Hi , i need to make a relay timer hold circuit to drive a relay when a input voltage is present but when the input is removed the pic chip will hold the relay on for approx 90 seconds. The 90 second timer part also needs to be reset as soon as the input (trigger signal) is present if this is before the 90 seconds has passed. This project is to detect when a car air conditioning compressor is on and then start the condenser cooling fan but when the compressor cuts out , the cooling fan needs to run for a extra 90 seconds etc to ensure the condenser is cooled . If the compressor cuts in be for 90 seconds the relay must switch the fan on again and 90sec timer reset ready to restart as soon as compressor is switched off. I hope that explains what i need the circuit to do and the cooling fan has its own relay so the second relay which will be driven by this circuit will only switch a max of approx 0.5amps. I was going to use a 555 timer but due to extra capacitors and heat from engine bay i was thinking the timing would vari alot from heat variations etc. I would have liked to use a small pic like a 12c508/9a etc and the circuit will require a input pin to detect 0v/12v and start up with power on in the relay off state unless the 12v input is present. The main part i need help with is a program for a pic which will do the function listed above and i will work the rest out as if i can. I have worked with electronics for many years and can program pics from a asm file after compiling the file to hex. Thanks for all your help in advance.