What's the 'best' way to get bipolar power from a wall-wart?

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Re: What's the 'best' way to get bipolar power from a wall-wart?

Post by Portabella » Mon Feb 22, 2021 5:34 am

I have 5x little boards available which will turn any dual voltage (AC and DC) into ± 12VDC
Input range: AC 12-16V or DC15-24V

If any of you want to buy such a board, drop be a PN. It's 5$ per piece
IMG_5046.jpg

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Re: What's the 'best' way to get bipolar power from a wall-wart?

Post by Altitude909 » Mon Feb 22, 2021 7:13 am

You might want to check out how Seismic did this thing: https://github.com/seismicindustries/IPS2 .

I use the same vReg to go from +5 to +/-12v and its pretty decent. There are dozens of chips out there for all sorts of different input conditions and loads, you just need to hunt down what you want (which is not trivial, there are a LOT of parts). I HIGHLY recommend purchasing development boards for whatever part youre interested in first, this will give you a properly configured and laid out board to test with to make sure that part you want to use will do what you want it to. The manuals for the dev boards are pretty much the instructions for making your own so highly valuable reading

The Seismic part uses the TI TPS65131 DCDC part, here's the evaluation board for it https://www.ti.com/tool/TPS65131EVM-839 and user guide https://www.ti.com/lit/ug/slvuaw7/slvua ... 131EVM-839

Also worth noting, the complexity of small SMPS devices is like that for a reason, the $5 aliexpress devices will probably get you the voltages they advertise but this will come with 100+ mV noise on the outputs. I have a drawer full of them and none have even come close to something usable noise wise.

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Re: What's the 'best' way to get bipolar power from a wall-wart?

Post by MikeDB » Mon Feb 22, 2021 12:57 pm

Altitude909 wrote:
Mon Feb 22, 2021 7:13 am
Also worth noting, the complexity of small SMPS devices is like that for a reason, the $5 aliexpress devices will probably get you the voltages they advertise but this will come with 100+ mV noise on the outputs. I have a drawer full of them and none have even come close to something usable noise wise.
Yeah - it's those things that have given SMPSes a bad name ! Done properly they can have noise lower than a linear supply, but it's so easy to take a short cut to reduce costs .... and kill performance.

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Re: What's the 'best' way to get bipolar power from a wall-wart?

Post by KSS » Mon Feb 22, 2021 8:32 pm

Low noise is only one of the classic reasons to employ linear over SMPS. Transient load response is another.

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Re: What's the 'best' way to get bipolar power from a wall-wart?

Post by Thomas73951 » Tue Feb 23, 2021 4:21 am

Altitude909 wrote:
Mon Feb 22, 2021 7:13 am
Also worth noting, the complexity of small SMPS devices is like that for a reason, the $5 aliexpress devices will probably get you the voltages they advertise but this will come with 100+ mV noise on the outputs. I have a drawer full of them and none have even come close to something usable noise wise.
That's quite a lot of noise. Do you think some (low pass) filtering would help eliminate the noise and just leave the ±15v DC or is the noise too bad for that?

I haven't done anything with my synthesiser for ages because my current power solution is bad. I'm now wondering whether these are just going to cause more (but different) problems.

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Re: What's the 'best' way to get bipolar power from a wall-wart?

Post by Troubleshooter » Tue Feb 23, 2021 7:10 am

These look very handy to put in pedals. Ordered a pair of 12V and 15 models to try out. Thanks for the tip!
MikeDB wrote:
Thu Feb 04, 2021 6:23 pm
plushterry wrote:
Thu Feb 04, 2021 5:45 pm
I'm planning a standalone filter box (not part of a modular) that I'd like to power from a wall-wart. I've been looking at various ways to get a negative power rail .
If you're happy to use a 5V wallwart (e.g. some phone chargers, Pi PSU, some CCTV PSU etc) then the TI TPS6513x devices are very good. Can produce +/- 15V 300mA from +5V.

https://www.ti.com/product/TPS65130


Available as a module from China if you prefer.
e.g. https://www.aliexpress.com/item/1005001869133587.html

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Re: What's the 'best' way to get bipolar power from a wall-wart?

Post by MikeDB » Tue Feb 23, 2021 7:55 am

KSS wrote:
Mon Feb 22, 2021 8:32 pm
Low noise is only one of the classic reasons to employ linear over SMPS. Transient load response is another.
'Classic reasons' are usually based on hearsay or fantasy, nothing more. As I've said repeatedly, a good linear PSU is always noisier than a good SMPS. Likewise the transient load response in a linear supply is purely down to the large capacitors used to smooth 50/60/100/120Hz. If you need that feature then put the same size capacitors in a SMPS.

Let's be quite clear, there are NO good reasons nowadays to employ a linear over SMPS. Designed properly a SMPS will always outperform a linear supply in ANY application, be it low noise or high power or anything in between. The sooner linear supplies are banned outright the better as they just create so many problems for the grid.

The only problem that needs fixing with SMPSes is people who don't design SMPSes properly, especially those idiots not putting PFC in them to save a few cents !

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Re: What's the 'best' way to get bipolar power from a wall-wart?

