12v UPS relays Trigger, 1 ~ 11v no trigger - diyAudio
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Old 25th August 2007, 07:33 AM   #1
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Post 12v UPS relays Trigger, 1 ~ 11v no trigger


Iím busy with some UPS circuit and I need it to switch a couple of relays on then the power is back.


Click the image to open in full size.

Can I replace the triac with a transistor because I donít want to let the relays on until the power is down,

I basically want a easy method to trigger a couple of relays then the mains is back, currently Iím using a 10volt transformer on a 12v relay and if the mains drop the relay drop very fast, but the transformer is to small for 3 relays and then using 3 relays I hear a buzz sounds because it probably under power, in my circuit I have a regulated power supply and a small crap 10 Ė 11volt power supply just to do the relay work and the regulated power supply with huge caps is for the timer section and some other components

Purpose needed for:

1 ~ 11 volt - no trigger
12 volt - trigger

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Old 26th August 2007, 05:38 PM   #2
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Join Date: Oct 2005
That circuit looks like a very complex diode, not what you need. What you neeed is a comparator, when the line is 1~11V the comparator does nothing, but when it hits 12V its output flips and enables or disables another circuit.

Click the image to open in full size.

Here's a site with lots of comparator circuits: http://home.cogeco.ca/~rpaisley4/Comparators.html
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Old 26th August 2007, 09:35 PM   #3
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Join Date: Dec 2001
Location: SIUE, Illinois, USA
use 120/240V relays off the line. the line will directly turn them on if its up.
if only it could be used for good, not evil...
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Old 27th August 2007, 09:07 AM   #4
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Well, I donít have any 250volt relays around me but itís a good idea though, I only have 6v and 12v relays

Iíve found something on the net


Click the image to open in full size.

In one of my circuits I use a gate, to make a yes a no; itís in my timer function in my UPS

I have a couple of ICís available that can be used for these purposes:



Click the image to open in full size.

Youíre Example:

Click the image to open in full size.
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Old 27th August 2007, 09:11 PM   #5
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Location: Lakewood, Ohio
Get a small 250 Volt to 12 Volt transformer to operate the relays that you have.
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Old 28th August 2007, 05:30 PM   #6
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Ok what do you think of my design?

The above is the mains input and then a power failure or voltage error happens it switches off the supply to the main UPS part

How its works:

High voltage have a higher value resister, and if that led starts to glow then the voltage is wrong

Low voltage have a lower value resister and if that led goes out then the voltage is also wrong

Normal state is just a medium value resister that will work fine with most voltage variables and with a zener connected to cut over voltages

And that last section before its connects to the relay drivers, thatís 2 transistors, it needs to yes signals before the relays closes
No.1 will always be yes and the no.2 will also be yes, but if a voltage error happens then that gate before it will powered and then it will switch of the no.2 transistor

Normal state is only there to speed up the process incase of the caps powering the bases of certain transistors that might happens
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