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Thanks! Just finished building the PCB. Works wonderfully without a hitch!

Excellent Do you still plan to try hacking it?. One mod I'd wanted to try but haven't had a chance to do is a barometric pressure sensor, there's a 'P' (Pascal) symbol available in the IN19A.

Hello, I've just finished building my PCB right up to the point of the first check (ammeter across the pins of R28). My multimeter doesn't do mA .

When I plugged it in then touched both legs of the resistor to the pads on R28, I get a single momentary flash from D17 then it goes off. Checking across the pads with R28 off I get a touch over 5v. With R28 on I get just over 0.313v. Voltage drop = current * resistor size, so I should be looking at .313v/.47 ohm = .666mA?

Coil L1 and tubes are not in place.

Checking all the diodes I get .55v drop forward and 0L (ie no connection) reverse. Except D10... there I get .51v forward and .88v reverse. Is there something hooked up in parallel with this one or is it bad? Would this cause my problem?

Bear with me I'm pretty new to electronics.

D17 is connected to the 5V supply and should be lit all the time it's connected. What voltage do you get between R28 and ground with it fitted?.
It looks like the power supply is going into current limit mode due to a short somewhere.

I'm seeing ~2.2 volts.

The D10 diode is nothing to worry about then?

Pics of the underside of my board:
https://plus.google.com/117440165111006 ... iEC1yxezpd

D10 isn't connected to anything that can cause a problem just now. It's either a partial short, faulty power supply or USB cable. It's rare but I have had one fail previously.
What is the resistance to ground measured at each end of R28? that may indicate if it's a short.

It's a little weird.

With R28 in place, the left leg gives me ~7.6kohms, but it starts up in the multi megohm range and goes down then up then down oscillating slowly before it settles on that value (takes about a minute). The right leg gives somewhere around 13kohms... even after a full minute it was still rolling up and down.

With R28 out, the left leg gives me 0, the right leg gives rougly 32kohms.

This is unpowered and the using the shield from the USB port as the ground.

Connected to the [apparently more powerful] USB port on my netbook and lo and behold, the 5v indicator LED came on and stayed on, and I started to get D6 and D5 more dimly (I believe this is by design?) illuminating.

But then I smelled something burning and noticed the DHT11 humidity/temp sensor imploding. It got hot internally and did a literal shrinky-dink! It's toast. Good thing I already ordered an extra to do an external hook up...

I checked for continuity between its pins and didn't find any, but then I flipped the board over and checked the SMD sensor on the other side and found the three pins on the upper left have continuity.

I unsoldered the toasted sensor and the voltage at R28 went from 4.2V to 5.1V.


I've gone over the SMD sensor on the back with a magnifying glass and I can't see any solder bridging and it doesn't grow warm when the board is powered. Should I unsolder it? No idea how to get it off there without damaging it.

Where the DHT11 was I get 5.1V to ground from the top three pins and the bottom pin is 0.3mV

That is weird...
The resistance should have been the same at both ends with R28 in so it looks like it's been damaged by a short. The 0 ohms reading after removing it, can you trace what was moved or bridged to cause that as it may have been responsible for the original problem?.

Edit - just saw your last post and it looks like you found the short

Was the sensor fitted with the label facing upwards?, I'm guessing so by the distortion and lead length. The SMD sensor sounds OK, those 3 pins are linked together.

Yeah, the sensor label was facing upwards... meaning I had it installed backwards like an idiot.

I guess it's ok to move on with the next part of the build then while my new one comes in the mail?