Haha. Foo is the first half of foobar, which is the polite spelling of fubar. Here's the lowdown:

http://en.wikipedia.org/wiki/FUBAR#In_computing_and_technology

http://en.wikipedia.org/wiki/Foobar

Hi Nishant,

I guess I don't fully understand what you want to do. Yes the Instructibles example won't let you control all 64 LEDs directly, but you use multiplexing to fake it.

Can you maybe give more explanation and I will try to help you out?

Chris

Thank you again for your help!

Will this help?

http://www.instructables.com/id/The-4x4x4-LED-cube-Arduino/

Thank you for that information. Where do Vbe and Voic come from? Are they standard values or from the specs of the transistors or the 74ac138?

Thanks again!

@Graynomad - Hfe is 130 @ 2A and 80 @ 3A, so I'm estimating I should be able to get at least 100 @ 2.4A. The data sheet on the 74ac138 (http://www.fairchildsemi.com/ds/74/74AC138.pdf) says it can provide up to 50mA; in another thread (http://arduino.cc/forum/index.php/topic,72866.msg547333.html) Crossroads said it should be able to do 24mA.

I think you're right, if I measure current from a TLC5916's ground pin I'd hope to see about 800mA (8 outputs @100mA ea) but my current meter only goes up to 500mA. I know I need a new meter but am trying to figure out if I should get a new basic multimeter, or if there's something fancier that would let me measure these pulses.

@Magician - sorry if I was unclear. The output pins from the 74ac138s are connected to 43 ohm resistors, which are connected to the bases of the DPLS350Y transistors. I'm using the formula from "Choosing a suitable transistor" at http://www.kpsec.freeuk.com/trancirc.htm ; Rb = (Vc x hFE) / (5 x Ic), so (5 x 100) / (5 x 2.4) = 500 / 12 = 41.67.

Thanks again.

Thanks for the scope info. I'll start researching.

BTW I do trust the TLC5916s, they're working great.

I'm trying to figure out if the row transistors are supplying enough current. 74ac138 outputs go to DPLS350Y-13 transistors via 43 ohm resistors. If I did the math right then 24mA from the outputs and a gain of 100 from the transistors will give me 2.4A on each row (for 24 LEDs @ 100mA ea).

The problem is with the setup I have right now is the lights aren't as bright as when I drive them directly with 20mA. I realize I won't be able to get exactly as bright, but I was hoping for more than what I have.

Here's the transistor data sheet:
http://www.diodes.com/datasheets/ds31149.pdf

I have a 24x16 LED matrix - the 16 rows are connected by transistors driven by a pair of 74ac138s and the 24 rows by 3 TLC5916s. Refresh rate is 10K Hz (0.1us).

I want the lights to be as bright as possible so I'm overdriving them with 100 mA pulses...at least that's what things should be if I did the calculations right.

When I measure a row's draw I know I won't see 2400 mA (24 LEDs @ 100 mA ea) since it's only being powered 1/16th of the time, but my meter says ~38mA instead of the 150 I'd expect (2400 / 16).

On each column the meter says ~63mA. I know it won't say 100mA because the display is off for 3-4ms each update, but 63mA seems low...

Maybe my meter is so off because it doesn't average pulses very well?

My meter only goes up to 500mA so I can't do the easy thing and just measure total circuit draw.

My question is should I just get a new meter with a higher current capacity, or is there something like an oscilloscope etc. to more accurately measure pulsed current? If so are there any models you recommend?

Thanks in advance.

Chris

Definitely the header pins; no need to go to the IC socket and risk damage.

Where are you connecting reset? I just looked at the Lilypad schematic and it looks like it should go to the DTR header pin? If so, is there any way you can try to bypass the capacitor and resistor since the Duemilanove will already have it?

Does the Lilypad work if you connect vcc and ground (hopefully it has the default program of blinking the LED on pin 9). If that works, can you connect the reset line and see if the Duemilanove's reset button can reset the Lilypad?

If you disconnect the Lilypad and plug the ATMega328 back in the Duemilanove can you program it r do you have the same problem?

That should work!

Chris

Sorry, I hit 'post' on the first reply too soon. I've edited it with more info.

Chris

Hi Ashley,

This should do what you want:

http://arduino.cc/en/Tutorial/ArduinoISP

Use the first example, "Circuit (targeting Arduino Duemilanove or Diecimila)", with your Lilypad on top.

Alternatively, if you just want to upload sketches to the Lilypad and don't want to go through all the ICSP stuff you could just remove the ATMega328 chip from your Duemilanove then jumper across wires connecting +5v, ground, reset, TX and RX and program it directly.

Good luck!

How about sscanf() ?