![]() ![]() If it is not working, please re-check your connection or the battery you use might be lower than 5 volts needed by Arduino to power up. When you plug the battery to Arduino Vin, it should work right away showing the voltage of your battery on your 16x2 LCD because Arduino is powered by that battery. Connect the other end to Arduino Vin and also to Battery + (positive).Connect LED cathode (large piece inside) to GND (next to D13).Connect LED anode (small piece inside) to Arduino D13.I think you should connect this one after you load the Arduino Sketch as I tell you my reason before. Connect one end to Arduino GND and also to Battery - (negative).Connect the middle of the resistors-in-series to Arduino A0.Align two 10K resistors in series on breadboard.Adapter SCL to Arduino A5 (or the pin next to SDA, two pins from AREF on Digital Pins side).Adapter SDA to Arduino A4 (or the pin next to AREF on Digital Pins side).The wire connections are simple as you can see on the images above. If (voltage < 6.50) //set the voltage considered low battery here Lcd.print(voltage) //print the voltage to LCD Int sensorValue = analogRead(A0) //read the A0 pin valueįloat voltage = sensorValue * (5.00 / 1023.00) * 2 //convert the value to a true voltage. Lcd.setBacklightPin(BACKLIGHT_PIN,POSITIVE) LiquidCrystal_I2C lcd(I2C_ADDR,En_pin,Rw_pin,Rs_pin,D4_pin,D5_pin,D6_pin,D7_pin) #define I2C_ADDR 0x27 //Add your address here. The middle (connection between two resistors) goes to Arduino A0 The other goes to Battery + and also to Arduino Vin One end goes to Battery - and also to Arduino GND with Voltage Divider (2x 10K resistor) ![]() In this instructable, I am not explaining about "how to get your LCD display works", but I will leave some links here (which I use) to get your LCD works through I2C connection: But I will never try it on purpose and risking my Arduino to get burnt :P I guess it will be okay, Arduino designers must have think of this possibility and prevent this power conflict. I am not sure what will happen if you have power from usb and also from Vin at the same time. Uploading this will show you nothing before you connect all the parts needed for this project, but sooner or later you will still need to upload this sketch. Well, I would like to upload this sketch to Arduino first before connecting it to a battery for testing. You can correct me if I am wrong and any better explanation to this is most welcome on the comment section. I am not that good in calculating such thing but that is what I summarize from sources I read. 1K to 20K resistors can be used, but the larger the resistance the lower the power consumed by the Voltage Divider. To divide the voltage to half, we need two resistor with the same value. It is simply made up of two resistors in series. Since Arduino pins support only 5 volts maximum, then we need a Voltage Divider. ![]() I would rather had noticed this battery condition on the last run but I am too lazy to check it with multimeter.Īrduino Uno needs 5 volts power to run, then we need at least 7.4 volts to 9 volts battery. Then they are disappointed and need to wait for charging time. Sometimes when my kids are about to run it, it moves very slow, low battery. I realize the explanation is not very academic, but it's the best I can do on a New Year's Day after a night of little sleep, not because I was out partying, but because the baby was sick and we didn't get much sleep.When we are using a battery powered Arduino such as RC robots or Temperature Controller, we might want to check the battery voltage if it needs to be charged or replaced. But if you do the test on the battery test scale, you read 1.3V and it stays there, it does not drop any further since they have enough "juice" to deliver. With HIMH batteries, their nominal voltage is 1.2V, but that us under normal load without load, they measure 1.3V, or even 1.45 when coming out of the charger. Now a flashlight may draw as much as 500 mA (or maybe even more), and those batteries will collapse under such load. With an older battery, you may read 1.4-1.5V on the voltage scale, but when you test it on the battery test function, you can see how the voltage drops, let's say it start with 1.3V and if you keep testing it for a minute or so (all this time the device consumes 75mA), you see the voltage dropping to 1.1V or even lower. When I put the same battery on the battery test scale (1.5V), it shows 1.55 or so (IIRC). So when I put a fresh battery and measure the voltage (using the 2000 mV scale), is shows 1.65V or so. I measured the current (with another multimeter) and I think it draws around 75mA DC. On each of these scales, the device applies a small load to the battery. My Craftsman Multimeter ($10 on sale, $20 regular price from Sears) has a battery testing function. ![]()
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