Electronics Guru Needed!

Does any know anything about controling stepper motors?

I want to experiment with a sequential shift or paddle shift to actuate the shifter cable in my Moke. The Moke shift pattern from top to bottom is a straight PRN123D.

The way I see it I could use:
- a servo
- solenoids
- a stepper motor.

The stepper motor options seems the best solution for accuracy of positioning of the shifter to avoid selecting two gears at once and the ability to "hold" the position with a decent amount of torque, so it does not easily bump into the next gear.

My requirements:
- I want controls or buttons, no Laptops or PDA's on the dashboard to control it! This is a Moke, not some "Fast and the Furious" wank car! So the controller and driver must be stand-alone. But I don't mind using a laptop to set it up initially.
- Must work on 12v (controller, driver and stepper) so there is no additional electrical requirements.
- Increments between gears (steps) must be "set and forget". I don't want to have to reprogram it every time I turn it on.
- I don't want to spend more than about $200ish on the project.

Nice to haves:
- Some limit switches would be nice, so I can't attempt to select beyond D or P and break something!
- An output to the dashboard to display what gear I'm in. I might simply use microswitches and LED's for this but an LCD display would be excellent.

I've been surfing eBay and Googling for stand-alone controllers and drivers for stepper motors and I've learned a bit. It seems like what I want to do is achievable, but I'm still a bit confused about unipolar and bipolar motors and which drivers/controllers I need.

I've currently got my eye on a high torque unipolar 12volt 1amp stepper motor which would seem to be suitable but I'd like some feedback before I buy one.

Obviously if this works I'd be happy to share the results with the Mini community so other owners of the ultra-cool AP auto box can benefit.

Cheers,

_________________
Brett Nicholson
Greendale (near Ballan) VIC.
1971 Morris Mini Moke
1966 Austin Mini
1965 Morris Mini Traveller
1973 LR Series 3 88
2007 LR Freelander 2

Oxymoron anybody?

Seriously though, I have looked into this in the past. I wanted the shifter to be completely gone from the floor, and controlled from a push button setup and buttons on a steering wheel.
On my travels I did find a kit designed for a hot rod, using a large programmable actuator.
Large is the key word, as there wouldn't be enough room to stash the thing under the car. It would have to sit in the dash or boot and run via cable.
Next thing is even bigger, designed for truck transmissions. Forget that too.
In an effort to go smaller I looked into a large servo unit (large for a toy anyway), but the control system to accurately drive it to 7 positions made things difficult, and reliability would be sacrificed.

In the end, the most reliable system would be a PLC system, but that'll break the bank.

I abandoned the auto shifter idea when common sense kicked in. As you said, it's not a fast and furious wank car.


The whole electronic thing makes the system complicated. The best way I worked out how do do it is also the cheapest, though function is restricted. Knowing there are two things in life garanteed to be reliable (things over-engineered and things overly simple), my way used two central locking actuators to select gears. They get rigged upto a ratchet system to make a simple pulse and retract operation move the transmission one click one way. The pulse function is a simple push button. The second actuator runs the system the other way.
It could work with one of those actuators too, but stroke and power becomes a limiting factor.


As i dig up more info and remember stuff, I'll let you know.

Yeah, I hear you Harley. But I still want to give it a go.

I've looked at motorbike sequential shifters and they may be a possibility but the price is extremely off-putting.

Drag car systems for B&M rachet shifters and similar only allow upshifts so are useless for the street.

The idea of using central locking motors had occurred to me, but I was unsure if they would produce enough torque. I have a couple of spare ones so I might have a play with them. Any info you have would be appreciated anyway, especially diagrams or pics.

_________________
Brett Nicholson
Greendale (near Ballan) VIC.
1971 Morris Mini Moke
1966 Austin Mini
1965 Morris Mini Traveller
1973 LR Series 3 88
2007 LR Freelander 2

This the sort of thing I was thinking of using to drive the stepper motor.

http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&rd=1&item=160256687061&ssPageName=STRK:MEWA:IT&ih=006

_________________
Brett Nicholson
Greendale (near Ballan) VIC.
1971 Morris Mini Moke
1966 Austin Mini
1965 Morris Mini Traveller
1973 LR Series 3 88
2007 LR Freelander 2

The average central locking motor (ie what $10 at jaycar will get you) has around 1.5 kg or torque, though heavy duty ones go up to 6kg (cost more though).
The units move quite violently, (fast and powerful) which is why they're good for the job, provided the ratchet system is built well enough. Any slop in connections and joints will wear quickly, making gear changes sloppy.

There's other things to consider into the design too.
If you don't need 1-3, the you can get away with four positions on the shifter.
If the system is used in a car for competition, then it will certainly get a workout,
so it has to be built to be tough. Linear actuators and most gear reduced stepper motors would provide a slow shift,
and that has to be though of too. Perhaps a cable operated column shifter would be better? Anyway I'm sure you've given some thought to those things.

Turbo, injected, 1415cc, stroker, twin cam ,16v, bmw cyl head-ed, paddle shifted, sequential automatic anyone??? Obviuosly with air con,remote doors & windows & motha f`ker mp3 player & dvd system, on air bag over hydrolastic suspension.

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

I know absolutely nothing regarding this subject lol....but what about sussing out the ol S model Valiant push button auto setup.....how were the done?

The idea is to use it for motorsport. The shifter is too short for me to reach with the harness on, so I have to compete in "D". I want to be abe to shift manually through the gears when I want or simply click enough times to reach D without removing my harness.

I have considered lengthening the shifter stick, but it will be too close to the dash in P. To move it closer to the seats I would have to remove the handbrake. So it's either relocate the shifter on the dash somehow or come up with another way of actuating it.

I had wondered how slow a high-torque stepper would be. It's looking more like the central locking motors are the go.

EDIT: MadMatt, I like the sound of the first half. But a Moke has no doors and a DVD and air bags would just weigh it down.

_________________
Brett Nicholson
Greendale (near Ballan) VIC.
1971 Morris Mini Moke
1966 Austin Mini
1965 Morris Mini Traveller
1973 LR Series 3 88
2007 LR Freelander 2

We looked into doing this for a manual. I would go with Harley's remote located cable operated idea.

But these look way cool!!!!!

http://twistmachine.com/shopping/index. ... fc112b71c6

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But he's thriving and striving and hugging the turns.

Why not use a pneumatics air cylinder with a reservoir in the car somewhere and a valve e.g. like an arb airlocker compressor and valve and just flick a switch to control between say 2nd and Drive using a air cylindere.g. back and forward.

Just an Idea.

You could do that, but I'd prefer a system that actually works, and doesnt run out of steam after three gearchanges.

Easy fix arb difflock compressor cheap and lots of air.

Just had a thought for the more technical minded and engineers.

A bolt on box for remote or rod changer which uses one of the systems discussed to manipulate the normal rod input. dont know if that possible or if its worth it but would be a great little kit to sell as a bolt on plug in set up for those interested.

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Enjoy Chris

Nice idea, but I'd rather something electronic as I don't want to weigh the Moke down with an ARB compressor.

_________________
Brett Nicholson
Greendale (near Ballan) VIC.
1971 Morris Mini Moke
1966 Austin Mini
1965 Morris Mini Traveller
1973 LR Series 3 88
2007 LR Freelander 2

The arb compressor and valves would only weigh about 1/2 a kg and the air cylinder about the same as they are all aluminium.

that way you could wire it up so when you press one button it pushes and another button it pulls.

Diff lock compressors are small and are made to fit in tight spaces about the size of 2 coffee cups and the valves screw on to it e.g. it has its own tank.