Post by Altitude909 » Tue Feb 23, 2021 8:32 am

Thomas73951 wrote:
Tue Feb 23, 2021 4:21 am
Altitude909 wrote:
Mon Feb 22, 2021 7:13 am
Also worth noting, the complexity of small SMPS devices is like that for a reason, the $5 aliexpress devices will probably get you the voltages they advertise but this will come with 100+ mV noise on the outputs. I have a drawer full of them and none have even come close to something usable noise wise.
That's quite a lot of noise. Do you think some (low pass) filtering would help eliminate the noise and just leave the ±15v DC or is the noise too bad for that?

I haven't done anything with my synthesiser for ages because my current power solution is bad. I'm now wondering whether these are just going to cause more (but different) problems.
Its not trivial to deal the noise, they are VERY fast transients and a typical RC filter wont do much for and the other issue is that many DCDC SMP devices have a capacitive load limit so you cant just pile on big caps hoping to solve it. LC filters are normally used in SMPS designs as a result and properly implementing those isnt trivial.


>I'm now wondering whether these are just going to cause more (but different) problems.

I would say yes, and I wouldnt even bother with them. A good SMPS should cost you about the same as a decent linear one. The power supply is the basis of any electronic device, you dont start with the cheapest shittiest thing you can find, you start with the best possible power and work backwards from there to find the "good enough" point. Having a better PSU than you need is a much better prospect than having a much worse one.

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Re: What's the 'best' way to get bipolar power from a wall-wart?

Post by MikeDB » Tue Feb 23, 2021 10:28 am

Altitude909 wrote:
Tue Feb 23, 2021 8:32 am
A good SMPS should cost you about the same as a decent linear one. The power supply is the basis of any electronic device, you dont start with the cheapest shittiest thing you can find, you start with the best possible power and work backwards from there to find the "good enough" point. Having a better PSU than you need is a much better prospect than having a much worse one.
Great advice for everyone. Why spend 1000s of $/£s on modules and then put a $5 supply on it and wonder why you have noise/unreliability/dead modules ? Buy something decent to begin with when building the case and base everything around that supply.

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Re: What's the 'best' way to get bipolar power from a wall-wart?

Post by KSS » Tue Feb 23, 2021 11:01 am

:agree:
and was going to make the exact same quote -and near same comment- but was working on reply to MDB first.
--------------------------------------------------------------------------------------------------------
@MikeDB
How about pointing us to a couple good SMPS 'replacements' for the typical PowerOne -and clones/derivs- in the 1A and 3A -/+12-15V ?

And aren't Linear's already fiunctionally banned from many countries? <--Yes, there's exceptions, but the trend and focus is clear.
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Re: What's the 'best' way to get bipolar power from a wall-wart?

Post by MikeDB » Tue Feb 23, 2021 1:17 pm

KSS wrote:
Tue Feb 23, 2021 11:01 am
:agree:
and was going to make the exact same quote -and near same comment- but was working on reply to MDB first.
--------------------------------------------------------------------------------------------------------
@MikeDB
How about pointing us to a couple good SMPS 'replacements' for the typical PowerOne -and clones/derivs- in the 1A and 3A -/+12-15V ?

And aren't Linear's already fiunctionally banned from many countries? <--Yes, there's exceptions, but the trend and focus is clear.
I don't use that sort of power supply so don't usually like to make recommendations. I always use an RS 12V or 48V lots of amps switcher and then DC-DC convert locally on each PCB to the voltages I need, which is what this thread was originally dealing with. But an RS 904-8486 switcher with something like the Behringer CP1A may deliver a reasonable result.

And whilst linears are banned in many countries for electronic uses, someone above was knocking together a halogen bulb AC-AC convertor and something off eBay to rectify/regulate it. There are always people who try to get round regulations.

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Re: What's the 'best' way to get bipolar power from a wall-wart?

Post by EATyourGUITAR » Tue Feb 23, 2021 5:09 pm

LM317 is pretty slow in response to big fast transients but other than that, I have no problems with it. If you know the magnitude and the frequency of the transients you expect then it is within spec. Good SMPS design is hard to do which is why people avoid it. I can agree with the benefits of SMPS but if you don't design it for me then I just use linear.
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Re: What's the 'best' way to get bipolar power from a wall-wart?

Post by plushterry » Wed Feb 24, 2021 4:54 pm

Altitude909 wrote:
Mon Feb 22, 2021 7:13 am
You might want to check out how Seismic did this thing: https://github.com/seismicindustries/IPS2 .

I use the same vReg to go from +5 to +/-12v and its pretty decent. There are dozens of chips out there for all sorts of different input conditions and loads, you just need to hunt down what you want (which is not trivial, there are a LOT of parts). I HIGHLY recommend purchasing development boards for whatever part youre interested in first, this will give you a properly configured and laid out board to test with to make sure that part you want to use will do what you want it to. The manuals for the dev boards are pretty much the instructions for making your own so highly valuable reading

The Seismic part uses the TI TPS65131 DCDC part, here's the evaluation board for it https://www.ti.com/tool/TPS65131EVM-839 and user guide https://www.ti.com/lit/ug/slvuaw7/slvua ... 131EVM-839

Also worth noting, the complexity of small SMPS devices is like that for a reason, the $5 aliexpress devices will probably get you the voltages they advertise but this will come with 100+ mV noise on the outputs. I have a drawer full of them and none have even come close to something usable noise wise.

