The Shop > Electronics & IC Programing
I need someone to ID a doohickey.
No1_sonuk:
The pic was off the bottom of the window while I was reading, but from the description I could tell it was an aluminium electrolytic that popped.
Why no photo of the mess? :(
:worthless:
--- Quote from: NickG on September 15, 2009, 04:04:09 AM ---I remember when we were at school purposely connecting little ones the wrong way around to get them to :zap: and get the puff of white powder ... no idea what it was!
--- End quote ---
That sounds like a tantalum type. They're polarised, but some look like dipped ceramic caps. They usually smoke rather than pop.
andyf:
I'm sure Dave BC is right on both counts - it wouldn't work at all if polarity was reversed, and I don't think the output of car battery chargers is smoothed at all, so they produce a dc voltage with a lot of ripple. The "average" voltage must be greater than 13.8V to charge a battery (a "12v" car battery is actually 13.8v fully charged) and the peaks of the ripple might exceed the rating of the deceased capacitor. If you can find a CB radio power supply, they have basic smoothing. The PSUs in scrapped computers are rated for lots of amps, have 12V outputs and are easy to convert as shown here:
http://www.instructables.com/id/Convert-an-ATX-Power-Supply-Into-a-Regular-DC-Powe/
Andy.
Bluechip:
I've been finkin' :scratch:
If you just want to drive a low voltage DC motor, they don't require a smoothed DC. In my projects, they get what I give 'em.
You can knock out a circuit similar to below, but ..
This will not work with steppers !
Thick lines are high current for motor, the rest only carry 12mA or so. SE is Switching Element: FET or whatnot.
You might have to ensure the input to 78xx does not exceed limit.
As shown max. AC input is about 18V r.m.s. otherwise 100uF 35V is pushing it's luck.
Andy is spot on with PC PSU's, to get more wallop it is often possible to parallel 12V outputs, although it may be you have to ballast them to get the PSU to fire up.
Have fun, check your fire insurance. :D :D
Dave BC
websterz:
Okay, I have pulled my back-up ATX power supply out of storage and will use it to run my power feed. It is a 450W rated for 17 amps @ 12 VDC. From what I read on Instructables this should be sufficient for my needs and provide more stable output as was suggested above. I will salvage, or buy new, a replacement capacitor for the controller and see what shakes loose. Thanks guys! :dremel:
websterz:
--- Quote from: Bluechip on September 15, 2009, 04:19:27 AM ---I think the DP switch must be after the PSU.
I doubt if the chip would work at all on reverse polarity, he does say it worked for a bit.
Dave BC
--- End quote ---
I have :
PS --> CONTROLLER --> DPDT --> MOTOR
Is this not right? Like I say even with the blown cap the controller still runs in the above configuration.
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