Light Machine Corp. Benchman XTr (retrofit)

Mac,

Yes, I am using the Copley controls and the Litton motors. All those are still originals. I was able to access the VFD and looked at the PID tuning for my unit. It is set in Velocity mode with a P = 632, I = 210 and no D. So it is configured as a PI system. Those might be a good starting point for your unit. They should be similar but probably not the same. I was going to attach the entire PAR file but it is not an accepted format for the forum software. I could change the extension to DOC if you think you need it.

Azik1 - at the moment, I am having to remap some of the wiring to the 7i77 and 7i84 because when my system crashed this last summer all the excel files with the data were lost. The expectation is that it will 1) help with future retrofits and 2) aid my understanding of how to finish up some of the incomplete functions (ie broken sensors, non-interfaced hardware, etc...)

As for the ATC: I am talking about the automatic tool changer, which should have the same components across the board. The idea is that if we all use the same HAL and classicladder nomenclature then the only remaining variable is networking to the controller signals.

Steve_a: do you have any thoughts on this part? Should we start a separate thread in the classicladder forum?

After reading thru this forum post again, I realized why it has been such a PITA to tune these servo drives. The servo power supply is unregulated!! Steve_a did the easy thing and replaced the toroidal xformer with a regulated PSU. However, not wanting to spend the money on a PSU that would not fit inside the case, I was able to use the schematic that someone posted. Attached is a reworked schematic to use the existing setup, and come off plug J9. Unfortunately, somewhere along the way, the original board came up missing, so I could not pirate the board for the components. However, Mouser has everything needed to make a new board, which comes in a little under $50. If someone who is a little more electronics savy could take a look at the attached document and help me out with the wattages for R37/R23 and specs on D26, it would be much appreciated.

The lower part of the circuit is a simple voltage divider to power the TIP122, which in the original configuration divided the +10V down to +5V. Since I seemed to have accidentally junked the original boards, using the +24V from the existing PSU seems like an easy solution. The ration needed to step down the voltage is 3.8:1 (R37:R23). It seems that a single 3.8K ohm resistor is a little hard to supply, but there are ways around that.

Can someone please confirm or destroy the logic used here before I take the step of ordering the parts?

Thanks!
Mac

Mac,

Yes! Exactly! I was really impressed when I saw you had gotten the original PS working. I thought you had rigged the smoothing caps. I wanted to avoid building a circuit board to accommodate 15 amps. Probably more like 20 amps for safety.The original board has a really large trace on both sides (one for + the other for - ) that feeds the supply to the Copley controllers. That's why I elected to use a self contained PS. I removed the toroids and demeled the holding bolts off to make room for the power supply. This was just a personal decision but I considered it a shortcut worth using.
I wish I could help you with the modified circuit. I'm not familiar with that configuration. It looks like a crowbar or power supply shunt or discharge circuit. I can't quite decide. Looks like Q1 is off as long as there is voltage coming in across the fuse. Once that is removed it looks like the circuit conducts until the voltage drops to the zener voltage BUT I'M NOT SURE. Could be that the VBUS voltage is an enable(?). If you have to build a circuit anyway, it might be safest to just include a 24V to 10V voltage converter and use all the original values. It would be hugely useful to discover what the 10Vbus is for. R37 and R23 are in parallel and the same value in the original circuit. Additionally there shouldn't be greater than 400ma (the fuse would blow otherwise) Worse case is if the fuse blew all the current through R17 would flow through R23. Since R17 is 5 watts I'd go with that for both fuses to be ultra safe. ( R17/R23 is a 5:1 ratio so 1 watt may be sufficient for R23, but not knowing what's coming from 10VBus, not certain that's the whole story.) Not telling you you should do that, I elected to whimp out on PS so this is all observation and not really suggestion since I have never tried this myself.
As far as a separate thread for the Tool Changer. I think that is probably a good idea. It's a whole subject all to itself and someone who just wants to explore that part would get lost in this 15 page thread.
Hope you get that PS going soon!

Spent the morning talking to my cousin, who is an EE. We have decided to just use C16, R11, C1 and C2 to smooth the circuit. From what he said, the other lower half of the circuit is to supply the +10V BUS out. I ordered the caps and resistor from Mouser for <$30. Once they get here, I will solder them in parallel and insert the circuit after the rectifier. Will keep you guys up to date!

Mac, I think your cousin is probably right. A bit weird to take the 10 volts from there but I guess it is not going to a data line where it needs to be particularly clean. I think the arrow point on the connection made me think it was an input but now that I look at it i guess it is just their notation. I checked the power supply I had installed just to verify the output and it is considered an unregulated supply. It looks a lot like the set up you are going to build; a couple of big caps and a couple of resistors. Looks like you are right on the money.