Meter Counter Circuits
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You can build an automatic gain control AGC for the superhet receiver with only a few additional components. The first AGC circuit is more universal. It is suitable for audio amplifiers with dual op amps like TL072, TL082, NE5532 and the broadband amp NE592.... -
This Circuit uses a CD40110BE, Up/Down Counter IC's. This IC is able to Source Each Segment with 25 mA, Giving a Very Nice Bright Display. The 7 Segment Displays MUST be a Common Cathode Type, as I have used here. All the UnMarked Resistors should be at.... -
I had designed up an oscillator with a Power Output circuit. Problem was when power was applied to the entire circuit, the output of the Oscillator gave a Momentary Spike into the output circuit. Thus Driving it full on for a split second. This Circuit.... -
The Inter-Power SWR-5 - upper right - "isn't worth a penny". Got it from a mate to use with a beacon, but I burnt it out with only 3.5-4W morse signal on 70cm. Removed the bridge and installed my own pick-up line (suggested by LA8OJ) and now it is fb for.... -
Noise level measured into 75ohm 3.1kHz BW using Siemens D2006 level meter: -80dBU (77.5mV) from zero to 1MHz and drops 3dB on 17MHz. Decrease the first coupling capacitor (68nF) to 10nF to increase the lower limit to 50kHz. The amplifier is copied from.... -
The schematic requires few components, because the timer function has been incorporated by Nutchip. For once, from the start, made up of contacts of the relay RE1 connected to terminal M2. If we turn on an appliance at the end of time, we will use the relay.... -
This project uses a four-point resistance measurement process also known as the Kelvin method. This procedure uses a current source to determine the value of an unidentified resistance. A constant current flows through the unknown resistance and the voltage.... -
This circuit controls very accurately a fan of any size. Just adjust the associated resistors for a different type like the R6 resistor of 100 ohm, 2 watt type and you're all set. The above circuit diagram is for a small 12 volt fan, the size and type.... -
Excellent clock generator to drive 4017 type cmos circuits. R1 = 10K to 10M, C1 = 100pF to 47uF. Fo is ±1Kz when R1=100K and C1=10nF. Input voltage can be from 5 to 15V... -
The Thermistor, or NTC (Negative Temperature Coefficient) of 10K, is a standard type. Most types will work. The one in the diagram is a 10K model made by Fenwal (#197-103LAG-A01). The resistance lowers as the surrounding temperature increases which affects.... -
A few months ago as I was surfing on the net, I saw an oscilloscope based on PIC18F2550 microcontroller and a KS0108 controller based graphical LCD. That was Steven Cholewiak's web site. I had never seen before so amazing microcontroller-only oscilloscope..... -
Mains frequency is pretty stable and it is unlikely that you have to measure it but if you have an emergency generator you might find this circuit useful as it will give an indication whether the generator is running too fast or too slow. Actually you can.... -
The circuit shown will switch on and off a resistive or inductive load up to 800VA with the possibility to adjust both the on and off period. Switching takes place during the zero crossing of the sine wave. The switch on point is around the zero crossing but.... -
A unified thermometric controller that can be programmed with simple scripts, integrating the "classic" thermometer/controller pair. You can build a variety of simple machines with the same hardware and a different script : a charting thermometer, a vending.... -
The circuit is powered by the receiver's pack, the current drain is low, specially if compared to drain of servos. U1a VZ2 and Q1 are the CURRENT source of the sensor VZ2 is temperature compensated, use the listed component except for Q1 there you can use.... -
Probably the best advantage is its very small size and the fact that it can run off the power supply of the circuit being tested. Although it has a low frequency range, it can still be used for most circuits. Its poor resolution will still allow for most.... -
This design uses a Motorola MPX4115 Silicon Pressure Sensor, a Dallas Semiconductor DS2438 Smart Battery Monitor (to perform 1-Wire analog to digital conversion), an operational amplifier, a voltage regulator, a diode, and several resistors and capacitors..... -
In this circuit, a simple calculator, in conjunction with a COB (chip-on-board) from an analogue quartz clock, is used to make a telephone call meter. The calculator enables conversion of STD/ISD calls to local call equivalents and always displays current.... -
This 4 1/2-digit DVM circuit is built around a Maxim ICL7129ACPL A/D converter and LCD driver. An ICL8069 CCZR 1.2-V band-gap reference diode is used for a voltage reference. S2a-b-c select one of four ranges up to 200 V (maximum). The meter also has a.... -
A simple test circuit to fault find audio and radio equipment. Can be used to inject a square wave signal, rich in harmonics, or used with headphones as an audio tracer. A single pole double throw sitch is used to switch between inject and trace modes. The.... -
This is a simple circuit which I built to one of my audio amplifier projects to control the speaker output relay. The purpose of this circuit is to control the relay which turns on the speaker output relay in the audio amplifier. The idea of the circuit is.... -
Sometimes when experimenting with different soundcards and MIDI interfaces it is useful to see if there is some data going in MIDI interface. This can be easily tested with this adapter, which converts the midi signals to visible light pulses. Just the.... -
Here is a circuit that implements phase-control of heaters, adjusting their power smoothly from zero to around 95% of the rated power, keeping the room temperature to within 1 or 2 degrees, while using few components. Notice that this is entirely an AC.... -
The design presented here works by applying a 50kHz, 200mV square wave to the capacitor under test, in series with a 10 Ohm resistor. The AC voltage appearing across that resistor is measured and displayed on a meter. So the whole thing is nothing else than.... -
The general (and very basic) principle of operation is shown in Figure 1. The test signal is simply derived from the mains, and is a sinewave at 50 or 60Hz. In most locations, the sinewave will be distorted, but this barely matters. With nothing connected to.... -
Testing loudspeakers is covered in some detail in the passive crossover article (see Design of Passive Crossovers), but it is irksome at best to have to fiddle about with clip leads and components lying all over the workbench. This simple project is.... -
This probe is useful for any low level RF work, and simply connects to your multimeter. The voltage shown will not be accurate, since this is a rectifier probe, but the measurements are good enough for you to be able to determine where the RF stops, or if a.... -
The design objective was to produce an hFE tester with switched collector currents for the DUT (Device Under Test) covering a range suitable for the selection and matching of output transistors for amplifiers such as the JLH Class-A, ESP DoZ etc. The tester.... -
This circuit uses a germanium diode (marked Ge) as a temperature sensor. I used an OA90 diode but others should do. The 'ring' of Tr1 and Tr2 bias each other. Tr1's collector current is stabilized by the 5v6 zener, causing Tr2 to operate at about 5mA: this.... -
The circuit was designed to work with an audio power amplifier which operated off +18v-0v-18v power rails. The actual voltage used is not too critical except that the feedback is referred to the LED chain which itself is anchored to a +12v rail, hence the.... -
For a transistor to conduct, it requires a voltage of about 0.6 between its base and emitter. This voltage is applied from the wiper of the 47K pot. Now if the pot is at minimum, this voltage is across the 22K, so the 47K will have about 1.28v across it - or.... -
This circuit as first published in Wireless World September 1975 and subsequently in MECRM. It's built around a TTL quad NOR gate, though CMOS could be used...
New Circuits
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This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of.... -
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is.... -
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to.... -
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This.... -
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the.... -
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,.... -
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the.... -
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power.... -
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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