I need to some help in figuring out how to detect if a DC motor has stopped or jammed. The first thing that crossed my mind was some type of RPM sensor tracking the rotation of motor but that is going to be a bit difficult mounting the sensor in front of the motor. The other thing was temperature but that might be be a bit touchy dialing it in. Is there a simple way to do this by monitoring the current or voltage? Or is there some other simple way to do this? I need to do this to a couple of motors and they are not being controlled by an Arduino. I need to build something with an Arduino that can cut the motor off and send a digital low signal to a embedded controller motherboard. Any ideas?
Thanks
Russ
You could use the hall current sensor.
They are very low impedance. They are sensitive for magnetic fields by wires and transformers.
To be sure you would also need to know if it is rotating. Is is possible to attach something to it ?
It that is not possible in any way, you could attack an accelerometer to the case of the motor.
These are sensors for current:
A DC motor will draw maximum current when stalled, so current sensing is a reasonable way to sense this.
If you are controlling the motor speed with PWM then the stall current will depend on the level of PWM too,
so a single current threshold probably isn't good enough in that case.
Is there a simple way to do this by monitoring the current or voltage?
Yes a current sensing detector will work. I have used it many times in the past. One of the first was my under grad project in 1974 and the latest in my Harp player made from old CD drives.
Just a current sensing resistor and a comparator will do, if you are using PWM then put resistor and capacitor filter across the resistor.
In the below schematic for the open servo project you will see the use of a ZXCT1009FTA chip to measure current usage by the servo. Haven't used one, but it might be of interest.
I forgot to thank everyone for their help. I found a current sensor pcb on eBay for $3.30 A "5A range ACS712 module current sensor module" It hasn't shown up yet so I hope it works. I will give this a try and see if it works. eBay seems to have a bunch of little sensor pcbs that do different kinds of things for cheap.
Thanks again for the help.
Russ
ACS712 works quite well. You'll have to take a train of samples and do averaging. Today I have tested one that I have bought from Ebay, from 100mA to 5A resistive load, decent accurate for a low cost device, not outstanding but should work fine for your project. Think you should read the datasheet and see if there is anything related to inductive loads.