PCB assembly discussion

[Tony]

Suggestions for improvements, mistakes, hints here please.

[alex]

Hello,

I completed assembly my nixie thermometer here a picture of it!


It work great except for one thing, when I power up the nixie thermometer it show the right temperature, but after a couple of hours running, the thermometer show a temperature around 5 degree higher than the reality.

This is obviously caused by the heat of the circuit. This could be corrected by adding a software compensation.

I was wondering if it possible to get the microcontroller source code, so I could try adding an offset in the temperature reading to have a more accurate thermometer.

[lostpckt]

Hey guys,

I received my kit today and started assembling it, but then got to the LED step and ran into a problem. 1 of the 5 LEDs has the flat side on the opposite side from the rest. Suggestions?

I went ahead and mirrored the anode/cathode layout of the other 4 for this one, but please let me know if one was actually supposed to be 'off'.

[Tony]

You did remeber the silicone pad under the temp sensor IC? - that thermally couples it to the case itself. There will always be some self-heating with an internal sensor, there's an option for an external sensor I'll be adding the instructions for shortly.

I have no objection to releasing the source as long as you don't mind the kludges and lack of comments in places, but I'll ask thinkgeek first to make sure it's OK with them.

[Tony]

Hey guys,

I received my kit today and started assembling it, but then got to the LED step and ran into a problem. 1 of the 5 LEDs has the flat side on the opposite side from the rest. Suggestions?

I went ahead and mirrored the anode/cathode layout of the other 4 for this one, but please let me know if one was actually supposed to be 'off'.

Thanks for pointing that out, I've checked the LEDs here and the notch doesn't appear to be used to indicate polarity on these as I expected it should. To clarify it, the notch should be next to the short pin - I've amended the instructions.

One of the two rightmost LEDs will be off, which will depend on the symbols needed at that part of the cycle.

[lostpckt]

Another question (can you tell how far I'm getting?).

In the picture http://www.lasermad.co.uk/instructions/therm/31.JPG (not sure what step it is, step numbers?) it shows R28 still open, and the following steps use it for debug/diag before final assembly.

In pictures http://www.lasermad.co.uk/instructions/therm/34.JPG and the following one (38.JPG, but not allowed to link to it), there is clearly something soldered into R38. Is there a step missing where the .47R fusible resistor should be soldered in? Or am I blind and missing it?

Thanks!

[Tony]

Ignore the resistor in that photo, it was just the best available to show the nixie anodes. The .47R is the very last component you want to put on the board, once everything else has been tested and is working.

[lostpckt]

Hey Tony, me again

Sorry for all these posts. I've managed to get up to first "power it on stage" but am not seeing any light from any LED (which one is supposed to light up?). Unfortunately, my MM doesn't do mA (just amps), but I get a flat 0.0 across R28 when plugged in. I've run across the board testing everything I can think of, and everything seems to be correct. Would you mind if I emailed you some macro shots of my work so far and maybe you can spot something I've missed? Or perhaps give some additional troubleshooting hints on what may be wrong?

Thanks, and this project is great. It's clearly "the next step" for me as kits I've worked on previously have been zero troubles (it's a GOOD thing to be pushed!!)

[Tony]

Hi,
Not a problem, please send them and I'll have a look. Silly question first though, the power supply is working and providing 5V?.

[lostpckt]

Yup, 5.5V from pin to ground. That was the first thing I checked