voltage operated relay

Thread Starter

turbo1600

Joined Jan 12, 2016
7
hi, after a schematic that will turn on a relay at about 13.2 vdc and stay on , until voltage drops to about 12.8 then turn of .,

anyone help ?
mark k
 

MaxHeadRoom

Joined Jul 18, 2013
19,677
For the average magnetic relay you would need to set up a comparitor circuit as the hysteresis of the average relay is way more than that.
Max.
 

#12

Joined Nov 30, 2010
18,167
For the average magnetic relay you would need to set up a comparitor circuit as the hysteresis of the average relay is way more than that.
Max.
True. The last time I looked, an automotive relay was guaranteed to pull in at 80% of the label voltage and persist below 50%.
 

crutschow

Joined Mar 14, 2008
24,055
You could use two LM339 or LM393 comparators in a window comparator configuration to control a transistor driver that energizes the relay.
 
Last edited:

crutschow

Joined Mar 14, 2008
24,055
I like your circuit Mike.
It's a simple voltage comparator and has a stable-trip point basically independent of the supply voltage.
I think it meets Albert E's criteria. :)
 
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