Go Down

Topic: Word Clock with RGB LEDs (Read 1 time) previous topic - next topic

extasey

Hi All,

I am fairly new to the Arduino/hardware scene. I decided that the best way to jump right in was to start a project.

I found a great one called a word clock, and theres already an existing project that can be found at http://www.dougswordclock.com/

I would like to use some RGB LEDs and make quite a large clock. My sketches at the moment use 26 groups of LEDs, totalling 130 LEDs all up.

I have the ability to wire it all up and construct the clock, however, I have no idea how I would control them!

At the moment, I am looking at wiring all the LEDs in a single circuit and using a relay on the grounds to control which groups of LEDs turn on. The relays would then be controlled by a couple of 8 bit registers.

(TLDR;)My question is: would this be an appropriate way to go about the project? Would there be a better way of setting up the LEDs and controlling them and is there any points that would not work/might cause me a lot of hassle.

Thanks in advance for your help!

tylernt

Relays are great when you need to switch mains / line voltage, like for a 1/2 horsepower motor. For low voltage DC things like LEDs, most prefer to use transistors or other ICs instead of noisy, bulky relays.

(Of course, if you're going for a steam-punk / retro kind of effect, then relays are perfect -- use the biggest, clackiest ones you can find.)

Anyway, if you use a vanilla shift register like the 74HC595, you can only power up to 70mA of LEDs at a time per chip unless you wire in external transistors to switch the actual load. And, you have to use a lot of current-limiting resistors. Instead, consider an IC like the STP16C596: it's a shift register designed to drive a bunch of LEDs directly without additional transistors or resistors.

florinc

Take a look at ClockTHREE (launched on kickstarter a while ago), a word clock with individually controlled RGB LEDs.

Riva

Once I almost saw Elvis but then my shovel broke. :(

extasey

Wow, those clocks look awesome!

I think transistors are the way to go. I am going for an extremely modern/neat looking design... something I could put in the data centre I'm working at.

Next question: is this transistor good enough?
http://www.ebay.com.au/itm/Fairchild-2N5089-NPN-GP-Amp-25V-100mA-TO-92-BC560C-/120717085331?pt=AU_Pro_Audio&hash=item1c1b4c8a93#ht_731wt_922

I had a look and I am really struggling to understand the different mA capacity I will need etc.  I was thinking of using these LEDs:
https://www.sparkfun.com/products/105

Riva


I had a look and I am really struggling to understand the different mA capacity I will need etc.  I was thinking of using these LEDs:
https://www.sparkfun.com/products/105

Great as Sparkfun is, for 130 RGB LED's your better off (price wise) looking on ebay. You can get 200 of them here http://www.ebay.com/itm/200-pcs-5mm-4pin-Tri-Color-RGB-Common-Anode-Red-Green-Blue-LED-/120953667490?pt=US_Car_Lighting&hash=item1c29667fa2 for just under $40 where Sparkfun would cost just over $200 for 130 of them. It's worth getting extra on ebay as you can sometimes end up with mixed common anode/cathode or the occasional dead led.
Once I almost saw Elvis but then my shovel broke. :(

extasey

Awesome! I knew they were overpriced but hadn't begun researching where to buy them from yet. I knew I'd find them cheaper and you've saved me the hard work! Thanks!

Go Up
 


Please enter a valid email to subscribe

Confirm your email address

We need to confirm your email address.
To complete the subscription, please click the link in the email we just sent you.

Thank you for subscribing!

Arduino
via Egeo 16
Torino, 10131
Italy