How do I make a relay turn off at 11 volts?

[GRM]

From my understanding, the trigger for a relay turns on at around 9.6 volts. I want to change that to 11 volts. From the best of my understanding, I need to add a resistor in line so that when the voltage hits 11 volts, the relay reads 9.6 volts.

My understanding of electrical components is decent, but my ability to calculate it all out, and know what parts to buy isn't the best.

Does anyone know what I'm talking about, or how to do it?

Thanks

[Fast Eddy]

You need to know how much current the relay is pulling. I=current. Then you want to drop V=1.4 volts. V=I*R and R=V/I. I'd guess it's probably around .25 amps, so you'd need about 6 ohms. The resistor needs to be rated for the power too. This is P=IV or about 3 watts.

Test, measure and adjust. You could get a rated potentiometer and just dial it down until you hear the relay click. I've got a variable power supply if you want to meet up over beers. My multimeter is currently on 'missing' status though.

[FJ40_owner]

??????????????????????????? I have never heard of ab 9.6 volt relay, nor have I heard of an 11 volt one. Relays come in fairly standard voltages, just like DC appliances and batteries.

There are discrete solid state components that can be trimmed by a bias voltage to enable a custom setpoint for say a 12 VDC relay to drop out at say 9.6 VDC.

You need to restate or describe in greater detail what components you have and their ratings.

Putting resistors in series mearly makes heat.

Tell us what you want to do.

JB

[GRM]

Originally Posted by Fast Eddy

You need to know how much current the relay is pulling. I=current. Then you want to drop V=1.4 volts. V=I*R and R=V/I. I'd guess it's probably around .25 amps, so you'd need about 6 ohms. The resistor needs to be rated for the power too. This is P=IV or about 3 watts.

Test, measure and adjust. You could get a rated potentiometer and just dial it down until you hear the relay click. I've got a variable power supply if you want to meet up over beers. My multimeter is currently on 'missing' status though.

I'll take you up on that! Biggest issue for me is trying to find a proper 11 volt system. Although, It may have to be after the new years, as I have too many projects on my plate to spend a day doing something like this.

What I am trying to do is to make my ARB Fridge kick off when the voltage in the battery hits 10.5 or 11 volts. This way I don't drain my 2nd battery to 1 volt, thus killing an odyssey battery.

Engel makes one of these controllers, Engel makes a controller like I describe, although I was told how to make one for $10 that was very effective.

[Fast Eddy]

He's saying the relay he has kicks off around 9.6v, but he'd like it to kick off earlier. A resistor in series should make it kick off earlier.

Garrett: This job should take an hour, not a day.

[GRM]

Ok then... since I have no idea what this rant is about, I'm going to go back into the tech of this...

A friend of mine talked with an engineer buddy of his, and said I need a Zener Diode. Something about calibrating it to cut off at 11v. Do you have any idea what he is talking about Eddy? Im reading about them on Wikipedia and am a bit lost.

[dfmorse]

Here are a couple of sources that may help:

Bowden's Hobby Circuits

Relay Circuits, Page #-N


...

[beaufort-fj60]

Originally Posted by Fast Eddy

You need to know how much current the relay is pulling. I=current. Then you want to drop V=1.4 volts. V=I*R and R=V/I. I'd guess it's probably around .25 amps, so you'd need about 6 ohms. The resistor needs to be rated for the power too. This is P=IV or about 3 watts.

Test, measure and adjust. You could get a rated potentiometer and just dial it down until you hear the relay click. I've got a variable power supply if you want to meet up over beers. My multimeter is currently on 'missing' status though.

Originally Posted by GRM

Ok then... since I have no idea what this rant is about, I'm going to go back into the tech of this...

A friend of mine talked with an engineer buddy of his, and said I need a Zener Diode. Something about calibrating it to cut off at 11v. Do you have any idea what he is talking about Eddy? Im reading about them on Wikipedia and am a bit lost.

Originally Posted by dfmorse

Here are a couple of sources that may help:

Bowden's Hobby Circuits

Relay Circuits, Page #-N


...

pick up a breadboard at radioshack and test a few setups...

[cruiser88]

Fast eddy has it......but you want normally open or closed?....edit I went back and read ..nevermind

[Fast Eddy]

Originally Posted by GRM

A friend of mine talked with an engineer buddy of his, and said I need a Zener Diode. Something about calibrating it to cut off at 11v. Do you have any idea what he is talking about Eddy? Im reading about them on Wikipedia and am a bit lost.

