I need a timer that after applied 127VAC/60Hz it counts let's say 20 seconds and then turn on a relay and stays on, using a transformerless power supply and a LM555 timer.
Try circuit as per attached drawing.
There are additional 2 associated circuits based on transistors: one triggs 555, second disables the RLY for a short period of time after power is applied ..
To estimate R and C values you can goto:
**broken link removed**
Hi,
I'm planning to use this circuit as power-on delay protector for appliances like freezer,aircon, refrigerators..etc..
My problem is that there are instances there is a very sudden power interruption in millisecond then it resumes again, will this circuit be able to recover that fast without turning on the load?
Hi ! I want to build a timer with an auxiliary input. When the input is hi, the output of 555 to be hi. When input goes low the output of 555 to remaint hi for a few seconds(20-30sec). Vcc and input: 12-14V. Is anyone who knows how to make it ??
Hi,
Is such short interruptions important for compressors, I mean will not the basic inertia of the system even out such fluctuations? Further, if you make your control system sensitive to short power breaks, your fridge/ airconditioner will keep switching ON/OFF whenever a welding machine is put on in the neighbourhood.
Any how, if you need this feature, you can derive a trigger pulse from an AC voltage sense circuit and use it to trigger 555.
Regards, Laktronics