Hello,

I am creating a new post, as I couldn't find the answer for my question. There is very similar post in the forum, but I think my case is slightly different, as I have a solenoid with higher resistance.

I have a very simple 12V circuit with a relay (controlled by 5V, very common relay) and solenoid. However, I would like to use some diode to reduce the arc effect when I break the circuit by relay.

The solenoid resistance is around 2 Ohm, which gives 6 amps current. The measured peak voltage during breaking circuit is up to 50V.

What diode should I use to reduce the arc effect? 1N4148 is usually used in this role, but it is up to 3A.

How can I calculate the current which will flow through the diode when I break the circuit?

 

You say a solenoid with higher resistance yet it is only 2ohms?
It sounds like you may have an AC solenoid at that resistance, in any case, if operating a DC solenoid, then a reverse EMF diode is connected across it Use a 1n4007.
Max.

 

The 1N4148 is not suitable. It's average curreent rating is only 150 mA andthe peak current rating is only 450 mA. This initial current trough the diode will be the same as the DC current through the coil. So in your case the peak current will be 6 amps. One of the 1N400x series diodes would probably be OK even though the average current rating is only 1 amp. It can stand a peak current of 30 amps for 8.3 mS but unless you know the inductance of the solenoid you can't calculate the way the current will decay. I would just use a diode with an average current rating of 3 amps. A 50 volt rating diode will be OK as it will only be subjected to the supply voltage of 12 volts.

Les.

 

Thank you very much for prompt answer Max and Les Jones. I have now a confirmation and will buy it as advised.

Could you please tell me how I can be sure, that 3 amp average current diode would be enough?

 

I'm curious, what kind of solenoid is it with only 2Ω resistance?
I have always used 1n4007 with no problems.
Max.

 

I'm curious, what kind of solenoid is it with only 2Ω resistance?
I have always used 1n4007 with no problems.
Max.

DC 12V 2.5A Push Pull Type Open Frame Solenoid Electromagnet 10mm 55N 12LB - please have a look at Amazon. It says that current is 2.5A, but to get 50N you need 6 amps.

 

So it is actaully 4.8Ω?
They quote 55n at 12v?
Max.

 

So it is actaully 4.8Ω?
Max.

Well, the measured resistance is 2Ω.
2.5 A merely moves the solenoid.

 

Bit of a discrepancy in the AD?
Max.

 

Looks like, I saw that someone was also complaining about this current, as it is much higher.

 

There is a report form on Amazon for wrong information.
Max.

 

A 1N4007 should work fine unless you are operating the solenoid more than a few times per second.