internals of a control module for 12vdc power steps

[downtowndarrel]

Now I'm looking at this system:

The 1987-1988 Fieros use a new headlight system, which is also used in 1987 and later Firebirds. This system has two motors and an electronic module which controls their operation. Here's how it works:


There are only two wires connected on each motor. Green(/black) and grey(black), and they connect to the output (4-pin connector) on the headlight control module. The other connector (5-pin) on the module is the inputs. The two red wires are the continuous power from the battery through two fusible links, as in the 84-86 system. The white and yellow wires from the headlight switch are also the same, as is the ground.


Everything on this system is done inside that little electronic control module. When the headlight switch is on, it trys to run the headlight motors in the up direction. When it is off, it tries to run them in the down position. Rather than having seperate wires for each (and ground), as the previous system did, this one reverses the flow of current across the wires to turn the motor in the opposite direction. Also, rather than having an internal limit switch inside the motor, the control module actually senses the current being used by the headlights. When there is a sudden rise in current draw, as happens when the motors can no longer turn, the module shuts off the power to the motors.

 

[4pyros]

Everything on this system is done inside that little electronic control module. When the headlight switch is on, it trys to run the headlight motors in the up direction. When it is off, it tries to run them in the down position. Rather than having seperate wires for each (and ground), as the previous system did, this one reverses the flow of current across the wires to turn the motor in the opposite direction. Also, rather than having an internal limit switch inside the motor, the control module actually senses the current being used by the headlights. When there is a sudden rise in current draw, as happens when the motors can no longer turn, the module shuts off the power to the motors.

One problum with the current sense solushoin is the movment could get stuck before it hits the end and stop.
Could this be allowed in your applicashoin?

 

[downtowndarrel]

One problum with the current sense solushoin is the movment could get stuck before it hits the end and stop.
Could this be allowed in your applicashoin?

No obstructions to prevent it from reaching the stopping point. Even if there was, yes it would stop, but because of the circuit design, it would be ready to retract back to the other stopping point. Imagine an automotive power window that has a safety feature; your arm is in the window as it goes up, the window starts to clamp your arm, the motor starts to load and stops. You can no longer put the window in the up position, but you can put it in the down position. Once it reaches the down position (stop) the motor loads and stops. It is now ready for the up position only, until it reaches the full up position (stop) the motor loads and stops. It is now ready for the down position only. Ect. ect. ect........

 

[Jaguarjoe]

A cheap microcontroller, a cheap pair of photo diode/transistors, and cheap LED's to sense the endpoints, a cheap pair of MOSFET drivers, and cheap current sense resistors (if you don't to use photodiodes) would set you back about $15 or less. The enclosure would cost more!

 

[KeepItSimpleStupid]

You never did answer the questions in #20.

We seem to be talking in circles because of the large amount of unknowns. Initially we were under the impression to reverse-engineer a step controller.

Voltage is only one aspect. The current of the motor matters too. If a fuse can work as a safety, all the better. So, we can go from a fuse to a light curtain there.

What is the reason for 12 V. Car or battery operated?

What do you do if the power fails completely?

Darn if you want the equivalent of an automatic curtain opener I made in 1975, so be it. I used a 24 VAC motor that inherently slipped if overloaded so the chain fell off. I glued aluminum wedges to the back of the curtain rod. I made an adjustable bracket to mount a limit switch, The motor was spring loaded and used ladder chain to move the curtain. This is when I had access to a machine shop.

There was a open/close center off switch and a manual/auto switch. The automatic mode came from a 120 VAC autonomic timer. The power came from a wall wart.

It got the job done.

I never did get a round to try to make use using a DC motor without limit switches and the ability to count pulses. This would have been difficult to do in the mid-80's.

I would have liked a (tap wile not moving) and it would continue in the direction it was moving unless at a limit. If at a limit, it would reverse. If it was moving and it was tapped it would stop. If double tapped it would stop, change direction and continue to the limit.

Autonomic time based control and and a flux sensor would be tried. Naturally at this point, i would consider networking and integration into a home control system.

Just don't have the time for it. A good supply of suitable motors that didn't require much machining would be really nice.

Se there, I described a couple of projects.

A couple of approaches already surfaced. A slip clutch? AC? DC? Fixed limits?

Encoder based with overcurrent sensing. FRAM memory for limits.

How would you do a network of these things? A central controller?

The reason for my lengthy post is we have nothing to go on and nothing to brainstorm with. We don;t even have any idea of the size, weight, torque required etc.

I prefer to "think out loud" even with unworkable initial ideas. That' the way a good design starts. We can a, b, c, or d.

A good because of something. B won't work at all because of something. This works for 1, but not 1000.

There is sometimes nothing wrong with a limit switch. But if we have to worry about a baby's hand, let's get that out in the open.

So, please answer the questions asked or at the very least create a formal specification. Which can include:
Givens:
Must have:
Wish it had this ability?
Would likes:

etc.

Otherwise I'll start asking 20 questions and start with "Is it bigger than a breadbox"?