Thursday, July 16, 2009

I've got glow-in-the-dark balls

Yeah, you heard me right!

I recently got very excited at the local Home-Despot when I found out they sold glow in the dark paint! I've painted a few things with it (including various parts of the kids - which was more their doing than mine!) but nothing really stood out until I realised I could coat ping-pong balls with the stuff, drill holes in them and insert LEDs where er... "the sun don't shine". I figured, periodic pulses from the LEDs should be sufficient to charge up the paint on the balls and make them glow.

One of the things that took the longest out of all of this was painting the ping-pong balls & getting them to dry without all the paint oozing off or collecting at one spot. The best technique I could come up with was to dip my balls in the paint and then dance around the room waggling them in the air (this was after connecting the LEDs). Ok, ok, this is getting too much, I'll be serious now. Unfortunately, that really was my technique for getting the paint to dry evenly. I'd tried just painting them with a brush and leaving them on some paper, but all the paint oozed down to the bottom and glued the balls to the paper, but left only a really thin coat on them. Bah. I think I'll look for spray on paint for any future project involving curved surfaces.

The parts list for this is pretty small: an ATTiny13, 5 LEDs, some perf-board, wire, 8 pin socket, some female header pins (single-row), some snappable male header pins (also single row), a battery pack (I used a 2AA pack) and some ping pong balls.

The circuit was easy, now that I've got the hang of soldering. I decided I'd make something a little more modular than normal, so the LEDs weren't soldered directly onto the board. First, I soldered the LEDs onto some wire (cut in pairs to a few different lengths). Then I soldered on header pins to the other end of the wires.

For the circuit board, I soldered on the IC socket and added some female headers. I included a row for all the ground pins as well as sockets for all the active uC ports (no need for the reset pin to have a header and I could have left off pin 8's header too). I used one of the cut-off LED leads to create a ground wire to easilly connect all the ground pins.

I wired up the power leads first - and completely forgot to include a power switch!

I drilled small holes in the ping-pong balls and hot-glue'd the LEDs in place. Then it was just a matter of connecting up the LED/balls to the correct pins. I had marked all the ground leads with a black ring at the base. I've used all wire of the same colour so that, if I make something interesting out of them, the wires won't stand out too much.

Wednesday, July 8, 2009

Solar powered fairy lights

Yes, I'm going through a solar powered phase right now. I'll have used up the parts I bought from soon enough & will have to move onto pastures new.

My lovely lady suggested it'd be nice to have some twinkling fairy lights in the kitchen; ideally, ones that didn't need to be plugged in to the mains. The simplest solution would have been to use a battery pack, but our kitchen gets a fair bit of light &, like I said, I'm in a solar powered gadgetry phase right now...

My ebay habit has brought me some colour changing LEDs (before I knew exactly what they did). These look like normal LEDs (two leads) but cycle through a few colours over the course of 15 seconds or so. I figured these would be perfect for the project, so I dug out 4 working ones (using the LED tester I posted about previously).

There are very few components for this (if you count the solar-panel/charger as a single component): 1 solar charging circuit, 4 colour changing LEDs, an Altoids tin, some wire and I used a couple of neodymium magnets to secure the tin onto the curtain rail in our kitchen.

The first thing to do is to cut the LED leads from the solar-charging circuit, this is where we'll attach the wires for our own lights. I also cut down the plastic 'pins' which hold the circuit board in place; this was to make the assembly fit nicer in the tin (and as an excuse for me to try out some new cutting disks for the Proxxon).

I then cut two strands of wire (about 1 1/2' each of red and black), marked where I wanted to place the LEDs/lights on the wires and striped away the insulation around these points. I ended up melting the insulation away with a soldering iron and then using a knife to scrape off the excess plastic. There must be a much better way of doing it.

Soldering the LEDs onto the wires was a little awkward, especially since I cut the LED leads down to about 1/3 cm to keep them close the the wires. I'm glad I decided to only put on 4 for this prototype! Hmmm... thinking about it now, I should have left the leads on and bent them around the other wires to hold them in place whilst soldering them, doh!

