Help - need to a circuit to trigger relay - Electronic Circuits Projects Diagrams Free

5neaker · 23rd November 2003, 06:24 PM

Hi

can someone help me. I need a circuit that will trigger an output to a relay when it get a predefined input voltage

input voltage - 3.19 volt, will be using ground to measure this input voltage

Any help would be greatly appriciated

Ray

nettron1000 · 23rd November 2003, 07:15 PM

Sounds like a good application for a comparator circuit. Heres a link to some info and schematics.

http://home.cogeco.ca/~rpaisley4/Comparators.html

Russlk · 23rd November 2003, 10:24 PM

Note the diode across the relay solonoid coil, that is needed to protect the IC output from the inductive kick when the relay is turned off.

Agent 009 · 24th November 2003, 11:43 AM

You could just implements a diode limiter circuit... I can\t draw you a schematics right now, but as soon as I get my hand on my PC, I'll post it. By the way, how does your input looks like? Is it a 3.19V DC?

Dialtone · 26th November 2003, 05:18 PM

Do a google search for datasheet on ULN2803. The ULN28xx family is an octal darlington pair driver well suited for driectly driving relay coils over a broad voltage range and fairly hefty power outputs from a DIP package. No need to build from discrete components when a perfectly good IC package exists than can do 8 for the price of 1.
Dialtone

pike · 27th November 2003, 07:06 AM

I would go and use something like a zener diode in series with a voltage dropping resistor to trigger a transistor, which then triggers the relay

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23rd November 2003, 06:24 PM	(permalink)
5neaker	Help - need to a circuit to trigger relay Hi can someone help me. I need a circuit that will trigger an output to a relay when it get a predefined input voltage input voltage - 3.19 volt, will be using ground to measure this input voltage Any help would be greatly appriciated Ray

23rd November 2003, 07:15 PM	(permalink)
nettron1000	Sounds like a good application for a comparator circuit. Heres a link to some info and schematics. http://home.cogeco.ca/~rpaisley4/Comparators.html __________________ Two roads diverged into a woods...i took the one less travelled by. R. Frost.

23rd November 2003, 10:24 PM	(permalink)
Russlk	Note the diode across the relay solonoid coil, that is needed to protect the IC output from the inductive kick when the relay is turned off. __________________ see my website: www.geocities.com/russlk

24th November 2003, 11:43 AM	(permalink)
Agent 009	You could just implements a diode limiter circuit... I can\t draw you a schematics right now, but as soon as I get my hand on my PC, I'll post it. By the way, how does your input looks like? Is it a 3.19V DC?

26th November 2003, 05:18 PM	(permalink)
Dialtone	Do a google search for datasheet on ULN2803. The ULN28xx family is an octal darlington pair driver well suited for driectly driving relay coils over a broad voltage range and fairly hefty power outputs from a DIP package. No need to build from discrete components when a perfectly good IC package exists than can do 8 for the price of 1. Dialtone

27th November 2003, 07:06 AM	(permalink)
pike	I would go and use something like a zener diode in series with a voltage dropping resistor to trigger a transistor, which then triggers the relay __________________ www.winpicprog.co.uk - Great PIC language tutorials.