make this simple delay on timer circuit


Posted on Feb 5, 2014

The post explains a simple delay ON circuit which allows the connected load at the output to be switched ON with some predetermined delay after power switch ON. The explained circuit can be used for all applications which calls for an initial delay ON feature for the connected load after the mains power is switched ON. The shown diagram is pretty


make this simple delay on timer circuit
Click here to download the full size of the above Circuit.

straightforward yet provides the necessary actions very impressively, moreover the delay period is variable making the set up extremely useful for the proposed applications. Assuming the load which requires the delay ON action being connected across the relay contacts, when power is switched ON, the 12V DC passes via R2 but is unable to reach the base of T1 because initially, C2 acts as a short across ground. Once C2 charges up to a level which develops a potential of 0. 3 to 0. 6V (+zener voltage) at the base of T1, T1 is instantly switched ON, toggling T2, and the relaysubsequently. finally the load gets switched ON too. I have a 1KVA automatic voltage stabilizer. It has one defect that when it is switched on, very high voltage is outputted for about 1. 5s (therefore cfls and bulb got fused frequently) after that the voltage becomes OK. I have opened the stabilizer it consist of an auto-transformer, 4 24V relay each relay connected to aseparatecircuit(each consisting of 10K preset, BC547, zener diode, BDX53BFP npn darlington pair transistor IC, 220uF/63v capacitor, 100uF/40V capacitor, 4 diodes and some resistors). These circuits are powered by a step down transformer and output of these circuit are taken across corresponding 100uF/40V capacitor and fed to corresponding relay. What to do in order to tackle the problem. please help me. Hand drawn circuit diagram is attached. The problem in the above circuit might be due...




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