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Old 12-02-2004, 04:36 PM   #26
Captain Bondo
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Sounds like you have it sorted now, but something like a 5 volt version of a MAX232 chip would simplify supply issues. Many versions of the 7805 can be picky about supply voltage as well- the project I mentioned earlier was powered by the 12v batteries form the power wheelchair. Something with a charge pump might be more reliable. Just a thought.

There are also lots of chips out there that contain multiple op amps on a single substrate. 2 pins for rail voltage shared by all of the op amps on the chip simplifies things too. Just another thing to clean up some of the implentation.
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Old 12-03-2004, 12:23 AM   #27
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Damn did this turn into a lot of reading.

Hey man, tell us what you want to do w/ the PIC, and we'll get you some code help.

I know x86 a lot better, but I can try.

EEs unite, eh?

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Old 12-03-2004, 01:06 PM   #28
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Well, you can take a look at the code if you'd like, but I'm fairly certain I'm going to be changing microcontrollers to something a little more advanced. For instance, the A/D conversion for our project is done by a separate ADC0838 IC that the PIC communicates with serially.

Something with an onboard ADC and the capability to actually do some PID control would be ideal. Right now it seems like the PIC16F84A is really best for just P control, possibly some D control, but certainly not suited for I control.

Then again, the alternative is to get some op-amps and just make an analog PID controller, that way I don't even have to worry about the code aspect.
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Old 05-11-2018, 02:25 AM   #29
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Seeing as this 14-year old thread is pretty related to a project I have in mind, and there were several EEs and EE students.... Let's try some CPR?

I want to make a crude TCS for my 740 w/LH2.4.
I want to build/program (or pay someone to make half of it for me) a PIC or Arduino that can ground the TPS "idle" switch using the ABS sensor in the driveshaft when the derivative of the speed of the driveshaft exceeds some value TBD.

Seems like the people in this thread know a lot more about it. Seeing as I only want this one project and don't really want to learn that much about Arduino or PIC controllers... anyone want to help me code or tell me if it's even possible?
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Old 05-11-2018, 11:06 PM   #30
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I skimmed the earlier part of this tread about making a DIY EBC, and I'll just say no comment.
-------
For making your own TCS, I'll give you a few minutes of off-the-cuff comments. As you've described it, it's not a particularly big nor difficult project.

First off, this is all at your own risk. I have no idea how well LH2.4 will behave if you close the idle switch while accelerating briskly at, or near, WOT. It may nicely do a decel fuel cut, it may drop into limp mode, it might ignore the idle switch and toss a diag code, it might do a partial fuel cut resulting in severe knocking and damage. Your first experiment should be connecting up a pushbutton switch to the idle wire and trying it out. Let us know what happens to your engine.

(The idle switch goes to both the EZK and ECU - there's a chance that triggering the idle switch for just the EZK, or just the ECU, might behave better than triggering both. You'd need to cut some wires to try it out.)
------------

For the TCS parts, try an Arduino Nano 5volt version (the small one with a mini-usb). This should be OK working off of battery voltage up to ~14volts. The $2.50 chinabay ones are fine but you'll need to find the USB driver for the Chinese RS-232 converter chip (the expensive versions use an American FTDI RS-232 chip with much better driver support).

You'll want to add a diode in the Arduino power wire so that it can't back-power anything in the car if you plug your laptop. 1N4001 or similar.

The speedo in the LH2.4 cars converts from the rear differential VR sensor to an open collector Vss signal to the ECU. You can tap into this signal between the speedo and the ECU for the Arduino, but you'll need a couple resistors to drop the voltage from 12v Vss levels to 5v levels for Arduino. 47K and 100K should be about right.

To drive the idle switch wire to ground, you'll want a basic NPN transistor and a resistor in an open collector configuration, 2N2222 or 2N3904 and 1K should work.

You'll want to add an LED so that you can visually see when the TCS is active.

A plastic box to put it in, and a 5ish pin connector, for convenience, should finish up the hardware parts.

For code, it needs to monitor the Vss signal - 12 pulses per axle rev, which should easily be within the capabilities of an Arduino (just avoid doing divide operations). If you need something more than a simple proportional control algorithm, there's a very nice and well documented PID controller library available for Arduino - see link
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Old 05-12-2018, 08:11 PM   #31
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Quote:
Originally Posted by bobxyz View Post
I skimmed the earlier part of this tread about making a DIY EBC, and I'll just say no comment.
-------
For making your own TCS, I'll give you a few minutes of off-the-cuff comments. As you've described it, it's not a particularly big nor difficult project.

First off, this is all at your own risk. I have no idea how well LH2.4 will behave if you close the idle switch while accelerating briskly at, or near, WOT. It may nicely do a decel fuel cut, it may drop into limp mode, it might ignore the idle switch and toss a diag code, it might do a partial fuel cut resulting in severe knocking and damage. Your first experiment should be connecting up a pushbutton switch to the idle wire and trying it out. Let us know what happens to your engine.

(The idle switch goes to both the EZK and ECU - there's a chance that triggering the idle switch for just the EZK, or just the ECU, might behave better than triggering both. You'd need to cut some wires to try it out.)
------------

For the TCS parts, try an Arduino Nano 5volt version (the small one with a mini-usb). This should be OK working off of battery voltage up to ~14volts. The $2.50 chinabay ones are fine but you'll need to find the USB driver for the Chinese RS-232 converter chip (the expensive versions use an American FTDI RS-232 chip with much better driver support).

You'll want to add a diode in the Arduino power wire so that it can't back-power anything in the car if you plug your laptop. 1N4001 or similar.

The speedo in the LH2.4 cars converts from the rear differential VR sensor to an open collector Vss signal to the ECU. You can tap into this signal between the speedo and the ECU for the Arduino, but you'll need a couple resistors to drop the voltage from 12v Vss levels to 5v levels for Arduino. 47K and 100K should be about right.

To drive the idle switch wire to ground, you'll want a basic NPN transistor and a resistor in an open collector configuration, 2N2222 or 2N3904 and 1K should work.

You'll want to add an LED so that you can visually see when the TCS is active.

A plastic box to put it in, and a 5ish pin connector, for convenience, should finish up the hardware parts.

For code, it needs to monitor the Vss signal - 12 pulses per axle rev, which should easily be within the capabilities of an Arduino (just avoid doing divide operations). If you need something more than a simple proportional control algorithm, there's a very nice and well documented PID controller library available for Arduino - see link

Dude, you're awesome! Thank you.

Two things:
First I would be turning this off any time I'm driving aggressively or fooling around. It's strictly a "not paying attention CYA" countermeasure. I totaled my 740 I'd had for 12 years driving on a crappy/worn highway late at night while tired. That's the kind of thing I want to avoid in the future.

Second, I had this idea because I misrouted a single TPS wire too close to the EGR and eventually experienced mysterious injector cut-out at highway speeds. Nothing much happened, it just assumed I let off the gas and shut off the injectors until the wire lost contact with the ground. It was pretty annoying to figure out. I never had any codes thrown at all.
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