This "On delay timer circuit" look correct?

Thread Starter


Joined Feb 1, 2019
I need a circuit to delay the on time of a relay. Needs to be adjustable by 0.1 seconds...

The website I found the rest of the project I'm working on, gave a circuit to do this but I just want to verify with you guys that it correct etc... (image below)

The one thing I'm unsure about is that it shows using a 4 diode bridge rectifier in order to get the necessary DC voltage for the timer circuit to control the 12v relay coil...

Does the circuit seem correct to you? Also it says to adjust R1 in order to adjust the "On delay"

New Project (3).jpg
Last edited:


Joined Dec 31, 2017
The bridge rectifier is OK and is normally done this way. For a 12 volt DC output would require a 9 volt AC rms input.
Yes, adjusting R1 will provide the delayed ON time. How much delay and how well it works maybe problematic.