Making a new display for power supply?

Discussion in 'General Electronics Chat' started by GRNDPNDR, Mar 22, 2014.


    Thread Starter Well-Known Member

    Mar 1, 2012
    I'm just toying with this idea in my head at the moment, and sort of thinking that what I want to do might not be too hard, but I thought I would ask here what the experts think.

    I recently purchased a Mastech HY3005F-3 power supply, and it uses multiple 7-segment displays for it's voltage and current meters.

    The resolution of the displays is only 0.1, meaning I can only adjust by 100mV at a time.

    I'd like a better resolution, like 10mV at a time.

    So I was thinking of designing a board with different displays that would give me the resolution I'd like (and maybe be more accurate who knows)

    As they are just current and voltage meters I figure it shouldn't be too hard to accomplish.

    Here is a pic of the back of the display panel, and it doesn't like terribly complicated.
    I'm not sure at the moment what the wires plugged into the board do, because I'm just trying to gauge this project right now.
  2. ScottWang


    Aug 23, 2012
    You need a op amp to amplify the voltage, the gain as 10, when you measure 10mV, after the op amp amplifying that it will became 100mV, using a switch to switching the range of measurement.
  3. Brevor

    Senior Member

    Apr 9, 2011
    Why ? ... Why on earth would you need 10mV resolution ?

    Thread Starter Well-Known Member

    Mar 1, 2012
    would it be pointless?
  5. Brevor

    Senior Member

    Apr 9, 2011
    I think so, Your power supply can't regulate with 10mV precision. Also with all but light loads you will have more than 10mV ripple and/or noise.
  6. #12


    Nov 30, 2010
    They make good points.
    I just wanted to say you can buy panel meters (about $11) and add a range switch.
    4 instance, 2V range will display 3 digits after the decimal point, 20V range will show 2 digits, and the 200V range would be limited to 100 mv resolution.

    Edit: unless you find one that displays 5 digits.
    Last edited: Mar 23, 2014
  7. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    Before you talk about the meter that reads the voltage to 0.01 volts...

    Does the supply have an adjustment knob capable of 0.01 volt adjustments?

    Thread Starter Well-Known Member

    Mar 1, 2012

    I was planning on adding multi turn pots for this reason
  9. MrChips


    Oct 2, 2009
    It may be desirable to have all your instruments and readouts with the highest degree of precision and accuracy.

    For a bench power supply, one rarely needs a resolution better than 100mV.

    Are you a gadget collector who likes to collect things for the sake of collecting or are you someone who gets the job done? Personally, I would leave the PSU as is and get on with some interesting projects.

    Thread Starter Well-Known Member

    Mar 1, 2012
    This is why I brought it up, to see if it was worthwhile. I can't really think of a reason to need that sort of resolution.

    to answer your question, a bit of both :) I get the job done, but that's usually because I have amassed a collection of things relating to the jobs I do lol.

    plus I don't have any interesting project aside from trying to learn to use eagle/design PCB's, and the rail splitter circuit I'm using to do that.
  11. alfacliff

    Well-Known Member

    Dec 13, 2013
    it would be much better to measure the voltage at the load, voltage drop in the wireing from the ps to the load is not seen by the display on the ps.
  12. Anaandrew01

    New Member

    Mar 24, 2014
    I think your power supply can't be regulate through 10 mv precision.
  13. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    Which is a good reason to have a display that shows 0.01v resolution. So you can see what is actually coming out of the supply.

    I couldn't live with a PSU voltmeter that rounds down to 0.1v resolution. Like my PSUs with analogue meters I would be constantly reaching for the multimeter to set it to the "right" voltage.

    And regardign regulation, many times you are powering soemthing with a relatively constant load current, like powering up a LED to test it. You can set to close to 0.01v precision and the PSU will hold it just fine.