HB-25 motor controller

terahertz

Actually this would've been forum appropriate since others could benefit from the questions and answers.· In any event the part about the not starting has been covered before.· In the other case it turned out the starting pulse value was too close to the out of bounds value of the HB-25.· The other person simply needed to start with a value like 10 less as I recall.· Any value outside the 1 ms to 2 ms range will shut the HB-25 down.· It may be that the initial pulse you're sending is tripping that circuit.· I don't think it has anything to do with inrush current.· Try a lesser value and see what happens.

As for the noise...This is noticable only on some motors and on some only at lower speeds.· What you're hearing are harmonics from the PWM of the power.· The voltage is being switched on/off at high speed at a certain duty-cycle to control the speed.· You motor's coils may be generating just enough harmonic noise that you're noticing that.· Complete specifications are published in the documentation so you may be able to filter that somehow.· I hope this helps.· Take care.

Chris Savage
Parallax Technical Support

terahertz

Concerning the above question about not getting full speed unless it's ramped. If I try to start the motor at PULSOUT = 1000 it wont start. If I start it at PULSOUT = 800 and then do PULSOUT = 1000 it will easily shift to the 1000 speed. Not a big deal in my application, it just seems wierd.

Another question: For any value over 1000 I will either get a jerky motor output or nothing at all. I assume 1000 is too close to the maximum value possible, but according to my calculations [noparse]:)[/noparse] --->

From the HB-25 manual "pulse time can be 0.8mS - 2.2mS". but in a different section it says "1.0mS = full reverse, 1.5mS = neutral, 2.0ms=full forward"

The PBASIC syntax guide says: "PULSOUT units in duration for BS2 = 2uS"

So: (0.8mS)/(2uS) = 400 units minimum ?
(2.2mS)/(2uS) =1100 units maximum ?

I are confused, am I reading too much into this or too little?

Chris Savage

·· Okay, I probably should've covered this in my reply earlier, but it's good that now everyone will benefit from the response.· The HB-25 and the BASIC Stamp have a·source which they derive their clocks from.· This is what all timing is based on.· The BASIC Stamp uses resonator which is pretty accurate since it's external, however the HB-25 uses an internal oscillator and is subject to a bit more variance in the tolerances.

·· Usually temperature can affect the clock but there is a percent of accuracy for the clock rating and it may be that your HB-25 is just enough off, perhaps just from the BS2 that when you send the initial pulse it's outside the 1.0 ms - 2.0 ms allowed range.· Yes there is a slight overlap which is supposed to absorb some of the tolerance, but you may be just borderline and the pulses can be off by a % or so...That's probably why at 1000 it seems jerky.

·· I would try lowering my numbers down from 1000 say, by 5, until it stops jerking.· That will be the magic number you'll want.· Besides, at the top end of the scale there shouldn't be any significant changes in speed among different values.· Once you find the right number you'll find you no longer need to start at 800 then go up.· I hope this helps.· Take care.

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Chris Savage
Parallax Tech Support

terahertz

Thanks Chris,

I have the HB-25 doing exactly what I need it to do now.

Stand by... I'll be buying a Parallax 433Mhz transciever set soon·

Chris Savage

I'm glad to hear you got it operating the way you need.· Take care.

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Chris Savage
Parallax Tech Support