Making Program to control G320

[grasshorse]

Hello,

I've been toying around with an Arduino board for a project I've been working on and I thought, wow I wonder if this thing could communicate with a Gecko drive. I've been looking at it and the documentation from the Gecko site and think that I have a figured a bit of it out, but I wanted to bounce it off the walls of the forum and see if anyone else has greater insight. From what I can tell there are only three control lines into the Gecko. Right now this is all speculation.

1. DIR
2. STEP
3. COMMON

DIR: I believe that DIR is a boolean 1 or 0. If 5 volts is sent to the DIR line it is equal to 1/True/CW and the motor will turn clockwise. If no voltage is sent to the DIR line then it is 0/False/CCW and the motor will turn counter-clockwise.

2. STEP: Really need help with this one. I see at the bottom of the spec sheet for the 320 that "step pulse frequency" is "0-250kHz". Does that mean that the number of steps is sent to the controller as PWM? For instance the motor is idle, then a frequency of 100 Hz is applied to the line and the motor will make 100 steps? I don't have an oscilloscope so I can't check for myself.

3. COMMON: I believe that this is just a 5vdc current.

Like I said before, any insight is greatly appreciated.

[TarHeelTom]

I'm not the expert on this, but as I understand it, each time you change the state on the "step" line, the Gecko will command one step.

Question is, how many steps do you want, and in which direction?

[MattTheNoob]

That's pretty much it. Feed it one step command, and it'll send voltage to your motor until it gets one encoder pulse back... at least that's the simple version. So if you want your motor to turn for 1000 encoder pulses, you'll send a thousand step pulses to the drive at a frequency corresponding to the speed you want your motor to go.

The drive continuously calculates its error, or the difference between the number of pulses you've sent it, and the number of pulses it's gotten back from the encoder. Based on the PID parameters you've set (with the pots), the drive will increase the voltage to the motor proportionally to the error. See the documentation about drive tuning and appropriate dampening.

[grasshorse]

I see. So if the pulses come in faster than the drive is moving, the drive is stores the pulses in a buffer and accelerates the motor. Inversely, it will then taper off the movement, as it clears it's "buffer" so to speak. That is really interesting and very helpful! Many,many thanks!

Steve

[Larken]

No, there is no buffer.
There is a step counter and an encoder counter within the drive. Your incomming step pulses increment or decrement the step counter.
The servo drive tries to make the encoder count the same as the step count by turning the motor shaft. (the difference between the two is called error)

Also you don't use PWM to output step pulses. You need to just toggle one output line (high to low then back to high) to make 1 pulse. Yes the direction line (high or low) determines which direction the motor will turn.

Larry K

[grasshorse]

Thanks for your post Larry. OK, so the program sending the steps to the Gecko drive needs to control how many steps it sends per given period of time to control the speed of the motor.

Any specific speed the steps need to be sent? Is that what the 0-250 kHz means? I tried just toggling 5vdc off and on with a push button. Didn't work, but I have a feeling the motor I'm using is not working right. 5 vdc as well?

I assume that the encoder counter within the Gecko drive does not send feedback, so any GUI that is created is basically displaying what was sent to the Gecko drive.