I need to connect 16 solenoids to an arduino/ESP32
Im playing with an MCP23017 to give me enough ports. This works really fine, and is fast enough for my use.
But the coils will be drawing 2A at 12V, so some kind of Mosfet/transistor will be needed. This is where I need some guidance.
If I take a TIP120 (might work fine) then I will always have 12 V to the solenoid. I really do not like this.
If I am using a PNP It will only send 12V when the solenoid is in use. I like this more. But can any of you guys help me find a suitable NPN for my need? One with a build in diode, and one that can be purchased as a SMD component would be preferred. And finally one that opens fully from 3.3V
The solenoid is only going to be running for less than 1 second. Heat should not be an issue.
Any good suggestions?
(Im a bit challenged when it comes to power electronics, so please bare with me. What Im after is a PNP high-side switch.)
All the best
What you are trying to do is make a High Side Switch. If you use a N-Channel MOSFET the gate needs to be about 8 volts above your positive voltage of 12V. If you use a P-Channel you can implement that with 2 resistors and a small NPN transistor. You can do a similar circuit with a PNP transistor but it will get much warmer than the MOSFET. You can use a couple of ULN2805 octal drivers where the output is connected to the gate of the P-Channel MOSFET which has a 1.2K resistor connected to the source (+12 in) and the drain is your output. If you use avalanche rated MOSFETs no clamp diode is needed. The V(ds) should be at least 15V. Logic level is not needed. The input of the octal driver connects to your output device. This should do exactly what you are asking. There are other ways but this is my prefered method I have used it many times.