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Topic: RGB SMT LED Cube, resistors, drivers, and shift registers. (Read 24 times) previous topic - next topic

Hippynerd

How about these little guys? they look good enough for 1 amp at 5volts.

Mosfet Type: P-channel
Current Rating: 2.6A
Rds (On): 40 mOhm
Voltage Rated: 12V
Package: SSOT-3

Mosfet Type: N-channel
Current Rating: 4A
Rds (On): 100 mOhm
Voltage Rated: 60V
Package: SOT-223

They are much smaller than the ones I actually ordered (from the previous post). but they look like they exceed my needs, take up less space, and are even less expensive. These seem much better than what I ordered, but maybe they are not?

Hippynerd

Im trying out TLC5940 chip on the SMT RGB LED cube, I have it wired up with 3 Chips, each have a 2k resistor, and I used 1 10k resistor, but the schematic didnt show any decoupling caps, so I didnt put any in.

Im trying it with the BasicUSe example software (just one plane of of 16 RGB LEDs, no multiplexing), and on Usb, it starts out really bright all on full, and after about a minute, it dims, and flickers each individual LED, but looks weird, and im pretty sure, wrong.

When I run it from 5v power supply, its similar to on USB, but its not bright at all, just flickering each individual led.

I know that I have some solder issues, since all the LEDs are not working (I buggered them up while soldering the wiring on the backside of the board.

Im using the info at:
http://playground.arduino.cc/Learning/TLC5940
and I wired it up like the example.

Heres a picture of the wiring, I havnt done the stuff for the planes, but I run a wire from the 5v to one of the common plane wires.


Hippynerd

I worked on this again tonight. I repaired the some wiring on the middle chip, now all the LEDs light up in order, but they are pretty dim. I also put .1uf caps on each 5940, and its a little brighter, but nowhere near as bright as they should be.

Im just running one plane at a time with a 5v wire to the plane, and the software running the 5940s. The cubes gotten kinda beaten up being knocked around my bench for the last month or two. I will need to replace some LEDs I think :(

ematson5897

This is sort of an old topic, but I straighten my wire for cubes by grabbing both ends with needle nose pliers and stretching it. You will feel it stretch and then its perfectly straight

Hippynerd

I tried that too. I used a vice, and vicegrips. The copper wire (24 gauge) breaks really easily, then springs out of control. The steel wire (19 gauge) did get straighter, but it was very difficult to stretch. I was able to do it, but when relaxing the wire, it still had curves in it. I also tried pulling real hard on the wire while smacking the wire with my hand, it didnt work either. I got straighter wire, but I couldnt get the curve out entirerly. I was working with about 6' of wire at a time, trying to get the longest section of straight I could get, but it just never got straight enough for me. I have some 22 gauge steel wire, but I havnt tried straightening large sections of it.

How were you doing it, how long and what gauge wire?

There is also a technique where you twist the wire, I actually got the best results with that technique, but when you look close, you could see the twist, even from 10 feet away, you could kinda see the twist. What you end up with is a wire that has very consistent tight twist to it that is roughly straight and rigid.  After a few days of trying things, I ended up going back to the original gentle uncurving metheod.

I was looking at the music wire that I had used on the charliecubes, and its got some rust on it, so its not stainless steel, its hardened steel.

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