I am trying to design a circuit to switch 12V 90mA on/off using an Arduino Nano as the trigger.
Is there an optocoupler/transistor/MOSFET that can tolerate 12V at 100mA on the load side while still being switched by 5V from the Arduino Nano without overtaxing the nano?
I've tried a FQP30N06L MOSFET but the connection between the [S]ource and [D]rain pins allows enough voltage/current to flow when the MOSFET is in LOW state to keep that 12V circuit closed enough to run the load device. I added a resistor between Source and Drain to lower that voltage to zero in Low state but that also has the affect of dropping the 12V output to 11V when the MOSFET is switched HIGH.
Any advice would be great. I've been beating searching Google and SE for a few days trying to solve this.
Added - Data Sheet for the FQP30N06L MOSFET
The Load is an OBD2 reader for car diagnostics. Model: LAUNCH Creader 3001
I ended up using a HE3621A0510 reed relay to switch the ground of the OBD2 reader on and off. It worked great. Unfortunately now the reed relay stays closed when the Arduino trigger power is removed, until I tap the relay. Then the circuit opens again and shuts the OBD2 reader off.
Though the measured load current of the OBD2 reader (90mA - mind you this was measured with a digital multimeter) was far less than the the reed relay capacity (500mA), I feel there must be a spike in the current at startup high enough to weld the relay contacts a little. I have tried multiple reed relays of the same model number and they all do this, so it shouldn't be just a single defective unit.
Any chance a resistor in line with the load could help keep that inrush down or should I use a fly-back diode to stop it entirely?