12V DC Motor with internal stop limit sensor

Thread Starter

rickinbay1

Joined Feb 27, 2021
4
I have a power seat motor that I am using for another application. I have the motor, momentary switch and related moving pieces. The motor contains the two expected power supply leads but also contains a three wire internal sensor that sits adjacent to a magnet on the motor. What I don't know is what that sensor actually is as well as to what and how I would wire it. My guess is that the momentary switch signals a polarity reversing relay to provide forward and reverse power to the motor and that the sensor reads a lack of rotation when the seat has reached it's limit, causing another relay (or another relay within the relay) to cut power. Would somebody be so kind as to help me understand any additional parts I would need and how to properly make this motor and it's sensor work as intended? I am not an engineer but rather one of those people that loves to tinker with things of all sorts. Thank you. I have attached pictures of what I have.
20210227_031830~2.jpg20210227_031722~2_resized.jpg20210227_031750_resized.jpg
 

LesJones

Joined Jan 8, 2017
3,476
The sensor will probably be a Hall effect sensor which as you suspect sends pulses back to to the BCM in the car cuts the power to the motor if it does not see any pulses for more than some pre-determined time. The simplest way for you to use it would be to use the pulses to trigger a retriggerable monostable with a suitable time constant. You will need to trace out the schematic for the sensor board to try to determine the connections to it. (Or measure the voltages with respect to ground on the connections to the sensor module with it in it's original position in the car.)

Les.
 

shortbus

Joined Sep 30, 2009
8,797
I think Les hit the nail on the head when he said, " sends pulses back to to the BCM in the car". Unless you have some sort of computer that will monitor and have a program internally to understand what the sensor is saying I doubt the motors sensor will be useful to you.
 

Thread Starter

rickinbay1

Joined Feb 27, 2021
4
Les, Thank you for taking the time.to reply. I was afraid that the answer would be as you stated. I pulled it out of a wrecking yard mini van of a model that was not familiar to me. At the time I paid no attention to the vehicle donor and only to the mechanism that suited my needs. Are there any other reasonable ways to bypass/omit this sensor and accomplish a stop limit? I've considered a micro switch to trigger a relay that removes power. I imagine that I would then not have power to go back the other way unless I wire up two circuts. As this will be in a well used woodworking bench, I fear the reliability of micro switches in a high dust and vibration environment. Your time and expertise is appreciated and valued.
 

Thread Starter

rickinbay1

Joined Feb 27, 2021
4
Shortbus, Thanks for your input and time. Adding something of this sort to a woodworking bench is already over the top so having it go any further just won't happen. I'll probably try and probe for some alternate "old school" solutions and if all else fails hook it up and let go of the switch at an appropriate time. The system does have a tiny bit of wiggle room through the use of rubber compression fittings on the shaft.
 

LesJones

Joined Jan 8, 2017
3,476
If you use micro switches you would need one at each end of the travel. If you take a correctly exposed and focused picture of both sides of the sensor board one of us MAY be able to work out the connections. I tried but failed to find any information on the Hall effect device on the board. Even if we work out the connections to the board you would still have to build something to detect when pulses stopped.

Les.
 

shortbus

Joined Sep 30, 2009
8,797
I'll probably try and probe for some alternate "old school" solutions
Don't quite understand the reason for not wanting a microswitch. They are made to work in dusty and vibration prone places. Another old school way would be to use a magnet on the moving part and a reed switch to control a relay.

Maybe explaining what you're tying to do/make would get some better ideas.
 

Thread Starter

rickinbay1

Joined Feb 27, 2021
4
Don't quite understand the reason for not wanting a microswitch. They are made to work in dusty and vibration prone places. Another old school way would be to use a magnet on the moving part and a reed switch to control a relay.

Maybe explaining what you're tying to do/make would get some better ideas.
I am building a workbench that has a fold down saw in it. When the saw is folded down, I will be inserting either a blank or a modular item such as a woodworking vice, sanding station et al. The inserts will be placed in like a leaf on a table. The section to the right will slide to allow insertion of the "leaf". I want to have that sliding portion operate with the electric seat motor and mechanism that was used in the vehicle it came out of. My reasoning is that it provides an effective way of tightly closing the top together without having to deal with multiple, hard to reach latches and because it is kind of cool.

I had the following criteria in mind. 1. Move slowly in a linear manner. 2. compact. 3. Does not slip from a given position. 4. Reliable. 5. Provides or works with a means to secure the top to the base in a way that slides but does not lift off. 6. Is reasonably cost effective. With those criteria, I could only think of a power seat from a car including the use of the tracks. Price $26.99 from Pick-n-Pull. What I didn't consider was that the system would talk to the vehicles ECU.

Micro switches are what I will likely go with although I am a bit stuck on the wiring and appropriate parts. I've attached a diagram of how it would likely wire without the micro switches. Here is where I am stuck. How do I add the micro switches? All of the micro switches I am finding are rated for acceptable amperage levels on AC, but very minimal on DC. Will I need to add additional relays to use micro switches and if so how would I then add that to the wiring? It seems that a diode is required for this application and I have no idea what kind of a diode to get. I did test the amperage load and with the motor under a near stall load, it was approximately 4.5A.

I've had a lot of fun (between the moments of banging my head against the wall in confusion) learning what I have so far but obviously have a long way to go.
Screenshot 2021-03-04 160550.jpg
 

LesJones

Joined Jan 8, 2017
3,476
You would just need to connect the limit switches in series with the push buttons in such a way that their contacts opened when actuated. Also you would probably need a diode with a higher current rating than a 1N4007.

Les.
 
Top