Questions About a Motor Protection Circuit

Thread Starter

K_Fun

Joined Jul 19, 2020
11
Hey guys, this is my first post on this forum, so sorry if it isn't organized correctly or in the right sub-forum. I've got a few questions about this circuit for use in preventing over-rotation of an electric motor actuating a butterfly valve. Firstly, can anyone explain to me how exactly it works? I have a vague idea of how it operates, but I'm a mechanical engineering student so circuits like these are a little bit out of my wheelhouse. It's operated by a 3 position momentary toggle switch. You click it in either travel direction for just a moment, and it returns to its central position when not being touched. Secondly, how exactly would I go about modifying it for a different motor it was not calibrated to operate? The original motor was destroyed, and the replacement only actuates the valve about 1/3 of the total distance it should travel. So I'm left with either open, or partially open. 20200719_103534.jpg20200719_103538.jpg20200719_103543.jpgThank you for any and all help.20200719_103534.jpg20200719_103538.jpg20200719_103543.jpg
 

crutschow

Joined Mar 14, 2008
25,247
Those are nice pictures of the device, but unfortunately that tells us little about how it operates.
So as a sudent in mechanical enigieering, It's rather like someone showing you outside pictures of a machine and asking how does the inside work.
We would need a circuit diagram for that.
 

Thread Starter

K_Fun

Joined Jul 19, 2020
11
Those are nice pictures of the device, but unfortunately that tells us little about how it operates.
So as a sudent in mechanical enigieering, It's rather like someone showing you outside pictures of a machine and asking how does the inside work.
We would need a circuit diagram for that.
Unfortunately I can't supply those, as they're likely proprietary to Granatelli Motorsports, which is where the device comes from. A few Google searches reveals nothing. I can't find anyone that has tried to reverse engineer this thing, hence why I'm asking.
 

Thread Starter

K_Fun

Joined Jul 19, 2020
11
I'd also like to add that there is an audible "click" from the device when the motor reaches the end of travel, which leads me to believe it is a thermistor of some kind. I think the stop function is actuated by some specific measurement of resistance, which doesn't correlate to this motor.
 

AlbertHall

Joined Jun 4, 2014
10,226
Maybe, just maybe...
That J260 component is a current shunt in series with the motor. The circuit detects the excess current when the motor reaches the end of travel and turns off the motor.

If this is the case then maybe (again) the new motor draws more current than the original.
 

MaxHeadRoom

Joined Jul 18, 2013
21,191
It is a 8 pin IC, but looks as though the circuit originally used a 14pin, according to the trace.
I thought maybe it was a micro.
Max.
 

Vytas Klyvis

Joined Dec 5, 2016
58
The clicking is most probably just the relays engaging.
Looking at the cables, I presume there are two power supply cables, two motor cables and three cables for your rotary switch. I am not seeing any kind of feedback device. Im assuming the valve is being driven by a regular dc motor.
Looking at the current would be the most easy way to determine if the motor has reached its position, but it could also be a timed event. So it would just assume that the motor has reached its position after x time.
You could trace the entire circuit to find out, as it doesnt look that complex.
 

Thread Starter

K_Fun

Joined Jul 19, 2020
11
The clicking is most probably just the relays engaging.
Looking at the cables, I presume there are two power supply cables, two motor cables and three cables for your rotary switch. I am not seeing any kind of feedback device. Im assuming the valve is being driven by a regular dc motor.
Looking at the current would be the most easy way to determine if the motor has reached its position, but it could also be a timed event. So it would just assume that the motor has reached its position after x time.
You could trace the entire circuit to find out, as it doesnt look that complex.
Yes all those wire designations are correct, and its a DC motor running on 12 volts. Im almost positive that its not a timed circuit, as I'm pretty sure the original motor took longer to cycle than the amount of time that the current motor runs for
 
That would follow if it is current based and the new motor needs more current than the original.
I agree, most likely it is looking at the current. If you could find out the current motor current and the old motor current, you could maybe fool the board by replacing the current shunt for one with a lower resistance.
 

Thread Starter

K_Fun

Joined Jul 19, 2020
11
I agree, most likely it is looking at the current. If you could find out the current motor current and the old motor current, you could maybe fool the board by replacing the current shunt for one with a lower resistance.
Testing the original motor is out of the question, it was completely mangled by a speed bump. The motor actuates an exhaust valve on a car that is pretty low to ground. How would I go about testing the current of this motor? I have a multimeter but one of the prongs delaminated. I tried repairing it with solder but I don't think it reads accurately anymore.
 
Testing the original motor is out of the question, it was completely mangled by a speed bump. The motor actuates an exhaust valve on a car that is pretty low to ground. How would I go about testing the current of this motor? I have a multimeter but one of the prongs delaminated. I tried repairing it with solder but I don't think it reads accurately anymore.
You could try measuring the resistance of both motors. This would give an indication of their power.
 
Top