalance between two points in the ground, it seems possible to....
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The excess small forward current flow in a tunnel or Esaki diode is a manifestation of quantum mechanical tunneling...
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This circuit features exit and entry delays, an instant alarm zone, an intermittent siren output and automatic reset. By adding external relays you can immobilize the vehicle and flash the lights. One of the inputs is connected to the vehicle`s existing....
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If you have no idea what is a "strobo", "strobe", "stroboscopy" or whatever way it is called, it is simply a flashing light. It is usually used on police cars, 'disco' places and many interesting applications, including scientific ones. This project is....
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Both parts of the circuit are biased with the constant current sources as shown, and the signal from the collector of the PNP is followed by the Darlington class A output stage whose idle current is controlled by the bias circuit. The transistors Q1 and Q2....
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This circuit above uses a 13 volt zener diode, D2 which provides the voltage regulation. Aprroximately 0.7 Volts are dropped across the transistors b-e junction, leaving a higher current 12.3 Volt output supply. This circuit can supply loads of up to 500 mA.....
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Here's a way to get a short range bidirectional RF (Radio Frequency) channel on a microcontroller, using the controller's tristatable I/O pins and on-chip comparator with a few passive components. The range with the firmware and simple I came up with for....
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Here`s the schematic of the device depicted in the photo. Each of the ten coil-assemblies has its own copy of the above circuit. The SS41 is a Microswitch Hall Effect magnetic field sensor IC that I found in Surplus catalog for $.50 each. Any similar hall IC....
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The circuit uses a 741 op amp operating as an inverting amplifier to amplify the voltage produced by an 8-ohm speaker used to detect any sounds. The feedback resistor R3, a 1-megohm potentiometer used to vary the gain of the amplifier determines the....
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At the heart of this simple circuit is the well-known type KTY10 temperature sensor from Siemens. This silicon sensor is essentially a temperature-dependent resistor that is connected as one arm in a bridge circuit here. Preset PI functions to balance the....
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This circuit develops an output voltage that is proportional to the magnetic induction, B, flowing through its probe"s coi..
The basic circuit illuminates up to ten LEDs in sequence, following the rhythm of music or speech picked-up by a small microphone. The expanded version can drive up to ten strips, formed by up to five LEDs each, at 9V supply. IC1A amplifies about 100 times....
I`ll eventually post an explanation, but in the meantime, here it is. Meanwhile, a slightly refined version (with flashing LEDs to indicate "lock") was posted a few weeks later:..
Using this simple resistor circuit, you can trick your oscilloscope into displayin..
Sound or light sensors corniected to J2 produce a voltage that is amplified by ICl-a and ICl-b. A positive trigger voltage that is developed by D1 and 1)3 and amplified by ICl-d, drives 1C2 and 1C1 to trigger SCR1. SCR1 is connected to a strobe. ..
According to the MSC1210 datasheet, you will perform an external reset by taking RST pin high for two tOSC periods as this stops device operation, crystal oscillation, causes all digitall pins to be pulled high from that point and then followed by taking the....
This circuit provides either latched switching or timed switching. U1A and UlB provide audio amplification from the ..
The TPS61040 is a highly integrated, low power, boost converter capable of delivering output voltages up to 28 V. However, using a coupled inductor enables the TPS61040 to be used in applications where higher voltages are required. Output voltages up to 75....
The electronic bagpipe mimics the sound of real instruments. This circuit uses two UJT oscillators and an amplifier (Q3,..
In the form it appears the theoretical circuit of filter. In first glance we see three different circuits that are mainly manufactured round two operational amplifiers. This circuits constitute mixed, amplifier with variable aid and a variable filter. The....
This VHF VCO circuit is suitable for 30 to 200 MHz. Q1 can be replaced by a 2N3563 for operation above 100 MHz..
The tube headphone amplifier in figure 1 is a high current mu follower, with a 12AU7 cathode follower driven by a 6CG7. Both sections of each tube are paralleled to minimize noise. It's a zero global feedback, OTL design of pretty high quality. I use it and....
