Light Machine Corp. Benchman XTr (retrofit)
steve_a wrote: saw appox .8 ohm on both the input coils. I hadn't noticed before but there is only 1 output coil. ( I can only assume that is because this is a custom built toroid specifically for Light Machines and they designed it specifically for this machine.) The output showed about .2 ohms. Since the two .8 input coils are tied in series that makes an equivalent 1.6ohm coil making the input to output ratio 1.6/2 or 8:1. That gives 230V/8 = 28.75 V out
Unless the primary and secondary are wound with exactly the same size of wire a resistance check won't tell you the transformer ratio.
Have you tried turning on the power and measuring the output voltage?
My observations were based on my probing and since the toroid is not marked with any information regarding in and out voltages I went ahead and did the ratio calculation to try to verify the voltage I might see. Still, if the motors are rated for 24V, the 28.75V seems a reasonable number. The motor data sheet has two specs; the Rated Terminal Voltage 12-60V and the Terminal Voltage 24V. I took this to mean Tolerance and Operating Voltage, however, I am not shy to admit my ignorance and say that is just an ewag. It may actually be saying that the motors will operate in the range of 12 - 60V and is optimal at 24V. Even so I would think a company would design for optimal. I'll work on doing the test. You are correct in pointing out the wire size issue. Thanks for your input.
steve_a wrote: Still, if the motors are rated for 24V, the 28.75V seems a reasonable number. The motor data sheet has two specs; the Rated Terminal Voltage 12-60V and the Terminal Voltage 24V.
It isn't at all unusual to run motors at a lot more than their DC voltage through a current-limiting drive.
This is especially true for steppers which have a typical DC voltage rating of <5 V but often run at 50V or more.
The voltage rating is the DC voltage that will drive the rated current, but if you limit the current then you can maintain that current (and torque) to much higher motor speeds with higher voltage.
Out of caution, I have not removed anything or disconnected the controller board that is underneath the board that looks like an interface for the encoders, air, etc. I was waiting until I received the replacement controller boards from Mesa. I must not have understood their availability or processes. I ordered the boards on October 21st so I'm still waiting 3 days shy of a month.
I've found a replacement controller board on line and bit the bullet. I know I will receive that on Monday so I can test my educated guess that the machine will come back to life using the old software and system. I still plan to do the upgrade but I need to try to have this thing up by January so I've kind of got my back to the wall. I am itching to get to this thing moving but without the new Mesa cards I'm stuck. On the plus side, if I CAN get it running I can test it and see what it SHOULD look like with the upgrade installed. I think I'll probably have to come up with some kind of PCB for things like the above mentioned caps and just interface in general.
The saga continues.
I will chime in on the modifications since those will still be relevant to the Mesa/Linux systems. Truth be told, there is little difference in the two when it comes to the rewiring and if at some future date Mesa becomes more readily available it would just be a matter of swapping cards and I can have a closed loop system. I just have to set up the Linux CNC and I already have a computer loaded and ready to go. I had set it up in anticipation of the Mesa cards.
Anyway, I have some pretty good ideas for the rewire and I will share those as long as they are possibly relevant to the Linux system.
steve_a wrote: I feel mislead by the posts on this forum that touted the virtues of the Mesa
I am starting to feel bad for recommending them too.
The Mesa boards are excellent, but if they are not shipping them then, as you say, they might as well not exist.
Eusurplus (in Portugal) do have stock and do ship promptly.