I see there are 11v zener diodes available, and from the little I understood from wikipedia the circuit should be simple. I couldn't just draw you up a circuit however.

I'm a software guy. My solution would involve a cpu and some programming.

[FJ40_owner]

We are talking about voltage not current. Using resistors will only make heat. You need a voltage sensing circuit that will "turn on" at the setpoint of 11 volts or whatever value is desired and open a set of contacts controlling your whatever.

Go to one of the web sites listed on this thread and search for low voltage alarm.

Plus if you lower your current to low you will be unable to pull in the relay.

I had something drawn up but used it to light my fire this AM.

[beaufort-fj60]

i would just buy one of these....

Engel Australia - Portable Fridge Freezers <---link


no way you could build one this nice for $10... maybe $50 and it would look cobbled.

[Fast Eddy]

Originally Posted by beaufort-fj60

i would just buy one of these....

Engel Australia - Portable Fridge Freezers <---link


no way you could build one this nice for $10... maybe $50 and it would look cobbled.

Huh? $10? Recommended Retail Price: $98.00

[beaufort-fj60]

Originally Posted by Fast Eddy

Huh? $10? Recommended Retail Price: $98.00

yup.. retail is $98, that's cheap. good luck making one that works and looks like that for $10.


actually, I'll double dog dare you to try to make one for $100.

[Fast Eddy]

Originally Posted by beaufort-fj60

yup.. retail is $98, that's cheap. good luck making one that works and looks like that for $10.

actually, I'll double dog dare you to try to make one for $100.

Pic processor, a few resistors and caps, a FET and a display; about $20 at Halted. The plastic to make it look nice is the hard part. Oh, and the 10s of hours of programming and debugging.

$100 is a deal. [sigh]

[Fast Eddy]

Originally Posted by GRM

Ok then... since I have no idea what this rant is about, I'm going to go back into the tech of this...

A friend of mine talked with an engineer buddy of his, and said I need a Zener Diode. Something about calibrating it to cut off at 11v. Do you have any idea what he is talking about Eddy? Im reading about them on Wikipedia and am a bit lost.

I saw zener diodes in 11v are available, but I don't know enough to draw up the circuit that you need.

[Fast Eddy]

Originally Posted by GRM

A friend of mine talked with an engineer buddy of his, and said I need a Zener Diode. Something about calibrating it to cut off at 11v. Do you have any idea what he is talking about Eddy? Im reading about them on Wikipedia and am a bit lost.

I saw zener diodes in 11v are available, but I don't know enough to draw up the circuit that you need.

Anyone?

[Fast Eddy]

I've got to agree with the pirate responses about a simple circuit resonating. We'll figure out something that works. I'm guessing you're not attached to the relay if we don't need it, right?

[GRM]

Originally Posted by Fast Eddy

I've got to agree with the pirate responses about a simple circuit resonating. We'll figure out something that works. I'm guessing you're not attached to the relay if we don't need it, right?

No, I'm not attached to the relay. It just seemed too simple. Guess not. Should be fun throwing something together tomorrow to see how it works.

[beaufort-fj60]

any luck

[Fast Eddy]

Originally Posted by beaufort-fj60

any luck

The relay he has cuts out at 4.4v and turns on around 5.8v. The beer was good.

I don't have any easy way to draw the circuit, but we need two resistors (2k, 3k) to make a voltage divider, one of these brown-out reset chips, or something like it:

4.5 Volt brownout reset chip

and a transistor strong enough to drive 250ma to hold the relay on.

Or there's this, for $25: http://www.safetycentral.com/batprot.html

[beaufort-fj60]

Originally Posted by Fast Eddy

The relay he has cuts out at 4.4v and turns on around 5.8v. The beer was good.

I don't have any easy way to draw the circuit, but we need two resistors to make a voltage divider, one of these brown-out reset chips, or something like it:

Catalog

and a transistor strong enough to drive .250ma to hold the relay on.

Or there's this, for $25: http://www.safetycentral.com/batprot.html

the zener diode is kinda like a brown out reset chip.


lol.. yeah 25 bucks, that's the deal. How long did it take to find that. Nice find by the way.