#Arduino car battery monitor serial
#Arduino car battery monitor code

Basically, the charge goes up to 14.0001V and the charger shuts-off. If you don't do that, you get 'chatter' (a mechanical relay would make a 'chattering' noise). Then shut it off, 'till it drops to 13.8 again. Leave the charger on 'till the voltage gets-up to 14.2V. Something like this - If the voltage drops below 13.8V, turn the charger on. If this is for a real battery charger and not just something you are playing with, I have a couple more suggestions: (Of course the actual value in the ADC register is always an integer.) If you want your sketch to treat integers as-if they are floats and get the result as a float, here is a short tutorial about typecasting. If my math is correct, all your sketch has to do is divide your count by 57, and you have Volts! (as a truncated integer) You can 'hard code' that constant into your sketch. Please double-check my math, but with your voltage divider and the 5V reference, 14 V should give you an ADC reading of 796, and 1V should give you about 57. Most of those numbers/calculations are constants, so there's no need to make the Arduino re-calculate every time you run the program. If you do mathematical operations on integers in C/C++, by default, the result will be returned as an integer, including temporary/intermediate results like (1500/(3900+1500)).

Where am I going wrong?ĭo you get what Delta & Mark are saying about integers? Integers are whole numbers or 'counting numbers' (no decimals or fractions). I have all grounds connected and the voltage divider to A0 through the resistor then +4.2v then through the other resistor to earth.

#Arduino car battery monitor serial

I have been testing with a 4.2v battery and a voltage divider of two 470ohm resistors after changing int r1 and r2 accordinglyīut it`s outputting in the serial monitor a negative voltage of -4109 I was hoping for 4.2? If (volts > 14.00) //if the volts are more than 14vĭigitalWrite (8, HIGH) //turn on the relay to join batterys for chargingĭigitalWrite (8, LOW) //if they are less than 14v turn off relay to separate batterys

Serial.println(volts) // print the value in volts Int val = analogRead(batteryPin) // read the value from the sensorįloat volts = (val / resistorFactor) * referenceVolts // calculate the ratio determine by voltage divider resistorsĬonst int resistorFactor = 255 / (R2/(R1 + R2)) Ĭonst int batteryPin = 0 // +V from battery is connected to analog pin 0

#Arduino car battery monitor code

I am having some trouble writing code for a car battery monitor, that controls a relay to switch to an alternate supply at a set voltage reading const int referenceVolts = 5 // the default reference on a 5-volt boardĬonst int R1 = 3900 // value for a maximum voltage of 18 volts