Delay automatic on timer circuit testing and power up.

Timer circuit testing

Here is youtube video English version on this subject:

Here is youtube video Hindi/ Urdu version on this subject:

The timer circuit which we discussed before in the last post which is here can be tested using power supply and some arrangement.

Here in the following lines I will discuss how to test the circuit. This delay automatic on circuit can switch on the power with delay of  a few seconds to a few minutes. The delay time can be adjusted using a potentiometer or changing the timing capacitor if a big duration of the time is required. This circuit is especially made for creating on delay for refrigerators, freezers and air conditioners. As these units are sensitive for ON and OFF. The refrigeration and air conditioner machine should not be switched on immediately after switch off. Instead there must be a delay of a minute to a few minutes say three minutes in most cases between off and on. Otherwise the compressor may damage or get serious defect if switched on immediately after switched off.

This delay automatic  on circuit is design in the way to automatically give a delay of specified time of a minute or a few minutes which is preset on every switch on. If this unit is installed with refrigerator or air conditioner machine, it will protect it from immediate switch on after every switch off due to power failure or any reason.

As power failures are very common now a days in our country hence problems to refrigeration system or to air conditioners are also very common due to such power cuts. The remedy is not very difficult or complex but us of such a timer! So in the next posts I will show how to connect it to a refrigerator or to an air conditioner to solve such problem and prolong the compressor life for such machines.

Here are a few images in which I will show how to power up and test such a circuit on a work bench to ensure and understand the function of such a timer.


Grab the circuit and locate the power supply connections for the circuit. Also look for the output or control of the circuit to understand the function of the circuit.

Take to appropriate length of hock up wire pieces and solder them on the power supply terminals to power up the circuit with required voltage which is 9 to 12V in our case.

Set up the meter to DC voltage and set the meter probes to V and Common terminals to measure the power supply DC voltage.

Measure the DC output voltage of the power supply or supply adapter to ensure the right voltage supply to the circuit which is 9.67V in our case.

Power up the circuit and look at the function of the circuit. We noticed that first the Green LED came then in a second or two the Red LED also switch on with a relay click. This ensured the timer function with time adjusted to very little delay of a second or two.

Change the multimeter to continuity and ensure the relay switching terminals continuity after powering up. You will see that the relay is changing the contact state after the timer completes the delay.

Adjust the time delay to the required delay time using a screw driver and adjust the potentio meter with the help of that screw driver. We set the time for above a minute to see the function of the timer.

If you require even more time delay from the circuit which could not be obtained even with the help of the potentio meter, you can replace the timing capacitor 330Uf in our case to some higher value say 470Uf or 1000Uf for larger delay time.

Hope this guide may give you understanding about the circuit operation as well as the circuit live understanding. If you didn't watched the video associated with this blog post, watch it now to get more understanding.

In the next blog post and video I will show how to install this circuit in practical way and how to get benefit from it with your refrigeration or air conditioning system to protect them from damage using such a timer. All you should do is stay tuned, subscribe on my channel and share my videos and blogs with your friends.