Can i take two wallwart power supplies (the AC to DC variety) and just tie them together in series and parallel to make a cheap diy variable powersupply.
I am thinking of getting a cheap variable DC 12V ($20 at Fry's), and then adding a universal DC adapter with up to 12 v also. So if i wire these in series or parallel or whatever, can i say add 3 v DC to 6 v Dc to get a usable 9v DC? Or is there gonna be some law of electronics broken?
thanks for your very expert consulting
Consider this instead - $19 from Radio Shack
snipped-for-privacy@mail.com wrote:
If they are in series and both on, then it may work within their current ratings.
But think about what happens if one of them is not powered on.
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my story is that i need 15v and 16v to power 2 different pc scanners. Local stores only have up to 12 v pot variable or 12v universal variable/switchable. So I figure buy the pot variable and just tie it to the various adapters I already have laying around the house. So i am planning to get my variable and wire it to say a 9v adapter and add 6v with the variable. In theory that should add up to 15v to power my flatbed scanner. I am thinking though that compound ripples off the rectifiers or something like that would cause a quantum superstring superorder megaohmachronicle power surge. I am very wary of these non-linear chaos electron interactions. Or perhaps synergistic effects from reactance and dilitheum crystal interactions might blow the power core. Not that i care about the power core, i more concerned about our rations of scotch.
would primary coil windings get blown open if the second unit was off? Would any power surge happen to the total output? I wouldn't want to blow the device powered off my budget diy supply. I know i can make one diy for the same money, but i am too lazy and the variable at fry's had something like 2 or 3 amps which i need.
i don't want to buy a real variable now cause i don't know anything about electronics yet and i don't know what is a good investment for my needs.
is there any ripple off AC adapters? Do i have to worry about compound inductance, reactance, stuff like that which i don't know anything about. Now i am scaring myself. I guess i would have to research this myself. I suppose that I could use as a reference two batteries tied in parrallel or series, then compare the waveforms to the compound adapters. Shouldn't take too long.
I hope this never blows up my guitar effects boxes!
the
No, but it will damage the smoothing capacitor of the adaptor that is not powered because reverse voltge will be presented across it. It will be limited to 1.4-ish volts by the bridge rectifier being forward biased, but it's still not good news.
Dave
this shouldn't be a problem. The variable would have serviceable parts. the fixed switcheable universal probably isn't serviceable cause all the parts are in those plastic cases and they are tightly manufactured, but these are also quite cheap. I can just replace the switcheable and fix the variable if needs be.
by the way, looking into power supplies more, why would someone need negative DC volts. They are below the 0 v line on a scope right? What uses negative DC? A 50 dollar elenco variable had a spec of -1 to
-15 dc v
seems to me like -15v is still 15 v (0 to peak). Don't really know of course, that's why i'm asking you...
Some devices have connectors that put the - voltage on the center pin, others put + on the center pin. (For center pin, you can substitute big pin/socket, funny looking pin/socket, yellow pin/socket, etc.)
In your PC, the power supply is generating both +12 and -12 volts - there's an instance where both voltages are needed - rather than just swapping the + and - pins.
It doesn't make much sense to talk of DC peak voltages; ideally, DC voltage is smooth and doesn't have peaks. AC voltage, on the other hand, can be measured in several ways (Average, RMS, Peak).
Are you sure that both of your scanners need DC? You said one required
15 volts, the other 16. In all likelihood you could use the same power supply for both. I'd buy 1 power supply (perhaps from the scanner mfr) and use it for both. Which to buy 15V or 16V? - whichever is cheaper.snipped-for-privacy@mail.com wrote:
you can probably just reverse the leads on one of the connections. So a parallel circuit/device goes minus plus, the other parallel device goes plus minus. The classic reverse parallel dive. Guess though these would have to share current. Maybe those professional power supplies devices are isolating the ground for some reason. Perhaps for less noisy signals. Is it possible to have a positive ground? Or is that just as Seussian as DC peaks? Thanks for your replies by the way.
I ordered a book by Witte on electronics instruments. Keeps on getting canceled and now the shipping is slow cause i am buying one of those limited distributed (illegal to possess in the west) Hindu pulp mass copies of copyrighted western textbooks. You can often find them at bookfinder4u.com.
i thought about that but decided on the variable 12 v cause its only 20 dollars and a 16v adapter would cost at least that much. Although i risk burning my house down with bad soldering connections, i also gain not having to buy all these little wallwarts i have. I think i'm gonna need a 6v soon too.
Distintinguish between ground and minus. Ground in electronic equipment like radios and PCs can be either positive or negative. If the negative pole of a power supply in a radio is tied to the metal chassis (or the common areas of a PC board, then you can say ground is negative. Alternately, if the supply's positive voltage is connected to the chassis or the common areas of a PC board, you can talk about a positive ground. In a PC, which uses both positive and negative 12 volts, each is measured in relation to ground (chassis/common) - thus if you connect a voltmeter's black/negative lead to the chassis, you'll measure +12 at certain points and -12 at others. If you clip the voltmeter to the + and - wires, you'll measure 24 volts.
Have you considered a trip to your local public library for an elementary book on electricity?
sorry for all the chat, I have already purchased some 12 textbooks on electronics but i am avoiding my basic electronics book that i had more than 15 years ago already cause basic electronics is more difficult than advanced electronics to me. I am pretty much using Electronics Workbench to get me past all the math and common sense. Sure i'm gonna get electrocuted some day......but if i ground myself at all times, the most i'll lose are a few eyebrows and maybe a few tongue taste buds and ear follicles. I just won't do electrical that's all. Stick to digital low volts stuff for now. Avoid industrial robotics.
at any rate, i ended up parchasing a cheap switcheable universal cause the variable at fry's turned out to be a switcheable. So i just went cheap and will save my money for a good Elenco or something affordable yet professional. I'm gonna run this through my scope and tell you all what the ripple is on single then coupled power supplies.
thanks for your help. Really appreciated it cause i did in fact review my basic electronics book (among others) and it didn't have anything on DC designs.
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