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I am back at trying to control the frequency of an SM1 AC inverter drive due to the fact that I never got it going the first time. However, this time I would like to use an Arduino. The manual for the TB Woods SM1 AC inverter is here.

As I understand it, the best methods for controlling the frequency are PWM or Rs-485. My questions for each are as follows...Note: As stated before, I'm no expert, but I love to learn.

PWM

I think this lacks the detail I am looking for. (0-60Hz in 1/10ths of an Hertz.) However, how would I hook it up to the SM1? A schematic would help. Do I use terminals M0-M5 (page 11 in the manual)?

RS-485

Again, do I use terminals M0-M5? I can't seem to find any setup instructions for sending commands like run, stop, go to 55 Hz, etc... Does anyone know what a sample Arduino code would look like in this configuration?

My application is fairly simple. A warper (spool winder) is running several threads onto a spool. As the spool becomes more full, the motor speed needs to be decreased constantly so the tension on the spool remains constant. The inverter drive runs the motor and an Arduino, hopefully, controls the speed of the motor through the inverter drive.

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  • \$\begingroup\$ Arduino defaults to 8 bit resolution for PWM. Depending on the exact microcontroller on the board, there are couple PWM pins connected to 16 bit timers which would allow for higher resolution, but you need to program the timers yourself. Check the datasheet for your particular ATmega. Then all you need is a linear PWM to (4..20mA) current converter. You'll have to check the input impedance for the inverter to know from what minimum voltage it can be driven. \$\endgroup\$ – jippie May 23 '13 at 6:36
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Based on a quick scan of the manual, it appears that the only means of remote control of the speed/frequency is by the analog input, either 0 - 10 volts or 4 - 20 mA.

I don't see any mention of RS-485 or PWM control (except that PWM may be used to generate the 0 - 10 volt/4 - 20 mA signal).

Please note that I have not used this device - I just quickly scanned the manual. I suggest that you carefully study the manual to see how, or if, you can control it remotely.

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    \$\begingroup\$ Page 26:Parameter 2-00 explains that the frequency is set via RS-485 when its value is set to 4. The next page mentions PWM under the heading 6.4.4 Parameter 2-03... I have studied the manual a lot, but still have yet to understand. \$\endgroup\$ – Robert Fleming May 23 '13 at 15:12

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