Yet another NOT QUITE AS simple power supply PCB... :)

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J3RK
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Yet another NOT QUITE AS simple power supply PCB... :)

Post by J3RK » Fri Nov 15, 2013 1:08 pm

Since this has evolved so far since the first idea, I thought I would post the final board here, and will start filling in details, doc links etc. here soon. The final prototypes will be ordered shortly, and this will be available in the next few weeks.

Image



Original Thread:

No pics yet, as I haven't ordered the protos yet, but I tossed together a new PSU PCB for my own use, and thought maybe other might like one eventually. (after I make sure they don't blow up or anything) :mrgreen:

It's a 3"x6" board, plus a "cutoffable" 3"x2" 12-connector distribution board. It takes a through-hole Amgis/Alfamag Toroid. This variety: http://www.amgistoroids.com/toroidal-po ... rmers.html

It's trimmable, and as long as you either install large enough heatsinks, or pick the same size (physical dimension) in a lower voltage, you could easily build this for +/-12V as well. (+/-15V is what I'm building mine for.)

It's nothing terribly fancy, but it's easy to build, very quiet, has easy distribution, and is fairly small. It's also got a ton of mounting holes, so mounting should be quite easy.

There's nothing fancy like sense lines, LEDs, etc. but I've built these before for various projects, and they work quite well. It's just like many of the ones out there, simple linear trimmable supplies. I'd compare it to something like Ray Wilson's (non-wallwart) or Ken Stone's or the like. It's also low parts count.

I can post a pic of the board layout when I get home tonight. I should be ordering protos next week, so should have at least a few spares on hand if someone needs one. If plenty of people want something like this, I'd be happy to talk to Synthcube/Thonk, and see if they want to stock boards or something like this.

Anyway, more soon.
Last edited by J3RK on Fri Jan 17, 2014 11:41 am, edited 1 time in total.
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J3RK
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Post by J3RK » Mon Dec 02, 2013 9:27 pm

Image

Image
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bloke_zero
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Post by bloke_zero » Tue Dec 03, 2013 9:34 am

Nice. Option for 230V? Checked the link but couldn't see anything.

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Post by Jarno » Tue Dec 03, 2013 9:54 am

You'd need to "adjust" the PCB (looks like primaries are hardwired in parallel now, big fat PCB track). But agreed, it would be good to have the option, for universal use.

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Post by J3RK » Tue Dec 03, 2013 11:46 am

That's a good idea. I'll see about adding a set of jumper/switch pads to set that up. :tu:
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Post by Reese P. Dubin » Tue Dec 03, 2013 12:29 pm

Yes please

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Post by diablojoy » Tue Dec 03, 2013 4:27 pm

looks good for about 6 -12 modules each current requirements depending
add in the 240v option and it will be nice
but I would need roughly 25 of them just to cover my backlog :doh: :lol:
if you produce them i will take a couple to start with .
It probably wont happen today but if it does it definitely wont go smoothly.

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Post by J3RK » Tue Dec 03, 2013 4:55 pm

diablojoy wrote:looks good for about 6 -12 modules each current requirements depending
add in the 240v option and it will be nice
but I would need roughly 25 of them just to cover my backlog :doh: :lol:
if you produce them i will take a couple to start with .
Hehehe, yeah I mostly had smaller systems in mind for these. I have about 10 modules going into a 5U setup that I whipped this up for. I was also thinking they'd be nice in 4U Bud-boat systems (if they're not too tall with a module-PCB overhead.)

I will definitely add the AC voltage select.
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Post by diablojoy » Tue Dec 03, 2013 5:37 pm

yeah i just started a small euro system recently
for something a little more portable than my main modular
4 rows of 84HP i found in amongst my salvaged crap
thinking a couple of these might stretch to power it
hmm thinking about it
maybe make that 4 , one per row ought to do it better
and run cooler.
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Post by Altitude909 » Tue Dec 03, 2013 7:29 pm

The vRegs look really close toghether, not much room for heatsinks

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Post by J3RK » Tue Dec 03, 2013 7:31 pm

I don't typically use regular sinks. I usually run an aluminum standoff from the tab to a piece of aluminum angle (which would then connect to the mounting hole in front. However, these could be tweaked slightly to allow other types of sinks.
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Post by oldenjon » Tue Dec 03, 2013 9:28 pm

I could definitely use a couple of these. It's nice to have everything together on the same board like that.
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Post by inlifeindeath » Wed Dec 04, 2013 1:38 am

this looks nice, i'd be in for 1. do you have a good US supplier for the transformer? I'd like to see what the cost is going to be.

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Post by Altitude909 » Wed Dec 04, 2013 11:04 am

inlifeindeath wrote:this looks nice, i'd be in for 1. do you have a good US supplier for the transformer? I'd like to see what the cost is going to be.
Digikey has the alfamag stuff.

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Post by J3RK » Wed Dec 04, 2013 11:17 am

Yep, Digikey has them, and last one I bought was around $18 a couple of months ago. I should have the test version built tonight or tomorrow, and will make the small updates to the layout after I know this one works as expected.
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Post by raisinbag » Wed Dec 04, 2013 2:22 pm

Cool! Power for the people. So I read thread twice but didn't see A mention of how much juice it can sqweeeeze. I this like a 1a or 2a or more :fap:

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Post by diablojoy » Wed Dec 04, 2013 3:52 pm

going off the board it's suggesting 800mA per rail
dont think i would try to pull more than 500Ma from it though
depending on the heatsinking and filter caps used .
It probably wont happen today but if it does it definitely wont go smoothly.

