Small switching supplies
HollyMinkowski
Posts: 1,398
I have a chance to buy a large lot of really small
pwr supplies at a great price (about .17 each) they are
marked as 5.5v plus or minus 5% out DC at 350ma.
They can take 100-240 VAC input.
I popped one open so I could perhaps get the datasheet
for whatever switching regulator IC it used and was surprised
that there is none! There is a super tiny transformer that I'd
hate to have to rewind. There are two npn transistors, one
a standard type similar to a 3904 and one high voltage one
rated at 600v. There is also one IC that is a 6 pin opto coupler.
The largish cap is a 400v 2.2uf unit. It appears that the AC
is going in through a high v diode so the circuit sees only
half the AC waveform.
It was my hope that it would be easy to drop these to 5v or
a bit below that and perhaps even 3.3v. These are meant as
chargers for devices like cell phones and have a pull out
ac plug and a usb port. each comes with a cheap usb cable
that is pretty short.
I have a few other cheap switching supplies that you can set
the voltage from 0 to 16v just by changing the value of one resistor.
I am hoping these might be the same. I guess I will put one on
the bench next time I am at my old workplace and just try adding
a bit of resistance to each resistor in the circuit to see if I can find
an easy way to drop the voltage.
Do these appear to be worth buying? If I buy them I am going to
have them shipped to my cousin in the US. I am trying to get
her set up to sell some small electronic devices on ebay.
pwr supplies at a great price (about .17 each) they are
marked as 5.5v plus or minus 5% out DC at 350ma.
They can take 100-240 VAC input.
I popped one open so I could perhaps get the datasheet
for whatever switching regulator IC it used and was surprised
that there is none! There is a super tiny transformer that I'd
hate to have to rewind. There are two npn transistors, one
a standard type similar to a 3904 and one high voltage one
rated at 600v. There is also one IC that is a 6 pin opto coupler.
The largish cap is a 400v 2.2uf unit. It appears that the AC
is going in through a high v diode so the circuit sees only
half the AC waveform.
It was my hope that it would be easy to drop these to 5v or
a bit below that and perhaps even 3.3v. These are meant as
chargers for devices like cell phones and have a pull out
ac plug and a usb port. each comes with a cheap usb cable
that is pretty short.
I have a few other cheap switching supplies that you can set
the voltage from 0 to 16v just by changing the value of one resistor.
I am hoping these might be the same. I guess I will put one on
the bench next time I am at my old workplace and just try adding
a bit of resistance to each resistor in the circuit to see if I can find
an easy way to drop the voltage.
Do these appear to be worth buying? If I buy them I am going to
have them shipped to my cousin in the US. I am trying to get
her set up to sell some small electronic devices on ebay.
Comments
I'm testing these out right now.
I have 3 of them loaded to 300ma and will
leave them on for about a week and see what happens.
I was alerted to these by a salesman in China that I
used to buy cheap cameras from. He can get a hold
of about 1600 of them but I have to buy all to get the
good price...the shipping is extra but shipping from China
seems to be really cheap.
I second this
I would also take some of them at random and do this to them .....> Torture them like your try to kill them and see if they hold up
I would power down and back up a few time and also would loaded them to 400 milliamps and see what happen as well
Torture them like your try to kill them and see if they hold up I going to start doing this more often my self to see how well they are made
I had a few 12 volt switch power supply that every one them the output cap puff in smoke (I got about two year before this happen) replaced cap...>work as good as new one note these power supplies ran very warm all the time
These where used used for my outside camera that on 24 hours 7 days a week all of them made in China
I upgrade the power supply to power all four outside cameras on one switching power supply instead four switching power supply made in China but this power supply is much better built one note this power supply only run a little warm all the time
I found a 32 " LCD TV in the trash pile a few week age in the 5 volt power supply found a bad cap puff in smoke replaced cap work good as new
What is with these Smile eeeeee caps nice TV real good find though
One last thing not all Made in China is Smile but some thing are real Smile buyer beware
the voltage from 0 to 16v just by changing the value of one resistor. <........... I have done this already
It was my hope that it would be easy to drop these to 5v or <.................. I want to do this part also so if you find a way
a bit below that and perhaps even 3.3v.
I am hoping these might be the same. I guess I will put one on
the bench next time I am at my old workplace and just try adding
a bit of resistance to each resistor in the circuit to see if I can find
an easy way to drop the voltage.
Holly if you find a way to do this PLEASE post your finding Thanks
Also how much would you sell ten of them to me for only if you buy the hole lot of 1600
Please email at sam1030@comcast in the subject put switching power supply for sale thanks
You know, I did not think about a fuse! It really should have
one huh!? Perhaps one of those things that look like diodes
that are connected closest to the yellow wires carrying the AC
is actually some type of fuse element. I'm VERY glad you
mentioned this, I'd hate to sell power supplies that have no fuse
for safety.
