Which diode to use across relay coil contacts

[Harry Muscle]

I'm putting together a circuit that calls for a diode across the relay
coils. However, it doesn't specify which one to use. I'm using a 12V relay
which draws 0.045A (265 ohm coil). Could someone help me out in choosing
the best diode for the job.

Thanks,
Harry

 

[CFoley1064]

I'm putting together a circuit that calls for a diode across the relay

coils. However, it doesn't specify which one to use. I'm using a 12V relay
which draws 0.045A (265 ohm coil). Could someone help me out in choosing
the best diode for the job.

Thanks,
Harry

Generally, the diode specified should be twice the voltage across the relay
when it's on, and a surge current rating at least that of the relay current.
To be conservative, choose a diode with forward current rating at least that of
the relay. That gives you a minimum diode spec of V(r) > 24V, and I(fmax) >
45mA. That would lead you to a 1N914 or 1N4148 as a first choice, but I'm
superstitious and never use those for anything other than reed relays. I'd use
a 1N4001 or 1N4002.

Good luck
Chris

 

[Michael A. Terrell]

Generally, the diode specified should be twice the voltage across the relay
when it's on, and a surge current rating at least that of the relay current.
To be conservative, choose a diode with forward current rating at least that of
the relay. That gives you a minimum diode spec of V(r) > 24V, and I(fmax) >
45mA. That would lead you to a 1N914 or 1N4148 as a first choice, but I'm
superstitious and never use those for anything other than reed relays. I'd use
a 1N4001 or 1N4002.

Good luck
Chris

Or go to the 1N4007 diode. its rated at 1000 PIV, and will replace
any of the others in the 1N4001-1N4007 series. It costs the same as the
1N4001, and you only need to stock one part instead of three or four.
--
2 days!


Michael A. Terrell
Central Florida

 

[Chaos Master]

In reply to a radio transmission from Harry Muscle(fake@AT) , located at Mars:

I'm putting together a circuit that calls for a diode across the relay
coils. However, it doesn't specify which one to use. I'm using a 12V relay
which draws 0.045A (265 ohm coil). Could someone help me out in choosing
the best diode for the job.

Thanks,
Harry

I've used the 1N4007. It's rated at 1000 PIV so it will replace any other in the
1N400x series.

 

[Watson A.Name - Watt Sun, Dark Remover]

I'm putting together a circuit that calls for a diode across the relay
coils. However, it doesn't specify which one to use. I'm using a 12V relay
which draws 0.045A (265 ohm coil). Could someone help me out in choosing
the best diode for the job.

Thanks,
Harry

Use the Harry Muscle kind, a 1N4002 Rectifier.


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