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power up delay timer with LM555

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fjpompeo

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power on delay timer

Hi,

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.

Regards,

Fernando
 

power up delay

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**
 

lm555 on delay timer

hi

try out this circuit with simualtion in proteus
 

lm555 power on delay

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?

rhonn
 

lm555

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 ??
 

power up delay circuit

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
 

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