The circuit has a frequency response ranging from 100Hz to 3 MHz; gain is about 30 dB. Field-effect transistor Q1 is configured in the common-source self-biased mode. Optional resistor R1 allows you to set the input impedance to any desired value;....
The charger"s output voltage is adjustable and regulated, and has an adjustable constant-current charging circuit that makes it easy to use with most NiCad batteries. The charger can charge a single cell or a number of series-conoected cells up to a....
This circuit is a simple form of the commercial UPS, the circuit provides a constant regulated 5 Volt output and an unregulated 12 Volt supply. In the event of electrical supply line failure the battery takes over, with no spikes on the regulated supply...
The pitch of the tone is dependent upon the resistance under test. The tester will respond to resistance of hundreds of kilohms, yet it is possible to distinguish differences of just a few tens of ohms in low-resistance circuits. Ql and Q2 form a....
The current source formed by Ql in conjunction with capacitor Cl set the duration time of the ramp. As the positive dc voltage at the gate is changed, the peak point firing voltage of the PUT is changed, which changes the duration time...
I decided to make a commercial surface mount PC board using the LED2 sensor concept. It is quite sensitive and can track to a few degrees of accuracy in bright sunlight. If a blocking shadow is used the accuracy is better then 1/4 degree, that`s about as....
A simple project, within most of homebrewers capabilities. Very simple tuning, a single stage to align, besides VFO frequency adjusting. Easy to find, cheap components. Reduced dimensions and low power requirement, a totally portable rig. It's worth while to....
The circuit is based on an LM3914N bar graph display driver device (IC1), which can be used to drive up to ten LEDs. This is connected so that with OV12 at the input only the first LED indicator switches on. This simple peak reading VU meter circuit uses six....
This circuit shows a simple way to add text information to a composite-video signal that might be floating at some indeterminate de level. The text generator and composite-video source must have the same sync signal. The video-input and -output signals....
The coil on the left is coil#1, and has 17 taps. The other coil is coil #3. The vertical strips are the lath material, screwed to the 1 foot long base. Holes drilled in the ends of the lath hold the dowel rod; it can be removed to change coils. The....
This is a high quality power supply with a continuously variable stabilised output adjustable at any value between 0 and 30VDC. The circuit also incorporates an electronic output current limiter that effectively controls the output current from a few....
There`re many, who built the Easy Programmer or C-52 Evaluation Board, asking for the RS232C level converter chip, DS275. Many have changed to MAX232 instead, because of not available in his home. Here is another simple and cheap circuit using small signal....
This circuit was designed on request to drive a Light-cluster formed by several LEDs that can be mounted in the vehicle as a tail and brake light. When SW1 is on, the cluster will illuminate at medium brightness. When brakes are operated, SW2 will be closed....
Just a handful of components builds an 8-pin microcontroller based circuit for temperature logging via a serial port; small, fast, and acceptably accurate...
This miniature transmitter is easy to construct and it`s transmissions can be picked up on any standard FM receiver. It has a range of up to 1/4 of a mile or more. It is great for room monitoring, baby listening, nature research, etc. L1 is 8 to 10 turns of....
The decoder is intended to be a reference quality prototype with maximum flexibility for experimental use with different speaker layouts. A new improved version has been added at the end. There are two main sections to the instrument. The UHJ decoder board,....
The output voltage of a thermocouple is converted into frequency measured by a digital frequency meter. The output thermocouple signal is proportional to the temperature difference between the hot junction and the thermostat kept at 0°C, it drives the....
Six LEDs are arranged to produce a display the same as the dots on a dice. When PBI is depressed, the display is blanked and the oscillator (ICl a, b, c) clocks IC2 at about 1MHz. IC2 counts from zero and resets on seven..
Two IC rf modulators convert a suitable baseband video and audio signal up to a low VHF modulated carrier-Channel2 through 6 in the U.S., and 1 through 3 in japan-the LM1889 and the LM2889. Both !Cs are identical regarding the rf modulation function,....
Here we use the PIC16711. Rechargeable battery capacity is rated in mAH (milliampere-hours). The total capacity of a battery is defined as "C", that is it can supply C mA for 1 hour, or 2C for 30 minutes etc. Charge rates can vary from trickle charges to....
