Re: short circuit :/

On May 11, 4:23 pm, Jan Nielsen
<nos...@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
Hi,

I made a circuit for a simple serial temperature system, it worked on
the breadboard, but something has gone wrong since.

Before I apply power to the board I have 4.3V (3xAA), when I apply power
the voltage drops to 2.5 and keeps dropping, I added a LED to see if it
worked, and it dosent.
-So im guessing its a short circuit right ?

The "diagram" is herehttp://codebin.dk/stuff/serialtemp.jpg
The green connections is made with jumpwire, the board is standard
single side that I etched.
The custom components are a jackconnector (bottom right), and just
3holes for a LM35 (VDC+, Output, GND), the 4dot is not used for components.
The IC is a picaxe 08-m.

I have tested the connections from the jack (bottom right) and they look
ok, however several places in the circuit where traces shouldnt be
connected together I get 5MOhm+ instead of a O.L. on my meter, is this
ok ? VDC+ to VDC- gives 11MOhm in disconnected state.

I checked the solder and traces and it looks ok, is there some mistake
in my diagram ?

Thanks,
Jan

Hi, Jan. First off, test the batteries -- 4.3V sounds a little low,
and suspicious.

If you've got a 100 ohm resistor around, try placing that across the
batteries, then measuring the voltage (anything up to 220 ohms will
work here, too). You should be getting a pull of 45mA (less for
higher ohms), a good load for AA batteries. Your battery voltage
shouldn't drop by more than a tenth of a volt. If it drops more, get
some fresh batteries and try again.

I wouldn't worry too much about high meg ohm readings as far as
finding a short. You did well in checking the unpowered resistance
from V+ to COM. Double check to make sure you haven't tied competing
outputs together, but it sounds like you've got that end covered. You
might want to put a cheapie DMM on your long list of things to buy.

One of the harder parts for hobbyists is the experience. You have to
buy it one "D'oh!" at a time. If it turns out to be the power source,
just keep it in mind next time.

Good luck
Chris

.