micro-controller driving isolated output

[Mad Professor]

Hi All

I am not sure if this topic would be best suited listed under Beginners or Projects section of the forum so please move as needed.

I am trying to work out the best way to drive two solenoid valves from a micro-controller, but both the micro-controller and the solenoid valves are on there own isolated power supplies and I can not share the power or ground rails.

The simplest way I can thing about doing this is by using optocouplers and mosfets.

Here is what I am thinking about using, I have not yet decided on the components to use, that is why there are no part numbers and or values listed.


Before I think about things to much, will the above work, or is there a better way?

Thanks for your time.

Best Regards.

[Zero999]

Yes, it'll work but don't expect it to be fast.

[Psi]

How big are the solenoids? You can get optoisolators with build in drivers that can do 500mA - 2A directly. It would cut down the amount of parts you need.

you could also use solid state relays.

[Andy Watson]

You might want to check the polarity of V01 and V02.

[TopLoser]

I use a lot of these for isolation, simple and easy.

http://uk.farnell.com/panasonic-electric-works/aqy212s/relay-photomos-60v-0-5a/dp/2095723

[Mad Professor]

Thank you for your replies.

I should not need to use any PWM switching with the solenoids, I am simply looking at on/off, and quite low cycle times something like 5 to 10sec on time. The off time varies.

I will need to re-check the current draw of the intended solenoids but from memory we are looking around 600ma at 14volts.

Thanks again for your time.

Best Regards.

[Zero999]

You might want to check the polarity of V01 and V02.

Oh yes, the phototransitors are upside down.

[mushroom]

Solid state relays are designed for that usage.

They are opto isolated. Get a DC solid state relay.

http://www.crydom.com/en/tech/tips/dc%20relays-technical%20guidelines.pdf

[Delta]

Fuck all this opto shit and just use some oldskool relays with cheeky low side NPN switches. KISSFFS :-)

Easy.

[TopLoser]

Fuck all this opto shit and just use some oldskool relays with cheeky low side NPN switches. KISSFFS :-)

Easy.

Click click click click 2 years later mechanical failure bits falling off...

More tea vicar?

[Delta]

Nah, but I'll take another ale, please.

Probably shouldn't be posting whilst I'm on the piss watching the election results roll in...

[TopLoser]

Your round mate, a cheeky half pint of vodka for me if you don't mind

[SL4P]

Thank you for your replies.

I should not need to use any PWM switching with the solenoids, I am simply looking at on/off, and quite low cycle times something like 5 to 10sec on time. The off time varies.

You may not 'want' to use PWM, but your solenoids and power supply may like you more if you do.
100% fast pull in, then 20% (approx) to hold the position.

[Jeroen3]

What voltage are the solenoids?
You can get DC high side drivers, and use opto's or digital isolaters to control them.
Such as ITS 4142N with Si8620. (total <$5)

You can use those profets, un-isolated, to control some larger (DIN rail) relays if your solenoids are AC or high voltage DC. Some are designed to switch inductive stuff, such as relays.