24v relay

[TurboTim]

Does anyone know where to get a relay that will switch 24v. I tried an standard bosch relay and tried to run the coil side of the relay and it smoked the wires like there wasnt even a relay in the circuit.

 

[rosco]

Sounds like the Relay was only rated to be actuated with 12V. As far as the switch part of the relay, as long as you don't exceed the current capacity of the switching part, it shouldn't care what the voltage is. How about using a small dedicated "voltage drop" to go from 24v to 12v to actuate the switch part, and giving the Bosch another try?

 

[Rusty nuts]

You should be able to find them anywhere that has electrical supplies. I usually get mine from Delcity.net and just searched and they have them for $3.69

 

[RangerBob]

I'm not sure if you are talking about a 'relay that will switch 24v' or one that is actuated with 24v.

If you were trying to actuate a 12V Bosch standard automotive relay with 24V, I'm surprised it smoked so quickly. I believe they draw less than 200mA, and at 24V it would still be less than 400mA. It should have worked for a while at least. Did you use a relay with a built in reverse-biased suppression diode? If so, that relay (unlike the standard relay) would require that you follow the polarity of the leads (pin 85 = positive) or it will smoke!

If you were trying to 'switch 24V', the standard automotive relay should work just fine, as long as you are well within the current rating (like rosco said).

 

[patracy]

I've got a bunch of smaller 24v relays from the MK48 harness I hacked up.

 

[Katahdin]

Here's the one I use with a brake controller:

http://www.amazon.com/gp/product/B004NIKVY0/ref=wms_ohs_product?ie=UTF8&psc=1

 

[Ford Mechanic]

I got mine from amazon also it was for 24 volt KC lights. Haven't gotten them hooked up yet though.

 

[MarcusOReallyus]

I'm not sure if you are talking about a 'relay that will switch 24v' or one that is actuated with 24v.

If you were trying to actuate a 12V Bosch standard automotive relay with 24V, I'm surprised it smoked so quickly. I believe they draw less than 200mA, and at 24V it would still be less than 400mA. It should have worked for a while at least. Did you use a relay with a built in reverse-biased suppression diode? If so, that relay (unlike the standard relay) would require that you follow the polarity of the leads (pin 85 = positive) or it will smoke!

If you were trying to 'switch 24V', the standard automotive relay should work just fine, as long as you are well within the current rating (like rosco said).

Something else is going on here. You need to find out what that "something else" is, or it's going to bite you.

 

[clinto]

Some discussion of 24V relays here: http://www.steelsoldiers.com/showthread.php?51161-Generic-relay-questions-(24V-12V)

 

[steelandcanvas]

Did you use a relay with a built in reverse-biased suppression diode? If so, that relay (unlike the standard relay) would require that you follow the polarity of the leads (pin 85 = positive) or it will smoke!

Why would it smoke? Wouldn't it just not work if the polarity was incorrect? Also OP, make sure the relay is DC, some relays are for AC circuits only. Make sure the contacts are rated for the load you wish to control. Watts divided by Volts = Amps.

 

[TurboTim]

View attachment 422356


Something else is going on here. You need to find out what that "something else" is, or it's going to bite you.

Dont think anything else is going on. Its pretty hard to hook up a relay wrong. It does have a diode inside. It will not work one way then will smoke the other way. I did try both ways though.

 

[TurboTim]

Here's the one I use with a brake controller:

http://www.amazon.com/gp/product/B004NIKVY0/ref=wms_ohs_product?ie=UTF8&psc=1

Im using it for my brake controller. Thanks for the link.

 

[RangerBob]

Why would it smoke? Wouldn't it just not work if the polarity was incorrect? Also OP, make sure the relay is DC, some relays are for AC circuits only. Make sure the contacts are rated for the load you wish to control. Watts divided by Volts = Amps.

If you hook it up with the polarity reversed, it will forward bias the diode and pretty much short plus to minus.

Here's a nice little blurb on automotive relays with pretty pictures...

http://www.bcae1.com/relays.htm

 

[steelandcanvas]

If you hook it up with the polarity reversed, it will forward bias the diode and pretty much short plus to minus.

I've seen diodes on electric door strikes and solenoids to prevent "kickback", but I don't understand the purpose here.

 

[RangerBob]

They are not really needed here. They are to protect more sensitive components. If you had a digital circuit controlling the relay, the high voltage generated by the collapsing field during an off transition could damage the gate or transistor controlling the relay. But if you are just throwing a mechanical switch supplying battery power to the relay, the diode is unnecessary.

 

[MarcusOReallyus]

Why would it smoke? Wouldn't it just not work if the polarity was incorrect?

A forward biased diode is pretty much a short circuit. If there is no other significant resistance in the circuit, something is going to smoke, and it's probably going to be that relay.

 

[TurboTim]

Just got the relay from Napa. Napa's PN is 192-4. They are the same as a bosch style relay so connector is the same. Cost me $6 a relay.

 

[RangerBob]

That relay has no diode, so you won't need to worry about smoking it, but don't wire it like this either!!!

 

[Heath_h49008]

That relay has no diode, so you won't need to worry about smoking it, but don't wire it like this either!!!

Wow... I suppose everyone has to learn sometime, but that was amazing.

 

[MarcusOReallyus]

don't wire it like this either!!!

I definitely have something incorrect here. Need Help please!