350 V DC-Voltmeter Voltage Divider for Arduino

142

01:28:01

The 5.1 Zener diode protects the analog input of the Arduino from over voltage.

published 9 years ago

faceblast

9 years ago

sort of. there will be some delay before the zener starts to break over. this is due to charge building on the capacitance of the junction, so there will be a brief period where the voltage rises and could still damage the arduino. easy solution is to put a small capacitor to ground on the output to absorb this spike; it turns the output into a low pass filter.

flowDAQ

9 years ago

The AVR mega328 has clamping diodes that can take 20mA so that zener may not be necessary to protect the Arduino. The zener is a good idea to protect your hands should the sense resister and AVR diode clamp fail, I would use a 7V 5W monster.

hurz

9 years ago

5mA at 100kOhm can you imagine how much power this is? Ok, its just for a very short time. And 100k to 1k is dividing any voltage by a factor of 100! You are loosing ~7Bit resolution. So 5V at input are only 50mV at ADC and 100mV are 1mV which is already below standard arduino ADC resolution. BTW, nice webpage!

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