Friday, May 1, 2015

8x8x8 LED cube kit completed

I completed the third application for my 8x8x8 LED cube.  First it was to use it with an Arduino, then with a Raspberry Pi and then this kit that I bought on eBay.  At first I thought it was not working because it is so dim that you have to turn down the lights to watch it.

Here is the front view of the completed 8x8x8 LED cube.

 This is the back view.  You can see the wires going up to the eight layers.

Here is the bottom view so you can see the IC's.

This it the video of it on YouTube.

The design problem is that there should be a resistor in each LED leg, that would take 64 resistors.  Instead they used 8 resistors in the common cathode circuit.  As a result the brightness of each layer varies depending upon how many LED's are lit up.  The more led's are lit the dimmer the layer becomes.  I might try to fix this by adding a resistor on each of the 64 legs and removing the ones on the common cathode connection to each layer.  If nothing else reducing the 500 ohm resistor to 100 or 220 ohms might do the trick.

Here is the quick fix just change 510 ohm resistors to 51 ohms.  Then the display is much brighter.  It is still not as bright as when you use 74595 shift registers.


Tuesday, April 28, 2015

I am working on a book of LED Cube Projects

I have been working on a book of LED Cube Projects.  It might end up being two books one for the Arduino and one for the Raspberry Pi.  So far I have built a 4x4x5 LED cube and a 8x8x8 LED cube. Coming up next is a Color Cube likely 6x6x6 in size.

Here is a picture of the 8x8x8 LED Cube from above.


This first picture is of a 3D slice cutting through the cube.


Here is a link to the video: https://youtu.be/g9kaYzO85oM

This next video is of "falling rain" 


Here is a link to that video: https://youtu.be/-tZJ-3NSlhY

Here is a picture of it running with a Raspberry Pi.
Here is a link to that video: https://youtu.be/eRgVuaLHWls

Thursday, April 23, 2015

Epson Powerlite 62C Repair

I recently purchased another pile of used projectors to repair and then send to Africa.  However three of them need more than just cleaning.  I have determined that the problem is in the optics.  Basically the blue LCD is about 30-50% shot.  There are lots of dark spots in a blue background.
The problem is that the LCD section is one unit otherwise I could swap the LCD's between the three projectors and hopefully get two of them to work.

I like the Epson LCD projectors because they are a lot more rugged that the Dell 2300MP DLP projectors.  However the LCD's have an air filter and if it gets clogged the projector overheats and damages the LCD's.  I explained how to replace the filter in a previous post.

Here is what the outside of them looks like.

Wednesday, April 15, 2015

RAWNY Mini Hamfest Buffalo NY

Once again this year I attended the mini Hamfest.  It is just for a couple hours in the evening but you get to talk to a lot of interesting people as well as sell and buy a lot of stuff.  I think I managed to leave with less stuff than what I came in with.

Here is a picture of my table.  I did not bring the bins from my shed this year.

Here is another table or two.

Here was some really nice radio's.  Sorry I chopped off the picture of the seller....

And here are some more tables of great stuff!


Thursday, April 9, 2015

Refurbishing Projectors for Africa.

I spent a weekend fixing 7 Dell 2300MP Projectors.  In every case the power supply was not working.  I replaced the same capacitor in all 7 projectors.  It is a 22uF at 50 volt cap.  I replaced it with a 22uF at 63 volt cap.  Out of the 7 projectors that fixed five of them.  One had some burnt parts in the power supply.

This is what my closet looks like.  The 2300MP's are on the right.

Here is a picture of how to bend the leads on the capacitor.

This picture shows where the capacitor goes.  It is not yet soldered in the picture.

 Here is a picture of a pile of projectors, I worked on them three or four at a time.

I had to glue some of the supporting posts in place.  The projectors had all been dropped, likely in shipping, and the posts that hold them together were loose.

Wednesday, March 18, 2015

Raspberry Pi and a DIY 4x4x4 LED cube

I have built a DIY 4x4x4 LED cube that I am testing with the Raspberry Pi.  It is up and working, I just need some code to make it do something that is "moving".  Pun intended.  It is only doing fixed patterns at this point.

Note that my design is quite different.  For one thing all 4 LED frames are easily removed for servicing.  So far I have had one bad LED and a soldering connection that needed fixing.  I also need to replace one LED that has a slightly different color.  It is the third one up from the bottom in the center.

My 4x4x4 LED cube is also designed to be expanded to 4x4x5 or 6 as adding them will not require any more IC's.  Also when you order LED's they come in bags of 100 so why not use all of them? There are currently two 74HC595's and a ULN2003 driving it.

I drilled a wood guide and rebuilt the arrays so they are right to left instead of front to back.  I also added the fifth row while I was at it.  I broke a couple of LED's in the process but it is up and running again.


Here is a picture of the LED test program running to make sure everything works.  I need to replace a bad LED and find a way to keep the LED arrays parallel to each other.  I might give in and add some wire braces across the top corners.  The braces could be un-soldered to work on the arrays if needed.


Here is the video on Youtube.