Light Machine Corp. Benchman XTr (retrofit)

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.

Ok. The ClassicLadder thread has begun

ATC THREAD

Hey, I just found this board and I may be able to help.
I did a lot of the design work for the Benchman series machines.
My notes are copious but not right in front of me.
That machine was developed in the early 2000s and incrementally upgraded during my stint at Light Machines/Intelitek.

I'm an EE so I can build them, but I do not know how to operate other than some very simple M&G codes to check if the machine is functioning. So if it's electrical in nature, fell free to ask. I'll check back on a semi-regular basis to see if I can help in any way.

Hey Guys, I just discovered this forum and think I may be able to offer some assistance.
I'm the guy that did most of the design work for the Benchman Series products for Light Machines/Intelitek.

I have been away from Intelitek for >10 years now, but if you have electrical questions about the machine and its operation, my notes are copious and I should be able to answer most any question about the machine. I see that Intelitek has provided my schematics, so that essentially frees me to offer any assistance I can.

I will check back periodically and if I find that you don't need me, I will just fade away.

Regards

Don

x-Intelitek wrote:

I will check back periodically and if I find that you don't need me, I will just fade away.

Don

Don,

Please, don't fade away!
I can only speak for myself, but any information you can bring to the Benchman XT discussion will be welcomed!

For a starter: Do you have an idea as to how many machines were built with an integrated SMW RT-5C 4th axis?

Rex

Rex,

Based on how often I saw them and how long I was there, I would estimate between 60 and 70 4th axis were shipped. Not all were shipped with machines. Machines could be configured and built for the fourth axis, but not shipped with the 4th axis due to budget constraints and the 4th axis was purchased at a later time. If I recall correctly, the 4th axis was common among all of our bigger (servo) machines.

Don