Created Date: January 31,2001

Created by: THOSEY

Hello all,

Currently I am rebuilding an older bucket printer. My counterpart and I have decided to chuck the A/B products and go with a dl-240, 9 slot base, E-com, and an High speed counter card to tell machine speed. I sized my op interface today for the 10 " Ez-touch and left enough space for a few neccessary buttons like the E-stop. Got home and started thinking about where are the pots going to go for the drives and such. http://forum1.automationdirect.com/board/eek.gif

Then I thought well I will just get a analog output card to drive the A/B inverter, "this is the same one that has always drove it and we are a company that likes to save money ", and chuck all those pots and go totally digital. Now the question! How can I control from the plc the other Dart drives that take a potentiometer for speed control?

Thanks

Created Date: January 31,2001

Created by: Russ

Now, that's a really good question!

I 've been saying for a long time now that the first DC controller company to make a competitively priced unit that can accept a MODBUS or other protocol signal instead of the analog / pot system will clean up the market! The trouble is, I think the DC drive companies don't understand digital electronics well and are having a hard time getting away from analog circuits.

For simple cases, I 've replaced the pot with a couple of "fixed " pots and relay outputs to give 2 to 8 preset speeds. Of course, this solution may not be a good idea depending on how your speed controller feels about the pot being swapped or disconnected. You'd have to use your own judgment and consult the drives manual or manufacturer.

I believe Dart has an isolated voltage board that can be added on some chassis models - you should check the catalog or http://www.dartcontrols.com .

Dart's newer RG610 & RG620 accepts both the standard pot and analog voltage in. It also has a serial control port, but it's their own protocol. I 've used the 250's ASCII out to setup & control the RG620, but personally never felt comfortable with it due to the inability to get ASCII reliably back into the PLC for command confirmation and drive feedback.

Also worth checking out is KB Electronics ( http://www.kbelectronics.com/ ) They have several new voltage control options for their drives, so they may have a solution to your problem. In particular, you may want to look at the KBSI-240D Signal Isolator, the KBEP-240D Electronic Potentiometer or the KBET-240D Frequency to Analog Follower. They can all be found on the page at: http://www.kbelectronics.com/catalog/speedcontrol.html . They have a few drives that accept pulse/voltage/current control in addition to a standard pot that might be a good fit with your application if complete drive replacement is an option.

Hope this helps!

Regards,

Russ O 'Rourke

Created Date: January 31,2001

Created by: Tom Jenkins

I don't know about the Dart drives, but the A/B and most inverters have the ability to take contact closure and either use them to go to aa number of pre-set speeds, or in many cases use a contact closure to increment the drive speed up or down in small steps, say 1/2 Hz at a time, just like using the Up/Down arrows on a keypad. You could then use the analog input to monitor actual speed and adjust as required. A few will even let you pre-set the speed from the drive keypad and control start/stop only from remote contacts at your PLC.

Cutler Hammer's SV900 drive and Robicon drives, among others, do offer Modbus RTU control, and allow you to put in a hardwired E-Stop to override the comm link commands.

Created Date: February 01,2001

Created by: THOSEY

Thanks to all that Replied.

I went with the 8 channel analog out to the inverter, and ordered from dart the isolated option cards for the 5 dart drives. The inverter takes a 0-10v and the darts take a 0-5v signal. Since you can only set the card as a 0-5 or 0-10v card I was thinking of setting it to 0-10v and only allowing the channels for the dart to go up to 5v. The card is a 12 bit or "decimal 4095 " for 10v then "decimal 2047 " should be my max for the darts to obtain the 5v.

Thanks again

Tim Hosey

Created Date: February 04,2001

Created by: Mike McClanahan

Another option that we have used to replace pots with a 4-20 ma input where it is not available is to use a DT13-120 isolator module from Kele and Associates (www.kele.com). Set the input and outputs up for 4-20 ma operation and place a resistor across the output to give you the desired DC voltage at maximum operating speed (5VDC would be 250 ohm - 10 VDC would be 500 ohm). The module also has jumpers for chnaging it's operation from ma to volts on both the input and output and adjustable pots to scale the output. But since we like the idea of replace and go on things like this we stuck with the 4-20ma operation and provided our own load resistor.

Mike