Cruise Control advice needed

gdr

I would like to build a cruise control for a semi truck but have no experience with micro-controllers etc. Is it possible to do this using the basic stamp? Will I need signal converters (ADC and DAC)?

The truck has a vehicle speed sensor (VSS) on the drive shaft that puts out 3260 pulses per mile. The throttle position sensor (TPS) feeds the engine control module (ECM) a 0 to 5 volt signal.

So basically I would like to replace the signal from the TPS to the ECM with a programmable cruise control signal from the micro controller.

Any suggestions or advice as to hardware products etc. that I will need to do this would be greatly appreciated.

Thanks and all the best!

kwinn

First a caution to make sure the cruise control shuts off as soon as the brake pedal is depressed. I would suggest a SPDT relay that connects to the ECM and switches between the cruise control and the TPS.

At 60mph 3260 pulses per mile works out to 0.906 pulses per second. Even at 90mph that is only 1.358 pulses per second so I would suggest measuring time between pulses to determine speed. A time count based on a frequency of 180Hz or more should be adequate for an accurate speed measurement. The output voltage to the ECM can be produced by a DAC or filtered PWM signal from one of the pins.

Not very familiar with the basic stamps but I think they should be able to handle it.

gdr

Thanks for the input. Will also need a clutch switch and an option to let the Throttle over ride the cruise control.

Anyone care to recommend BS1, BS2, or Propeller? Thanks!

erco

It's a simple job, processor-wise; you could probably get a BS1 to do the job about as well as a Prop IF you don't need a fancy interface or lots of extra I/Os. The most important thing is your actuator mechanical hardware, that is, what pulls your throttle linkage. It needs a failsafe design to ensure that when something goes wrong that it returns to the closed throttle position to avoid a runaway condition. A big servo would be a BAD choice for this. Typically, it's an engine-vacuum-actuator (bellows) with several electric valves in it to apply vacuum (open throttle) or vent to atmosphere (close throttle).

I installed a ZEMCO aftermarket cruise control on my 4-carb, 4-speed '67 Corvair many moons ago, similar to this one: http://cgi.ebay.com/ebaymotors/VINTAGE-ZEMCO-UNIVERSAL-CRUISE-CONTROL-KIT-NEW-BOX-_W0QQcmdZViewItemQQhashZitem35ac41033aQQitemZ230523208506QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

The unit worked quite well. It unit used a vacuum actuator and an ECS (electronic clutch switch) which compared engine RPM to axle halfshaft speed (magnets on halfshaft, coil mounted on nearby bracket). Note that unit sold for $73. Might be worth looking for one like that; the legwork is all done for you.