How to check continuity or shorting using arduino

Question

I was trying to build a multimeter using an arduino (just for learning purpose). I am able to measure voltages directly using analogRead() and for measuring currents I am using a o.o1ohm shunt resistor. However, I cannot figure ot how to built a circuit to check shorting (i.e the buzzer would beep if there is a short just like in a DMM). Can anyone help me please?

Thank you.

• Prasan Dutt: Go through a similar question and corresponding answer: electronics.stackexchange.com/questions/116175/…

Answer 1

schematic

^{simulate this circuit – Schematic created using CircuitLab}

Figure 1. A simple pull-up resistor will form a potential divider with the DUT (device under test).

The voltage at the GPIO will be given by $$ V_{TP} = \frac {R_{DUT}}{R_{DUT}+R_1}$$

You should be able to work out the rest.

• Change the resistor value if you want more or less sensitivity.
• There is no protection on the input to this tester so make sure your DUT is unpowered before connecting up.

Answer 2

Use a GPIO as output and another one as input, use these GPIOs for probes and while testing if you get a high on the input GPIO then there is contnuity. Use this logic to turn on the buzzer with another GPIO or connect the buzzer to the input GPIO.

Answer 3

Avoid damage to whatever you a probing (whichever way round your probes are) by constraining the voltage/current applied to it. You could use a resistor divider from 5V, set to deliver a few hundred milliVolts. Your probes would connect to the centre of the divider and ground. Measure the positive probe voltage with the Arduino's ADC. Choose an appropriate (low) threshold to detect a low resistance and then drive the buzzer on.

Float the Arduino power supply with respect to the device being probed, e.g. by powering it from a battery.