Author Topic: New 12 volt power supply.  (Read 705 times)

hutch--

  • Administrator
  • Member
  • ******
  • Posts: 6758
  • Mnemonic Driven API Grinder
    • The MASM32 SDK
Re: New 12 volt power supply.
« Reply #15 on: November 09, 2019, 10:33:16 PM »
The 300KW would be a ton of fun, you would need a power station to run it. With audio amps, you usually put the power supply well away from signal circuits to avoid the magnetic fields but torroids are a lot cleaner than the old I+E lamination transformers. Somewhere in between were C core transformers but you rarely see them any more as torroid manufacturing techniques have become a lot more efficient.

Something I have forgotten is a technique of using another much smaller and faster capacitor across the output DC lines that already have a large value capacitor to level out the space between sine wave peaks. I could not find it in the internet but the general drift was the smaller size and speed difference further cleaned up the DC output. It really only applied to nit picky audio supplies but I have forgotton how its done. A power supply I built 20 years ago that still works perfectly has an 8000 mf capacitor and a 0.1 mf capacitor across it and I think it was a polycarbonate film capacitor.
hutch at movsd dot com
http://www.masm32.com    :biggrin:  :skrewy:

daydreamer

  • Member
  • ****
  • Posts: 942
  • watch Chebyshev on the backside of the Moon
Re: New 12 volt power supply.
« Reply #16 on: November 09, 2019, 10:50:48 PM »
nice stuff,what I want is a PSU with battery backup builtin,so I dont get my computer os and hd wrecked by sudden storm
well old gaming box I need to have lots of 900kw+ to drive powerhungry gpu and box full of several cooling fans

Quote from Flashdance
Nick  :  When you give up your dream, you die
*wears a flameproof asbestos suit*
Gone serverside programming p:  :D

K_F

  • Member
  • *****
  • Posts: 1519
  • Anybody out there?
Re: New 12 volt power supply.
« Reply #17 on: November 09, 2019, 10:52:40 PM »
Larger size caps as you mention are 'bulk' capacitors and hold 'reserve power'. Those smaller value caps filter 'higher frequency' noise on the power rails, which can creep into the audio range.

That 8000 mf cap is probably (sorry is - just looked at pic ;)) electrolytic type.. I'm amazed it's still working as the electrolytic's 'wet' dielectric eventually dries up, and it goes with a bang and some smoke signals. It must be a good quality cap.


We nowdays have stricter electrical requirement at our high power ratings, such that basic transformer PSU's must now have Power Factor Correction (PFC) in them.
The PSU like you have (and many older types) introduce spikes/harmonics back into the utility power line, that the Utility supplier gets really excited when he see his power line 'going to pot'. A PFC unit (essentially a SMPS pre-stage) in the psu eliminates this problem.
'Sire, Sire!... the peasants are Revolting !!!'
'Yes, they are.. aren't they....'

hutch--

  • Administrator
  • Member
  • ******
  • Posts: 6758
  • Mnemonic Driven API Grinder
    • The MASM32 SDK
Re: New 12 volt power supply.
« Reply #18 on: November 10, 2019, 02:27:18 AM »
I recently powered up some old and cheap 2200mf 16 volt caps but one popped the top so they are all trash. Funny enough with the old power supply, the 8000mf 75 volt one seems to be fine and I have 3 others that also worked fine when I tested them but they would have to be suspect at that age. The one in the photos about is a new 10000mf 100 volt one so it should be OK for some years. Back when I bought the 8000mf ones, they were really expensive but were a good brand at the time.

I know very little about power factor correction as I have usually seen it as something that is done back at the power station or sub station and I know they used to use very big capacitors with 3 phase to keep the phases properly spaced. My old factory has a 3 phase 400 amp power supply that I used to switch on and off with a remote.

Many years ago before this house was rewired, some things used to run hot, I have a small bench grinder that used to heat up in less than a minute but after the rewiring and the main power coming in having been replaced from the sub station, it does not happen any longer.
hutch at movsd dot com
http://www.masm32.com    :biggrin:  :skrewy:

hutch--

  • Administrator
  • Member
  • ******
  • Posts: 6758
  • Mnemonic Driven API Grinder
    • The MASM32 SDK
Re: New 12 volt power supply.
« Reply #19 on: November 10, 2019, 02:44:38 AM »
Magnus,

My older brother ran his own electronics repair business for many years and one thing he regularly had to do was repair things like TV sets and other electronic stuff that had been trashed by lightning strikes. Apparently the voltage spike is so high is blows the power supply off the board. I don't know what mains voltage you have but you would need a decent big battery supply to safely get off grid with your computer. Lightning strikes that hit the ground can do the same as hitting the wiring.

