PWM/HPWM Stepper Motor Controller

[DavyJones]

Mark you obviously have experience with this controller (I hope) I am stuck with the connections to ena-, ena+, dir-, dir+ and pul-, pul+
I was assuming ena went to - and ena+ went to + dir - to - and dir+ to + and pul- to - and for pul+ I connected that to the pic to send the 1 and 0
I'm trying to find an example on the web haven't found one yet i am sure I am wrong as the stepper does not spin

Mark, Never mind I got it... the 12F683 did not like ROTOR=1 and ROTOR=0 I needed to high ROTOR and low ROTOR
it's spinning now going to try and make it smoother and faster mess around with those a bit

[DavyJones]

Mark, so I have been messing around with the time and seems to work pretty smooth. I am running 12v power supply and have the controller set to 1.5a and 1600 pulse per revolution. It is very smooth and easily see how to adjust the timing to speed it up or slow it down. One thing at these settings there is not much torque. I can grab the spindle and dont have to hold to tight to get it to not turn and growl at me. Motor says it is rated at 2.8amps but doesn't list the voltage but many people are saying 24v is optimum and can run up to 48 volts. If I up the current on the driver will that give me more torque or do I have to also up the voltage. At this configuration I doubt this will move my parts on the converyer once I have it built.
Thanks

[mark_s]

You are making a lot of progress. Increase the current setting, just monitor the motor for excessive heat while experimenting. 12 volts is on the low side for what you are doing. For small projects I have used old laptop wall supplies. They are usually around 18v at 3amps. You can find them in the thrift shops for cheap.

[DavyJones]

Mark thanks.... I was looking at power supplies online last night. Do switching type power supplies present any problems for the stepper motor? I see quite a few cheap ones online and some even have 24v/12v/5v output which would be perfect for my project without have to have any type of step down converters. 24v for stepper, 12v for solenoids and 5v for pic and accessories. I've probably pitched to many old pc's with perfectly good power supplies in them over the years whats wrong with me.... I just re-read your post I've got boxes of old laptop power supplies around here I just found an old dell one that is 19v 3 amp

Thanks
David

[DavyJones]

I know we are getting a little off topic with regards to PIC's and Picbasic I hope that's ok my project overall is dependent on the PIC and the programming needed.

Sorry about the noise in the background my wife was watching TV.


I'm thinking of something like this to power the overall project which needs 3 different voltages.
Then the step down for the other 2 both are relatively inexpensive.

[DavyJones]

I was thinking ahead a little bit and for now my testing has been to test the solenoid activation and stepper motor each by themselves. Now they will need to work in conjunction with each other wherein the stepper motor will need to continue to move (and keep the conveyer belt moving) at the same time the solenoids are cycled on and off. There will be gaps in between the items I will be spraying. I am sure I can complete this using 2 picks, one to control the solenoids and another to control the stepper motor. I would add an interupt test to the stepper pic so after the last row has passed I can stop the stepper anywhere in it's loop. I don't see anyway around this since everything is single threaded (at least thats what I've always thought) and branching from the stepper routine would add timing to the stepper loop which I think would through everything out of whack. using 2 pics is no problem and getting them to talk to each other not going to be a problem either because I think I'd just need to use interupts either with an INT function or just checking the state of a pin at some point.

I wanted to know though if anyone has ever used one of these and/or if there is any support in Picbasic for this dsPIC33CH. It's funny the example they choose to show what you can do with this is pretty close to what I am needing this for.

[HenrikOlsson]

David,
You've done a great job so far!
As you might know the torque of step motor falls off as the speed increases. Increasing the drive voltage counteracts this drop in torque. Doubling the voltage pretty much doubles the speed at which the motor stalls due to "overload". This is within reason of course, too much will only result in heat in the motor and if you do get what you need out of it with whatever voltage there's no real gain in increasing it even further.

One rule of thumb from a drive manufacturer (Geckodrive) is that supply voltage to the drive could be as high as 32*(sqrt)L where L is the inductance in mH.

Lets say your motor has an inductance of 2.8mH, then the drive voltage can be around 50V. Obviously the drive has to be rated for the voltage as well.
I don't know any details on your particular motor but I'd certainly try a 24V supply or even a 48V if you still need more speed.

Slow speed torque is highly dependent on the current setting of the drive.

Finally, it's hard for a motor to start "instantly". You'll be able to reach much hiher speeds by ramping the speed up/down.

If you generate the step pulses in hardware, like with the CCP module (as with HPWM ) then you have all the time in the world to figure out when to fire the solenoid(s).

Nope, PBP is for 8-bit PICs only, no 16 or 32bit devices.

/Henrik.