Tuesday, January 22, 2013

Binary LED Calculator

After comparing the new solder joints to the ones I was making with the old iron, I decided to start completely over with the LED Binary Calculator. This time I used DIP sockets and new protoboard I was able to buy when I bought the new soldering stuff. This protoboard is 25 holes wide which is really convenient since each of the eight LEDs needs three holes width. There were also just enough of the old red LEDs I was using before to start over with. The solder didn't take to them very well at the beginning so I had to scrape off a lot of the coating that had formed on it. Because I didn't have a battery holder, I soldered on an 8 pin DIP socket to use as a power connector. I taped wires to a CR2032 battery and I stick the ends into the socket for power.

After soldering everything together I ran a test of the LEDs. They only worked correctly once and the only way to get them to work again was to remove both the shift register controlling the LEDs and the MSP430. Toggling the master reset of the shift register didn't help either. Upon closer inspection it turned out the ground connection to the MSP430 had come loose. I was surprised that it ran at all with no ground connection but I have seen it do something similar on a breadboard too. The buttons worked fine from the beginning except that two of them were linked by a solder bridge. After I fixed that, the whole calculator worked as expected.

Sunday, January 20, 2013

More Soldering Practice

There don't seem to be any local shops that sell good soldering iron tips here. Luckily, though,  I was able to buy a few good ones in another city. I was a bit skeptical when the best tips they had only cost a little over a dollar but I brought them home and they work great! I also bought some good 61/39 solder. Using this instead of the cheap 30/70 solder available locally probably helps a lot too. Later I'll see if any of the cheap tips I have work alright with good solder. I don't think I'll risk using cheap solder with the new tip.

With the protoboard I was using to make the LED Binary Calculator I practiced some more with old soviet chips. Interestingly enough they all have different markings. It was easy to make good solder joints very quickly with my new setup.