Once down the country it was just starting to rain and I heard this almighty BANG when lightning hit a transformer up the road, it sounded like a bomb going off. It took out 1 phase and luckily the house I was staying in was on another phase so nothing was damaged. Where you are at risk, you completely unplug a computer if a storm is coming in.
hutch at movsd dot com
http://www.masm32.com    :biggrin:  :skrewy:

K_F

  • Member
  • *****
  • Posts: 1519
  • Anybody out there?
Re: New 12 volt power supply.
« Reply #20 on: November 10, 2019, 05:56:46 AM »
... you completely unplug a computer if a storm is coming in.
I unplug everything wired from PC, modems and printers - All power and network connections.
Then run off and do something rebellious... read a book :thumbsup:

Very little survives a power strike... instant charcoal  :biggrin:
'Sire, Sire!... the peasants are Revolting !!!'
'Yes, they are.. aren't they....'

mikeburr

  • Member
  • **
  • Posts: 93
Re: New 12 volt power supply.
« Reply #21 on: November 11, 2019, 10:33:27 AM »
hutch
K_F is completely right with his advice .. since ive built a few audio amps in my time which use supplies vaguely like yours
1) a common trick to improve filtering is to take the main cappy and add progressively smaller values in ||  division being by 10
    eg 10000 uf 1000uf 100uf 10uf as this significantly improves filtration
2) build a Pi filter with a large inductance ,my pal JD Marney's priniciple being as much metal as you can muster
regards mike b .. didnt read much of it   ..what are you doing  i hope your not trying to automate that p..y little lathe youve got

hutch--

  • Administrator
  • Member
  • ******
  • Posts: 6758
  • Mnemonic Driven API Grinder
    • The MASM32 SDK
Re: New 12 volt power supply.
« Reply #22 on: November 11, 2019, 12:34:08 PM »
Hi Mike,

The one above is only a single sided supply, with audio long ago they were always double sided as the class of amplifier I used to build was Class AB with dual voltage rails. What I used to do when my oscilloscope was still running was test the output for ripple and these ones with a big capacitor and torroidal transformers were always very clean. You could get some rather ugly ripple from badly designed IE core transformers and while a pair of big capacitors usually cleaned it up a lot, you could still see it on the oscilloscope.

Using the smaller and faster capacitors across the big one is an idea that I understand but I have yet to find a formula for making it work. I don't feel like forking out a fortune for another oscilloscope so I don't really have a way to test the output any longer. I will be using power supplies of this type for DC brush motors which generally like a very low ripple power input.
hutch at movsd dot com
http://www.masm32.com    :biggrin:  :skrewy:

daydreamer

  • Member
  • ****
  • Posts: 942
  • watch Chebyshev on the backside of the Moon
Re: New 12 volt power supply.
« Reply #23 on: November 12, 2019, 04:08:33 AM »
Magnus,

My older brother ran his own electronics repair business for many years and one thing he regularly had to do was repair things like TV sets and other electronic stuff that had been trashed by lightning strikes. Apparently the voltage spike is so high is blows the power supply off the board. I don't know what mains voltage you have but you would need a decent big battery supply to safely get off grid with your computer. Lightning strikes that hit the ground can do the same as hitting the wiring.

Once down the country it was just starting to rain and I heard this almighty BANG when lightning hit a transformer up the road, it sounded like a bomb going off. It took out 1 phase and luckily the house I was staying in was on another phase so nothing was damaged. Where you are at risk, you completely unplug a computer if a storm is coming in.
It was an epic storm big enough to have a name and it disrupted powersupply
Car battery is forbidden inside house, because risk of risk of fire
Quote from Flashdance
Nick  :  When you give up your dream, you die
*wears a flameproof asbestos suit*
Gone serverside programming p:  :D

hutch--

  • Administrator
  • Member
  • ******
  • Posts: 6758
  • Mnemonic Driven API Grinder
    • The MASM32 SDK
Re: New 12 volt power supply.
« Reply #24 on: November 12, 2019, 06:18:23 AM »
If its a lead acid car battery it should not be a fire risk but you do need to ventilate them if its an older type that has dilute sulphuric acid in it. You can get fire risks from lithium ion batteries if they are too old, shorted or incorrectly charged.
hutch at movsd dot com
http://www.masm32.com    :biggrin:  :skrewy:

hutch--

  • Administrator
  • Member
  • ******
  • Posts: 6758
  • Mnemonic Driven API Grinder
    • The MASM32 SDK
Re: New 12 volt power supply.
« Reply #25 on: November 21, 2019, 05:17:02 PM »
All things come to those who wait long enough, my 160 VA transformer turned up today. It will fit into the case but the wire thickness of the 9 volt outputs will be a ton of fun to connect. Combined output wired in parallel is specified at 8.8 amps x 2, 17.6 amps which should have enough grunt to do what I need.

