Now the mosfet switches the divider on/off not at the top, but in the middle, where they (R1,R2) are joined. Then connect source to R2 and analogue pin.ĭivider R1,R2 needs recalculating for 1volt at the analogue pin.Īnd the pin has to be measured with 1.1volt Aref enabled in setup(). Move R1 (top of divider) to the drain of the mosfet (between 'voltage to measure' and drain). You will have some switched voltage on the analogue pin, but not a representation of what's on the drain of the fet. Figure 5-4: Combined USB and 12V DC power adapter With the.
#Arduino 12v battery voltage monitor driver
Sorry, but this circuit can not work the way you think it does. The monitor I suggest has a separate driver board that powers. With 5volt max on the gate, the top of the divider (R1) will never see more than about 2.5volt. Gate must at least be Vth(gs) higher (~2.5volt) than source, for the fet to turn on. With the divider between source and ground, and tap to an analogue input, you can indeed turn the divider OFF.īut you can't turn it ON. Gate can be connected directly to the Arduino switch pin.
Those resistors are not really needed, because the gate charge of this fet is very low, and bleed during bootup is not destructive.
#Arduino 12v battery voltage monitor series
I get the 0/5 volt switching voltage at the gate, with 330ohm series and 100k bleed to ground. Voltage to be measured to a P channel MOSFET drain. This means that the ADC assumes 5V is 1023 and anything less than 5V will be a ratio between 5V and 1023.Īnalog to Digital Conversion - SparkFun Learnīy gating off/on the voltage to be measured to the voltage divider, the voltage divider is only drawing battery power when being read, instead of drawing battery power continuously. You can do an analog read without gating on, an experiment, MOSFET to find that the AX pin will return a 0 volts measured. You don't have to shrug.Īrduino pin used, output a 1, to gate on MOSFET, to allow voltage to be measure to be felt at the top of the voltage divider, than measure voltage with an analog read. I put in delay because I found the AX pin requires a little time for voltage to become stable on the pin. Input of 330 ohm resistor to an Arduino pin to gate on/off voltage to be measured. Source of MOSFET to top of resistor divider network resistor R1, bottom of R1 connected to R2, Bottom of R2 connected to ground. Junction of gate of MOSFET and 330 ohm resistor place a 10k resistor to ground. I use 2N7000's.Īrduino pin, your choice, to one side of a 330 ohm resistor, other side of 330 ohm resistor to gate of MOFFET. Tab: Terminal assignment temperature sensor DS18B20 Fig: Test circuit with shunt, load resistor and temperature sensor equivalent to the circuit diagram on the back of the battery monitor Fig: circuit Further information. But it will damage the Nodemcu esp8266 module as the esp8266 is a 3.3v microcontroller, applying more than 3.6v on any pin can damage the chip. so this sensor can be used with the Arduino without any problem. Voltage to be measured to a N (corrected) channel MOSFET drain. Vout (7.5 x 1000 x 25) / (30k + 7.5k) Vout (7500 x 25) / 37500.
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