Revisiting TOD discussions

[bobmumgaard]

There has been alot of TOD discussions on this forum and I am revisiting the TOD controller idea.

First, if you want some back ground, start here:TOD discussion I know its alot of reading, but who knows, you might learn something new and useful.

Ok, this topic has been dormant for awhile. I see many new names on this forum that probably haven't seen this discussion and it is a useful insight into how the VX does its driveline magic.

Reviewing:

• TOD control sends a PWM (50Hz) signal at 14V to transfer case
• Front and rear driveshafts are mechanically linked by a ball/ramp mechanism, this coerces them to rotate at the same speed
• The electronic soilenoid applies resistance and thus transfers torque to the front wheels
• PWM varies from ~5% to ~95% depending on what is called for ("2wd" to 4hi)
• No, the TOD won't let you do burnouts, and tone proves the same for a dyno run
• This type of mod will let you do 4hi and the slide around on ice as if in 2wd
• mbeach has a prototype going using readily avalible stuff (analog)

There is also a thread that follows mbeach's progress:
Knob or switch voting

The reason I am revisiting this is because I need a project. And I think I am going to do a digital control scheme of this TOD thing.

Until now we have all been figuring out how to trick the TOD outputs using analog components (relays, 555 timers, poteniometers and what not). Instead I think I am going to attack this using a microprocessor.

I propose to use a Basic Stamp II to act as the PWM and control the lights. The reasons for digital are:

1. We can eliminate the signal and voltage drift that mbeach was getting from his analog setup.
2. Control of the display lights becomes much easier.
3. A knob with set values works well here (and this was winning the voting).
4. A change to the settings would only require changing the switch leads instead of redoing the whole circuit, so if you just wanted a single switch with 4hi it would be simple.
5. Ease of installation you would only need to cut 5 wires, plus power (however, read on)
6. I have a digital controls class that I need a project for and we have to use the BSII! (alittle selfish, I know )

Downsides:

1. Cost, Instead of pennys, were talking like 80 bucks for the chip, and voltage regulators and what not, this could go down to 30 or up to 200, it all depends on what I come up with.
2. Construction. Probably forget about putting this together youself, unless you've had experience building simple microcontrollers. It would probably have to be mostly a kit to be of much use
3. Serviceability: If it broke, troubleshooting it could be hard (think troubleshooting a check engine light without any diagnostic tools)

I just brought this back because I am starting to investigate how it could be done. I have a cicuit designed and a basic program scribbled out. The next few weeks I will be collecting components. Hopefully I will have a working model set up by the end of April. (otherwise I fail the course )

If anyone has an extra TOD display sitting around or knows where to get one I would be much appreciative.
Also, I don't think we ever figured out how to post an excel file. mbeach has alot of experimental info on this.

If anybody has anything to add, feel free. I've been thinking about this TOD thing alot (despite the lack of posts) and hopefully I can come up with something just in time to miss the snow

bobmumgaard

[Triathlete]

I plan on doing away with the TOD all together. Plan on going with a manual T-case.

[VehiGAZ]

Go Bob go!!! I was in contact with mbeach recently about this, and he mentioned that you two had sort of hit a wall on the project. I still want this mod and am wiling to pay for the parts and someone's assembly of it.