Latching solenoid

[dark]

Hi Board,

I need to know what type of ark supressor is use at the drive of latching solenoid , zener back to back etc. As the polarity reversed a single diode would mostlikely short.

Rgds

 

[colin55]

I think you will find the ark on Mt Ararat.

 

[alec_t]

A reverse-biased diode should suffice. What current does the solenoid draw?

 

[dark]

The current is 1Amp .

 

[MrAl]

Hi,

I would try the two zeners. Say the 1 watt kind. It depends how often you have to power the solenoid though. If it is not often then the zeners wont overheat, but too often they might overheat unless you use larger power rated zeners.

You could also use one zener and a bridge rectifier. The zener goes across the DC side and the solenoid across the AC side. The zener voltage should be higher than the drive voltage to the solenoid ever gets.

 

[dark]

I am sorry for not providing solenoid details , It has 12VDC coil and its latch time is about 100ms.

 

[MrAl]

Hi,

What are you driving it with? Can your drive circuit take a reverse voltage of say 15 volts either way?

 

[dark]

Hi, I am driving it with Relays 10A/24DC rated contacts. I am also concerned about EMC.

 

[MrAl]

Hi,

You should be able to use the zeners then, say 15v zeners or something like that. The main idea is you dont want them conducting when you turn the coil on, you only want them conducting when the voltage jumps up to a level higher than the normal drive voltage. Because the drive voltage might vary a little you'll want the zener voltage higher than the highest the drive voltage can go.
To minimize electromagnetic radiation (assuming that's what you mean) you would want to slow up the rise and fall times of any switching signal. To do that you'd have to use a capacitor across the coil combined with a small value resistor in series with the coil. The resistor value cant be too high though or the coil wont get enough voltage, so the resistor would have to be sized according to the resistance of the coil.

 

[dr pepper]

Mr Als suggestion will work fine.
In industry electrical contactors use a version of a solenoid, the most common way I've seen to suppress back emf and contact flash is to make a snubber circuit from an x rated 100nF capacitor in series with a 100 ohm resistor placed across the coil.