Car Battery Voltage Indicator

This circuit tries to follow the voltages based on this image: https://i.pinimg.com/originals/be/e3/3e/bee33e3900f485e036ab48387b4b2e54.jpg I'm sinking the current from the LEDs via the open collector path of the comparator. The comparators are not using a Schmitt trigger since the signals are not being used for digital logic, just the LEDs. The LEDs are low-current ones, to avoid large current usage. The zener diode is a 1N4740A from Vishay, with a test current of 25mA. Sadly I have no idea how to take the junction temperature into consideration. But I can't simulate it here either. The quiescent current is 90uA (@9V). The current while the car is stopped is 30mA (<12.5V). The current while the car is running is 50mA (<14.7V). I believe this can be more efficient if done with a low-power microcontroller with analog pins, or using an LDO instead of a zener (being the largest consumer @27mA). Inspired by: http://everycircuit.com/circuit/5241387998773248

published 6 years ago