+/- Supply Rail Modules.

Thread Starter

Hymie

Joined Mar 30, 2018
991
For those of you looking for an affordable solution to +/- supply rails, this looks an interesting option at just over $2 (available supplying +/-5V, +/-9V, +/-12V, +/-15V), although there is a shipping fee, additional items do not add to this.

Each rail is rated up to 100mA; the +/-15V version I tested had approximately 50mV supply ripple (at around 10MHz) under full load.

https://www.ebay.co.uk/itm/DC-DC-Boost-Step-Up-Converter-Dual-Output-5V-9V-12V-15V-Voltage-Regulator/124408231408?ssPageName=STRK:MEBIDX:IT&var=425278334390&_trksid=p2060353.m1438.l2649

Note that the supply is not isolated, the GND in and out are commoned; normally such inexpensive devices subject to output overload/fault die rather than recover.
 
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Irving

Joined Jan 30, 2016
2,065
If people are looking for a +/- supply for op-amp stuff, wouldn't the SMPS modules add unwanted noise?
Most modern quality opamps and instrumentation amps have common mode supply line rejection of 110dB or better and much lower bandwidths than 10MHz, so this level of ripple, with the right supply decoupling at the power pins (eg 1nF + 100nF + 10uF paralleled) is going to be 150+dB down and unlikely to have much impact...
 

Thread Starter

Hymie

Joined Mar 30, 2018
991
If anyone else has purchased one of these modules – it would be interesting if they posted their review (good or bad).
 

Wolframore

Joined Jan 21, 2019
2,342
I can’t imagine where I would use them. I would love to see a schematic, I’m sure they’re based on capacitive divider with a virtual ground but can’t tell looking at them.
 

Thread Starter

Hymie

Joined Mar 30, 2018
991
I’m planning on using them to build a small box having the outputs +5V, +9V, +12V & +15V on banana sockets, all powered from a 5V mini USB input.

The +5V version will need a diode in the 5V supply (to reduce it to 4.3V) and I’m considering an 80mA polyfuse in each output – but I doubt it will be fast enough to protect against short circuit/overload conditions.

Such a project will give a simple/neat solution to having easy access to a range of dual range voltages.
 

Wolframore

Joined Jan 21, 2019
2,342
Anytime need dual voltage, it always seems like I need more current to drive the output. I use my lab supply for testing then decide afterwards. Where would you use them? I suppose they might be good for inamps if clean and accurate enough.
 

Thread Starter

Hymie

Joined Mar 30, 2018
991
Over the Christmas break I put together my proposed project consisting of each of the modules supplying +/-5V, +/-9V, +/-12V & +/-15V all generated from a 5V usb input. The total cost of the parts is less than £15.

I regularly mess about with low voltage/low power circuits and reckon this will suffice for most of my needs – despite not having an adjustable output, very few of my circuits need a precise supply voltage not covered by this unit.
 

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Thread Starter

Hymie

Joined Mar 30, 2018
991
At the risk of appearing to be the seller of these units – I conducted an output overload and short circuit test on a +15V module.

With an input of 5V, limited to a maximum of 1A - with a 30 ohm resistance attached across the 30V output, the output voltage dropped to 10V.

With the output rails short circuit, the input voltage dropped to 3V at 1A.

After removing the faults the module recovered operating normally, although the faults were only applied for the order of 20 seconds.
 
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