What diode should i use?

Thread Starter

John appleseed

Joined May 20, 2020
72
I have a 1n4004 diode that says 213 on it. I need a fly back diode for a 12v dc 7amp relay that i have installed in my truck for led strip lights. Will this diode work to protect my bcm from flyback voltage?
 

Thread Starter

John appleseed

Joined May 20, 2020
72
As Bernard says... IF youre "213" is actually a 1N4004, you should not expect it to handle more than 1A:

View attachment 207685
It says 213 and then underneath says 1N4004 its a little black cylinder. Im a nube to this type of thing. Im not sure what the amperage would be on my relays coils flyback. Its a finder 12vdc relay and is rated for 7amps. The coil uses about .1 amps. Would this handle my fly back voltage? And how would i install it
 

BobaMosfet

Joined Jul 1, 2009
1,117
You can use a clamp-on ammeter with a HOLD feature to see what your max amperage is. Coils are inductors- as such they can create massive voltage and current spikes. If it's really short duration, the 1N4004 spec sheet says it can handle 30A for a spike that is no more than 8.3ms. It's a coil- diode is installed backwards. So if you apply positive to one side of the coil, the diode's cathode attaches to that end. Anode of diode would then attach to the negative side of the coil. This prevents main voltage from going through diode, and the diode simply catches what comes out of the coil and loops it back through the coil over and over as it diminishes.

Try it. 1N4004 are not expensive. If it pops. try a different diode.
 

Thread Starter

John appleseed

Joined May 20, 2020
72
You can use a clamp-on ammeter with a HOLD feature to see what your max amperage is. Coils are inductors- as such they can create massive voltage and current spikes. If it's really short duration, the 1N4004 spec sheet says it can handle 30A for a spike that is no more than 8.3ms. It's a coil- diode is installed backwards. So if you apply positive to one side of the coil, the diode's cathode attaches to that end. Anode of diode would then attach to the negative side of the coil. This prevents main voltage from going through diode, and the diode simply catches what comes out of the coil and loops it back through the coil over and over as it diminishes.

Try it. 1N4004 are not expensive. If it pops. try a different diode.
Well i do have a bunch of the 1n4004 i got them from an alarm panel so maybe i could use two of them at once? Sorry if these are stupid questions but how do i know what end is the cathode and anode? My understanding is its wired backwards bc the diode catches the fly back volatage and sends it back through the coil To dissipate. But if its wired in parallel to the coil how come the extra voltage travels through the diode? Cant it still go back to the bcm? my negitive from my bcm goes straight to the negative terminal on my relay
 
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