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Thread: Is there a cheap precise variable A/C -> D/C power supply (up to 12v and 3a)?

  1. #1
    Senior Member+ MichaelMeissner's Avatar
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    Question Is there a cheap precise variable A/C -> D/C power supply (up to 12v and 3a)?

    This isn't quite teensy related, but perhaps people know of an appropriate D/C power supply, it would be nice. I've been doing some runs at testing how much power my digitial cameras consume when doing various things like record 4K video. I've been using some fixed A/C to D/C converters and a variable D/C power supply similar to this one:


    I find in practice, the rotary encoder is not quite accurate. I would like to get exactly 9 volts (to get repeatable results when testing multiple items, and to find out exactly when the camera says there isn't enough power). Using the encoder, I might get 8.97 volts and it jumps to 9.03 one time and another time it might go from 8.93 to 9.01. So I would want one that either has digital inputs or more finely grained encoder. What I need is:

    • Under $US 50 would be nice;
    • Output range at least 3 volts to 12 volts;
    • Support for at producing least 3 amps of power (including 12 volts at 3 amps);
    • US electrical plug for 110 volt/60Hz power input (220/50Hz volt support would be nice but not needed);
    • It would be nice if it had a standard 2.1mm x 5.5mm male power plug for output;
    • Digital output to at least 2 decimal places for voltage;
    • It would be nice if it displayed amps and watts, but I do have ammeters that show this;
    • It would be nice if it had push buttons to track total power used between button pushes, including maximum amps/watts; (and)
    • It would be nice if it had a graphical interface showing the volts, amps, and watts over time either directly or through bluetooth to an android phone.


    For reference, this is the voltmeter and ammeter that I'm currently using:


    I did hook up a Teensy with an Adafruit INA219 FeatherWing to measure the maximum amps/watts, but I recall there were issues with it.
    Last edited by MichaelMeissner; 08-23-2021 at 05:55 PM.

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    > Teensy with an Adafruit INA219 FeatherWing to measure the maximum amps/watts, but I recall there were issues with it

    I expect that with calibration and lookup table corrections, this could achieve the .1% accuracy you are looking for. But it might not be fast enough.

    My RD6006 seems to meet it's displayed .01V accuracy. Other power supplies have a fine adjust knob.

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    Senior Member BriComp's Avatar
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    How about one of these, Agreed its not 110/220v input but you could run it off one of your existing supplies. Amazon have similar versions.
    Or one of these mains powered bench power supply.
    Last edited by BriComp; 08-23-2021 at 07:21 PM.

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    Senior Member+ MichaelMeissner's Avatar
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    Quote Originally Posted by BriComp View Post
    How about one of these, Agreed its not 110/220v input but you could run it off one of your existing supplies. Amazon have similar versions.
    Or one of these mains powered bench power supply.
    Thanks, I will check into those. That mains supply from Amazon looks rather big.

    In terms of the push/pull DC converters, I was worried about them being able to handle > 1 amp of power. I guess I will need to inspect the data sheets.

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    Senior Member+ MichaelMeissner's Avatar
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    Quote Originally Posted by jonr View Post
    > Teensy with an Adafruit INA219 FeatherWing to measure the maximum amps/watts, but I recall there were issues with it

    I expect that with calibration and lookup table corrections, this could achieve the .1% accuracy you are looking for. But it might not be fast enough.

    My RD6006 seems to meet it's displayed .01V accuracy. Other power supplies have a fine adjust knob.
    Just to be clear, when I said 2 digits of accuracy, I meant total digits (i.e. 9.1 volts instead of 9.10 volts).

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