To say I was crap at soldering would be a massive understatement. I’ve not been at it long, and for a guy who burns easily on things like toast and cups of tea, let alone hot soldering irons and solder, I think I’m doing pretty alright. I’ve pottered about with a couple of different irons, often finding them too big and clunky or hampered by some giant cable. Help, though, came in the form of my Geek app and some kindly souls in China, selling USB soldering irons. At a couple of quid a throw I thought I’d give it a shot, and a few agonising weeks later, the iron arrived. Geek sellers also offer a plethora of electronic kits, as do Maplin, of course, and to the latter I repaired recently in the hope they had something cheap in a bargain bin (or similar) which I could have a go at. They came up with a rather natty Velleman kit, purporting to be one of those LED matrix signs you can program to write scrolling messages, such as Jeremy Clarkson once used in an episode of Top Gear, to display James May’s phone number to motorists following their slowly moving car and caravan.
The kit features 35 small red LEDs which form a 7×5 matrix. For someone with fat fingers and thumbs like me, they were a sod to solder. In the end, only one needed a bit more solder adding as it didn’t light up when I tested it, but afterwards all was well. The CPU, a Microchip PIC16C58B, is a powerful (100 nanosecond instruction execution) easy-to-program 33 single-word instruction CMOS OTP-based 8-bit micro controller. Apparently. The board is powered by either a 9v PP3 effort, or externally via the power socket thoughtfully solderable to the board. Other components included about 15 resistors, three or four diodes which I managed to get the right way round this time, a transistor and three capacitors, three microswitches, potentiometer and a nice piece of 70s red perspex to cover the LEDs. A handy PP3 holder is stuck to the back of the board and held in place with three small screws.
I was infinitely chuffed that it lit up at all when I connected the battery. I saw straight away that there was a LED out, and a closer inspection revealed my soldering was a little shoddy on one of the legs. Quick touch-up and she was lighting up nicely. Inputting the text is a little fiddly a) because the microswitches are, well, micro, and b) you have to go through this complicated routine of using two switches to scroll up and down the character set. The potentiometer controls the scroll speed, which is a nice touch.
I would have included a video of the thing working, but my iPhone 7 Plus doesn’t ‘do’ LED displays very well, scrolling or otherwise. If I figure out how to work the video function on my Sony RX-100, I’ll add one at a later stage.
Next project is a surface mount one, which I’m a little hesitant at doing a) because it’s even fiddlier than the Velleman, and b) my fingers are going to be much too close to the soldering iron for my liking.