Tip 120 Trouble

Projects General Guidance
1

Hi,

I currently have an LCD connected to an Arduino that is suppose to turn on a pump when a button is pressed. I used a tip 120 transistor where the base is connected to pin 9, the collector is connected to an outside 9v battery and the pump is connected to the emitter. When I have everything connected, the pump is running even when I did not press the button yet. Can someone please help me solve this problem. Thank you.

2

The TIP120 should be used on the low side to switch a motor. In the schematic, L1 is the motor. The base resistor and the diode are required. The diode can be any rectifier diode rated for motor stall current.

TIP120 solenoid DRIVER.jpg