The Most Outlandish Case Mod Evar.

[berichandcreamy]

I'm going to take 2 of these:

That you can order from here.
and Velcro them onto the back of my Pandora because I want a light show like:
This or to display text like This

I'm just unsure how to control the LEDs via usb. I found people using arduinos mostly. Thoughts?

 

[torpor]

I'm just unsure how to control the LEDs via usb. I found people using arduinos mostly. Thoughts?

Use an Arduino.

 

[gp32rich]

go to www.evilmadscientist.com and have a look around.

plenty of display driver projects there

 

[lulzfish]

That'll actually be 2x64 or 8x16 LEDs.

 

[gp32rich]

That'll actually be 2x64 or 8x16 LEDs.

well - if you're being pedantic ... 8 x 8 x 3

 

[Exophase]

You'll probably need a microcontroller to interface this. To talk to the microcontroller you can get a USB device capable one, but you can also get a USB to serial chip.

I'm very much not an electrical engineer, but from what I understand you may need to use a driver to supply power to the LEDs, because otherwise they might draw more current than a microcontroller can provide over its GPIOs. You may also have to provide a higher voltage than the microcontroller's power (usually a microcontroller's I/O and power voltages are the same). You may also need to put some impedance between some of the inputs and the controller.

But I'll leave it to someone who knows more what they're talking about to provide electrical advice. I can only confidently help you with things like writing code for the controller >_>

 

[Geuben]

Arduino would be able to do what your after. However, it would require some extra ICs as it doesn't have enough IO pins to interface with all those LEDs (unless the LED matrix itself has that hardware built in). Also as mentioned, the current draw is going to be a big problem, to be portable you would want it to be powered by the pandora's USB but that probably won't be able to supply enough current. Finally, size, the arduino alone would look pretty massive stuck to the bottom of the pandora (unless you go for an arduino mini or nano) and then two of those LED matrices would make for a pretty bulky device.

The arduino website and forum at www.arduino.cc is a great place to get help.

 

[Exophase]

However, it would require some extra ICs as it doesn't have enough IO pins to interface with all those LEDs (unless the LED matrix itself has that hardware built in).

The datasheet wasn't totally clear, but from what I've seen on similar products from the same vendor the LED matrix inputs are muxed by row/column. So there'd be (8 * 3) + 8 I/Os. I'm guessing this still is more than Arduino provides.

Also as mentioned, the current draw is going to be a big problem, to be portable you would want it to be powered by the pandora's USB but that probably won't be able to supply enough current. Finally, size, the arduino alone would look pretty massive stuck to the bottom of the pandora (unless you go for an arduino mini or nano) and then two of those LED matrices would make for a pretty bulky device.

I was really talking about the current load on I/O pins, but you're right, the main power won't be able to supply more than 500mA and if each LED takes as much as 10mA you could end up using as many as 2A with all of them on.

 

[Geuben]

The Arduino has 13 digital IO pins but 2 are used for the UART, there are only 6 (I think) capable of PWM too, so it wouldn't be possible to interface directly with one of those matrices. I'm pretty sure I've seen multiple posts on the arduino forum using those exact LED matrix so reading them would give the OP details of the ICs required and everything else he/she needs to know.

FYI: the arduino can handle about 30mA on each IO pin, I think there's a limit on the total current that can be source/sunk across the whole board. That's the duemilanove , I'm not sure if the other variants have different current capabilities, but the smaller versions lack the USB port for power/programming/comms (the require a USB to FTDI cable)

 

[berichandcreamy]

Holy hell this is more complicated than I imagined =(

I was totally thinking I'd have more power over USB. Well from what I can tell there will be some left over case space if I needed to strap on batteries. Although it appears that others haven't done so:

From the video comments:

"I cheated and bought the sparkfun serial backpack - it takes care of driving the leds and acts as a framebuffer, displaying whatever you send to it until it is refreshed"

"Didn't use any additional components other than Arduino and the LED matrix with backpack."

There is still a way for me to add more power!

Specs of the Arduino Nano:

"The Arduino Nano can be powered via the Mini-B USB connection, 6-20V unregulated external power supply (pin 30), or 5V regulated external power supply (pin 27). The power source is automatically selected to the highest voltage source.

The FTDI FT232RL chip on the Nano is only powered if the board is being powered over USB. As a result, when running on external (non-USB) power, the 3.3V output (which is supplied by the FTDI chip) is not available and the RX and TX LEDs will flicker if digital pins 0 or 1 are high."

So I'm assuming I can power it over pin 30... not sure what batteries can interface with that. Then I can use the mini usb to usb to control the colors, display messages?

 

[Geuben]

Holy hell this is more complicated than I imagined =(

I was totally thinking I'd have more power over USB. Well from what I can tell there will be some left over case space if I needed to strap on batteries. Although it appears that others haven't done so:

From the video comments:

"I cheated and bought the sparkfun serial backpack - it takes care of driving the leds and acts as a framebuffer, displaying whatever you send to it until it is refreshed"

"Didn't use any additional components other than Arduino and the LED matrix with backpack."

There is still a way for me to add more power!

Specs of the Arduino Nano:

"The Arduino Nano can be powered via the Mini-B USB connection, 6-20V unregulated external power supply (pin 30), or 5V regulated external power supply (pin 27). The power source is automatically selected to the highest voltage source.

The FTDI FT232RL chip on the Nano is only powered if the board is being powered over USB. As a result, when running on external (non-USB) power, the 3.3V output (which is supplied by the FTDI chip) is not available and the RX and TX LEDs will flicker if digital pins 0 or 1 are high."

So I'm assuming I can power it over pin 30... not sure what batteries can interface with that. Then I can use the mini usb to usb to control the colors, display messages?

Sorry if I confused you, you can power the arduino via the USB or via a power supply, the smaller versions don't have a dedicated DC jack. I think they have either a little header to plug a battery in, or just pins for you to wire up a battery etc.

If you used a nano and the same LED matrix as in the video (as it has the extra stuff to interface it with the arduino) then it should be pretty easy to make the circuitry. Then it's just a matter of coding it to do what you want. If you want to be able to control it via the pandora then you either need to write an app for the pandora that sends commands on a serial connection via the usb port or use an app that already does (there is probably some command line tool).