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Post by mechie » Wed Dec 04, 2013 4:06 pm

diablojoy wrote:going off the board it's suggesting 800mA per rail
dont think i would try to pull more than 500Ma from it though
depending on the heatsinking and filter caps used .
Transformer datasheet says 694mA per winding.
Maybe 650mA would be a safe expectation for the PSU.

edit: corrected typo

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Post by diablojoy » Wed Dec 04, 2013 4:23 pm

Transformer datasheet says 694mA per winding.
Maybe 650mA would be a safe expectation for the PSU.
there you go, lowest common denominator -20% should be safe
so yeah good to about 500mA.
I don't typically use regular sinks. I usually run an aluminum standoff from the tab to a piece of aluminum angle (which would then connect to the mounting hole in front.
for anyone going this way make sure you isolate the regs from each other in this case, isolating washers and thermal grease , the usual safe guards.
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Post by J3RK » Wed Dec 04, 2013 4:33 pm

diablojoy wrote:for anyone going this way make sure you isolate the regs from each other in this case, isolating washers and thermal grease , the usual safe guards.
Yeah, you don't want to short the two tabs together. I use two separate pieces. One for each regulator. I don't isolate from the tab, but I do keep them separate from each other. The mounting holes on the PCB are plated, but they're not connected to the ground-plane, so you don't have to worry about them connecting through the board.
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Post by ElectroSteam » Wed Dec 04, 2013 6:44 pm

Just a quick heads-up: If the load per rail is limited to 400mA per rail (not 500), then the transformer is overloaded by 4%, compared to the maximum load current quoted by mechie.

The secondary RMS load current of the transformer in a linear PSU with a capacitive filter, like this one, is emphatically not identical to the load current on the DC supply rails. The current through the transformer is highly non-sinusoidal, as the diodes can only conduct very briefly during the AC mains cycle, when the secondary voltage is higher than the instantaneous filter cap voltage.

In this case the RMS secondary current is 722 mA per secondary for DC load currents of 400mA, a ratio of 1.8:1. This is a typical value for a simple DC supply.

At +/-15V output voltage, nominal AC mains voltage and 2x 400mA load current the transformer will dissipate 3.0W, each diode 160mW, and the pair of regulators dissipates 3.3W each. Total dissipation is then 10.2W for a DC power output of 12W, giving an efficiency of 54%.

All this assumes the AC mains voltage is perfectly sinusoidal, no flat topping, which is probably a stretch in many locations around the world.

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Post by diablojoy » Wed Dec 04, 2013 7:43 pm

thanks for the clarification :tu:

hmm there are 35VA and 50VA versions they are rated at 972mA
and 1389mA on the secondaries respectively dont know if they share the same footprint however and they are physically larger so perhaps not
suitable for this board ?

edit: ok so after having a look at the datasheet again L01-6384 is the 50VA version which i dont think will even fit within the pcb size , so not as simple as just adding some extra pads, pity a little extra grunt would have been a bonus
The 35VA version maybe could fit
if some extra pads could be added to the pcb
pin space requirements are at 66.04 x 66.04mm - 1.3mm pins

http://www.amgistoroids.com/assets/file ... ormers.pdf
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Post by J3RK » Thu Dec 05, 2013 12:18 pm

An extra pin/pad set for the next step up could definitely be added. I don't really mind making a different board for the largest one either. Once again, I had these mostly in mind for a panelized sort of synth like a single boat situation, but I could definitely make a bigger version. It would be a simple update. I'm wondering though at what point it would be better to start having more in the way of safety features, sense circuits, and other protection. (Technically, probably from the bottom up, but in my mind, the more one is expecting it to do, the more of those features it should have.)

There is a sticky on E-M with some really nice design tips/info. I don't think it contains anything about sensing though. Should also probably add real terminals of some type for the AC input, so insulated connectors can be used. The feature creep is setting in... :mrgreen:
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Post by J3RK » Thu Dec 05, 2013 2:56 pm

Yeah... I don't think I want to deal with sensing. For the simple applications that these are intended for, I think just the fact that they can be trimmed should be fine. So, I'm not going to worry about that. However, I will do a bit to make them a little safer on the AC end, allow for more AC standards, and see about adding footprints for the larger (and maybe even smaller) toroids. :party:
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Post by diablojoy » Thu Dec 05, 2013 4:20 pm

Yeah... I don't think I want to deal with sensing. For the simple applications that these are intended for, I think just the fact that they can be trimmed should be fine. So, I'm not going to worry about that. However, I will do a bit to make them a little safer on the AC end, allow for more AC standards, and see about adding footprints for the larger (and maybe even smaller) toroids.
Simple is good
If you can get the 35VA version onto the board that would be good
its a better size to suit the number of outputs on the distribution buss
given a low average module consumption. obviously you dont have to use all of them but some people will try without thinking about it first.
I would like to see a 50VA version with the same style of torroidal. :tu:
it would be more appealing to a greater audience IMO.
Should also probably add real terminals of some type for the AC input,
I tend to like the PCB mount 3 pin insulated screw terminal types
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