This system uses a Microchip's PIC16F877A as a main controller, LM339 as sensor interface, UM3561 as a tone generator and ?PC2002 as a speaker driver (audio amplifier). LM7805, LM7812 and LM317 voltage regulators are used to obtain +5V, +12V and +3V....
The output of the detector contains a term related to the cosine of the phase angle. Two signals of equal frequency are applied to the inputs. The frequencies are multiplied together, producing the sum and difference frequencies. Equal frequencies cause....
The digital navigation PC board may be configured for a number of navigation functions, see figure 1. It may be made into a simple visual digital compass, or a microcontroller based compass. The microcontroller based compass can be used for mobile robotics....
The µCurrent is in many cases also able to improve upon your meters current range accuracy by using your meters more accurate mVDC or mVAC voltage ranges instead to display the DC or AC current. With AC the frequency response extends flat up to 10KHz, but....
The design consists of an amplifier, a double-pole changeover switch and two loudspeakers: one for the master station and..
This device is a microprocessor controlled waveform generator that can be used for driving a voltage controlled stereo panner for music applications. Panning is simply the movement of a mono audio signal between the left and right channels of a stereo sound....
Circuit with electronic symmetrical input, with possibility of regulation of the gain from the pontesometer RV1 and the level of signal with the RV2. The quality of pontesometer RV1 (as other material), should be very good, in order to we avoid annoying....
High quality, noise free, wireless FM transmitter/receiver operates over standard power lines. Complete system is suitable for high-quality transmission of speech or music, and will operate from any ac outlet anywhere on a one-acre home site. Frequency....
The frequency of this sine-wave oscillator is determined by a direct voltage, U" of 0 to 15 V. The distortion on..
This circuit utilizes the quasi-complementary output stage of the popular LM380 audio power IC. The device is internally biased so that with no input the output is held midway between the supply rails Rl, which should be initially set to mid-travel, is used....
The output goes high when the supply falls below a value determined by zener diode Dl. If Dl is a 5.6-V zener, the op..
The device is a dc switch that is normally on via the forward biasing of Ql via R3. Ql now clamps Q2 into a forward state by biasing its complement well into a saturated state via R4. The dc switch is turned off via a negative voltage above that of the zener....
Anyone who has been to a night club, concert or school dance has probobly seen a colour organ. Colour organs cause lights to blink and flash to music from your TV, stereo, guitar and even your own voice. The colour organ presented here needs no connection to....
LDR1, a cadmium sulphide (CDS) photoresistive cell is used as the lower leg of a voltage divider between Vcc and ground. The timer terminals 2 and 6 are connected to the junction of the photocell and SENSITIVITY control Rl. The resistance of the....
This circuit is intended for charging lead-acid batteries with a solar panel. The customary diode that prevents the battery from discharging through the solar panel has been replaced by a FET-comparator combination. The charger will stop charging once a....
It is the essential continuity of circuits Sel 8 Sources and Up/Down Sel 8 Sources, but can work and autonomously, collaborating with any suitable circuit of control. The Relay 1-8 can be 6-24v DC. For current of collector of transistors Q1-8, bigger the 10....
Op amp Ul and its associated components comprise the 67-kHz bandpass filter. A twin-T network, comprised of four 1100-12 resistors and four 0.0022- capacitors, is connected in the feedback network of the op amp. That gives some gain at 67 kHz and heavy....
The Wireless Keylogger consists of two main building blocks: the transmitter, and the receiver. The actual keylogging takes place in the transmitter, which is in fact a PS/2 hardware keylogger, with a built-in 2.4 GHz wireless module. Captured keystroke data....
This project is a miniature, VHF FM (wideband) Wireless Microphone transmitter of the type that are commonly refered to as BUG's. Note that "BUGS" are illegal but "Wide-Band Frequency Modulation Wireless Microphones" (WBFMWMs) are not, as so many people have....
