motorcycle cooling fan, below 35 mph

Would be pretty simple with an 8 pin microcontroller. Set up an external interrupt to read the speed pulses. Set up a digital input to monitor the temp switch and a second digital input to monitor ignition power. One digital output can power the fan(s) (through a transistorized output). Power the circuit from battery power so you can power the fans after the ignition has been shut off. You could then write the logic to make the controller do whatever you want. Dealing with the speed pulses is a bit challenging for a novice, but it really isn't that bad once you understand the concept. You basically will use a timer that resets every time the external interrupt is triggered. The timer will provide a "time stamp" that you can compare to a preset value. If the time stamp is longer then the preset then the time stamp is a lower value (the lower the speed the longer the pulse will be). When dealing with speed signals you'll need some code to detect when the signal is gone (ie bike not moving) to prevent overflowing the timer register and possibly getting undesired operations. All the digital inputs and the timer to keep the fans on after ignition is shut off is typical "novice" tasks. Kevin Pierson

KPierson wrote: Would be pretty simple with an 8 pin microcontroller. Set up an external interrupt to read the speed pulses. Set up a digital input to monitor the temp switch and a second digital input to monitor ignition power. One digital output can power the fan(s) (through a transistorized output). Power the circuit from battery power so you can power the fans after the ignition has been shut off. You could then write the logic to make the controller do whatever you want. Dealing with the speed pulses is a bit challenging for a novice, but it really isn't that bad once you understand the concept. You basically will use a timer that resets every time the external interrupt is triggered. The timer will provide a "time stamp" that you can compare to a preset value. If the time stamp is longer then the preset then the time stamp is a lower value (the lower the speed the longer the pulse will be). When dealing with speed signals you'll need some code to detect when the signal is gone (ie bike not moving) to prevent overflowing the timer register and possibly getting undesired operations. All the digital inputs and the timer to keep the fans on after ignition is shut off is typical "novice" tasks.

Cool, thanks, that invites a little confidence, I apreciate it. I'm rather persistent once I get my mind set on something. It may take a long time But I will fgure it out eventually. Once I research enough info to be comfortable with these tasks and I get the components together I may check back in for some assistance.

Just swap any two wires, it should work then.

fabrik8r wrote: I don't know that much about Six Sigma either, just that the basic premise is maximizing efficiency.

Classic! Nor do most companies that I've worked with despite them "implemented" Quality, TQM, 6-sigma etc for decades. Ha - my last couldn't even version track or date their documentation (guess who recruited a former GE executive? He was probably attracted by the bonus scheme...).    But 6 sigma is not about efficiency, it is about quality. It is IMO simply reverse engineering of Demings principles (ie, from stats and back to stats). A key attribute of 6σ is research. Sorry I confused the fan above 35mph. I was thinking along the lines of why fan below 35mph if it isn't hot. One engine desire is to reach operating temp ASAP. Another is not to over-cool. But your research should have uncovered that. As for the PIC, try to estimate the number of program lines you require. That often set the minimum PIC "size".

Ok, just read a little on the PICAXE site,  and watched some Utube vids, not even close to understanding how to do what I want to do, but I do see that it is totally possible and relatively easy once I gain an understanding. I'm already thinking of ways to use this thing to do other stuff. Before I get to far along, my bike has its own CHT sensor in the front cylinder, can I tap this signal for the thermal trigger instead of using a thermal snap switch to ground like my original set up? I just see a lot more potential for custom adjustment of the on/off temps. I'm considering a possibility of adding individual temp sensors to control the front and rear cylinder fans independently. ,So will the 8 pin PICAXE still be big enough to incorporate all the elements of my switching function, if I use the OEM speed and temp signals, or if I use two independant temp sensors for each cylinder?Just swap any two wires, it should work then.

What type of sensor is it? What does it's output look like? I am not familiar with PICs but a typical 8 pin AVR chip has 6 usable I/O pins and two pins for power and ground. To run the fans independently you would need: CHT1 CHT2 VSS Fan Out 1 Fan Out 2 Ignition Assuming you have 6 pins available for I/O you should be able to pull it off with one chip. If your CHT is an analog voltage back you'll have to make sure you have two AD converters as well.Kevin Pierson