EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: DzAnej on February 19, 2017, 11:54:50 am
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Hi there,
I'm working on a 2 Channel power supply using a transformer with 2X 25V/5A outputs. Next, i would need a supply (5V) for the regulation circuit (microcontroller(s)).
Now, because i have 2 channels - how do I measure the voltages on the both outputs without clamping all the grounds together? For now I was testing using an instrumentional amplifier but with that I had to put the grounds together to make it work...
For now I thought one way of doing it - Each channel would use its own supply to power the measurment circuit and then send it digitally to the main controller via an optocoupler - that way the 3 grounds (2 channels and main controller) are isolated.
Is there a better way than this and how is this done in commercial multiple channel power supplies?
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Two meters.
These days, they are cheap enough.
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Yes, they are cheap: http://www.ebay.com/itm/DC-100V-10A-Voltmeter-Ammeter-Blue-Red-LED-Dual-Digital-Volt-Amp-Meter-Gauge/162237038985 (http://www.ebay.com/itm/DC-100V-10A-Voltmeter-Ammeter-Blue-Red-LED-Dual-Digital-Volt-Amp-Meter-Gauge/162237038985)
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Well, I forgot to mention, the supply will be programmable... There will be one display showing preset and actual voltage/current...
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You mentioned "one display" so the MCU running that can run the side powering it. As for having the other side isolated and yet controlled by the same MCU, that'll likely require high-speed optical circuitry (shifting out and latching DAC data along with getting ADC data back to the MCU on the other side). That may be a stretch for this beginners forum.
*Edit - Skip the separate 5v supply, since 7805's can do it fine (and plan for 12 or 24v to run beefy output relays too).
Q - Have you considered a slaved, display-less MCU to efficiently run the other side?
(You'd still need to opto-exchange command, display and relay data, but the throughput rate wouldn't be so high.