You need some sort of electronics to:
1) Read the thermidor temperature
2) Set a control point for the bed
3) Adjust the power into the bed to hold that control point.
There are some pretty good > $40stand alone solutions to do this with various temperature sensors. A Mega + Ramps will run about $40. The Ramps / Mega will run with the parts you already have. The stand alone gizmo probably won't like your thermistor.
An added benefit, the Ramps understands gcode and you can move the heated bed temperature up and down as you print. That's not going to happen with a stand alone PID box.
1) Read the thermidor temperature
2) Set a control point for the bed
3) Adjust the power into the bed to hold that control point.
There are some pretty good > $40stand alone solutions to do this with various temperature sensors. A Mega + Ramps will run about $40. The Ramps / Mega will run with the parts you already have. The stand alone gizmo probably won't like your thermistor.
An added benefit, the Ramps understands gcode and you can move the heated bed temperature up and down as you print. That's not going to happen with a stand alone PID box.