Computing stuff tied to the physical world

Accurate power supply

In Hardware on Mar 14, 2012 at 00:01

My existing lab power supply delivers 30V @ 3A, which is more than enough for normal use, but it uses linear fine + coarse potentiometers, which are in fact not optimal for really fine adjustments. I’ve been using it a lot, and I really have been wanting something more convenient for quite some time.

So I decided to get a second and more high-end unit, the GW-Instek GPD-2303S:

DSC 2950

It even comes with a “calibration certificate”, FWIW:

DSC 2951

There are many lab power supplies out there, and I intend to come up with a really good option for low end use in the context of the Thursday Toolkit series, but I’ve got enough future projects piled up here to justify this instrument for JeeLabs. Everything other than the ultra-low power experiments will benefit from this.

BTW, if you’re looking for a DIY design which is coming along very nicely, check out the EEVblog episode list, where Dave Jones has over half a dozen fascinating videos about how he is designing a really nice Arduino-compatible power supply, with all the bells and whistles you might be after: finely programmable voltage and current range, an LCD display, rotary switches for adjustment, etc. Here’s the first one in the series.

The GPD-2303S delivers 2x 30V @ 3A, i.e. up to 180W of controlled DC power. There’s a 3-channel unit with extra 2.5/3.3/5V output, even a 4-channel unit, but I’ve got enough supplies here now to cover such needs.

Note that lab power supplies are designed to “float” w.r.t. ground. The reason for this is described in my two weblog posts here and here. So you can hook them into your setup in any way you like. Even doing some totally crazy stuff like a adding a 50V DC component to AC mains would be possible…

Anyway. The nice thing about this supply (even though its shape is a bit deep for my workspace), is that it includes two independent supplies which can be used in series (double the voltage) or in parallel (double the current) to get 0..60V or 0..6A capability, and that both voltage and current can be controlled and measured very accurately (not quite down to the 1 mV/mA levels as they claim, but close).

This power supply is not a really high-end one, though (which would cost even more), since there is no remote sensing, for example. So small losses over the cabling are not compensated for. I’m not too worried, because with large currents I’m usually not really concerned about 10 mV error.

More important is that it’s a linear power supply with only 1..2 mV ripple, and that the current limit can accurately be set to very low levels. By setting it to 50 mA, say, you can avoid most damage when hooking up things the wrong way – as so often happens while messing around with circuits.

Also very nice is that this unit is programmable – meaning that you can control it fully via USB. That opens the door to all sorts of stress and limits testing, i.e. plotting the effects of a slow voltage ramp on a circuit, for example.

Sooo… with this new addition to JeeLabs, I hope to stay out of Mr. Murphy’s path a bit more!