Author Topic: lab power supply  (Read 7488 times)

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Offline glinjik

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lab power supply
« on: December 12, 2019, 10:46:09 am »
hi i need to build variable power supply can anyone point me to the eev blog power supply diagram please
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Offline tooki

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Re: lab power supply
« Reply #1 on: December 13, 2019, 06:22:20 am »
It never came to fruition, but instead morphed into the still unfinished μSupply portable PSU project. (I originally joined the forums while looking for the same thing as you, wondering what had happened to the PSU design!)
 

Offline German_EE

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Re: lab power supply
« Reply #2 on: December 13, 2019, 07:49:15 pm »
Two alternatives:

Build one of these https://www.electronics-lab.com/project/0-30v-laboratory-power-supply/
He even supplies the Eagle files and the Gerbers-

Buy one of these
https://www.ebay.com/itm/0-30V-DC-Power-Short-Circuit-Module-Board-2MA-3A-Adjustable-Protection-Tools-Kit/323969090433 Seven bucks and free shipping.
Should you find yourself in a chronically leaking boat, energy devoted to changing vessels is likely to be more productive than energy devoted to patching leaks.

Warren Buffett
 
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Offline MarkF

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Re: lab power supply
« Reply #3 on: December 14, 2019, 12:14:34 am »
Here are a few DIY circuits you can play with:

[attachimg=1]

[attachimg=2 width=1024]

[attachimg=3 width=1024]
 
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Offline glinjik

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Re: lab power supply
« Reply #4 on: December 14, 2019, 09:56:46 am »
wow thank you for replys i rather like the look of the last one do you think possible to replace the c1061 with a 2n3055 and the bc337 doing the volt adjust for an igbt and last the bc337 doing the curent adjust to 2 e13005-1 in paralel? im sorry for the questions but its items i already have my transformer puts out about 17v after rectifier at about 3 amps max (i only need about 1 amp or less
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Offline glinjik

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Re: lab power supply
« Reply #5 on: December 14, 2019, 10:05:09 am »
this is what i have built so far but find the voltage meter unstable under load
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Offline MarkF

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Re: lab power supply
« Reply #6 on: December 14, 2019, 06:59:02 pm »
For my first byte of the apple, I would use:
  - a TIP3055 for the C1061
  - 2N2222 for the BC337
« Last Edit: December 14, 2019, 07:10:47 pm by MarkF »
 

Offline glinjik

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Re: lab power supply
« Reply #7 on: December 14, 2019, 07:35:48 pm »
after experimenying with it im not gonna continue it seems flawed by voltage variations for input changes and output changes so lookang at this next one looks more stable although im not sure about the qulity of the 317 i have here 5 of them and they all give different output on same power supply  :palm:
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Offline glinjik

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Re: lab power supply
« Reply #8 on: December 14, 2019, 07:39:31 pm »
only going to use 1 2n3055 i dont need high amps il only fry myself (again) forgetting to unplug the transformer them moving it makes an interesting tingly feeling just before dropping it again and usind bad words :-X
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Offline glinjik

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Re: lab power supply
« Reply #9 on: December 14, 2019, 07:40:59 pm »
and why is my country uk? im in Russia although im english
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Offline glinjik

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Re: lab power supply
« Reply #10 on: December 14, 2019, 08:11:44 pm »
can anyone tell why there is caps on the rectifier part or is this just simbolising the internals of the bridge rectifier?
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Offline george.b

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Re: lab power supply
« Reply #11 on: December 14, 2019, 08:34:02 pm »
after experimenying with it im not gonna continue it seems flawed by voltage variations for input changes and output changes so lookang at this next one looks more stable although im not sure about the qulity of the 317 i have here 5 of them and they all give different output on same power supply  :palm:

I would only use an LM317 that came from a reputable source. Had my share of woes from counterfeit LM317s. :--

can anyone tell why there is caps on the rectifier part or is this just simbolising the internals of the bridge rectifier?

To reduce noise when the diodes switch. It's not absolutely necessary.
« Last Edit: December 14, 2019, 08:38:15 pm by george.b »
 

Offline glinjik

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Re: lab power supply
« Reply #12 on: December 14, 2019, 08:44:11 pm »
thank you for your replies unfortunately here its difficult and expensive to get parts from a reputable dealer even they sell fake parts for a 317 from like rs it can take several weeks to get it, just for me to fry the thing
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Offline MarkF

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Re: lab power supply
« Reply #13 on: December 14, 2019, 09:00:01 pm »
after experimenying with it im not gonna continue it seems flawed by voltage variations for input changes and output changes so lookang at this next one looks more stable although im not sure about the qulity of the 317 i have here 5 of them and they all give different output on same power supply  :palm:
[attachimg=1 width=500]


If you are not doing any current limiting, why are you NOT using the suggested high current configuration from the datasheet?

[attachimg=2 width=500]
 

Offline David Hess

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Re: lab power supply
« Reply #14 on: December 15, 2019, 02:29:28 am »
can anyone tell why there is caps on the rectifier part or is this just simbolising the internals of the bridge rectifier?

To reduce noise when the diodes switch. It's not absolutely necessary.

Whether they are needed depends on the diodes and application.  Some rectifiers have a very fast and hard reverse recovery like a step recovery diode which produces broadband RF spikes at the power line frequency.  This varies by type, manufacturer, and even lot but usually occurs with standard recovery rectifiers which are often constructed with a PIN structure like a step recovery diode.

