[RESOLVED]Shapeoko 2 - Improved Tram but speed controller degraded

Woodshop
#1

I spent some time on Sunday tearing down part of the Shapeoko case and wiring so that I could more easily access the bolts to improve the tram which was slanted front to back by more than 1mm. I used a heat gun to break loose the old hot glue holding some of the wires down so that I could partially pull the case off. In doing so I discovered that the variable speed control wire splice is sub-optimal and wiggling it causes random behavior of the spindle. If you use this machine near term make sure you watch for that as it can cause the spindle to run even when the knob is all the way to the left (off).

To address the wiring issue, and make the case completely removable, I’ll be stopping up sometime this week to install JST or Dupont connectors on all the wires that run to the case itself which will make it easy to remove and fix the flaky wiring along the way.

The case is also in need of some attention but that’s less of an issue right now.

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#2

For clarification, is the machine in service for general use?

#3

Best to wait but if you know what you’re doing you can most likely work around this issue.

1 Like
#4

I installed connectors today but I think the Potentiometer itself is bad and not the wiring. I did resolder a suspect wire but no dice. I then dug around in E-Lab for awhile looking for a replacement but couldn’t find much in that regard. I put a sign on the machine that it’s down and will look around at home for a part, I might just have one.

@artg_dms, think we may have a 100K POT sitting around somewhere by chance?

#5

As you enter the Electronics Lab, go to your immediate right and look in those metal pull out drawers of the metal cabinet. There is an assortment of pots in one of those drawers.

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#6

Not sure I have anything that high. Will check.

Assuming your looking for something like this
https://www.mouser.com/ProductDetail/Bourns/PDA241-HRT02-104B0/?qs=itG3xFeL1F3d8lnCDEh%2B6Q%3D%3D

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#7

@richmeyer, thanks. I did try that area and there were only a few, nothing suitable I’m afraid.

@artg_dms, that’s right, like that.

I’m also trying to find the instructions for the variable speed controller we have on the Shapeoko to see what it calls for and if it has to be 100K or something else might be suitable.

#missingtanners

#8

Missing Tanners, Radio Shack, Fryes… :frowning_face:

#9

Well I have at least one 100k pot. I know that I have more but remembering where they are at is a different story.

image
image3024Ă—4032 2.77 MB

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#10

If you care to donate one of those to the cause you can drop it in my bin or in the red toolbox on the Shapeoko and I’ll install it.

#11

I think we’re back in business. I replaced the old 100K Ohm POT with a 5K Ohm that I had on the belief that the variable speed controller board is only using that to measure a voltage drop between the wiper and one of the lugs and so the current isn’t (hopefully) a concern. Seems to be working fine though I have not run any long running job yet. Maybe somebody with more knowledge about these things, like @artg_dms, could comment.

Here’s the board. Back side is a big heatsink. Takes in 48V AC and puts out 24V DC to the spindle. It can use a POT or PWM (J21 or J25 jumper) if we ever wanted to hook it up and use G-code to control speed.

PXL_20210327_154325913
PXL_20210327_1543259134032Ă—3024 2.88 MB

Staff: I created this thread but it’s been some time and I don’t seem to be able to update the title. If someone can tweak it to say “Fixed” or something that would be great. Thanks!

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#12

Current through the pot would be the main concern. 20x greater (100k/5k) Probably not a problem for the pot. Wiper probably feeds into some kind of op amp ckt and should not be a problem. Will put an increase in over all pwr demand by the brd.
Assuming one end of the pot is tied to +V = 24 Vdc and the other to Gnd. I thru the pot is 4.8 mA and the pwr is 115 mW. Should be ok.
Do “long” runs at different settings and feel the back side of the pot. Temp will tell you if you’re ok.

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