Darn it! I bet this is what makes this hot deal turn cold :-(
I would add this ...>
I would also take some of them at random and do this to them .....> Torture them like your try to kill them and see if they hold up
IF they do not fail when testing them this way they might be all right but
I would let buyer know that they are not fused If I were to use one these power suppys to charge battery I would use one of these ........>> I use allot of these in battery packs and power supplys
"Raychem "Polyswitch" # RXE-065S-1. General purpose circuit protectors for power supplies, alarm systems, speakers, motors etc. Unlike traditional fuses, they automatically reset when fault condition is cleared. Can be paralleled for higher ratings. Current: 0.65 Amps. Trip Current: 1.3 Amps. Max Voltage: 60 Volts. 0.33" diameter. UL, CSA listed."
I also found this http://www.goldmine-elec-products.com/prodinfo.asp?number=G16102 3 for $1.00
I also found these here
http://www.mouser.com/ProductDetail/Littelfuse/0875800MXEP/?qs=n5MbhIql%252bRm3wEM5W5RqbQ%3d%3d 1 at $1.37 each or 500 at $1.09 each
I hope this helps
You should also verify that the output is isolated from the line voltage.
C.W.
http://www.mouser.com/ProductDetail/Littelfuse/0259062T/?qs=sGAEpiMZZMseCiJT91fwItxHhNY84ZZRV05DgLu7tVw%3d
Kwinn
Are these the type of fuses that you are talking about
also these
http://search.digikey.com/scripts/DkSearch/dksus.dll?Selection
be able to investigate further. I will also ask an EE to take a quick look at
one of these for me...perhaps one of the parts in there is a type of fuse since
they take so many forms.
Thanks samx3 and the rest of you guys for the advice about fuses :-)
No, the ones I bought were almost identical to a standard 1/8 watt thru hole resistor. Only difference I could see was that they were slightly longer, but the difference was so small you had to put them beside each other to see it.
http://www.littelfuse.com/products/Technology/Fuses/Mounting+Method/Through+Hole/Product+Category/PICO%26reg%3B+Type/search.html?No=0&RT=Part
'some are moulded green some are in a yellow but are marked direcly and Be aware the ones we sold were 125v only not 250 so Ill bet that is one reason why they are not in the circuit . as the SMPS in question is for up to 250 AC.
and those wires going from the plug to the PCB are so small . to a catastrophic failure they most lilky would fuse open anyways ...
a normal AC socket can do 50A+ for a few cycles . if there is a dead short on that board is gonng blow that wire real fast .
'
Thanks for the link for this type of fuses
'some are moulded green some are in a yellow but are marked direcly and Be aware the ones we sold were 125v only not 250 so Ill bet that is one reason why they are not in the circuit . as the SMPS in question is for up to 250 AC.
Here is a 250 volt series
http://search.digikey.com/scripts/DkSearch/dksus.dll put in the keyword search 263 series - pico
Perhaps that was the designers thinking, I was a bit shocked at how frail
those yellow wires carrying 240 vac are. So maybe the yellow wires are
the fuse and these cheap supplies are just fine.
. So maybe the yellow wires are the fuse
Yes they are know as fuse-able-link in they are use car and truck all the time
I would test one of those yellow wire to how fast and what amperage they blow at if you reley on this for a fuse
You can do this very easy by using a transformer and a rheostat type resister pot or a wire wond type pot amp meter
I know this because of I use to be auto mechanic and certified in Auto Electric
Knowing that how frail those yellow wires make me feel a lot better about using this type of switching power supplys
If you Torture them like your try to kill like I was talking about earlier and pass ALL of these TEST they would be a real good deal
I second this.. SURELY it has a fuse, maybe it just doesn't look like a fuse. Those I've been exposed to were beige in color, looked exactly like a resistor excluding the bands and have the value printed on the side without a decimal or units. e.g. 03129 for 3.129A....... I assume due to all the numbers that 3.130A would have blown
C.W.
without access to tools. I thought I would get a chance
to escape for a day but it did not pan out.
I went ahead and bought them though, I did not want to
miss out and I figure they just have to be worth the small
price anyway. :-)
p.s. I just adore your burning-the-candle-at-both-ends
avatar!
lol, thanks. Someone sent me an email with a bunch of images the artist does using objects and paper clips, knew it was the perfect avatar for me as soon as I saw it.
Here is the site for the artist:
http://bentobjects.blogspot.com/