This is not a sophisticated automatic keyer but it is lot QRP to build and to have fun operating it. When the paddle is connected to the DOT terminal, C1 starts to charge. When C1's charge reaches sufficiently high value, it causes the transistor BC157B....

I had a Basic Stamp project that needed to measure a nominal 12 volt battery, and I wanted a simple solution. This is the simplest I could come up with. The 555 timer will put out positive pulses. The pulse width is inversely proportional to the difference....

Sawtooth wave generators using opamp are very common. But the disadvantage is that it requires a bipolar power supply. A sawtooth wave generator can be built using a simple 555 timer IC and a transistor as shown in the circuit diagram. The working of the....

This circuit is the electronic emulation of the I Ching, a form of divination originating in China. In the classical form, the response is obtained by the manipulation of 50 sticks or, more practically, by tossing 3 coins. The process must be repeated 6....

The National Physics Laboratory broadcasts a time signal, previously known as the Rugby clock but now called "Time from NPL." Its most commonly known as the MSF signal due to it originally being identified in Morse code those letters. It is broadcast from....

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....

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....

This simple circuit is a good solution to the powering a dual supply op amp from a single battery problem. The circuit simply takes a positive voltage and inverts it. It uses only one 555 timer and a few other passive components, so it doesn`t add much in....

Using modulated rectangular waves of different time periods, The circuit presented here produces ringing tones similar to those produced by a telephone. The circuit requires four astable multivibrators for its working. Therefore two 556 ICs are used here.....

The choice of material to read or drive is the definition of three digits (Bit), RA0, 1,2 PORTA of the PIC at the entrance of 74HC138A. To select a material for reading or driving an output of 78HC138 is '0 '(Low), forcing the transistor (2SA1015) to conduct....

IR appliances use pulses (control signals) sent over a modulated IR carrier wave. The carrier wave may be modulated at various frequencies, 36-38KHz being the most popular.Some Satellite receivers use even higher frequencies than this. The IR1 remote module....

This circuit takes standard 0-10V control voltage (for example from analogue light controlling desk) and outputs a standard 1-2 ms RC servo motors control pulse. Power supply: 4-5V DC (same as for RC servo), consumes 15 mA of current. Control voltage range:....

Using a single 555 Timer IC and a small transformer to generate a high voltage, this circuit will test zener diodes of voltage ratings up to 50VDC. The 555 timer is used in the astable mode, the output at pin3 drives a small audio transformer such as the....

Here's a circuit to create a buzzcoil using a standard automotive ignition coil. A 556 dual timer is used to establish the frequency and duty cycle of the coil current. One of the timers is used as an oscillator to generate the 200 Hz rectangular waveform....

This circuit detects metal and also magnets. When a magnet is brought close to the 10mH choke, the output frequency changes. ..

A small circuit that can find a lot applications of measurement time. She has the possibility us inform with sound signal from the BZ1. At the same time, exist the possibility drive a external circuit via the optocoupler IC2, after we connect the applicable....

This is a very simple circuit utilising a 555 timer IC to generate square wave of frequency that can be adjusted by a potentiometer. With values given the frequency can be adjusted from a few Hz to several Khz. To get very low frequencies replace the....

This is an image Schematic. No Description available...

This simple circuit has helped me out on many occasions. It is able to check transistors, in the circuit, down to 40 ohms across the collector-base or base-emitter junctions. It can also check the output power transistors on amplifier circuits. Circuit....

A continuously working wiper in a car may prove to be a nuisance, especially when it is not raining heavily. By using the circuit described here one can vary sweeping rate of the wiper from once a second to once in ten seconds. The circuit comprises two....

The charger consists of two stages: The first is a capacitive voltage doubler, which uses a 555 timer IC driving a pair of transistors connected as emitter followers, which in turn drive the voltage doubler proper. The doubler has power resistors built in,....

This circuit can be used to construct an attractive Christmas Star. When we switch on this circuit, the brightness of lamp L1 gradually increases. When it reaches the maximum brightness level, the brightness starts decreasing gradually. And when it reaches....

Moreover, the method does not entail programming and the concomitant, almost inevitable, debugging. A CD4016 CMOS analog switch, IC1, forms the heart of the system. Depressing the key labeled "1st" closes the topmost switch (between pins 1 and 2), which....

A wide rage auto turn OFF timer covering 1 minute to 20 hours in three ranges with S1. As soon as power is applied to the circuit the IC1 [555] starts to oscillate happily and feeds clock pulses to the IC2 [4017]. The IC2 [4017] and IC3 [4020] give a....

The resulting timer circuit is made from a CD4060, includes an oscillator and a 14 stage binary counter, two CD4040's, which are 12 stage binary counters, a CD4012 Dual Nand gate and a CD4013 Dual D Latch. The CD4060 is connected to a 32768 Hz ECS 3X8....

The circuit uses independent timers to flash two light emitting diodes. Any time that light emitting diode D1 is lit__light emitting diode D2 will be switched off. Light emitting diode D3 is on if both D1 and D2 are off. Two versions of the circuit are....

The circuit in Figure 1 is an RS-232/485 converter that uses the transmitted signal itself to control the flow. The circuit uses MAX232 and MAX483 interface circuits, IC1 and IC2 from Maxim Integrated Products (http://www.maxim-ic.com) to convert between the....

Light emitting diodes are advan- tageous due to their smaller size, low current consumption and catchy colours they emit. Here is a running message display circuit wherein the letters formed by LED arrangement light up progressively. Once all the letters of....

A time delay relay is a relay that stays on for a certain amount of time once activated. This time delay relay is made up of a simple adjustable timer circuit which controls the actual relay. The time is adjustable from 0 to about 20 seconds with the parts....

A very regular configuration of the 555 astable timer to work as a timer to trigger an alarm or any other equipment connected to pin 3. R resistor should be replaced with a potentiometer that will change the time delay. Capacitor C should be calculated too....

The interest for circuits of tubes, remains big. Thus I will give completed in enough big degree, circuit of preamplifier. It is mainly constituted by the department of main preamplifier, the department of input selector, delay of application voltage and....

This is a very basic power failure lighting circuit based around a relay. This simple circuit has many uses, from lighting up rooms and walkways in the case of a power failure, to monitoring and security uses. There are many different power failure circuits....