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13740Re: [mill_drill] Re: DRO from Spokane on the way

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  • Glenn N
    Jan 2, 2006
      I agree, after looking over the traces and measuring a few things I think cutting a line and adding a daughter board with a regulator and filter would about do it.  May need the caps in the scales still though. 
      I believe my LCD's have the backlight in them but they just didn't wire them up.  A schematic would be a real time saver :)  I looked into hooking them up awhile back but didn't do it for some reason I have now forgotten.  I guess I need to take some pics and post em so we can compare notes.  I need to find out what voltage the backlights take too.  I assume +5vdc would be good but :)
      ----- Original Message -----
      From: miker557
      Sent: Monday, January 02, 2006 1:25 PM
      Subject: [mill_drill] Re: DRO from Spokane on the way

      The LCD's on my readout box are lit, and come on whenever the unit
      is powered up.

      Since my last post I have talked to a friend of mine who is more
      familiar with power supplie than I am, concerning the apparent
      arrangement of the (unused) circuit on my Shars box. It is
      acceptable to raise the ground potential up from 0 to 3.5 volts,
      giving a total voltage across the + and - pins at the scales of 1.5
      volts ..... but ....

      There are 4 pins connecting the scales on the display box; battery -
      , data, clock, and battery +. The data and clock lines send pulses
      to indicate the value of the measurement, which are either low
      (below 0.2 volts) or high (above 1.3 volts). The thing is, these
      voltages are measured from ground (that is, zero volts). While they
      would be in reference to the ground side of the scales power input,
      if that ground id actually 3.5 volts above the ground used by the
      display box, then the display box *might* not be able to correctly
      interpret those signals (and if it is set up to receive a maximum of
      1.5 volts on a data line, then that 3.5-5.0 volt signal *might* be
      enough to damage something.

      Hmmm ......

      I'm going to make a 1.5 volt power supply according to the
      schematics from the Shumac web site, and see about tying it into my
      display box (by cutting the traces on the circuit board to isolate
      that area from the 5-volts the box uses). I'll let you folks know
      how it turns out.


      > Mike,
      > Just finished reading the PDF file on the shumatech website and
      now know the caps are for filtering as you said and I suspected.  I
      was just about to head out to the shop and see what I could figure
      out about the readout and see if the wires are there to supply the
      power.  They used a 100uF and a .01uF cap to kill high and low
      frequency noise.  I think I have a couple LM317's out in the junk
      box so ... Play Time :)
      > My readout also has some pads for lights to light the readout.  I
      was going to put lights in but added more light to the shop
      and "cured" the problem that way.  I heard that the newer readouts
      have the lighted display?

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