Hello everyone!
I am currently using an Arduino to trigger a tip120 darlington transistor.
I have a pin from the Arduino hooked up to the base. I have a 12v hooked up to the collector and then the emitter goes to a solenoid valve. The problem i am having is the arduino is supplying a full 4.5V to the transistor, but the transistor is only outputting 3.5V out of the 12v it is getting supplied. I am not sure what is going on? The transistor has a HFE of 1000, so i only need to supply 5ma(arduino can putout 40) to saturate the transistor. I believe the solenoid is drawing around 4 to 5 amps as the transistor gets pretty warm.
After doing some more research i read you can put a resistor between the arudino and the base of the transistor. I put a 1k resistor between the two, but it was still a no go.
I then used this website http://kaizerpowerelectronics.dk/calculators/transistor-base-resistor-calculator/
to calculate what value resistor i need. Collector current 5A, HFE 1000, Supply Voltage 5, Voltage drop 1.4, came out to 720 ohms. Do you think my resistor is too big? Why would only 300ohm make that much of a difference?
Any help would be apprecaited, thanks!
I am currently using an Arduino to trigger a tip120 darlington transistor.
I have a pin from the Arduino hooked up to the base. I have a 12v hooked up to the collector and then the emitter goes to a solenoid valve. The problem i am having is the arduino is supplying a full 4.5V to the transistor, but the transistor is only outputting 3.5V out of the 12v it is getting supplied. I am not sure what is going on? The transistor has a HFE of 1000, so i only need to supply 5ma(arduino can putout 40) to saturate the transistor. I believe the solenoid is drawing around 4 to 5 amps as the transistor gets pretty warm.
After doing some more research i read you can put a resistor between the arudino and the base of the transistor. I put a 1k resistor between the two, but it was still a no go.
I then used this website http://kaizerpowerelectronics.dk/calculators/transistor-base-resistor-calculator/
to calculate what value resistor i need. Collector current 5A, HFE 1000, Supply Voltage 5, Voltage drop 1.4, came out to 720 ohms. Do you think my resistor is too big? Why would only 300ohm make that much of a difference?
Any help would be apprecaited, thanks!