Electronic PRNDL selector possible?

quantum · 03-05-2009, 12:17 AM

Anybody ever replace an automatic transmission gear selector with an electronic version of some sort?

I saw this cool pic of a car online (maybe off this site?) with an iDrive-type knob for a gear shift control. I think I have the "mechanicals" ironed out, but the electronics have me a little confused.

The mechanical part would most likely be a linear actuator of some sort, attached to either the shift cable itself, or even maybe the shifter "stalk". The car has a floor console with floor mounted shift. Attaching it to the cable would be an option. But I think I may be able to do it more simply by leaving the existing shift mechanism in place, hacksawing the stalk down a few inches, and mounting the linear actuator to it. This also would allow me to shift it manually if the actuator or one of the components fails.

Browsing the web I found these and these. The first one says it is programmable, and I think that means you could move it back and forth a fixed distance based on a signal? That would be a crucial component, precision movement. Correct me of I'm wrong, help understanding this part is what I could use the most.

Having the whole thing controlled by a PC is SO not an option, since the risk of a PC meltdown or reboot could be annoying at best and deadly at worst. So it would need to be an independant, simple system, perhaps with a redundant system in place.

What kind of hardware / controller would the knob need to be? I was searching for a controller that would have defined stops (7) and require a little force to turn, more resistance than a volume knob, and less than a fire hydrant.

Oh, and a nice finishing touch would be tying in a nice alpha numeric gear indicator from Dakota Digital.

Suggestions? Ideas?

quantum · 03-06-2009, 11:00 PM

*bump*

Bugbyte · 03-07-2009, 10:37 AM

Well, you can control a linear actuator with either a PIC or something like the Arduino board.

The PIC has the advantage of being hardware and thus not dependent upon whether the PC is working or not. The Arduino can be programmed from the PC but isn't as compact as the chip.

A linear actuator is basically a motor with a screwjack in it. Some of them have feedback via a potentiometer. You could measure the resistance of the potentiometer on the Arduino board and have it correspond to the various positions of the gear selector.

CraziFuzzy · 03-07-2009, 10:49 AM

The other, even more reliable option, would be a pot feedback on the linear actuator, a bank of resistors a multiposition switch, and a comparator. Basically, each position of the switch would produce a 'desired' resistance (which is used in a voltage divider). This voltage is compared to a matched divider using the feedback pot on the actuator. If less than, move the actuator one way, if greater than, move it the other way. comparitors would be set up with a slight offset so there is a deadband between pos and neg differences, preventing 'hunting'.

This is basically turning the linear actuator into a servo, with preselected positions. This is done when building full-sized RC cars (a really fun, but expensive hobby)

quantum · 03-07-2009, 12:18 PM

Now we're talkin' fellas!!! You think its a cool idea or stupid idea?

What type of know or rotary controller could be used?

OK, short of being spoon fed, where can I learn out how to put these various options into play? I never really programmed a PIC or Arduino board before, but would love to study up on it since it looks like it opens some cool doors for this and other projects.

Is it a software thing, a coding thing? Are there tutorials or even sample code I can download and modify? Samples of projects similar (or not) to this anywhere online?

Once again, many thanks for guidence.

Bugbyte · 03-07-2009, 01:48 PM

Go here for more info about Arduino.

CraziFuzzy · 03-07-2009, 04:20 PM

Quote: Originally Posted by quantum

Now we're talkin' fellas!!! You think its a cool idea or stupid idea?

Not really stupid, but to be any point, it would really have to have some sort of practical reasoning as well. The only way I would even think about doing this would be to eliminate the space that is wasted by the shifter, in the incredibly important next to leg space. Would have to put a decent compartment, or specialized controls there, or SOMETHING that makes this worth it. In most cars, the actuator could actually be installed below the floorboard, and all that space could be gained.

Quote: Originally Posted by quantum

What type of know or rotary controller could be used?

Any rotary multi-position switch would work. You don't really need a 'rotary controller', as you don't care about analog positioning, just 5 discrete positions.

Quote: Originally Posted by quantum

OK, short of being spoon fed, where can I learn out how to put these various options into play? I never really programmed a PIC or Arduino board before, but would love to study up on it since it looks like it opens some cool doors for this and other projects.

Is it a software thing, a coding thing? Are there tutorials or even sample code I can download and modify? Samples of projects similar (or not) to this anywhere online?

Once again, many thanks for guidence.

I would be careful getting in over your head on something as important as the gear shift. This is something that really should be very well engineered, and you would still want to have some sort of ignition lock as well.

quantum · 03-07-2009, 11:24 PM

Quote: Originally Posted by CraziFuzzy

Not really stupid, but to be any point, it would really have to have some sort of practical reasoning as well. The only way I would even think about doing this would be to eliminate the space that is wasted by the shifter, in the incredibly important next to leg space. Would have to put a decent compartment, or specialized controls there, or SOMETHING that makes this worth it.

That is exactly why I was kicking this around, to make that area of the console a nice little command center like the pic above. Safety and all that jazz being #1 priority of course.

Quote: Originally Posted by CraziFuzzy

I would be careful getting in over your head on something as important as the gear shift. This is something that really should be very well engineered, and you would still want to have some sort of ignition lock as well.

I totally agree, which is why so many questions. Definitely not something I will take lightly if I decide to do it. It would need to be basically bulletproof, or at least as dependable as any other system in the car. Also why I want to take the carPC out of the equation.

I want to keep is simple, so my goal would be to hacksaw off 3-4" of the gear shifter stalk so it sits under the face of the floor console. This way the neutral saftey switch, revers lockout and press brake to shift functions still work as designed from the factory. The actuator would simply move the stalk (instead of moving it with my hand) is all I am trying to accomplish.

BTW, I actually have PRND321, so I would need a 7 position switch I guess. Something like this maybe? http://www.allelectronics.com/make-a...-SWITCH/1.html it was the only one O found.

CwF · 03-07-2009, 11:47 PM

Aren't alot of modern autos already fully electronic with dummy mechanicals?

corvettecrazy · 03-08-2009, 12:44 AM

Don't forget your shifter has the button for reverse lock out. Unless you plan to completely eliminate that, you may need to be thinking of a second actuator.

quantum · 03-08-2009, 10:47 AM

Quote: Originally Posted by corvettecrazy

Don't forget your shifter has the button for reverse lock out. Unless you plan to completely eliminate that, you may need to be thinking of a second actuator.

Fortuantely in my case the shifter handle doesn't have a button to move it. Pressing the brake allows the shifter ro move, no button press needed. That makes life a bit easier.

turbocad6 · 05-03-2009, 01:45 AM

Quote: Originally Posted by CraziFuzzy

The other, even more reliable option, would be a pot feedback on the linear actuator, a bank of resistors a multiposition switch, and a comparator. Basically, each position of the switch would produce a 'desired' resistance (which is used in a voltage divider). This voltage is compared to a matched divider using the feedback pot on the actuator. If less than, move the actuator one way, if greater than, move it the other way. comparitors would be set up with a slight offset so there is a deadband between pos and neg differences, preventing 'hunting'.

This is basically turning the linear actuator into a servo, with preselected positions. This is done when building full-sized RC cars (a really fun, but expensive hobby)

crazifuzzy, that is a great solution & something I would love to learn more about. is this something that can be bought or does it have to be built? any info or advice to persue this would be much apreciated, I'm looking to do similar to quantum & just started a thread here I'm sure if I could develop something like this to work it could benifit me & quantum & perhaps others who could benifit from gaining very valuable & usable & otherwise wasted space. any help or advice would be great

User Name		Remember Me?
Password