I'm working on a project at work and I have to sync two BLDC motors to run at 10,000 rpm. At the moment have two IC's, these are - (ST)L6229N and a (Texas)UC2625's. which I can use for driving a single motor for now. I just need a little help
I have this idea to control the rpm over a PWM signal? Or say square wave...??
Basically, though I think I might be over complicating this? I could use a 555 timer or the arduino to generate a control signal for rpm control..
I'm looking at using the tach outputs from two BLDC Drive IC's as RPM signal inputs to send an IC or the arduino to analyse and work out the differentials in RPM's. Then the outputs would be sync control signals sent back to the BLDC IC's so as the two motors will run in perfect sync. "So if one of the motors drops in RPM slightly the other will compensate and drop to match and the IC will then bring the RPM back up, that goes the same if the RPM spikes the other motor will match RPM and the IC will drop the RPM down to the set input signal".... All this can be analogue too as the IC's can use a pot to contal RPM..
Is there an IC that can input and output the signals in a manner? I'm sure the arduino can do this?
I hope this makes sense...
I've only skimmed it, but http://docs-europe.electrocomponents.com/webdocs/0daf/0900766b80dafb9c.pdf on page 14 describes how to setup up a closed loop speed control for an individual motor. It's not entirely clear whether/how you could use the actual speed of each motor as the target speed of the other (and I suspect it would be easy to get something that just hunts wildly as each motor chases the other) but since the target speed seems to be set as a voltage, you may be able to figure something out using analog electrics. Hooking that up to an external PWM controller might lead to unwanted interactions between the internal and external PWM controllers, so I would try to work with the internal controller rather than try to override it with an external controller.
Thanks for this, I'm just trying get a better over all idea of this and to look at the bigger picture of speed and sync control rather then looking at one item/topic but, looking at it. The L6229 it is easier to work with... I've been looking at PLL IC's too.
I could use a Mater/Slave setup, but the problem there is, there would be a small amount of delay in reaction time if one of the two motors fluctuated. After the "system" reacted to compensate, the end result of rpm's would be in sync but one of the motors would be out by X amount of degrees, this would be very undesirable.. I'll look into analogue electrics.