The supply voltage should be about +/- 35 Volts at full load, which will let this little guy provide a maximum of 56 Watts (rated minimum output at 25 degrees C). To enable maximum power, it is important to get the lowest possible case to heatsink thermal....
This circuit has been designed to alert the vehicle driver that he/she has reached the maximum fixed speed limit (i.e. in a motorway). It eliminates the necessity of looking at the tachometer and to be distracted from driving. There is a strict relation....
This circuit simulates the sound of an American police siren. IC2 is wired as a low frequency astable that has a cycling period of about 6 seconds. The slowly varying ramp waveform on Cl is fed to pnp emitter follower Ql, and is then used to frequency....
This technique uses digital I/O pins to multiplex analog voltages into an analog input on the microcontroller. The method is most suitable for signals that do not need to be sampled frequently and it may be extended to accommodate a large number of inputs,....
The ignition substitute provides a constant power source for the ignition coil. Its frequency, 0.5-1.0 kHz, is that used by an 8-cylinder engine with an idling speed of 650 RPM, and the unit provides a rapid spark at a 17% duty cycle, while staying within....
We have developed a powerful yet inexpensive and easy to construct experiment control system. The construction of the system together with the control software is described here. All circuits and software are free to download and use for nonprofit. The....
An Intersil 7101 31/2-digit A/D converter is used to display the duty cycle of a pulse train as a percentage. The frequ..
With RFT illuminated, point R goes to 0 volt and LM runs. With LFT illuminated, point R goes to 0 volt and RM runs. With RFT and/or LFT not illuminated, points R/L go to +9 volt; P1 and P2 controls threshold point when RM/LM stop or start running. Remember....
This circuit measures the distance covered during a walk. Hardware is located in a small box slipped in pants` pocket and the display is conceived in the following manner: the leftmost display D2 (the most significant digit) shows 0 to 9 Km. and its dot is....
The electronic darkroom timer is built around a 555 oscillator/timer, a pair of general-purpose transistors, a buzzer, and an LED. The 555 (Ul) is configured as an astable multivibrator (free-running oscillator). The frequency of the oscillator is....
A single connection change permits division by any integer between 2 and 10. The RCA CD4017A Johnson decade counter is shown connected as a divide by 7 counter. The resistor is used to hold the reset line low. When the appropriate number is reached, that....
This wave shaper needs an input saw that goes from Vss to (ideally) Vdd. It works well with the 4069 VCO designed by Ren? Schmitz. Any saw will work as long as the wave is centered halfway between the rails. It works as follows: The upper set of 2 linear....
The purpose of this circuit is to power a lamp or other appliance for a given time (30 minutes in this case), and then to turn it off. It is useful when reading at bed by night, turning off the bedside lamp automatically in case the reader falls asleep... 30....
The driver in the package is connected as a Schmitt trigger oscillator (A) where R1 and R2 are used to generate hysteresis. R3 and C are the inverting feedback timing elements and R4 is the pull-down load for the first driver. Because of its current....
The mixer is the common "virtual earth" mixing amplifier, and there is nothing special about it. Note that it is inverting, which complements the tone controls (also inverting) so the absolute signal polarity is maintained. As shown, the mixer also has a....
IR detector diode D1 intercepts the IR signal at around 40 kHz and feeds it from U1, a high-gain preamp, to PLL, U2, a 4046 configured to serve as an FM detector. U3 is an audio amplifier that feeds a pair of headphones or a speaker...
Stabilised tendency of catering: Vcc=9~12V. Frequency of reception: 88~108MHz. Consumption: 100mA. If you know some language of programming as C ++, PASCAL, VISUAL BASIC, DELPHI etc you can write a program which will send in the parallel door (378 I) of PC....
The direct conversion receiver described consists of only a bandpass filter, mixer IC, VFO and audio filter. With only 22 parts, this simple circuit should take a few hours at the weekend to construct. For extra simplicity, eliminate L1 & C1 and connect C2....
This small circuit is a Linear amplifier for driving small UHF TV transmitters. Its gain is 7dB and can amplify a signal between 450-800 MHz. You can drive the circuit with 1 to 1,5 Watts signal. Better use double layer PCB with the second layer connected to....
