Shopsmith Forums

nuhobby wrote:Here was some info provided by charlese back in Jan-2011:


Let me go back and correct my error from two posts ago. The light used is infrared not laser.

The PowerPro manual has - in the troubleshooting section - a statement referring to "Common PowerPro Control Error Messages"

From the Manual:
"The error message is "RPS State Error 0" -
Definition: None of the receivers are sensing infra red light from the receivers.
Possible reasons:
a. Light path is blocked by dust or dirt.
b. Signal cable is broken or has a poor connection.
c. Sensors or electronic components are damaged.

Possible solutions:
a. Remove belt cover and motor pan. Use compressed air to blow dust out from under cowling where where 5-wire connection is made.
b. Check connection of the small, white, 5-pin plug between the Power Supply and Motor. If these wires are cut, they must be repaired or replaced at the factory only. Call Customer Service for shipping instruction.
c. Electronics are repaired or replaced at the Factory only. Call Customer Service for shipping instruction."

Aha! It does have a position sensor - an optical encoder with an infrared LED light source. Three-to-one that RPS stands for Rotor Position Sensor. This could theoretically be used to control the absolute position of the motor shaft, but in this application is most likely used only to know exactly how to divvy up the current to the various stator windings, so as to generate torque most efficiently. Oh, and also to measure the motor velocity.

I learned that I know almost nothing about what is being discussed here! But, learning that you are ignorant is important.

charlese wrote:Thanks, Guys - Especially Dennis!:) Very interesting!

The light at the end of the tunnel is dim, but at least I can see there is light. A little more study and I might be able to see the actual light source. Oh yea! I'm a little slow, but still "limping" along.

I think I now understand an inverter is used to change AC to DC or vice versa. Not necessarily change voltage. Is that true?

Actually, the term "inverter" is generally used only for DC-to-AC conversion devices. A (usually much simpler) device which converts AC to DC goes by the more pedestrian name of "DC power supply".

And then there are devices that shift one DC voltage to different DC voltage. They are called DC-DC converters. Internally, they are usually made up of an inverter on the front end, followed up with a DC power supply to generate the DC output, all in one device. But details can vary, especially for low-power stuff.

[quote="JPG40504"]
The use of the terms is not always consistent, so that is why the nebulous statements above.]

Amen!

For an engineering discipline, electrical engineering is relatively new. (I'm pretty sure that JPG interned under both Edison and Tesla. ). And it still changes rapidly. The terminology struggles to keep pace.

Sometimes, one of the biggest challenges is figuring out what the same terminology means from different component manufacturers. Or even the SAME manufacturer on two different data sheets. You would be amazed at how many different methods are used to rate the power of a machine-tool spindle.

[quote="BuckeyeDennis"]Amen!

For an engineering discipline, electrical engineering is relatively new. (I'm pretty sure that JPG interned under both Edison and Tesla. ]

You left out Ben and his kite!:D

Also dynamotor!;)

[quote="JPG40504"]You left out Ben and his kite!:D

Also dynamotor!]

What? Moving parts?!!!

BuckeyeDennis wrote:What? Moving parts?!!!

Gotta love the 'math' too!!!:rolleyes:

BuckeyeDennis wrote: anyone know if there is a motor-position feedback sensor on the PP? A clue would be a bundle of four or more small wires connected between the drive and the motor, in addition to the usual (heavy-gauge) motor-winding leads.

Not sure about the PP specifically but in an interview on FWW's podcast the Tekna Tool rep was talking about a new drill press they were building using the same motor and he mentioned that it would detect spindle position. He also hinted at the potential for a software based tool brake and the ability to slow down and then stop a tool as it exited the wood to reduce tear out. Pretty cool stuff. Hopefully as they update the software for the motor we'll see some of these new features from ShopSmith.

dlbristol wrote:I learned that I know almost nothing about what is being discussed here! But, learning that you are ignorant is important.

What He Said!!

reddog5362 wrote:Not sure about the PP specifically but in an interview on FWW's podcast the Tekna Tool rep was talking about a new drill press they were building using the same motor and he mentioned that it would detect spindle position. He also hinted at the potential for a software based tool brake and the ability to slow down and then stop a tool as it exited the wood to reduce tear out. Pretty cool stuff. Hopefully as they update the software for the motor we'll see some of these new features from ShopSmith.

The DVR motor is a light year ahead in motor design. I am sure with time, there is many other very unique and helpful features that will be developed. An instant stop feature without damaging the saw blade should be one of these designs as the computer knows where the shaft rotation is at all times.

I tried unsuccesfully to get one of the original DVR motors to experiment with but they wanted to keep this type of work in house. They was reluctant to discuss specific details with me at that time. I had a really good motor test station setup that I was using and thought I could offer some of my knowledge at that time. Since proprietary information would have been involved, I was not able to learn any additional information on the DVR concept other than what was publicly available or get my hands on one of the motors and controllers.