MOSFET Tester and Ohm Meter
Purpose: To use a DIP switch to switch between a mosfet tester and a ohm meter.
IO Devices used: 16x2 LCD panel, DIP Switch
Ohm Meter¶
Using the code below, the LCD screen will display the resistance and current flowing through a resistor. It was found to be accurate within about 60 Ohms.
Ohm Meter Technique:
- Run the 3.3V source (the red wire) through the unknown resistor (running vertical)
- Put the unknown resistor in series with another resistor (1 kOhm running horizontal) with a known value
- Connect the other end of this known resistor to ground.
- Run an analogIn(p20) from the node that is touching both the unknown resistor and the 1 kOhm resistor.
The Code for the Resistance Calculator:
main.cpp
//Declarations AnalogIn V1(p20); AnalogIn V5(p17); //Resistance calculator if (DIP4 && !DIP1) { current = 3.3*V1/1000; Voltage1 = 3.3*V1; resistance = (3.3-Voltage1)/current; lcd.printf("Current is \n%.6f\n", current); wait(2); lcd.printf("Resistance is \n%4.2f\n", resistance); wait(2); }
MOSFET Tester¶
Technique: Run the 3.3V source(with a pull-down resistor) into the Gate of the MOSFET. The AnalogOut pin is connected to the Source running 3.3V out of p18 (with a pull-down resistor). Connect an AnalogIn pin to the Drain.
main.cpp
//Declarations AnalogOut TestVoltage(p18); AnalogIn DSVoltage(p19); //MOSFET Tester int main() { t.start(); lcd.cls(); wait(1); while(1) { lcd.cls(); //MOSFET Tester if (DIP1 && !DIP4) { TestVoltage = 1.0f; if (DSVoltage >= 1) { lcd.printf("MOSFET is good!\n"); wait(2); } else { lcd.printf("MOSFET no good!\n"); wait(2); } }