Basic Relay circuit keeps re-latching when timer resets

Thread Starter

kierend

Joined Jun 4, 2019
4
hi everyone

I have made a little timer circuit for a toy project.

Its just a a 12 volt timer, 12 volt relay and 12 volt sound board.

problem i am having is when the timer runs out the relay chatters and comes back on.

I am thinking i need to add more load to the relay coil to the de-latch is stronger?

its all 12 volt DC and i dont have much experience with this stuff, mainly do computer electronics

i have a video, when i connect the trigger, after a 2 second timer you can here the relay clicking

any advice would be great (there is a kid waiting for this toy to be made!)


 

ericgibbs

Joined Jan 29, 2010
8,733
hi kierend,
Welcome to AAC.
Do you have circuit diagram of the project you could post.?
E
 

Thread Starter

kierend

Joined Jun 4, 2019
4
not really I just sort of made it up on the spot.

its quite simple, the timer closes a volt free contact, which powers the relay coil, on the relay it starts the music and also the motor to run the machine

the time i have used is a SC relay switch
 

ericgibbs

Joined Jan 29, 2010
8,733
hi,
A common cause of relay 'chatter' is when the relay coil is switched the supply voltage to the rest of the circuit rises or falls by a small amount, the circuit responds to that change and switches the relay over, this chatter can be continuous.
Without a diagram it is difficult to suggest a modification that will stop the chatter.
E
 

Dodgydave

Joined Jun 22, 2012
8,389
Could be that you dont have a Back Emf diode and it's retriggering the timer, or the psu is not giving out enough current... Can you draw the circuit how its wired?
 

Thread Starter

kierend

Joined Jun 4, 2019
4
its ok i figured it out, i added some 12 volt LED lights to the coil +/- and the timer works correctly now, looks like it need more load to de-latch.
 

Thread Starter

kierend

Joined Jun 4, 2019
4
but a diode is a good idea, if i need to get rid of the lights i will add one
 

ebeowulf17

Joined Aug 12, 2014
2,942
As i said in post#5,,, Back Emf Diode...
Yeah, I was wondering if the LEDs might be solving the problem by being accidental back EMF diodes.

IIRC, most LEDs have very low reverse breakdown voltages, so I'm wondering if they might be conducting in the reverse direction every time the relay opens. Of course, if that's the case, the LEDs won't last very long and the current solution will be only temporary.

On the other hand, maybe the resistors inline with each LED would prevent them from providing significant back EMF relief and that's not what's going on. I'm not sure what the practical limits are on such things - just speculating and brainstorming a bit.
 
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