Holding 12VDC relay closed for 1 second

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Powhyfo

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I have a 12VDC **broken link removed** that I need to stay closed for about 1 second after power is removed.
Can I add a capacitor and diode in parallel to the feed to accomplish this?
Any recommendations of capacitor size?
I am sorry I do not have specs on the relay, I have looked & looked and have found nothing more than what is available at the link above.

Thanks.
 
A quick Google shows that this type relay requires about 150mA at 12VDC...so the coil resistance is 12v/0.150A=80Ω. Assuming the contacts open at about 8V...about one time constant...it would require a 12,000µF/25VDC cap across the coil. And a diode between the +12V supply and the top of the parallel coil/capacitor.

You might also want to add a low value resistor (1-10Ω) in series with the diode to limit inrush current to the capacitor.

Haven't tried it, but it should be within that range.

Ken
 
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One other consideration: So you do not weld the contacts on whatever switches it ON/OFF, you need a current limiter in the path to the capacitor.
 

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Powhyfo said:
I see. Is R1 4.7 ohms?
Click to expand...

Yes. It limits the peak current required to charge the capacitor to 2.5A. Without it, the peak current would be tens of A, and could weld the switch contacts.
 
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