13735Re: DRO from Spokane on the way
- Jan 2, 2006The 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.
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.
>now know the caps are for filtering as you said and I suspected. I
> Just finished reading the PDF file on the shumatech website and
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. Iwas 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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