I am trying to build a board game that has curved paths. I want to illuminate the player's position on the path during gameplay. I need 3 rows of 120 lights each to make this happen. The kicker is that it is under a strict $100 budget. I have the Arduino Uno, which isn't factored into the budget.
Does anyone have any idea how to do this? Thank you for your help!
Richard
You can get bulk packs of LEDs quite cheaply on eBay (I've just found 100x 5mm LEDs for GBP 2.99). The best way to drive them is probably either 6 x 60 multiplexing (requiring 8x 8-bit shift registers such as 74HC595 and 60 series resistors), or 8 x 45 multiplexing (requiring 6x 8-bit shift registers and 45 series resistors).
The best way to wire the LEDs to the shift registers and column drivers depends on what combinations of LEDs need to be lit at a time. The 74HC595 has a total current limit of 70mA. If you need to light all the LEDs attached to it at once, then this limits you to 9mA per LED. But as you will be showing a path, by choosing the layout of the matrix appropriately, you can probably reduce the number of LEDs connected to each shift register that are concurrently illuminated, allowing you to use higher currents.
Can you get it done with a digital strip like this?
KirAsh4:
Can you get it done with a digital strip like this?
The depends on whether or not the spacing of the LEDs matches his board.
Plus ... they're not very good at going around corners, he says his paths are 'curved' so I'm guessing they won't work unless his board is enormous.
rickcjmac:
I am trying to build a board game that has curved paths. I want to illuminate the player's position on the path during gameplay. I need 3 rows of 120 lights each to make this happen. The kicker is that it is under a strict $100 budget. I have the Arduino Uno, which isn't factored into the budget.
Budget isn't a problem - LEDs are cheap. eBay sells them in bags of 100 for $3-$4 each. It might be worth buying a small quantity of 2-3 different models to see what they look like.
You don't say what your brightness requirements are (or ambient lighting) so you might have to pick and choose. If you're going to be looking at them directly then get "diffused" LEDs. It might be worth trying 3mm LEDs as well - the light is 'concentrated' in a smaller area and they look more intense. They're slightly more expensive though - budget an extra $5 for those.
For driving them you need shift registers. I'd get "constant current" shift registers so you don't have to worry about power requirements or LED resistors or anything like that. They also occupy less space (no resistors!) and need a lot less soldering, that's important when you're doing hundreds of LEDs.
Which chip? I'd go for the MBI5026 - you get 16 LEDs per chip and they're easy to get hold of. eBay has them for about $1.50 each. Get a few spares, just in case...
Add in a decoupling capacitor for every chip (important!), some chip sockets, some chip sized PCBs to solder everything onto and you'll be in the $65 range.
Thank you for your replies! Fungus, you are spot on. I agree with dc42 as well, however a 16 output chip will be that much easier to utilize than the 8 output chips. KirAsh4, thank you for your response. That is what I was running into, but as fungus said I can't control the spacing or layout direction. If it weren't for those your suggestion would work great for me.
Thank you all again. Problem solved! 
How about some MAX7219's?
Control 64 LEDs each, $1.25 each, 6 will control 384 LEDs.
Layout the LEDs however you'd like.