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I guess while I was at school I got comfortable in technology. But I don't have an oscilloscope anymore and I don't have even a real soldering too.... haha.
Anyways, I thought this would be a piece of cake:
I was gonna make one for my desk cause I kinda thought it was cute :P Anyways, for some reason no matter what, the voltage potential is stuck at around 7 volts from the source. I built the circuit described exactly and than I built with a 12V power supply, and they both would only output 7V to the circuit.... the 12V power supply I had was hissing, sounded PISSED.. so I didn't feel comfortable leaving it on for more than enough time to get the reading. I went through the circuit twice and it's wired correctly from what I can tell.
With an oscilloscope I am sure I can identify the issue quickly, but I only have a simple oscilloscope where I currently reside... anyone have incite?
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Are you using a transformer or a switching supply for the power soure?
Please note that with a switching power supply, they have internal fault circuits which may be kicking in prematurely due to the noise and interference the coil may be producing.
Try using a transformer if you are not already using one.
Right, I was originally using a transformer and it was handling the problem well, but there is still a problem. My point was that I was using exactly what you see in the circuit and than I thought MAYBE it's a power issue, so I switched to a switching power supply, but clearly not... something is forcing the circuit to 7 volts.. but nothing in that schematic would make me think such a thing likely. So I am extremely puzzled to say the least. Than again, like I said I don't have an oscilloscope so I have no clue what's REALLY going on.
However, you do make an interesting point to remember for any potential issues in the future. Thanks.
I went back to the transformer... but I was measuring from pin 3 of the LM7812 to ground.
edit - I elevated the secondary coil up thinking maybe it had some crazy influence on the circuit potentially. No effect.... simply trying to exhaust the possibilities... whatever is left however improbable must be the cause :P BTW - does anyone watch Sherlock on BBC? OMG, season 3 is so epic.
Registered Member #834
Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644
The first thing to debug is these 7V. What you measure at pin 1 of the 7812? Check the connections of the two ICs (are they hot?) and the polarity of the 470 uF capacitors. Disconnect the power transistor and test it.
Didn't test the power transistor yet, however!: I got the same voltage to the chips, the 555 is outputting .5 volts ish constantly.... getting about the same reading to the input of the mosfet driver.
Some interesting results: I looked at the antenna voltage and it was different every time I shifted the board or the antenna itself... which makes we wonder if thats the issue? It still doesn't make sense to me, but sometimes I get hissing from the coil if I move the circuit around and the antenna.... strange right?
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Maybe someone can identify the problem
