Isolated power supplies


Senior Member
Isolated power supplies

This project may at first glance appear to have nothing to do with the Picaxe world. In fact, if you are just starting out in electronics or just a casual hobbyist, right now you’re probably thinking “Meah… power supplies, so what”. However, if you are an engineer/techie with a few years experience working in heavy industry or robotics under your belt, isolation is not a conversation we need to have (you’ve already been bitten by that dog).

Alright… a few examples to show you why the little boogers in the attached .pdf may be of some value for you:

01 You just bought a new amp display for your shiny new boat’s trolling motor. You’ve wired it up & the amp readout is
way out of whack. Just double-checked the wiring, no screw-ups. Now you go back to the installation diagram & there it is in small print: “The amp display system must be powered from a source separate from the motor power”. You gotta’ be kidding! I gotta’ buy another battery!

02 You just installed a nice industrial pressure sensor on your solar water control system, then you read the spec. sheet
“requires +24vdc power for 4...20mA signal”. Oh no, my control system runs on +12vdc! Oh no!

03 Just wired up that new analog-to-digital panel, time to connect the power supply. Wait a minute… on-board op-amps
need -12vdc. Dammit! I wanted all this stuff to run off my +12v battery! I ain’t got no room on this damn thing for another power supply! Bad enough, but my ma-in-law’s poodle won’t get off my leg! Uh-oh… probably shouldn’t have kicked the dog.

04 My little Picaxe controller goes bonkers every time I connect that shunt! Oh no… not that stupid isolation thing again.


Ok… let’s read the attached .pdf & see if we can’t make a few light bulbs come on.

Problem 01: I need an isolated power supply for my amp readout

problem 02: I need a +24v supply

problem 03: I need a +12v/-12v supply

problem 04: I need an isolated +5v supply for my Picaxe controller

Now, just like most other stuff in technology, there’s always a few caveats:
The lil’ power supplies shown below won’t supply a lot of current (e.g. the +12v output can only source ~80mA)
Can’t drive a lot of capacitance

The B...S-1W modules can all use the same lil’ board. Although, the suggested capacitor specs vary for each module, I have used all 10uF caps with all & they work just fine (I had a drawer full of the 10uF caps).


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Well-known member
Uh, OK. What's the point? I might be a little dense. I think maybe if you could type a leetle bit slower?


Senior Member
Uh, OK. What's the point? I might be a little dense. I think maybe if you could type a leetle bit slower?
No problemo: Se habla Texan: “It’s just one a them thangs’. Either you git’ it er’ you don’t git it. Simple as pie.”
It’s early morning, so try an IEC (Intellectual Enhancement Concoction). Coffee & Tequila should clear out any cobwebs.


I use this cct for an isolated supply for the lcd volt/current meters. (adjust device for supply volts and maybe require a zener to limit the input supply)


Or use a double pole switch with a large electro cap (2200uF or so) to power the meter. You charge the cap with the switch across the supply and then isolate the cap and use it to power the meter with the switch the other way. Works well as the LCD meter uses minimal power and depending upon the size of the cap can power the meter for more than enough time to take a reading.


Senior Member
Perhaps a link to the isolated power supplies on eBay that mickeyBoo is obliquely referring to in his first post would make it easier to understand why he posted.

Makes more sense to me now. :D
Had you looked at the attached .pdf, you would see that each of the examples had the part# (in large letters) right under a very clearly-drawn example. The part #s also appear on the the schematic.
Pay attention Tex, it couldn’t have been any simpler or clearer.
There is nothing oblique about it.