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The black box, say is a portable electronic consumer device - say for example a mobile phone or a CD player or a currency counter for that matter.. Working on less than 24 V for example..
Apologies, I should have mentioned that earlier..
Mike.
Then, it's definitely time to either X-ray it, open it, or toss it.
Do you know what this "box" is supposed to accomplish?
Good Luck! Rich
"There is no spoon." - A potential in "The Matrix"
Something I thought up, could be quite close:
Assuming it is a low voltage consumer device as I mentioned earlier:
- Give the black box under test an AC voltage at about 0.2 Hz with frequency increasing linearly over a period of time(?), 4V peak to peak.
- The AC wave would be current limited, say to 100mA
- Save the V-I curve in memory
- A computer algorithm determines the most probable polarity as a function of the saved V-I curve and V-I curves of generic models for various input configurations (several thousands?).
Am I missing an ingredient? There seems little possibility to damage the black box using my method..except???
Mike
If similar V-I curve is found for both directions { }
Something I thought up, could be quite close:
Assuming it is a low voltage consumer device as I mentioned earlier:
- Give the black box under test an AC voltage at about 0.2 Hz with frequency increasing linearly over a period of time(?), 4V peak to peak.
- The AC wave would be current limited, say to 100mA
- Save the V-I curve in memory
- A computer algorithm determines the most probable polarity as a function of the saved V-I curve and V-I curves of generic models for various input configurations (several thousands?).
Am I missing an ingredient? There seems little possibility to damage the black box using my method..except???
Mike
there is no universal answer. What is best to do depends on what risk youre willing to take and what the input crcuitry is.
well, that could explain it. I'm not ure you've fully grasped the nature of the problem.
With no further info the best I can suggest is that the majority of dc input consumer goods have either a doide across the input or no polarity protection, and centre + seems the more common of the 2 options. So if I were left with no other workable option, I'd apply current limited 1.5v and wait and see what happened to the current. If i stays high forevermore youve got the wrong way round. If it charges a cap theres really no knowing, and upping the v to check for signs of life is the next move.
You will lose a precentage of goods doing this. If youre an individual flogging used consumer bits, it may be worth building your own xray machine. If youre a business with employees, or live in a terrace, dont even think about it.
NT
If you know how many Watts it's supposed to consume, you may get a clue by starting off with a low voltage, and increasing it while monitoring the current increase.
Failing that and nothwithstanding your request, open the damm thing. Failing that, hit it with AC, that way you are bound to get the right polarity, at least for a short while!!
Barry Lennox
IT'S STILL NOT FUCKING AMUSING THOUGH, IS IT!!!!!!!!!?
DNA
I don't think this is a real box. Seems to be some kind of brain puzzler which the OP made up himself, but without knowing if it has a solution.
Mark
Purrrfect answer!
I had a currency counter that would test open...until you put a coin in for sort / count. And it did not care about polarity..
Briefly apply current limited ac and curvetrace the result.
(assumes no humongous input capacitors; if present, lower the frequency)
Most any commercial device will often include input protection. Such as a diode or two.
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This sounds to be like the black box problem we had in college many moons ago. We were given a 4 terminal black box and had to determine a circuit configuration for the contents. We used 'Oscopes, signal generators, and VTVMs. Twas fun! Oh, one set of terminals was called the input and the other set the output.
Al
..and the power went in to the plate (at zero volts DC) and the power came out from the grid at half the input frequency (real device designed over 30 years ago).
That's fine, i would be more likely to ask an octopus.
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OK, so let's be serious.
Do a voltage/current characteristic testing using a curve-tracer. Limit the current to 10 microamps. Most semiconductor electronic systems will show a breakdown at about 0.5vdc when biased in the reverse direction. In the forward direction, the forward breakdown voltage for TTL devices will be about 7 Vdc.
That's your starting point. Figure it out for other technologies.
Al
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