This is a project I've always wanted to do but I never got around to making a topic for it. As you know, it's pretty darn hard to see what the keys are in the dark so I thought about back lighting them. As I was looking at Sam's TI 84 Plus CE tear down image, I noticed that the keys are slightly hollow and might be able to fit an LED!
(Click for full size image)
I foresee a few problems trying to put an LED in the keys.
0. I'm not sure where to find the products I need for this project such as a small enough LED that's the correct voltage (3.7v I think) or a thin wire that won't short if it touches other wire/metal. I also don't know the best way to wire so many LEDs together. Do you have an recommendations for this?
1. The keys may be too thick or dark to adequately backlight them with a small LED. The only solution I think could work is what Pieman suggested, 3D printing all new keys. However, I don't have the dimensions of the keys nor do I have a 3D printer.
2. If a LED does fit within the hollow space, it might mess up the grey rubber membrane and cause buttons to stop working properly. It might work to cut into the rubber but I think you could easily risk cutting in too far. Does anyone have any suggestions for that?
3. The arrow keys are a very strange shape and the top 5 buttons are thinner than the rest. I'd think either those need a different type of LED (which may not be as bright) or can't be backlit at all.
4. How are the LED's going to get power? I have a few ideas for that
Of course, before I go ham and try it to my own CE, I need to do some tests first. Sam (or anyone with a TI 84 Plus calculator keys), if you still have your calculator apart, could you see how well an LED will shine through the plastic? (the dimensions of the LED doesn't matter right now) Also, could to take a picture of the back side of the big grey rubber key membrane?
(Click for full size image)
I foresee a few problems trying to put an LED in the keys.
0. I'm not sure where to find the products I need for this project such as a small enough LED that's the correct voltage (3.7v I think) or a thin wire that won't short if it touches other wire/metal. I also don't know the best way to wire so many LEDs together. Do you have an recommendations for this?
1. The keys may be too thick or dark to adequately backlight them with a small LED. The only solution I think could work is what Pieman suggested, 3D printing all new keys. However, I don't have the dimensions of the keys nor do I have a 3D printer.
2. If a LED does fit within the hollow space, it might mess up the grey rubber membrane and cause buttons to stop working properly. It might work to cut into the rubber but I think you could easily risk cutting in too far. Does anyone have any suggestions for that?
3. The arrow keys are a very strange shape and the top 5 buttons are thinner than the rest. I'd think either those need a different type of LED (which may not be as bright) or can't be backlit at all.
4. How are the LED's going to get power? I have a few ideas for that
- Connect the lights directly to the battery leads. Then remove one of the metal contacts (the one at the bottom of the CE that's used for dock charging) and replace it with a switch. This switch will be used to turn the backlight on and off, it'll be recessed so it wont interfere with the slide case and wont be accidentally toggled when you're using the calculator outside of the slide case. This could be a bit difficult, though there are plenty of holes and spaces in the PCB so I don't think wire management would be too bad.
- (I have no idea if this'll work) Connect the lights to the USB leads. That way the backlight only turns on when the calculator is charging.
Of course, before I go ham and try it to my own CE, I need to do some tests first. Sam (or anyone with a TI 84 Plus calculator keys), if you still have your calculator apart, could you see how well an LED will shine through the plastic? (the dimensions of the LED doesn't matter right now) Also, could to take a picture of the back side of the big grey rubber key membrane?