ARDUINO BASED MULTIMETERJul 15th, 2019 | by: ELECTRONOOBS
ou have the schematic for this project below. You need the Arduino, the ADS1115 ADC module, the OLED display, the ACS712 current module, the TP4056 based charger and a few more components. You have all the values below. After you make the connections, you can downlaod the code and upload it to the Arduino and give it a test.
- 1 x Arduino NANO/UNO: LINK eBay
- 1 x ADS1115 sensor: LINK eBay
- 1 x i2c OLED screen: LINK eBay
- 1 x TP4056 charging module: LINK eBay
- 1 x ACS712 current sensor: LINK eBay
- 1 x LM324 OPAMP: LINK eBay
- 10 x female bullet connectors: LINK eBay
- 2 x male bullet connectors: LINK eBay
- 3 x push buttons: LINK eBay
- 1 x sliding switch: LINK eBay
- 1 x 3.7V lipo battery: LINK eBay
- RESISTORS: 1x150, 1x220, 1x330, 2x2K, 1x6.8K, 1x10K, 1x20K, 1x470k : LINK eBay
- 2 x 1n4001 diode: LINK eBay
- 2 x 1uF nonpolarized capacitor: LINK eBay
- wire, solder, soldering-iron, 3D case, etc
But first, let's go step by step and see how we measure each value: voltage then resistance, then capaciance, inductance and current. Let's start with volage since that is very easy. Below you have an example code for the ADS1115 module using the library. We read and print the values to the serial monitor. The ADS1115 has its own refference so it doesn't matter if the voltage battery is 3.7 or 4.2 or any other value, the output will always be precise.
So, make the connections and uplaot it to the Arduino. It will measure voltage with high precision.
On our schematic, the resistance measurement is made with the 2k, 20K and 470K resistors connected on pins D6, D7 and D8. By that we have 3 different scales. If we set D6 as OUPTUT and set to LOW, that will our GND for the voltage divider. The other pins, D7 and D8 are set to INPUT so they have high impedance. So our volage divider is amde out of the 2K resistor and the unknown resistor. We measure the voltage on the ADC1 pin and using the formula we get the resistance. We do that for all the scales.
So, in the code, when capacitance mode is selected, we charge the capacitor, discharge it and count time. When the capacitor reaches 63.2% of Vcc, we stop the time counter and calculate the capacitance value using the formula.
This part is also simple. We use the ACS712 module to measure current. The ACS712 current sensor is an economical solution for measuring current, it works internally with a Hall effect sensor that detects the magnetic field produced by induction of the current flowing through the line being measured. The sensor gives us a voltage output proportional to the current, depending on the application we can use the ACS712-05A, ACS712-20A or the ACS712-30A, for ranges of 5, 20 or 30 amps respectively.
V = mI + 2.5
Downlaod the 3D files from below. I've used 2 perimeters, 20% infill and a 0.4mm nozzle and PLA amterial. The case is made out of 2 parts and 3 plastic buttons. Cut your PCB to the case dimensions and place that inside. It has space for the OLED screen, sliding switch and the USB connectors for the Arduino and charging module.
|3D case STL files||DOWNLOAD|