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Topic: Picqueno free PCB build (Read 2570 times) previous topic - next topic

Picqueno free PCB build

Hi folks,

I just wanted to share my Picqueno building experiences with you.

I've put the the power supply and FT232 part of the circuit together first and made a quick power up check using my laptop (USB should be protected against overcurrent, so I put it to the test :] )

powerupcheck by kajak_attack, on Flickr

It works.

I've omitted the 5 V regulator and the external power plug, mainly because I couldn't find any 1117-5.0 regulators in my improvised workshop where I do not have my parts inventory at hand.

Just in case you're wondering: the Q-tip in the picture wasn't used for digging in my ears. I use them to apply flux. I once bought a few one liter bottles of flux cheaply on ebay. This stuff is at least 20 years old but is still working well.

IMG_0710 by kajak_attack, on Flickr

With the usb interface part working I populated the MCU and its accompanying circuitry and used my ICD 2 clone to upload the bootloader:

IMG_0718 by kajak_attack, on Flickr

After successfully uploading the "blink" sketch nothing visible happened. The red LED I used for LED4 was soldered the wrong way 'round. It had anode markings while the other LEDs had their cathode marked.

After swapping the LED the board did what it was supposed to do.

IMG_0713 by kajak_attack, on Flickr

Now I will add the voltage clamping circuitry on the analog pins and all the pin headers.

Thanks, Ian, for sending me the board.



Re: Picqueno free PCB build

Reply #2
While populating the voltage clamping diodes a possible design improvement regarding component availability came to my mind. I'd suggest replacing the SOT 363 diodes by something more common - in a SOT-23 case for example. There are lots of common cathode double diodes (BAS70, BAV70, BAV74, BAT54).


Re: Picqueno free PCB build

Reply #3
That is pretty cool so far!
Also,  the second I saw the Qtip I thought you did the same as what I did with a Qtip and PCB's. Use rubbing alcohol to clean the bare copper just before I solder on the IC's. I see that you left a lot of flux on the board though, from what I understand some types of flux if left on the PCB eats through it after a while. Is your flux the one that is just put in water and goes away, or do you have to clean it manually using a Qtip and some rubbing alcohol or nail polish remover?

Also, I really suggest you clean the flux before continuing, it is conductive and may cause a short or some little smoking. At least, that is what happened to me when I was assembling the Buspirate, the flux left on the board started to make a tiny spark between  5V and gnd, eventually leaving a black mark on the PCB between the two traces. I had to cut the traces around the black mark and go around it, the charred section of PCB seemed to still be conductive even after the flux smoked away.

Also, just curious and off topic, did you use Flash for taking those pictures or did you use a tripod or something else?

Re: Picqueno free PCB build

Reply #4
I usually clean PCBs after soldering but I didn't want to use stinky solvents in my living room.

I took the pictures without a tripod.


Re: Picqueno free PCB build

Reply #5
[quote author="hak8or"]
Also, just curious and off topic, did you use Flash for taking those pictures or did you use a tripod or something else?[/quote]

I never use flash for PCB photography. that will give overexposed area's. I prefer daylight or a lightbox as lighting. A tripod is a must for high quality pictures.


Re: Picqueno free PCB build

Reply #6
Thanks for the part update suggestion, will add it to the next design.
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