Using cell phone charger as a power supply?

[911pcars]

I need 5 VDC to power a mobile experimental circuit. Is there a problem in using a car cell phone charger to do this? It's basically a DC-to-DC converter. How would the charger circuit live on a permanent basis? Is there a more elegant solution? I understand most chargers use an IC to limit ultimate current thus protecting sensitive circuits. My old cell phone required 5V 1A max (according to the charger jack on the phone) so I figured that unit's cell phone charger might work.

Thanks for any info you have.
Sherwood

[slodave]

Heck, I'd try it. I've also fried stuff, but that is part of the fun.

Dave

[island_dude]

My guess is that it isn't a good idea. Chargers run at higher voltage that straight power supplies, and they tend to play a lot with both voltage and current so they can avoid overcharging a battery. I would try something more like regular DC power supply wall wart or something first.

If you don't care about the potential to blow up your circuit, go for it. I would keep a close eye on things initially.

[slodave]

I disagree. A power supply for a cell phone is like a power supply for any other low voltage device. If the project requires 12V 1A and a cell phone 'charger' (transformer) fits those requirements, then it should work.

Dave

[Joeaksa]

Island is somewhat correct about the voltage.

I have done what you are talking about with no problems. Take a digital VOM and read the output on the transformer. Usually a 5v output on a small transformer like this will read 6.5 or even 7v under no load, but drop down closer to its rated 5 volt output when placed under a load.

Depending on your application I would get one that is very light duty, like 200 or 300 miliamps, or try one that size at first. The ones that are higher duty (say 500 miliamps) tend to go even higher on the unloaded voltage.

Another option for power in this range is to find an old desktop power supply. They output 12 and 5 volts and are much more stable. Most of us electronic nerds have one or two of these around the house.

[id10t]

If you want to use the computer power supply like Joe mentioned let me know - I've only got about 20 of 'em in the garage.

[911pcars]

Thanks for the suggestion guys. I think I'm looking for more of a permanent solution, maybe part of a product down the road, so it must be low cost, vibration-proof and very adequate.

Did some research on the web last night, and the 12V power supplies/chargers for cell phones and MP3 players use an IC chip and a couple of capacitors, pretty compact. While MP3 players require more current, they operate on the same principle but with a more robust IC. I've got an old cell phone charger that I'll take apart and take a look. Will post a pic and see why they range from $.99 to $20.

Sherwood

[rick-l]

Originally posted by 911pcars
Is there a problem in using a car cell phone charger to do this? Thanks for any info you have.
Sherwood

I don't see why there would be a problem. I think this was an LG phone but I'll look when I get home. rated for 5V@1amp

[Joeaksa]

Nice toys. Damm I miss having an electronics bench to work with!

[911pcars]

Hi Rick,
Nice rig. I have only a version of your Fluke in my arsenal .... and limited electronics b.g. as a bonus. Does a 5V battery have to be on the receiving end to work for a long time (e.g. stabilize current, self-limiting, etc)?

Sherwood

[rick-l]

Originally posted by 911pcars
Hi Rick,
Nice rig. I have only a version of your Fluke in my arsenal .... and limited electronics b.g. as a bonus. Does a 5V battery have to be on the receiving end to work for a long time (e.g. stabilize current, self-limiting, etc)?

Sherwood

Those pictures were taken with just a pot on the output.

Those old Fluke 8600As are available all over for $5 each but the 4 D Cell ni-cads that they all need are $6 each (+ shipping)

[Joeaksa]

Rick,

Where can you find the Fluke for that price? Looked on Ebay and they are $30 or so....

[rick-l]

Originally posted by Joeaksa
Looked on Ebay and they are $30 or so....

The one I got was non-working off of e-bay.

[Joeaksa]

Thanks and I have enough "non-working" stuff around the house now! Want one that works...

[rick-l]

Originally posted by Joeaksa
Thanks and I have enough "non-working" stuff around the house now! Want one that works...

I searched the net and found a site to get the manual for the 8600A for free. Don't remember the link but I have it if anyone wants it.

[Joeaksa]

Rick,

Am bidding on one on Ebay so would appreciate the link.

Joe

[rick-l]

Originally posted by Joeaksa
Rick,

Am bidding on one on Ebay so would appreciate the link.

Joe

Go here sbc.edu Click 8600A.

With Internet Exploder when the error screen

The page cannot be displayed

comes up hit the refresh button. (???? I don't know why but it works) The PDF file is 5 meg.

The ROM file is how to program a small PROM to replace an obsolete part which you shouldn't need.


If that doesn't work PM me your e-mail address and I'll send it to you.

[Joeaksa]

Rick,

Got all of them, appreciate the link.

Question for you. Are the test leads on this meter the same as other digital VOM's or something special.

As well if I find one that needs a battery or more do you have any sources?

Thx,

Joe A

[rick-l]

The leads are plain old bananas.

D Cell ni-cads are kind of hard to find. I got them here but there may be a better price somewhere else. I think I convinced myself I couldn't use nickel metal hydride batteries.

One D size 5000 mAh NiCd Rechargeable Battery Flat top with TAB
Part#: CD-D5000TB
(Qty: 4 x $5.65)
Subtotal: $22.60
Tax: $0.00
S&H: $7.77
Final Total: $30.37

[Joeaksa]

Thx much!

Sherwood, how you coming with your power supply?