Simple electronic timer

Until now, some people use an hourglass to count small periods of time. Watching the movement of sand grains in such watches is very exciting, but using them as a timer is not always convenient. Therefore, they are replaced by an electronic timer, the scheme of which is presented below.

Timer Scheme

Simple Electronic Timer
It is based on the widespread inexpensive NE555 chip. The operation algorithm is as follows: if the S1 button is pressed briefly, a voltage equal to the power supply voltage of the circuit appears at the OUT output and the LED LED1 lights up. After a predetermined period of time has elapsed, the LED goes out, the output voltage becomes zero. The timer is set by the trimming resistor R1 and can vary from zero to 3-4 minutes. If there is a need to increase the maximum time delay of the timer, then you can raise the capacitance of the capacitor C1 to 100 microfarads, then it will be approximately 10 minutes.As the transistor T1, any bipolar transistor of medium or low power of the n-p-n structure, for example, BC547, KT315, BD139, can be used. As an S1 button, any button for closing without locking is used. The circuit is powered by a voltage of 9–12 volts, the current consumption without load does not exceed 10 mA.
Simple electronic timer

Making a timer

The scheme is assembled on a 35x65 PCB, a file for Sprint Layout is attached to the article. A trimmer resistor can be installed directly on the board, or it can be brought out on wires and a potentiometer can be used to adjust the running time. To connect the power wires and the load on the board provides space for screw terminal blocks. The board is executed using the LUT method, several process photos:
Simple electronic timer
Simple electronic timer
Simple electronic timer
Download fee: After all the parts are soldered, it is imperative to clean the board from the flux; ring the adjacent tracks to ring.The assembled timer in the configuration does not need, it remains only to set the desired time of work and press the button. The relay can be connected to the OUT output, in this case the timer can control a powerful load. When installing the relay parallel to its winding, a diode should be placed to protect the transistor. The scope of such a timer is very wide and is limited only by the user's imagination. Successful assembly!


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