After soldering the LEDs, I drilled a couple of small holes in the Altoids tin, threaded in the two wires and soldered them onto the solar charging unit.
Slide everything into place and there we go:

My better half has been making lots of playdough for some lovely projects (see: Dinosaur Island and playdough rain table) as a result, we've used up a lot of food colouring. It turns out the bottles make quite good LED diffusers. The picture below shows the Fairy Lights in front of our kitchen window. I used two magnets to make the tin secure (the magnets are on the inside of the tin). I also ended up taking the lid off the tin and securing the solar panels in-place with a couple of elastic bands.

Saturday, July 4, 2009

Personal empowerment through skill acquisition (or how I fixed a Vtech Tote 'n Go)

Phew, what a poncy title! Well, that's me through and through :) But what I wanted to post about was how empowering learning something pretty simple like soldering has been for me.

The kids have been playing with various incarnations of Vtech laptops (ones that play 'learning' games to do with letters and numbers). Their first laptop, the Vtech Tote 'n Go, broke about 6 months ago, the speaker stopped working as did the mouse button. Normally, that'd mean landfill for this big bit of plastic, but, having learned a little bit of electronics, I took it apart to see if I could figure out what was wrong.

It turns out that the speaker wires had broken off and the small push button inside the mouse had broken completely. I got the speaker wire soldered back in place the same day, but the button fix had to wait a while. I was tempted to hack together some Frankenstein creation using the huge push buttons I bought ages ago, but decided against it (I'm sure the kids would have loved it though).

I recently found (see the solar power upgrade to the fireflies) and, as part of the initial order, I bought some small push buttons which were exact matches for the one in the kids laptop. So I took a second stab at fixing it. I couldn't successfully de-solder the original button, so I just clipped it off, trimmed the leads of the replacement and soldered it in place.

All very simple stuff. I left the laptop out somewhere I knew the kids would find it and the next morning I hear our youngest waking up our oldest by crying "Carys! Carys! Come see! Come see! The monkey laptop! It's working!". It was lovely.

The shocking part of this is that our friends have the same laptop and it's mouse button has stopped working as well. I'll fix that one too, but it must mean that loads of these things become landfill just because a single button breaks...

LED tester

I have to be honest, I've not been very er... meticulous when it comes to keeping my LEDs in check. Let's be frank, I have a big mess of them and I've no idea which ones work or what colour they are. I'm about to start on a solar powered fairy lights project and realised I'd be spending a lot of time working out which LEDs were the ones I wanted (hence the subject of this post).

To date, I've been using a torn down dollar store hand fan for testing; I'll take a picture to show you what I mean:

It's not the easiest to use, but it outputs ~3V, has a switch and two leads (not obvious which one is positive and which one is ground though since they're both red). I ended up getting frustrated whilst holding the ends of the wires onto the LEDs and then switching over wondering if the batteries were dead, the LED was dead or if I was just crap at getting a decent connection between the leads.

Anyway, what all this blathering is getting to is that I wanted something simpler and more reliable to use. You know, something that doesn't make me want to throw it against the wall in frustration... I'd been messing with 8 pin IC sockets and perf board for other projects and realised that they are perfect for this as well. So I got together the old battery pack from the JarOFireflies prototype (which is why it has a magnet still glued on top), a small bit of perfboard, an 8 pin IC socket and 4, 330 ohm, resistors.

I soldered the resistors and socket onto the board at the same time.

I used the wires from the last resistor to solder all the connections on each side together forming two rails (positive and ground):

Then I soldered in the wires from the battery pack, connecting one to each rail, and voila!

The nice thing about this is that it's easy to check a single led without messing much with it's leads (since there's 4 holes a side, there's plenty of room) and it'll also accommodate, up to, 4 LEDs at a time:

This took about 20 mins to put together including frequent interruptions from the kids wondering what I was doing by myself in the garage.

UPDATE (2009-09-19): The resistor set-up I created is obviously crazy, I'm not sure what I was thinking (or not) at this point... The resistors should be separating pins 1 - 4 from the positive rail.