90% of this thread in a nutshell.
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Oh, I missed that it says āregulate your existing DC powerā because the āfixed voltage rating and 1 amp output with thermal shutdown and short circuit protectionā bit sure sounds like a 78xx. My updated guess is that this is even simpler than I thought; this is just the 78xx/79xx pair from a typical wall wart supply, and you need one of the others to rectify and smooth the AC input into something you can regulate.
Pretty sure you can buy the components for less from Tayda.
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yeah it seems that a PCB from Frequency Central , MFOS , Befaco or several others used with wall wart or center tapped transformer would be your safest bet . they are made to power modules and really are not that expensive , especially when considering how much it would cost if you cooked a module due to a flaky power supply .
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There is good reason. No point in trying to find a cheaper solution to a cheap solution that is reliable.
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As Iāve discussed on the Mail Day thread, the supplies I have include a Frequency Central (ready built) and a Sourcery V2.0 kit (from Kristian BlĆ„sol of Modular in a Week). In addition to the +/-12V rail to rail, both boards nominally provide a 5V supply but the current draw appears to be too low to be of much use. Frequency Central quotes a maximum capacity of about 100mA on the 5V line. Raspberry Pis and similar systems typically draw several hundred milliamperes.
I think I should probably power the digital systems through their own 5V DC power sources. I suppose this can be done by yoking the 0V of the 5V DC supply to the 0V of the Frequency Central power. Has anybody else faced this problem? Iām a little concerned that I may be creating a ground loop problem, but I suppose Iāll deal with this when it happens.
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Of course these suppliesā 5V rail is intended to power the odd 5V chip in Eurorack modules, not Raspberry Pis. And few Eurorack modules use it.
What limits the 5V rail to 100 mA? Is it just the amount of heat produced in regulating 12V down to 5V?
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Modern raspberries need 2.1-3.0 A depending on model, so youāre outside what a LM78xx can supply even with decent heatsinking.
The FC uses a 78L05 iirc, which is specced for 100 mA (and sinking 0.7 W without a heatsink will put you above max operating temperature unless you put the supply in your fridge).
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Iāve been referencing this drawing from the Mutable Instruments forum:
In my current Eurorack case I use a supply cobbled together from three wall warts including one that is 5V, 5A. I got the idea from:
Though that one uses a regulator for 5V.
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The most thirsty Raspberry Pi Iād want to use is a 2, because I think the later ones are overpowered for my needs. The Beaglebone Black is similar to the B in many ways, and its main attraction is its maturity as a music platform. The Beaglebone-based Bela is pretty relaxed as to how you power it, and there are open source designs for powering from the +12V line as well as the built in 5V barrel connector and the USB port.
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Mean Well RT-65B keeps making an appearance. I can get these on eBay for a little over Ā£30. The 5V on those is a hefty 5A maximum, which would seem to be very handy for my vision of a hybrid system.
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Theyāre ~16 GBP (18 EUR) at tme.eu. Havenāt checked shipping, though.
Not entirely sure you should power analog audio and a raspberry from the same supply but havenāt tested it so maybe thatās good enough.
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Seems reasonable, though that particular seller has a wait of months to restock it.
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Yeah, the RT-65B powering my Kosmo case hasnāt broken a sweat. I plugged some LEDs into the 5v supply to give it something to do.
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Giving each output at least its minimum load is said to be the way to minimize noise from the Mean Well. Thatās as good an excuse as any to light up the panel like a Christmas tree.
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I finally went with my eBay seller. They can get a RT-65B to me in a week or two and when factoring in the shipping from other sources Iām happy with the price of Ā£31.17.
Meanwhile I just received a bag of heat sink kits to go with those 78 and 79 series regulators on the BlƄsol kit.
I know linear regulation is popular for analogue modular, but throwing away so much energy as heat doesnāt sit well with me. I want to give a well constructed switching supply a chance. The headroom on the 5V line makes it especially attractive.
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More fool me. Iām still waiting for the thing to ship.
Edit August 18: I put out a query when the item didnāt ship by the estimated arrival date at the weekend. Just now I received a full refund. Oh well, I would rather have received the power supply, even a few days late.
Iāve ordered another from a second eBay seller, for a pound or so more. This is due early next week, 24-25 August. Iām looking forward to it.
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Really blown away at how cheap the RT-65B is direct from Jamecoā¦
I may have to get one of these and a distribution board.
What else is needed @ChristianBloch
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One thing to notice about the RT-65B is that itās certainly not optimized for synth modules, in that it can supply 2.8 A at +12 V, 0.5 A at -12 V, and 5 A at 5 V. Judging from what I see on modulargrid.net it seems Eurorack modules on average require about 2ā3 times as much current at +12 V as at -12 V, rather than more than 5 times which is what the RT-65B can do. And of course few Eurorack modules (and no Kosmo modules) use the 5 V rail at all, let alone 5 A in a case. In other words an RT-65B will work fine for a not too large case, but youāll probably max out the -12 V supply well before reaching the +12 V supply limit and youāll barely if at all touch the 5 V.
(As a comparison, the TipTop ĀµZeus, designed for Eurorack, supplies 2000 mA @ +12 V, 500 mA @ -12V, and 170 mA @ 5V.)
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Yeah, RT-65B makes much more sense if you plan to use mostly 5V. Itās ideal for the kind of hybrid system Iām planning, with multiple small computers at 5V or 3.3V and only a few analogue modules, all communicating at Eurorack signal levels.
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Yeah, I would get two cheap 12V MeanWell supplies in steadā¦ then add a 5V if you ever need it.
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