I am using a standard NPN transistor-as-a-switch set-up to use a Teensy 4.0 to switch a bunch of shape memory valves (valves controlled by a wire that changes shape when heated by a current). I have previously got some advice here on the use of a buck converter set-up to run this, but this did not work out well so I decided to go this simpler route and accept the ~0.35W power waste in the 8.2 Ohm resistor (2W type).
When I connected the "Teensy DIO" point directly to the 3.3V DC power source, the transistor switches fine, giving the desired .25A current required to the SMV. When I instead set the Teensy DIO to High as in the circuit, I only get a 0.05A current, and the voltage at the Teensy channel is only .8V, with a current flow from the Teensy at 0.5mA. when disconnected from the circuit the channel goes to 3.3V when set to high, so the Teensy seems fine. Does anyone know why this set-up does not work? Thanks in advance!