hutch at movsd dot com
http://www.masm32.com    :biggrin:  :skrewy:

K_F

  • Member
  • *****
  • Posts: 1519
  • Anybody out there?
Re: New 12 volt power supply.
« Reply #26 on: November 22, 2019, 07:35:22 AM »
Make sure you have the output winding polarities correct before you parallel them, or there will be instant smoke.
If you don't have a oscilloscope to check you can connect them in series with the following results.

1) Double the voltage means you have the phases head to tail - then you 'slide' the connections for parallel configuration.
2) Zero voltage means they're anti-phase, you then connect the two unconnected ends together (leaving the other connected points together) for in-phase parallel connection.
;)
'Sire, Sire!... the peasants are Revolting !!!'
'Yes, they are.. aren't they....'

hutch--

  • Administrator
  • Member
  • ******
  • Posts: 6758
  • Mnemonic Driven API Grinder
    • The MASM32 SDK
Re: New 12 volt power supply.
« Reply #27 on: November 26, 2019, 11:01:11 AM »
 :biggrin:

I cheat, the transformers come with the winding order inside the plastic wrap around the windings and also on the box. The only real problem is the secondary wiring is so thick that I gave up trying to connect them together and used connector strip. The 15 amp wire I have is just short of the 17.6 amp output so I have to double it to make sure nothing gets fried. Got some nice panel mount fuse holders as the transformer specifies a 3 amp fuse.

I have the 35 amp bridge rectifier mounted on a piece of aluminium angle which acts as a heat sink but its easy enough to add an extra heat sink behind the rectifier as I can make one out of sheet aluminium. I have used audio connectors for the output as they are far better quality than the plastic ones and just found some very nice banana connectors that fit tight enough to handle some decent current so its just about ready to put it all together.
hutch at movsd dot com
http://www.masm32.com    :biggrin:  :skrewy:

mineiro

  • Member
  • ***
  • Posts: 452
Re: New 12 volt power supply.
« Reply #28 on: November 27, 2019, 09:58:55 AM »
Hello sir Hutch;
Try a virtual oscilloscope. I'm using freeware LTspice program to my tests before mount things. This program do not come with some "standarts" components like diode rectifier d1n4001 because is done by rivals; but you can find a ".model" in internet, import to the program and do your tests. Most of component sellers dispose these data (.model) in their own homepage. Have some examples about how to create transformers from inductors from Ltspice point of view.
https://www.analog.com/en/design-center/design-tools-and-calculators/ltspice-simulator.html#

Power factor correction is necessary to pay less money in energy (watts/hour) because more eficient the circuit design was. Generally you insert a capacitor (reatance) to adjust total impedance, the power factor to be 1. How much close to 1, more eficient the circuit.

I'd rather be this ambulant metamorphosis than to have that old opinion about everything

hutch--

  • Administrator
  • Member
  • ******
  • Posts: 6758
  • Mnemonic Driven API Grinder
    • The MASM32 SDK
Re: New 12 volt power supply.
« Reply #29 on: November 29, 2019, 11:23:46 PM »
The deed is done, I finished off another project today and swapped the 80va transformer for the 160va transformer. Rectified output is about 13.25 volt, slightly lower than the smaller transformer. I still need to put the fuse above the input plug but it works fine. The AC amperage output in parallel is supposed to be 17.6 amps but I really only need 10 amp, 15 at a pinch and it should be comfortable with that level of output. I built it in the first place with everything over sized, 35 amp bridge rectifier, 100 volt 10000uf capacitor and 15 amp wire and after running it for some hours, it was still stone cold. The mains fan moves a lot of air, I did it as a puller rather than a pusher to get the level of turbulence I wanted with the holes in the base.


hutch at movsd dot com
http://www.masm32.com    :biggrin:  :skrewy: