Crazy Petes Projects




March 20th, 2012:

So, I was looking around on Hackaday and found this post about a starlight project from Zach. That inspired me to make one of my own (my 3 month old baby loves the results.) As with any project, there are a few ways to get anything done, none of them necessarily wrong. I chose to use a gear reduction motor instead of a servo and micro controller. I also found some automatic RBG leds that change color every few seconds, by themselves. The details are below.

Materials:

Part no.
 Description
 QTY
 Price
 Source
LED-158 RGB COLOR-CHANGING LED 2
 $0.75
 All Electronics
7805T
 5V POS REG 1 AMP 1
 $0.50
 All Electronics
DCM-276 5 RPM GEAR MOTOR, 12VDC 1
 $9.00
 All Electronics
B000AR8Q36
 3M emi 1181 3/8 x 18yd; copper foil
 1 roll
 15.50/
 L-com via Amazon
n/a
 100 Ohm resistor
1
 n/a
 my parts bin
n/a
 6 pack of
ping pong balls
 1
 1.59
 in store at local Walmart
n/a
 12VDC, 500mA power adapter
 1
 n/a
 my parts bin
n/a
 a box some fuses came in
 1
 n/a
 my parts bin

Schematic and Theory of Operation:

Please forgive my crude schematic. I think it gets the point across.
schematic
  • 12 volts comes into the motor from the power supply to turn the light ball.
  • 12 volts also goes to the 7805T to regulate the voltage down to 5VDC for the LEDs
  • I used a 100 Ohm resistor I found for current control, should draw ~0.050 amps (~50mA), nice and bright.
  • The circles you see in the picture are the foil tape slip rings, the LED leads drag along these rings as the light ball rotates.
  • I also tied the anodes and cathodes of the LEDS together, so if one lead looses contact with the slip ring, the other could still conduct.
 

Assembly Steps:
  • First, I poked holes in the pingpong ball, small ones to let light out and two large ones to hold the LEDS
  • After I soldered and epoxied the LEDs in place I painted it black.


  • The copper foil tape, was simply placed on the motor, around the rotating axis.


  • Then a small strip cut away to make two conductors for the slip ring. Note the wires already soldered to the strips. and extra piece of foil was placed over the blue wire for continued contact:


  • I soldered all the components together:


  • and put the in a fuse box, with some double sided tape:


  • In the above, you can also see I have bent the LED leads to contact the foil slipring as the ball rotates
  • To attach the light ball I found a sharp screw, with a head that fit snugly into the center of the motors shaft. Then, I applied  power to the motor to rotate the shaft counter clockwise. This caused the screw to turn as I held the light ball, pulling the assembly down on the screw threads and ensuring the leads had a good connection to the slip ring.
  • Below is a short clip of the unfinished finished device (just to show the effect of the LEDs):



If you made it this far, Thank you for viewing. I know, I'm no good at building webpages, or even designing them, I just wanted to get my version of this project out there. I do welcome any comments or questions  you might have.