Designing a Programmable DC Motor Controller for a BMW Convertible Soft Top

[Dsrq]

Hi my name is Bruno !
I don't really know about circuit board hardware ect ect
But i have a pretty good knowledge about Dc and Ac , relay , ohm law ect ect ! And I am learning fast !

There is my problem !

I have a Bmw Convertible with a soft top controlled by an electronic box that communicate whit the central body controler of the car via Data link wires. The module just stopped working , there is a problem between the body controler module and the soft top module and its probably going to cost more than 1K to fix it ! ( bmw parts are exepensive )

So i decided to try to find a way to built my own Soft top module controler using a kind of programable dc motor contrôler ! Its probably the simple thing on Earth for you guys but for me its chineese.

The car have 2 different Dc motor ( looks like wiper motors ) One for opening or closing the softtop , and the other one to open and close the cowl panel (compartment where the roof is stored ) There is a lot of micro-switches and a Hall sensor that can be used for the cowl panel . The softtop is pretty heavy to get out of the cowl panel , so the motor seem to use around 20 to 25 amps on 12vdc but the cowl panel motor should use only 10A to 15A.

The button that controls the top is a 2 way momentary button , you need to hold it up during all the closing process and hold-it down during all the opening process

I found a pretty good video on youtube of the action of the soft top , to help you guys to understand how its moving.

http://www.youtube.com/watch?v=Nqnar55EeQc&translated=1

And there is a PFD document about how the top is working and what each micro-switches are used for with a description of each sequences of the top !

http://www.unofficialbmw.com/e36/exterior/e36_convertible_adjust.pdf

My top is the Semi-Automatic version , and i don't care about windows going down by it self before the top moves , and i don't care about the speed sensor security that cuts the top if the car is moving more than 3mph.

Sorry for my very poor english ! I learned it by my self !

Thx a lot
Bruno !

** If you need more information, just ask them here ! ill try to give you answers !

 

[famousken]

Seems like that would be a pretty big project for someone with little or no experience making electronics. Watching the video, it looks like the motor for the top runs for about a second, stops, then the motor for the hatch opens, stops, and then the top goes down and the hatch closes. Then when you put the top back up, it needs to do it all over again, except in reverse. There is no way to make a simple circuit to the two motors in that way, with the exception of a microcontroller, but then you will have to learn how to write code and program it. I think there is a reason BMW charges $1000 to fix it lol. Honestly, I would say it would be cheaper and easier to fix the one you have, most likely, it was just the motor driver that went out. Did you make sure to check the obvious things first (Fuses, Switch, etc)?

 

[Dsrq]

I checked out on the internet for micro-contolers ,, but it was all for stepper motors ! I didn't found any micro-controler strong enought to take the Amps from the Top motor. But programming a module with a serial port ou usb port dosent scrare me ! I just want to know which one i should use , or if someone here know a good user friendly micro-controler. Everything works with micro-switches so the programming will be mostly base on moving the motor in X way util mirco switch is pressed and/or time delays.

I want to buy something that is arealy made ! There is a lot of Teenagers making small robots making sequences by them self ! I guess that using 2 DC motors in a sequence should be not so hard !

 

[famousken]

Well since you seem ambitious, I would recommend either the Basic Stamp or PIC controller. The Basic stamp is a lot more expensive ($50) but you can get one of their development boards which come with software, microcontroller, development board, a book with a ton of projects to get you started, and a few components. There is also a development program you can get called Flowcode that uses a simple flow chart style of writing code with if/then statements. For example, if you had pin 1 connected to one of the microswitches on your top, and pin 2 connected to whatever you are using to drive your motors, you could say IF:pin 1 is high, Then pin 2 high for 5 sec., etc. Oh ya, you can't directly drive a motor with a microcontroller, you need what is called an H-Bridge, which will give you both forward and reverse motion. You could even make that with MOSFETS if you want to, they are pretty simple.

Here is a link to Parrallax, which should have everything you should need, and they also have a forum which can be quite helpful.
http://www.parallax.com/

H-Bridge:
http://en.wikipedia.org/wiki/H-bridge

Using MOSFETS in an H-Bridge:
http://www.armory.com/~rstevew/Public/Motors/H-Bridges/Blanchard/h-bridge.htm

 

[story645]

if someone here know a good user friendly micro-controler.

The arduino boards are picking up a reputation for being just that, but I don't think they're anywhere near powerful enough for your task. Start off small, and prototype everything so that you don't break some very expensive equipment.

 

[skeptic2]

I don't believe you need a micro-controller for this, in fact I think you could do it with a number of relays which you say you're familiar with. It looks to me like all the functions are RS FlipFlop (RS for set-reset) operations which can easily be done with relays.

Do you know how to make an electrically self latching relay and how to release it with the contacts of another relay or switch? The switches would provide the current to activate the coils and the relay contacts would both the logic functions and provide the power to the motors.

Find some 12 V relays with multiple contacts such as 3PDT or 4PDT that fit into sockets and wire them to provide the operation you need.

 

[Dsrq]

OK i think i will do it , with very small low amp relay for my controls that will trigger the H-Bridge with higher Amp rating. And put everything in the same box with the dual h-bridge for both Dc motors. They suck around 20a total both motors.