Need 3 or 4 Circuit 12V Relay @180-200W max

Thread Starter

Justpassinthru

Joined Aug 13, 2009
4
I have a vehicle lighting device that needs a 12V relay with 3 or 4 switchable circuits that can handle 180W-200W total max.

Loads

Circuit #1= 35W
Circuit #2=70W
Circuit #3=180W
Circuit #4 Off(Open)

The circuits need to be triggered by a 12V momentary switch.

Relay needs to fit in a 4" X 4" space.

Any ideas on where to get such a relay?

If a relay's not available and other ideas to make this happen?

Thanks

Joe
 

mik3

Joined Feb 4, 2008
4,843
If you want to switch all the circuits with one relay, you can use a relay from an old car which can switch 35 Amps (some of them).
 

kkazem

Joined Jul 23, 2009
160
Hi,

As a practicing and degreed engineer for over 30+ years, I highly recommend that if you're going to go thru the trouble to make this, then do it right. Although you could use a relay from an old car, it may not have all the poles you need and it likely will have arc'd contacts. Go online to digikey.com or mouser.com or newark.com and do a search on relays. They should all have a good selection and you can pick the type that's appropriate for your needs. Note that the contact ratings are based on current and not on power, so make sure you compute the maximum current needs for each pole and then get a relay with at least 15-20% extra current rating on each pole for a long-lasting circuit. If you drive the relay coil with DC, be sure an use a diode like a 1N4004 or similar across the coil inputs with the cathode side of the diode connected to the positive side connection to the coil and the anode side to the other coil input. If not, you'll likely burn-out whatever electronics your using to drive the coil. Usually a medium sized transistor or MOSFET will easily do.

Good luck,
Kamran Kazem
kkazem
 

Thread Starter

Justpassinthru

Joined Aug 13, 2009
4
I have a vehicle lighting device that needs a 12V relay with 3 or 4 switchable circuits that can handle 180W-200W total max.

Loads

Circuit #1= 35W
Circuit #2=70W
Circuit #3=180W
Circuit #4 Off(Open)

The circuits need to be triggered by a 12V momentary switch.

SWITCHING NEEDS TO BE AS FOLLOWS;

Circuit #1
Circuit #1 & #2
Circuit #1 & #2 & #3
Circuit #4 Open(Off)

Relay needs to fit in a 4" X 4" space.

Any ideas on where to get such a relay?

If a relay's not available and other ideas to make this happen?

Thanks

Joe
Sorry if I wasn't more clear. I edited the quote to clear things up.

Thanks Kazem,

I've never built a relay are there a DIY pictorial/exemplar that I can look at. I have very entry level electronics building skills but can usually figure things out.

I would use multiple/separate 12v relays but I have a space limitation and a MAX 3 wire feed/trigger limitation.

Joe
 
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