Troubleshooting

[Tony]

Hi,

You should be able to find all the parts at RS or Farnell except the KM155, though the pack sizes can be a problem. I use RS, Farnell and Rapid over here.

Yes that resistor is compatible, the seller you linked to just dumps the entire Farnell catalogue onto ebay with a big markup so it's exactly the same part originally supplied. These links might be some use:

http://au.element14.com/on-semiconducto ... dp/1879964

http://au.element14.com/multicomp/mpsa9 ... dp/1574392

http://au.element14.com/fairchild-semic ... dp/1017719

http://au.element14.com/te-connectivity ... dp/1898500

[66LUX]

Cheers Tony.
I searched the element14 Australian site and couldn't find those resistors anywhere.
It doesn't help that they're not noted as fusible.
They'd still have to come from the UK, but at least they're a lot cheaper.
I found the same ones on the RS Austalia site and they're local stock, so I'll go for those.
Thanks very much.

[Higginz]

Hey Tony,

A while back I had asked about my thermometer kit that was acting strange and sometimes not powering up. So I finally got around to looking into it. I did replace the DHT11 and allowed it to run a day. After about 8 hours the display would freeze at the same temp, a few minutes later the first 3 tubes would not display numbers, but would light during the transition effect. After a few minutes of no numbers, the whole thermometer would stop all display, including the LEDs, as if no power. If I unplugged the USB and allowed it to set for about 20 minutes, it sometimes would power back on, starting the whole process over. Going by you earlier post about a bad batch of PIC16F1847s. I got adventurous and decided to pickup a PIC programmer on the cheap. For $25 I bought a Chinese knockoff of a PICkit3. The included PIC board wasn't much help, I was not able to figure out the jumper and PIN layout, as all the documentation was in Chinese. Not too bad in all, considering it came with MPLAB IDE and MPLAB X IDE. I also picked up a replacement PIC16F1847 then attempted to learn PIC programming. After some fumbling and trial, I was able to program the replacement PIC with the code you had provided. MPLAB kept giving the same error for 'Unable to get device ID', but MPLAB X allowed me to skip the ID error. I've had my thermometer running all evening with no issues so far. I will see if this works. I have just 1 question: What is the nominal voltage to power up a PIC for programming? 3.5v? 5v?

[Tony]

Those clone programmers work well, I've used a couple. The programming should be at 5 or 5.5V for a 16f device. The 'device ID' error is unusual thoughI've only used MPLAB IDE 8.x with them, it might be a X compatibility problem.

[Bernieb627]

I just finished my thermometer and all the parts are in except the LEDs for the tubes and the on-off LED and the IR LED and R28. I am getting power from the transformer to the PCB- USB at about 5 volts. I check R28 and it's about 80 ma. The problem I have is that the voltage to all the LED pads is less than 1 volt. Also, when I check the voltage from the + side of the PCB to the - side from pads on the PCB that go directly to the + and -, I also only get less than 1 volt, even though the pads at the USB are 5. What's my next step.

[Tony]

Temporarily fit R28 and measure the 5V again, check IC4 is the correct way around. There won't be a high reading on the LEDs as they're driven by a PWM signal, to your meter it will look like 0.5-1V.

[NixieFan1116]

I'm completely frustrated. I had it all together and it was working beautifully... but when I assembled the case, the ir control wasn't working. I determined the that the ir led was too far down and not "showing" through the plastic lid... so I attempted to bring it up a little, and when I plugged it back in... NOTHING! D17 lit up fine, and I was finally able to get the fourth tube (to light up and a few seconds later, the other tubes faded in to life and the leds underneath lit up... whew... then I had to disconnect power to get it all back together and plugged it back in and... NOTHING AGAIN... and still nothing...

I am new to electronics, have fairly good soldering skills, but am a dummy when it comes to technical jargon. I understand the basics of electricity and part names, but don't really understand troubleshooting well... oils you walk me through a check of the board? I am frustrated and don't want to throw it through the window just yet...

[Tony]

Hi,
The actual problem was too much IR being reflected from the lid, swamping the sensor. The meatshrink MUST seal all the way to the lid with no gaps.

I'd guess it's just switched off, make sure the heatshrink is in place and no IR reaches the sensor until needed and it should change mode and work. Use a phone camera to view the LED just to confirm it's still emitting IR.

[NixieFan1116]

Thanks for the prompt reply! And thanks for the phone trick... I didn't realize it would "see" it, that would've saved me a lot of frustration last night when I broke the ir led (that's why I asked the wavelength value in the other post) because I need a replacement. I got the part about the heat shrink, just didn't know which ir nm value was which.

[Tony]

If you have any scrap or unused IR remotes you could probably use the LED from that, the type isn't critical as long as it's the correct wavelength.