Intro: Alternating LED Display
In this instructable, I will show you how to make LEDs flash from one word/ drawing/ color/ brightness to another. This is very easy to redesign to carry out different functions, and is very simple to make. The parts can all be purchased at radio shack, so are easy to get. I made this one for my sister, so I made the LEDs into letters that spelled her nick name " A Shef". I made it oscillate between A and Shef about once every second, but the rate that it oscillates as well as what the LEDs do can be changed.
Step 1: Gather Materials
You shouldn't really need over $20 for this project, but if you buy a ton of LEDs you may need more.
- 10 uf capacitors (x2)
- 1k resistor
- 10k resistor
- 100k resistor
- 470 ohm resistors (x2)
- NE555P IC
- 9v battery snap
- PC board
- as many LEDs as you need
- project box (Keep in mind the larger the box the more LEDs that can be used)
- drill (and bits)
- soldering iron
- wire cutters
Step 2: Plans
The first thing you should do, is decide what you want your display box to oscillate between. You make two words, one word outlined with more LEDs, you could make two pictures with the LEDs, make it change from color to color, or using varying resistance on the two options to make it oscillate between two different brightnesses. The possibilities are endless. next you need to decide the layout of your LEDs, and draw it onto your project box. It is also a good Idea to plan your circuit at this time. I will include the schematic that I used.
Step 3: Drill!
Once you know where you are going to put all of your LEDs, drill holes in the box for the LEDs where you want to put them.
Step 4: Preparing the LEDs
Place all of the LEDs in their correct places, and glue them down. Once this is done, solder all of the cathodes and anodes of the LEDs you want to be on on one of the oscillations together, and attach two leads to the group witch will go to the timing circuit. when soldering, line up all of the LEDs one way to make accidentally wiring the lights backwards less likely. to keep it organized and help prevent shorts, bend the leads on top of one another and solder that way (see picture) I didn't do this on the first letter, and it is very messy.
Step 5: Making the Timing Circuit
With the kind of PCB I used it was easy to get globs of solder stuck together and cause a short circuit. try to space things out as much as possible.
Step 6: Wire It Up
connect the groups of LEDs to the board, according to the schematic. it would be a good idea to add a switch. do this on the ground wire of the battery. after this, plug in the battery, close the box, and you're done.
Step 7: Testing
flip the switch to make sure it works.
Step 8: Problems and Troubleshooting
if only one of the groups of LEDs turns on, then this means you probably have a short. check the PC board and make sure no globs of solder are connecting things that aren't supposed to be connected, and make sure there are no shorts on the LEDs (this is where they are most likely going to occur) you might need to unsolder some parts and resolder. One thing that happened to me was that the green LEDs in the larger group barely emitted any light. I solved this problem by replacing the 470 ohm resistor going to that group with a 100 ohm resistor. If your display box is like mine where it has a small group and a large group of LEDs, then the small group is going to be very bright compared to the large group. I tried to solve this by lowering the amount of resistance going to the large group, but that was not enough. You might try raising the resistance going to the smaller group, but no matter what you do the smaller group will probably remain brighter. One thing that has no solution is that when you first turn on the display box, it will linger for a few seconds on the first group of LEDs before moving on to the regular oscillating pattern. I think this is more of an artifact of the state of the IC than a problem, and either way it is not very damaging to the affect, although can lead you to think it doesn't work for the first few seconds when you turn it on the first time.