Arduino Powered Multimeter
Introduction: Arduino Powered Multimeter
In this project, you will be building a voltmeter and ohmmeter using the digitalRead function of an Arduino. You will be able to get a reading almost every millisecond, much more precise than a typical multimeter.
Finally, the data can be accessed on the Serial monitor, which then can be copied onto other documents, e.g. excel, if you want to analyze the data.
Additionally, since typical Arduinos are limited to only 5V, an adaptation of the potential divider circuit will allow you to change the maximum voltage that the Arduino can measure.
There is also a bridge rectifier chip incorporated into this circuit which will allow the multimeter to measure not just DC voltage but also AC voltage.
Supplies
1) 1 x Arduino nano/Arduino Uno + Connecting cable
2) 5cm x 5cm Perfboard
3) 20 x jumper cables or wires
4) 1 x 1K resistor
5) 2x resistors of the same value (doesn't matter what the values are)
6) 1 x 16x2 LCD screen (Optional)
7) 1 x DB107 bridge rectifier (Can be replaced with 4 diodes)
8) 1 x 100K or 250K potentiometer
9) 6 crocodile clips
10) 1 x Latching push switch
11) 1 x 9V battery + connector clip
Step 1: Acquiring the Materials
Most items can be purchased off amazon. There are a couple of electronics kits on amazon which provide you with all of the basiccomponents such as resistors, diodes, transistors, etc.
The one I have found to give me a bang for my buck is available on this link.
I personally had most of the components already as I do a lot of these types of projects. For the inventors out there in Singapore, Sim Lim Tower is the place to go to purchase all electronic components. I
recommend Space electronics, Continental electronics, or Hamilton electronics on the 3rd floor.
Step 2: Understanding the Circuit (1)
The circuit is actually slightly more complicated than you might expect. This circuit makes use of potential dividers to measure the resistance and add the feature of variable maximum voltage for the voltmeter aspect.
Similar to how a multimeter can measure the voltage at various stages, 20V, 2000mV, 200mV so on and so forth, the circuit allows you to vary the maximum voltage the device can measure.
I will just go over the purpose of the various components.
Step 3: Understanding the Circuit: Purpose of Components
1) Arduino is used for its analogRead function. This allows the Arduino to measure the potential difference between the selected analog pin and its ground pin. 769
Essentially the voltage at the selected pin.
2) The potentiometer is used to vary the contrast of the LCD screen.
3) Building on that the LCD screen will be used to display the voltage.
4) The two resistors of the same value are used to create the potential divider for the voltmeter. This will make it possible to measure voltages above just 5V.
Oneresistor will be soldered onto the perf board while the otherresistor is connected using crocodile clips.
When you want more precision and a max voltage of 5V, you would connect the crocodile clips together without any resistor in between. When you want a max voltage of 10V you would connect the second resistor between the crocodile clips.
4) The bridge rectifier is used to turn any AC current, maybe from a dynamo, intoDC. Additionally, you now don't have to worry about positive and negative wires when measuring the voltage.
5) The 1K resistor is used to make the potential divider for the ohmmeter. The drop in voltage, measured by the analogRead function, after 5V is inputted into the potential divider will indicate the value of the R2 resistor.
6) The latching push switch is using to switch the Arduino between the Voltmeter mode and Ohmmeter mode. When the button is on, the value is 1, the Arduino is measuring the Resistance. When the button is off, value is 0, the Arduino is measuring the Voltage.
7) There are 6 crocodile clips coming out from the circuit. 2 are the voltageprobes, 2 are the ohmmeterprobes, and the last 2 are used to vary the max voltage of the multimeter.
To increase the maximum voltage to 10V, you would add the second same value resistor between the varying maximum crocodile clips. To keep the maximum voltage at 5V, connect those crocodile pins together without any resistor between them. 1003