Hey folks, I need a simple circuit that will turn on a 12v relay when the input voltage of the circuit reaches 13v. I can't use an op-amp as I will not have a reference voltage. Any ideas?
....Well not super accurate. Maybe from 12.6v to low 13's I suppose....How accurate does the switch at 13V need to be?
Why can't you create a reference voltage, that's usually the procedure?Hey folks, I need a simple circuit that will turn on a 12v relay when the input voltage of the circuit reaches 13v. I can't use an op-amp as I will not have a reference voltage. Any ideas?
I am not totally sure I can't however the research I have done so far does not support it. I fly an extensive collection of RC planes and drones from micros to giant scale and have a 125 amp deep cycle marine battery in the rear of my Ford Flex to run my system to recharge all my LiPo batteries while I fly. This battery gets charged from my car however the connector in the car is always live and I fear that at some point I will be at the field all day and kill my car's battery. The voltage of the plug will only be at 13v when the car is running so if I have a circuit that energizes a relay at 13v I will only have the car connected to the marine battery when the car is running...Make sense?Why can't you create a reference voltage, that's usually the procedure?
this is very good valueI have a circuit that energizes a relay at 13v
You can easily create a reference voltage from the battery supply either with a zener diode or even a fixed voltage regulator e.g a 7805. There are plenty of comparator based low-battery-voltage detector circuits on-line that may just require minor changes to suit your application. It is important that the circuit incorporates some hysteresis otherwise it will oscillate around the set-point as the battery voltage will rise a little when the load is disconnected.I am not totally sure I can't however the research I have done so far does not support it. I fly an extensive collection of RC planes and drones from micros to giant scale and have a 125 amp deep cycle marine battery in the rear of my Ford Flex to run my system to recharge all my LiPo batteries while I fly. This battery gets charged from my car however the connector in the car is always live and I fear that at some point I will be at the field all day and kill my car's battery. The voltage of the plug will only be at 13v when the car is running so if I have a circuit that energizes a relay at 13v I will only have the car connected to the marine battery when the car is running...Make sense?
Thanks. I will give this a try and let you know.View attachment 112509 Here, this will take the jitter out of it.
by Duane Benson
by Aaron Carman
by Jake Hertz