A simple count-down LED timer that counts in minutes and seconds. Three buttons below the LED provide control of the unit, allowing you set the desired countdown time in minutes and seconds and a start/stop button. Completion of the countdown is indicated....
This simple AVR Programmer will allow you to painlessly transfer hex programs to most ATMEL AVR microcontrollers without sacrificing your budget and time. It is more reliable than most other simple AVR programmers available out there and can be built in very....
Many applications require analog signals to be sensed and digital signals to be controlled. A way to detect these p..
The bicore is the basis of advanced BEAM! Most intermediate to advanced BEAM robots are built off of the bicore. Uses go all the way from photovores to servo motor drivers to walkers to.... You get the idea. What it is is basically just an oscillator who's....
The circuit is a microphone amplifier for use with low impedance (~200 ohm) microphones. It will work with stabilized voltages between 9-30VDC. If you don`t build the impedance adapter part with T1, you get a micamp for higher impedance microphones. In this....
As dusk begins to -fall, the sensor (a cadmium-sulfide light-dependent resistor or LDR) operates a small horn to provide an audible reminder that it's time to turn on your lights. To turn the circuit off—simply turn your headlights on and the noise stops.....
This converter enables reception of 800 to 1000 MHz on any scanner covering the 400 to 500-MHz range. The converter can be set up to cover either 800 to 900 MHz or by readjustment 900 to 1000 MHz. Sensitivity is very high because of the GASFET front end. ..
When the comparator`s output changes its state from low to high, the rising edge of the output pulse, differentiated by the Cl/Rl chain, opens Ql. This blocks comparator via its strobing input and sustains its output in the state for a period of time,....
A low-frequency, op-amp oscillator and a VCO, both configured from a single MC3405 ~dual op amp and dual comparator, are tbe major components in a siren circuit tbat can be made to produce various warbles and wails, or serve as an audio sweep generator. ..
The purpose of the Kapagen is to suck the free electrons from the Earth. The Earth is a big capacitor which contains free electric charges. If it is possible to create or to find a potential imbalance between two points in the ground, it seems possible to....
The excess small forward current flow in a tunnel or Esaki diode is a manifestation of quantum mechanical tunneling...
This circuit features exit and entry delays, an instant alarm zone, an intermittent siren output and automatic reset. By adding external relays you can immobilize the vehicle and flash the lights. One of the inputs is connected to the vehicle`s existing....
If you have no idea what is a "strobo", "strobe", "stroboscopy" or whatever way it is called, it is simply a flashing light. It is usually used on police cars, 'disco' places and many interesting applications, including scientific ones. This project is....
Both parts of the circuit are biased with the constant current sources as shown, and the signal from the collector of the PNP is followed by the Darlington class A output stage whose idle current is controlled by the bias circuit. The transistors Q1 and Q2....
This circuit above uses a 13 volt zener diode, D2 which provides the voltage regulation. Aprroximately 0.7 Volts are dropped across the transistors b-e junction, leaving a higher current 12.3 Volt output supply. This circuit can supply loads of up to 500 mA.....
Here's a way to get a short range bidirectional RF (Radio Frequency) channel on a microcontroller, using the controller's tristatable I/O pins and on-chip comparator with a few passive components. The range with the firmware and simple I came up with for....
Here`s the schematic of the device depicted in the photo. Each of the ten coil-assemblies has its own copy of the above circuit. The SS41 is a Microswitch Hall Effect magnetic field sensor IC that I found in Surplus catalog for $.50 each. Any similar hall IC....
The circuit uses a 741 op amp operating as an inverting amplifier to amplify the voltage produced by an 8-ohm speaker used to detect any sounds. The feedback resistor R3, a 1-megohm potentiometer used to vary the gain of the amplifier determines the....
At the heart of this simple circuit is the well-known type KTY10 temperature sensor from Siemens. This silicon sensor is essentially a temperature-dependent resistor that is connected as one arm in a bridge circuit here. Preset PI functions to balance the....
This circuit develops an output voltage that is proportional to the magnetic induction, B, flowing through its probe"s coi..
