Current sensing buzzer for 12vdc motor

Thread Starter

thisistheusername556

Joined Feb 21, 2021
2
Hi all,

I'd like to have a current sensing buzzer sound when the motor pulls a certain amount of current.
The power supply is 12v 7A.
The motor is a car wiper motor - unknown statistics thus far.

I'd ideally like to add an adjuster so the buzzer would sound at different currents.
The use is to pull a weight, but buzz when the kg/f is reached.
It is necessary that this can be adjusted through a potentiometer or similar dial.

I have little experience in electronics but can follow the helpful guidance of someone from this forum.
I originally thought it might have only been possible with an arduino or similar, but there could be a simpler solution out there.

Thanks in advance!
 

Thread Starter

thisistheusername556

Joined Feb 21, 2021
2
It also hit me that maybe a current limiting circuit could work, with an adjustable limit being used. As long as it is still possible to buzz after the limit is reached
 

AlbertHall

Joined Jun 4, 2014
11,318
Possibly the simplest overload indicator, though not a buzzer, would be a car light bulb in series with the motor. They come in various power ratings so you could select one that gives you a good indication. Such bulbs have a very low resistance when the filament is cold but as the current rises, the filament gets hotter and the resistance increases. Thus the brightness of the bulb will tell you about the motor loading.
 

Marley

Joined Apr 4, 2016
411
Nothing digital about this! A current relay is an option. One zero cost option is to find a relay, remove the coil and replace with a few turns (say 10 to 50) of thicker wire. You would need to experiment to find the right number of turns.
Don't forget that when the motor starts it will take a peak current (only limited by winding resistance). So the relay will always close momentarily when the motor starts.
 

AlbertHall

Joined Jun 4, 2014
11,318
Nothing digital about this! A current relay is an option. One zero cost option is to find a relay, remove the coil and replace with a few turns (say 10 to 50) of thicker wire. You would need to experiment to find the right number of turns.
Don't forget that when the motor starts it will take a peak current (only limited by winding resistance). So the relay will always close momentarily when the motor starts.
Or, to avoid dismantling a relay, wind that current sensing coil around a reed relay (would probably be more sensitive too).
 

LowQCab

Joined Nov 6, 2012
597
If you would describe exactly what it is that you are trying to accomplish,
you would probably receive many solutions,
one of which will probably be very close to ideal.

What are you trying to measure ?
Are you measuring, Torque, or Linear Force, or Linear Pull, / Weight,
and on what, a Cable on a Drum, a Mechanical Linkage, etc.

Do you have to use a Wiper Motor ? and Why.

What Input Voltages are optional in this design ?
We know it's a 12 Volt Motor,
but is this a Car Battery operated device, or 120/240-VAC ?
.
.
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