It is a major problem with audio and instrumentation circuits.  Solutions to prevent it include adding bypass capacitors directly across the diodes, adding EMI suppression beads in series with the diodes, selecting standard recovery diodes which do not have the problem, and using faster diodes which have a controlled recovery characteristic.  Trying to filter the noise at the input and output of the rectifier is a lost cause because it will already be radiating, parasitic capacitance will allow it blow by the filters, and because it will already have become common mode noise through the transformer's primary to secondary capacitance.

I first ran across the problem with some home built 7815, 7915, 7805 power supplies which only had to be powered on to cause problems with audio circuits anywhere in the room and to show up on oscilloscopes.  Tests determined that swamping the junction capacitance of the diodes with roughly 10 times the value prevented the interference so that is what I did.  Later I noticed capacitors across rectifiers in many service schematics and sometimes EMI suppression beads as well.

Below is the lab power supply schematic that I would emulate from National Semiconductor linear brief 28.  Instead of using expensive LM395 integrated power transistors, the power pass element could be replaced with suitable integrated regulators or bare transistors or some combination of the two.
« Last Edit: December 15, 2019, 02:37:07 am by David Hess »
 
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Offline not1xor1

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Re: lab power supply
« Reply #15 on: December 15, 2019, 06:03:27 am »
Below is the lab power supply schematic that I would emulate from National Semiconductor linear brief 28.  Instead of using expensive LM395 integrated power transistors, the power pass element could be replaced with suitable integrated regulators or bare transistors or some combination of the two.

that's a nice circuit (unlike the other ones >:D) but it looks like LM308 is no longer available and LM101 is hard to find and very expensive, although there are cheap LM301 in sot8 package from onsemi.

replacing those opamps with modern parts would require a different compensation network and careful selection of parts complying with the same input range (and other features) of the original ones or mirroring the design (regarding polarity) to rather use the so-called single power supply opamps that usually include the negative rail as input range.
« Last Edit: December 15, 2019, 06:05:45 am by not1xor1 »
 
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Offline glinjik

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Re: lab power supply
« Reply #16 on: December 15, 2019, 07:45:34 am »
sorry misunderstood i am limiting the current but what i meant was i dont need high amps, i want a range between ma and 1 amp. as i understand it if i dont limit the current then if i put a big load on then it will just suck the amps untill the transformer gets hot and i get my own global meltdown unless im wrong (high probability) :-DD
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Offline glinjik

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Re: lab power supply
« Reply #17 on: December 15, 2019, 10:07:14 am »
can someone advise please which of these caps is best for this part the electrolitic i have its the non polarised ones im strugling with
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Offline glinjik

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Re: lab power supply
« Reply #18 on: December 15, 2019, 10:09:09 am »
some reason this capture didnt upload in last post
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Offline glinjik

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Re: lab power supply
« Reply #19 on: December 15, 2019, 10:23:10 am »
ref post 20 the blue ones are not caps they are resistors at 0.67 \$\Omega\$ oops
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Offline Calvin

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Re: lab power supply
« Reply #20 on: December 15, 2019, 11:56:44 am »
Hi,

You might want to have a look at "High Performance Portable DC Bench Power Supply: Save Money and Free Up Bench Real Estate by Building Your Own" https://www.analog.com/en/technical-articles/high-performance-portable-dc-bench-power-supply.html on AnalogDevices´s website (actually a LinearTechnology design). They include gerber files and BoM (search for DC2132A).
Add a decent SMPS or Trafo-supply, a nice casing and a couple of those cheap ebay voltage modules (up to 5 digits) and You´re there.
Seems that that design is really top notch.

regards
Calvin
« Last Edit: December 15, 2019, 12:14:40 pm by Calvin »
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Online EEVblog

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Re: lab power supply
« Reply #21 on: December 15, 2019, 11:58:15 am »
It never came to fruition, but instead morphed into the still unfinished μSupply portable PSU project.

It has always been the uSupply portable USB PSU project.
 
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Online EEVblog

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Re: lab power supply
« Reply #22 on: December 15, 2019, 11:59:59 am »
Hi,

You might want to have a look at "High Performance Portable DC Bench Power Supply: Save Money and Free Up Bench Real Estate by Building Your Own" https://www.analog.com/en/technical-articles/high-performance-portable-dc-bench-power-supply.html on AnalogDevices´s website (actually a LinearTechnology design). They include gerber files and BoM.

Beware though, the LT3081 has design issues, which is why I eventually dropped it.
 
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Offline glinjik

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Re: lab power supply
« Reply #23 on: December 15, 2019, 12:16:30 pm »
hi thank you for your replies but from ebay is no goer here as for real estate lol not much needed here 3 dmms one soldering station oh and a mastech esr meter all in my portacabin 6 x 3 meters so space not a problem i suppose i could just go buy a power supply but i really am learning soooo much from building this i mean like using transistors in parralel caps in parralel balast resistors the list is endless and i damn well enjoing doing it apart from burning 7 out of 8 fingers both thumbs and frying myself on the transformer and my wife moaning when i stole the wire cleany thing for my soldering station and ive just learnt just cos it looks like a zener it dont mean it is actually a fast switch and whet i thout were caps turn out to be resisters ive not enjoyed learing like this for years im a happy chappie  :) 
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Offline Calvin

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Re: lab power supply
« Reply #24 on: December 15, 2019, 12:35:28 pm »
Hi,

@eevblog
Would You mind to elaborate on the issues of the LT3081.
I saw that You tried the LT3080 and had issues.
Searching for ´LT3081´ didn´t find me a thread with valuable infos about LT3081 probs.

regards
Calvin
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