Thanks, thats an interesting design. I did consider that TPS65131 part initially, well, it's little brother the TPS65130. I decided against it as I wanted to be able to use up to a 12VDC input and the TI part had a max of 6V iirc. the part I went for in the end (LT3741) allowed upto 16V on the input, gave a better output current at the target voltage and was a couple of quid cheaper.

I hadn't considered using USB C as a power source. now that is a good idea.

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Re: What's the 'best' way to get bipolar power from a wall-wart?

Post by Altitude909 » Wed Feb 24, 2021 6:13 pm

plushterry wrote:
Wed Feb 24, 2021 4:54 pm
..
I hadn't considered using USB C as a power source. now that is a good idea.
Its not really being leveraged here, its just "dumb" USB C meaning that its just the connector and it doesnt have any of the cool high voltage stuff. USB C is pretty fricken complicated to implement properly if you want to use any of the voltage switching features

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Re: What's the 'best' way to get bipolar power from a wall-wart?

Post by plushterry » Thu Feb 25, 2021 3:18 pm

Altitude909 wrote:
Wed Feb 24, 2021 6:13 pm
Its not really being leveraged here, its just "dumb" USB C meaning that its just the connector and it doesnt have any of the cool high voltage stuff. USB C is pretty fricken complicated to implement properly if you want to use any of the voltage switching features
hadn't even thought that far, I was just thinking about using USB C as a power adapter :oops:

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Re: What's the 'best' way to get bipolar power from a wall-wart?

Post by MikeDB » Thu Feb 25, 2021 8:08 pm

plushterry wrote:
Thu Feb 25, 2021 3:18 pm
hadn't even thought that far, I was just thinking about using USB C as a power adapter :oops:
The only decent USB C adapter I've found is the Raspberry Pi 4 one which gives a proper 5V 3A without sagging or excessive noise. There may be others that are good, but I haven't seen one yet :-)

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Re: What's the 'best' way to get bipolar power from a wall-wart?

Post by bawbag » Mon Mar 01, 2021 9:14 am

Has anyone explored using the LT3581?

https://www.analog.com/media/en/technic ... 3581fb.pdf

Page 19 of the datasheet has an interesting configuration using two of the ICs in a master/slave configuration to provide +-12v.

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Re: What's the 'best' way to get bipolar power from a wall-wart?

Post by Portabella » Mon Mar 01, 2021 4:17 pm

bawbag wrote:
Mon Mar 01, 2021 9:14 am
Has anyone explored using the LT3581?

https://www.analog.com/media/en/technic ... 3581fb.pdf

Page 19 of the datasheet has an interesting configuration using two of the ICs in a master/slave configuration to provide +-12v.
see first post on this page

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Re: What's the 'best' way to get bipolar power from a wall-wart?

Post by bawbag » Mon Mar 01, 2021 9:59 pm

Portabella wrote:
Mon Mar 01, 2021 4:17 pm
bawbag wrote:
Mon Mar 01, 2021 9:14 am
Has anyone explored using the LT3581?

https://www.analog.com/media/en/technic ... 3581fb.pdf

Page 19 of the datasheet has an interesting configuration using two of the ICs in a master/slave configuration to provide +-12v.
see first post on this page
I don't understand - I see that you're selling some boards, but how does that relate to the LT3581?

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Re: What's the 'best' way to get bipolar power from a wall-wart?

Post by Portabella » Tue Mar 02, 2021 3:40 am

bawbag wrote:
Mon Mar 01, 2021 9:59 pm
Portabella wrote:
Mon Mar 01, 2021 4:17 pm
bawbag wrote:
Mon Mar 01, 2021 9:14 am
Has anyone explored using the LT3581?

https://www.analog.com/media/en/technic ... 3581fb.pdf

Page 19 of the datasheet has an interesting configuration using two of the ICs in a master/slave configuration to provide +-12v.
see first post on this page
I don't understand - I see that you're selling some boards, but how does that relate to the LT3581?
It features them dude

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Re: What's the 'best' way to get bipolar power from a wall-wart?

Post by bawbag » Tue Mar 02, 2021 4:58 am

Portabella wrote:
Tue Mar 02, 2021 3:40 am
bawbag wrote:
Mon Mar 01, 2021 9:59 pm
Portabella wrote:
Mon Mar 01, 2021 4:17 pm
bawbag wrote:
Mon Mar 01, 2021 9:14 am
Has anyone explored using the LT3581?

https://www.analog.com/media/en/technic ... 3581fb.pdf

Page 19 of the datasheet has an interesting configuration using two of the ICs in a master/slave configuration to provide +-12v.
see first post on this page
I don't understand - I see that you're selling some boards, but how does that relate to the LT3581?
It features them dude
I see a couple of TO-220 package regulators (LM series?) but not the DFN / MSOP package of the LT3581. Are they mounted on the underside of the board?

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