Long.... Project overview: Converting JRC 1800CP Marine Radar 18" radome to open array configuration.
I had to upgrade the tiny unipole stepper drive for the antenna to a much more robust bipolar motor with an aux 2 amp driver board.
The antenna board has an onboard driver clocked to turn the antenna at
32 RPM. I'm using the clock input to this driver to drive the aux driver board. However.... The difference between bipolar and unipolar drives is unknown to me, inasmuch as I don't know if the clock will run the bipolar motor at the proper RPM. There is no feedback on the original stepper, and I don't know if the antenna board might be able to 'goose' the clock if it sees less or more than 32 RPM from the heading sensor on the antenna (hall sensor that triggers once per revolution). If not: I will need to implement a micro controller board to use the clock as input for enable only, and output the correct clock for the aux stepper board. I will need help with this. I managed to blow up the ST200 board because I fabricated a heatsink that was connected to both the L298 and 5V reg tabs. Blew the L298. While I wait for a replacement IC, I'm stewing on this. Ideas? Opinions? JR
Home Page: http://www.seanet.com/~jasonrnorth
The issue isn't the unipolar/bipolar difference, the issue is the number of poles of the motor (which for steppers is usually specified as steps/revolution). If the two motors are the same, and if the new board is clocked the same, then you're probably OK.
One generally uses steppers _because_ one wants to avoid using feedback, so this isn't surprising. Most likely the antenna board resets a reference to zero when it gets the index pulse, and increments it by
11.25 degrees each pulse. If you're _really_ unlucky the antenna board will pop a fault each time the index is missed.
What kind of help? Technical? Psychological? Aesthetic?
If you're unlucky enough to not have a 32 step/rev motor, but you do have some easy multiple thereof then you just need a micro that'll issue one step for every two of the input, or two steps for every one input, or something like that. If you're unlucky then you may need something like a PLL-based frequency synthesizer that'll generate the correct number of steps for your motor from the number given -- if it came to this it could even be something like a 4049 and some counters, although you could do it in a micro.
If the driver board you have supports microstepping it'll be easier to make a mis-matched motor work.