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24V / 2A hydraulic solenoid driving

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Zedman

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I would like to control 24V DC hydraulic solenoids (approx.: 20 of them) and a same amount of sensors (simple on/off switches) with a PIC MCU.

Are there any checklist / rule of thumb to follow on doing this? I mean optoisolation, port protection, transient suppressors etc?

What's the best to use to switch 24V DC / 2A? (Relay is not an option because of it's short lifetime)

thanks,
Zedman
 

Hi Zedman,
Use simple MOSFETs or transistors :)...
For these relative small currents its possible to select SO8 versions with double FETs.
Karesz
 

thanks,

and what about port protection / isolation?
I think SMD package wont be a good selection as 2A can generate much heat, it'd be better to use TO220 with heatsink attached.
And it would run all day so even a ventillator may also needed.
 

ü-ü-/nem- nem......
Sorry, but you should read some IR , Vishay or Fairchild... datasheets: :)
IRF7493 is i.e. a ca. 7 years old type in SO8, 80V & layout depending 7-9 Amps...
K.
 

Okay you win.

But I'll try it before putting it into the real thing.

Anything about the port protection? Simple optoisolator + a transient suppressor before the mosfet will do?

What about the inputs if those sensor switches are close to the solenoids?
 

ADI has butyfull (ADUM140X) Isodriver family :)...
But there are not so very good, they has "only (max.) 100Mbps...
K.

Added after 1 minutes:

You see; transientprotection you will need so & so at the FET drivers!...

Added after 1 hours 11 minutes:

Hier the actuellst & nice FET developments (from TI)...
www2.electronicproducts.com/New_packaging_MOSFETs_meet_power_supply_needs-Article-fapo_TI_mar2010.html.aspx
K.
 

I would go for optos driving mosfets. There are Mosfets around with logic inputs and built in snubber circuits for applications such as these. The reason that I suggest that you use optos instead of direct drive, is the fact that you can then use active low outputs to drive the opto leds. If you do not do this, during the reset pulse all outputs will go high and your solenoids will briefly pull in, this is not usually desirable, apart from all the current they will pull. You can of course use an inverter instead of an opto, but the former is a safer and better option. I would tend to go for darlington optos as a preference.

Added after 4 minutes:

I have used VNP7N04 Mosfets for this type of appliction. No issues as yet.

http://www.datasheetcatalog.org/datasheet/SGSThomsonMicroelectronics/mXuxryw.pdf
 

    Z

    Zedman

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Thanks,

I think I'll use a mosfet with same parameters like the one you mentoined + darlington optos as a driver.
 

Just a further thought. Optically isolated solid state relays would be the easyist solution, but a little more costly. There are also now Mosfets available with opto input.
 

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