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How to control pneumatics with a MCU?
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aah136:
I am a part of a liquid fueled rocket design team at my university and we have a nitra pneumatic valve bank we are trying to use in our plumbing system. Each solenoid in the system turns on with 24 VDC +/- 10%. I am trying to work out a circuit where I could send a signal from our Tiva MCU to trigger individual valves. My first thought was to use enhancement MOSFETs in some kind of high/low side configuration. How can I achieve this though? It seems to me that however I set it up I have some Vds drop across the FET when it is in saturation that pulls down the 24V supplied. Should I just try to get the FET operating in the linear region to have a lower Vds? I'm pretty new to electronics design and any advice is appreciated.
tpowell1830:
Hi aah136, welcome to the forum. Some preliminary schematics would be helpful, in order to help direct you. A system block diagram would also be helpful ( you can draw on a napkin and send jpeg if you want), but if you want help, send info that we can work with.
Smokey:
If you are working as part of a university project, you might want to go talk to pretty much anyone from the EE department.  It sounds like they would be able to hook you up, and they would probably like to get a credit on the project if it works out.
Rerouter:
My main comment would be to make sure your using logic level mosfets,  e.g. your tiva board i am guessing is a 3.3V system, so you would want a mosfet that is fully turned on at atleast 2.5V

Then are you measuring across the mosfet when switching to say its dropping voltage, not just across the solenoid?
as depending on your power supply a beefy solenoid valve could be pulling the supply lower just from its load.
Marco:

--- Quote from: aah136 on October 27, 2018, 12:52:12 am ---Should I just try to get the FET operating in the linear region to have a lower Vds?
--- End quote ---
You're always designing to be in the linear region when you are using it as a switch. Why would you intentionally lower the Vgs?
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