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Shars scales with Touch DRO
#7
I found that the Shars scales that I have are severely lacking in power supply decoupling.  Starting and stopping the lathe would cause the readings to jump sometimes.  And then I turned on my gooseneck LED lamp!  Whoa!!  I don't know what kind of dirt cheap switching line converter it uses, but it's crazy noisy.

You might get away with little or no supply decoupling if the scales are running on batteries and isolated from the environment.  But powering the scales from the Mixed Scale board couples them to all kinds of "world" noise.  So much so that just changing wall warts made the difference between connecting or not connecting.  Even running things from a bench power supply, while improving things, didn't solve the problem.

So I opened up the read heads of the scales and added 0.1uF ceramic capacitors between Vdd and Ground, which is a pretty standard value in the digital world.  Vdd has a conveniently labeled test pad.  A nearby bare spot on the copper pour provided the "ground" connection.  I just tack-soldered the leads to the two pads.

So far so good, even with the LED lamp on.  Here's a picture of the mod (yes, the leads are a little long), and of the X-axis scale installed on my Logan lathe (without the chip guard). The head is positioned so that the nut runs off the end of the crossfeed screw just before it runs into the head.
   
   
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Messages In This Thread
Shars scales with Touch DRO - by Shawn_Howell - 02-12-2017, 01:36 PM
RE: Shars scales with Touch DRO - by Yuriy - 02-12-2017, 05:20 PM
RE: Shars scales with Touch DRO - by Shawn_Howell - 02-12-2017, 07:17 PM
RE: Shars scales with Touch DRO - by Yuriy - 02-12-2017, 09:17 PM
RE: Shars scales with Touch DRO - by Shawn_Howell - 02-12-2017, 09:21 PM
RE: Shars scales with Touch DRO - by Briney Eye - 02-26-2017, 05:53 PM
RE: Shars scales with Touch DRO - by Briney Eye - 02-23-2017, 06:43 AM
RE: Shars scales with Touch DRO - by geiges - 04-21-2017, 10:31 PM
RE: Shars scales with Touch DRO - by Briney Eye - 04-22-2017, 02:38 AM
RE: Shars scales with Touch DRO - by geiges - 04-22-2017, 03:50 AM
RE: Shars scales with Touch DRO - by Briney Eye - 04-22-2017, 03:36 PM
RE: Shars scales with Touch DRO - by Yuriy - 04-22-2017, 04:33 PM

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