servo/stepper controlled velocity stack
tillertracker
Posts: 1
I don't know where to look but this seemed like a good place. I need help designing a stepper motor that is controlled by engine RPM. It's for a single cylinder racebike with 12volts available. The signal is once per revolution and I need the servo (or stepper) to start moving around 9000rpm and be done by 13000rpm. I can handle the physical construction but I need help with the electronics. Even if you can just point me in the right direction I would be most grateful. Thanks.
Comments
The stepper motor is likely to allow you to use more of your microprocessor time to manage sensing RPM and you can get a 12 volt driven·stepper to exact specs for your project.· Mechanical attachment could be a direct·drive rather than having sloppy linkages or gears involved.·Take a look at standard NEMA stepper motors as these are industrial. {Hobby servos·very handy for learning and small robotics.···But with plastic gears and dependency on constant update to maintain position, I suspect they might wear out very quickly on a motorcycle.}
If the BasicStamp works well, fine.·It certainly is a good place to start.·But the SX-28 programed in SX/B might give your even better control due to inherent additional speed and one protoboard could handle most of the additional electronics hardware you require·unless you·need to drive the stepper through some larger darlington transistors or MOSfets with heatsinks. It costs less too.
How are you going to sense RPM?· Either·you do so·from a mechanical source with something like a hall effect sensor·or electrically·from the ignition·output itself.· If you can safely sense when the magneto fires, that is probably the easiest interface - just tap into a wire somewhere.· A hall effect sensor might work·attached to the outside of·an ignition wire and be safely isolated. Alternatively, since the ignition is thousands of volts, you want to find a point to tap the magneto before it ups the voltage and you want to divide the voltage down to a safe level for the BasicStamp to sense.· Putting in an opto-isolator between the BasicStamp and the modified·magneto output would protect the BasicStamp from any goofs or miscalulations as it can be quite hard to measure high ignition voltages for design purposes.·
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
PLEASE CONSIDER the following:
Do you want a quickly operational black box solution or the knowledge included therein?······
Post Edited (Kramer) : 2/14/2008 9:15:52 AM GMT