1 Servo?

What would be the cheapest way to control a single DC servo for positioning?

What I have is an automated fence stop for a chop saw. The control for it got fried, but I believe that the analog servo amp, servo motor and powersuply are fine. I just need an inexpencive way to control it, for positioning.

If the cheepest way is beond my skillset, what would be an easy and realtivly cheap way?

Can you give details of how it is setup and what you need

Probably the cheapest would be to use the parallel port for PWM/PDM, convert this to +-10V analog with an op amp or 2
and use the parallel port for reading the encoder.

Limitations are: Maximum encoder rate (limit determined by encoder resolution X motor RPM vs
how fast a base thread you can run) and PWM/PDM resolution/frequency ( again determined by base thread period)

Setup a single axis NC machine would be one approach. The cheapest solution would likely be a amp that takes step and direction. This is in part dependent on how feedback is done with the current system.

Another possibility is to buy an integrated amp and controller from your local motion supplier. Then hook it up to either a PC or a dedicated terminal. Most of these drives are easy to setup for indexing systems. Cheap is another issue.

A third possibility would be to pick up some servo code for a micro controller and a prototyping board and build your own controller.

I've been trying to reply to this for 2 days now and for some reason the site won't let me do it from my windows box running ie.

It is just a DC servo that is used to drive a belt that that moves a stop on the fence for the saw. You program the measurment of the peice you want to cut, and the servo moves the stop to the appropriate posion to cut a peice that size. There are two limit switches at the extremes of travel one of which was used for reference position.

Here is the only info I have been able to find on the amp that it uses.

translated from: www.easys.it/prod_file/azionamento_dc_ind.pdf
----
Compact size 100x90x90 mm (open frame)
? Power supply 90 Vac, 50/60 Hz (directly from an external transformer)
? Suitable for DC brush motors up to 90Vdc
? Power 0.4 Kw payable
? analog inputs: ? 1 +-10v Input (tachometer / speed)
? RS485 serial position commands, parameters, etc. ..
? Applications: ? Axis autonomous control, in parallel with other drives / devices on RS485 bus

The manufacuter of the stop wants about $2500 for the controler for this thing. I felt that is a bit excessive for no more than what it does. The bean counters here where I work bauked at this big time, so the saw opporators have been stuck using a tape measure and a clamp to hold the stop ever since (its been on the fritz for more than 2 years). I thought that if I could come up with a more reasonable solution, we could get it working again. I thought that if I could use a spare PC that we have laying around, to run as much of the existing hardware as possible. Then maybe the costs involved might be OKed by the higher ups.

How much do they want for a replacement board?

Is it still available?

The price I was quoted for the board was $2612.74. It was avalible two years ago, it might not be anymore.

I went out the machine and gathered as much information as I could off of it.
The stop system was manufactured by (for) Omga
The control was made by an Italian company called Easys for Omga.
The whole system is called a model FP2000.
The control interface has a small lcd screen with 3 or 4 lines and about 15-20 characters, a 12 key number pad, plus 10 other function buttons.
The main circuit board for the interface has a sticker saying “Easys (Italia) FP”. (this is the part that the magic smoke escaped from)
The servo amp has a sticker saying “Easys (Italia) MDCI Rev. 2.0”.
The main power supply is a transformer outputting 90v, 18v, and 7v DC that supplies power to the controller and the servo amp.
All of the above parts are housed in a small 12x12x8 inch cabinet with interface panel on the front.

The servo motor was made by Siboni Motoriduttori,
model # 75PL130DSG63 omga C-8MT

90 Volt DC
3400 RPM
4.5 AMP
2.2 Nm Stall
370 Watt

Encoder manufacture is Eltra
Model # EH63GB500S8/824P10XPR8.L384

I missed the price earlier

That's a tough one, I come from the school of thought of what does not fixing it cost you in the
long run. If it was for personal use I'd be tempted to make a replacement, but in a commercial
setting it would probably cost less to fix it right than the wasted man hours.

Pay a guy $10 an hr and it takes him an hr a day extra where he could be doing other
things in a years time that is $2500 just in wasted labor cost. Now what could he have
produced in that time add that in and you can't afford to Not fix it right.