Wiring a light to relay that is driven by another 12V source

[bhollehday]

I have a 2.25A light that I want to connect to a string of low wattage LED lights (about 3A). I dont want to overload the thin 16 guage wire the string of lights are on. So I want to connect the 2.25A light directly to the battery but then have it turn on and off using the string of 3A lights.

Can I use a normal relay like this one?

https://www.amazon.com/Switch-Pre-w...4116182&sr=1-1-spons&keywords=12v+relay&psc=1

I watched this video:

https://www.youtube.com/watch?v=Tw9QkkT2ptU

but looks like youll have to drive another contact in order to turn the device off (87a)...

 

[Scott Danforth]

16 gauge wiring is good for 10 amps

on a standard VF4 relay, contacts 85 and 86 are your coil that makes the relay move. contact 30 goes to the power source, contact 87 is normally open (gets wired to what you want to turn on when you energize the coil), and contact 87a is normally closed (what you want to turn off when you want to energize the coil).

simple wiring 101. you DO NOT DRIVE ANOTHER CONTACT IN ORDER TO TURN OFF DEVICE.

FYI, the ISO VF4 relay is only $1.49 each if you buy them from newark or digikey. they are about $5 at my local parts store. would only pay $10 if I absolutely was in a pinch at 3am.

if you go to any salvage yard, you can get them from free as they are under the hood of nearly every vehicle ever made over the past 35 years.

 

[sam am I]

^^^

 

[NYBo]

You don't really need a relay. You are just adding complexity and additional potential points of failure.

 

[DouglasW]

FYI, the ISO VF4 relay is only $1.49 each if you buy them from newark or digikey.

Pretty close, but that does not include shipping at about $5 more for the pair.

 

[Scott Danforth]

I guess we buy a large quantity. Our cost comes out to $1.49 each.