LED Cube 8x8x8

Step 42 Build the controller: Make an RS-232 cable

To connect the LED cube to a serial port on your computer, you need to make a serial cable with a female D-Sub 9 pin connector.

Our employer deployed 70 Ethernet switches with management last year. With each switch comes an RS232 cable that is never used. We literally had a big pile of RS232 cable, so we decided to modify one of those.

On the LED cube, a 0.1" pin header is used, so the RS232 cable needs a new connector on the cube side.

We didn't have a 4 pin female 0.1" connector, so we used a 4 pin female PCB header instead.

The connector on the LED cube PCB has one pin removed, to visualize the directionality of the connector. The pin numbers goes from right to left.

Pinout of the RS232 connector:

1) GND (DSub9 pin 5)
2) Not connected
3) RX (DSub9 pin 3)
4) TX (DSub9 pin 2)

Follow these steps to make your own RS232 cable:

1) Cut of the connector at one end of the cable. If your cable has a female and a male connector, make sure to remove the male connector!

2) Strip away the outer sheath on the end where you removed the connector.

3) Strip all the wires inside.

4) Set your multimeter to continuity test mode. This makes the multimeter beep when the probes are connected. If your multimeter doesn't have this option, use the resistance mode. It should get close to 0 ohm when you connect the probes.

5) Connect one multimeter probe to the DSub9's pin 5, then probe all the wires until you the multimeter beeps. You have now identified the color of GND in your cable. Repeat for pin 2 and 3 (TX and RX).

6) Write down the colors you identified, then cut off the other wires.

7) Cut the three wires down to size, 30mm should do.

8) Pre-tin the wires to make soldering easier. Just apply heat and solder to the stripped wires.

9) Slide a shrink tube over the cable. Slide three smaller shrink tubes over the individual wires.

10) Solder the wires to the connector.

11) Shrink the smaller tubes first, then the large one. If you use a lighter, don't hold the shrink tube above the flame, just hold it close to the side of the flame.

Don't make your cable based on the colors we used. Test the cable to find the correct colors.

Comments

[jwestenberg]

I build the led cube (got all the LED's soldered together) and am now ready to order all the other parts. I am still a little confused about the whole rs232 thing since I don't have access to a serial port. On the internet I read a lot of posts saying rs232 doesn't work with a usb to rs232 cable, and if it would work it would be very slow.
I this just a problem when u try to program the AVR, or also when u try to directly 'stream effects with rs232 input?

If it is a problem should I just buy all components listed and in addition order something like this: http://www.futurlec.com/RS232_Converter.shtml , or should i buy other components to make this work with usb?

Thanks very much!

[chr]

USB RS232 will work just fine. Some USB dongles don't communicate at high enough voltage, and that's not a problem for the MAX232 chip in the LED cube.

[jwestenberg]

Alright, thanks for your quick reply.
Btw, great instructable!

[qwertyboy]

Would it be possible to use an Arduino for the serial connection? I know the entire cube could be run off of it, but I want to use it just for connection between the computer and cube. Would any code have to be written, or would I be able to just send data to the TX and RX pins on it?

[bennytheblender]

I think you could send the pulses through the tx and rx pins. Pins 0 and 1 on the uno. I think you would have to write very little code to do so.