DIY Cruise Control FAQ (2006-2010 Yaris)

[bobor]

Originally Posted by CTScott

Here's a pretty good intro to transistor switching.

http://www.kpsec.freeuk.com/trancirc.htm


Rather than switching back and forth, it may actually make more sense to put the microcontroller in between the pedal and the ECM. That way, the ECM samples the pedal outputs and then in normal mode, just emulates what it sees. Then, in CC mode it ignores the input and sends its own output.

The other advantage of this method is that you can improve the throttle response in normal mode (like the Blitz throttle controller does).

Thanks for the link, I will have a look on it. Your idea seems quite interesting, maybe I will change my plans a little bit and implement it that way. But I still have a feeling, that switching between DAC and pedal accelerator outputs is a little bit more safer.

Another idea came to my mind how to avoid switching delays with a relay. If I connect the DAC output directly to output line of the relay (to ECM) and accelerator pedal to one input of the relay (the second input remains unused), I can first set the output voltage on DAC and then switch the relay (cut the accelerator pedal line). On a switch back, the accelerator pedal is switched on first and then DAC disabled. This way, there is no voltage drop on signal line to ECM.

The only drawback is, that all time, when DAC is not in use (even just before switching off the accelerator pedal line, when DAC output is set) there is voltage from accelerator pedal to DAC output. I have no idea, if it can harm it in any way and what the impedance between DAC output and ground. If the impedance is too low, it can make a short connection and damage the ECM, that I obviously would like to avoid

And finally, do you have any idea, what size the input impedance of ECM could be?