Coldturkeys 1972 Datsun 240C

[coldturkey]

How do I turn it on/off and make it safe?

Well the safety thing will probably spark different opinions (onions).

The worst that can happen is that the accelerator locks on, which is really no different to a sticky cable. In theory your brakes should be powerful enough to overcome a stuck throttle anyway.

The problem with servos are that when you cut the power they remain in the last position. Fortunately my accelerator springs are strong enough to pull it back to "zero" if you kill the power.

The control is as follows:

• Turns on via an "on button"
• Turns off when either:
  • the engine stops
  • the clutch is pressed
  • the brake is pressed
  • the "off button" is pressed

I also set up a kill switch, which kills the power to the servo and microcontroller, (but obviously then cant drive the servo back to "zero").
 

[coldturkey]

The circuit:
I had problems initially with the Servo sapping all the available power out of the voltage regulator when it moved, causing unpredictable shit.

Im not really worried about the Servo not having all the power it needs, cause it still works sweet (3A should be plently).

But I ended up moving the micro onto it's own Vreg which solved all my issues.

 

[coldturkey]

The installation:

A couple of push button switches mounted under the steering column for the On/Off:

 

 

 

An indicator LED to tell me it is on (also useful as an output for debugging)

 

 

The base circuit (note this is before I added the 2nd Vreg):

 

 

 

So this is what it looks like now, after debugging etc. Wires everywhere.

Eventually it will live under the dash somewhere in that black plastic case.

[coldturkey]

The code

 

Well im not going to include my source code for a few reasons but if anyone is interested I am happy to discuss.

It took a fair bit of messing around. I really am pushing this micro to it's limits so a lot of braincells went into this, it really is more complicated then you think.

The guts of it is:

• it continously monitors speed 
• it continously drives the servo (drives it to zero when cruise is not selected).

Then when cruise is selected it captures the current RPM as a reference and runs PI control (may add D later) to maintain the revs at the reference setpoint.
 

[coldturkey]

The verdict:

It actually works pretty damn well considering.

 

It struggles a bit at the beginning of a hill, might lose 10kmph, and over the crest of a hill it might go 10kmph too fast. But modern cruise control isnt much better and the beauty of it is that I can modify my algoritim.

Adding the derivative PID term will probably help but cant be bothered at the moment.

 

 

Hmm so the total cost of components was about $80. The thing to program the micro was about $200, but I have wanted one for ages anyway and will use it for many more wacky and zaney shit.

Im not sure how to demonstrate that it works, apart from a big thumb's up and bring on the 8 hour drive to hamner!

Discussion Thread/Tell me im crazy

[coldturkey]

 

Mechanical fuel pump was leaking oil and rather then get a new one out of the states or a second hand one thats just going to fail again I have upgraded to an electronic one.

 

The temporary blanking plate I made really needs to be thicker, as you can see I had to space out the bolts on in as they didnt have enough thread. But it's all I had/could be bothered with at the moment.

 

Im quite impressed with the quality and service of the "fuelflow" pump though, works well, simple, clear instructions and came with everything needed and no BS, plus made in NZ with a 2 year warranty. Awesome.