stepper motor and CMB16D DC Controller

[dave carlstedt]

Is it possible, or has anyone tried to use a stepper motor controlled by the CMB16D DC Controller. It seems it would work. Perhaps, not as simple as using an arduino, or something similar.
I have an idea, and hopefully the CMB16D DC Controller will save me programming and integrating another board outside of a LOR product. I know it will be a bit awkward to program, but if it will do it,===that is all I need,
thanks ahead of time.

[Ken Benedict]

I saw one on Youtube somewhere; they were using a 4-line stepper (12 volts I think) and using 4 channels of a LOR DC controller board.

Firing off channels 1+2, then 2+3, then 3+4, then 4+1, then 1+2, etc. And the opposite sequence for reverse rotation.


You didn't say how many phases your motor has, but the sequence should be similar; it's just a circular chase sequence in LOR Sequencer. If you run your show off a PC, you could probably setup sub-sequences for the different rotations and speeds. That would make your programming very easy; kinda like having macros.


If using a stepper less than 12 volts, the DC board needs an external 12vdc supply.

If using higher voltages and 4 amps per channel, you might want to minimize the inductive kickback with a low voltage snubber circuit (resistor and capacitor in series, across each phase). That would be a big stepper for sure.

[dave carlstedt]

thanks. I don't have the motor(s) yet, but do plan on under 12v. Not only due to board limitations, but cost as well. They are pretty cheap when under 12v. and, at this point, motor power is not an issue. Now, I can continue with the experiment...

[-klb-]

You are looking for a unipolar stepping motor. A 4 pole unipolar motor usually has six leads. Phase 1 & 3 share a common, and 2 & 4 share a common. In this case, you will be using them as common positives.

You will also need 4 fast diodes rated for at least the motor current, and 4 power resistors sized for the application. Let's say you find one rated 2v and 500mA. I would go with a 6 V power supply, which should run the card, but not supply any accessory power.

The resistors need to drop 4v at 500mA, and safely dissipate that much power. (4=6-2). So 8 ohms, (4/0.5) and rated >2 W (0.5*0.5*8). The idea here is that the resistor should limit the current to the rated motor current. The diodes get installed reverse. Biased in parallel with the motor windings and resistors, to dissipate the energy stored in winding inductance, rather than causing voltage spikes.

Sequencing should actually be 1, 1-2, 2, 2-3, 3, 3-4, 4, 4-1 etc.

All calculations subject to lunch break napkin sketch corrections later. Peer review welcome.

[Max-Paul]

I might be all wet, but thought that the minimum voltage for the brain side of the card has to be 9VDC. Then the other side can go down to either 3 or 5VDC. But it has been a year sense last time I read the manual.

[Denny]

Max-Paul wrote:

I might be all wet, but thought that the minimum voltage for the brain side of the card has to be 9VDC. Then the other side can go down to either 3 or 5VDC. But it has been a year sense last time I read the manual.

I believe on the CMB16 that you can use a wall wart to power the card if the voltage on the "brain side" of the card is not at least 12 volts. I don't have one in front of me now, but I think that is correct. Then you can use whatever voltage you want, up to the maximum, on either side of the card. Would have to look at the instructions to be certain though.

[dave carlstedt]

A minimum of 12v. is needed to at least one side (1-8) is required to power the board in and of itself.

[hdracer]

Anyone interested in buying a http://store.lightorama.com/servodog.html
New never used?

[dave carlstedt]

KB
are you suggesting this additional circuitry because, and only because of the inductive circuit? rather than resistive?

If so, it is not necesary, as LOR has assured me the board (with mosfets) can handle the motor...unlike the CTB16 board, which is only safely used for resistive loads. (Triacs)

I am only going by what I was told. If this sounds incorrect, please clarify. Thanks.

[-klb-]

The diodes are to prevent voltage spikes when turning off the current to the motor. I've seen Dan post that they were a good idea when pointed out before.

Depending on how fast you want the motor to turn, how fast the current ramps up in the coils may be important. Lately, this is normally done with a chopper drive, using much higher voltage than the motor coils, to push current up quickly, then regulate it at the designed motor current.

The older way to do it was to run the motor coils and resistors in series, with a higher than motor rated voltage. This way, the inductance of the winding sees full voltage when current is zero, and voltage to the coil falling off, as current ramps up to rated current.

Also, how fast is fast will depend on how many steps per revolution on the motor. LOR can only sequence to 1/100th of a second. If you are half stepping, and have a 200 step per revolution motor, the fastest rotation speed is 4 seconds per turn.