Fast Solenoid Control Circuit

Hi All,

I am working on a water fountain application that will require me to power around 40 Solenoids (Waterfall printer). Since I have very limited knowledge about electronics calculations, I am wondering :

1.- What will I need to look in a transistor to control de solenoid with the fastest speed possible.
2.- What would the simplest multiplexing implementation be to control all 40 Solenoids with the I/O available on the Photon?

I understand the power supply demands and I think I have that figure out with a big power supply and a good regulator between that supply and the particle, so that I can draw power directly to the solenoids from the big power supply.

Any help appreciated!

  1. I’m not sure what you’re getting at here; I think pretty much any transistor would be fast enough compared to the time that it takes for a solenoid to actuate.

  2. The answer to the his depends on your requirements. How many solenoids need to be turned on or off simultaneously?

Thank you. So to clarify.

1.- Should I use MOSFETS or a simple (current abiding) transistor suffice.
1B.- Should I use an opto coupler to drive the final transistor/fet?

2.- I need to drive a maximum of 60 solenoids controlled independently.

  1. I would use MOSFETs since they draw a lot less current than bipolar transistors. I’m not sure what you mean by “the final transistor”. If you use MOSFETs to control your solenoids, I think you should be able to hook them directly to whatever multiplexing chip you use.

  2. To be able to control up to 60 solenoids at once, I think you probably want something like serial to parallel shift registers (for instance, 8 CD4094’s) or I2C port expanders (for instance 4 MCP23017’s). The latter would probably be faster.

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I agree with @Ric on the MOSFETs. There is also an SPI of the I2C 16-port expander - the MCP23S17.

With so many concurrent solenoid activities, you will need a properly designed power supply and distribution system to handle the peak current demands. Depending on switching speed, you will need to carefully select your MOSTFETs and possible heatsinks as well.

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I would suggest you check They offer a 16-CHANNEL 8W 12V FET SOLENOID DRIVER VALVE CONTROLLER that might be worth considering and/or provide some insight as to how to best proceed. Three of those would handle your needs. You’ll also learn a bit more about switching on/off inductive loads and associated considerations.

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Thank you!

Any recommendations on what to look in a MOSFET? Current?

This looks like a Great Way to start experimenting! Thanks for the recommendation.

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