View Full Version : Hacking Gemmy

01-13-2008, 08:59 PM
I think most of us have seen these trees in stores this holiday season. Some as small ones, some as combo's of three, and the fnal 7' by itself. Well...guess what folks, while cool as they were, the average person could not afford these (small ones were $75!). I bought the set of three for the wife ($250)....but you can't put a price on her smile.

So back to the topic at hand. Places are liquidating these now at 80% off. Yes..I said 80% off. So I picked up about 5 of them for $50 each (one @ $25 because it was the floor model) of the 7' single tree. This thread will indicate my progress on what it takes to hack these trees to tie them in what has been developed here already. I've already had some poking inside, but I will blog it picture by picture. I'm hoping it will be simple as adding a few jumpers with the current DC module.

Notes on the tree

1. It is like the current mega tree where it is bascially slices (so no horizontal effects).
2. LED's powered of 24V
3. It is RGB
4. Mixes pretty well but white is the typical "bleh".

01-13-2008, 10:17 PM
Well, I opened up the main box. Here is what I know.

The supply is a 24VAC and not 24VDC like I first thought.

The supply is regulated to 24VDC. However, if I don't have the music box running the transformer doesn't load down therefore the regulated drops a lot of voltage and gets hot (actually toasty).

(1) The LED's are chained together. Each RGB chain has a effective common anode (i.e. they all get +24VDC).

(2) The driver is a ULN2903 (http://www.st.com/stonline/books/pdf/docs/1536.pdf). Because it is the 03 version, you can drive it directly from +5V. (That lynx freestyle is looking tasty).
The star is its own channel. So in effect you need 33 channels (10 slices + star).

The star resistors get toasty. The current limiting resistor for a single LED powered by +24V is a bunch-o-power. My finger has a ilttle less skin.

In short all I think I will have to do is make a little board to rectify and regulate the 24VAC to 24VDC, add the 2903's with the appropriate resistors, and a few ethernet jacks (5) to accept the lynx free style commands. In short, i'm looking at maybe adding $20 cost to each tree to make it be able to be controlled by hardware already designed (well, mostly designed).

01-14-2008, 10:31 PM
Well, got the board half routed. Need to wait for my diptrace license to get here (I broke 250 holes my first board :shock: ). Should be pretty easy to add the AC -> DC linear supply.

Looking @ $10/board for parts (ordering enough for 6 boards).

Looking @ $10 per PWB from futurlec (6 boards) but no soldermask or silkscreen.

01-15-2008, 07:00 PM
Well...I changed things.

There are 10 strands and a star for a total of 33 channels (3 colors per element). I really wanted control of the star but I didn't want to add a 9th ethernet connector and waste three channels. I also wanted to try and get 4 trees into a single "lynx freestyle".

So I decided to remove the "star" from the "hack" board. I will put the star on its own DC SSR board (wjohn design). This way I am still wasting three channels, but it will work better when hooking the whole system up.

I went back and forth on whether or not to buy a stand alone 24VDC supply or use the transformers. In short, I need about 0.6 Amps per tree @ 24V or about 2.4 amps total. Add in a safety buffer and I am looking at 3 Amps. I also have a fifth tree as a backup...but I may just add it in. So now I need nearly 4 Amps of 24Vdc current. I hunted a bit and didn't find anything that really fit my needs. So, I am going to stick with the transformers that came with it. Therefore I bought the diptrace license (should be here tomorrow) and will add in the AC to DC supply.

Here is the current board, will be adding the supply on tomorrow. Baord will still be ordered through futurtec unless somebody can get a better price than about $10 a board w/o silk/soldermask.

01-16-2008, 11:07 PM
Well, I did some more hacking today. Here is what I've learned.

1. Resistor values are 150 (Brown Green Brown) and 510 (Green Brown) Brown). The two 150's had 4.3 and 3.5 volts across them for green and blue respectively.

2. I was using my meter in current mode to try measure the current through the resistor by just pulling the resistor to ground while the 2803 was off. However, one time I missed on the red line and POP.

3. So I opened up the bulb that popped and found this. The system is simple like I thought. The + is passed through and each of the diodes is ganged through. However, the Green LED has another diode in parallel with it. Wish I could get a better look at it. My guess it is a zener...just not sure what value.

4. I'm not sure at this point on the new board. If I just desolder the control boards out (pretty easy), I would have easy tap spots. Question is do I just put the RJ45 connects upside done and glue them down and just run jumper wires? It would be very ghetto...but would only cost me $5.00 a gemmy instead of $20-30 for a whole new control board.

5. And yes...that RED LED did explode. Not sure how many more I burnt out. However, there are 6 LED's in a chain..so I will have to find difused alternates and tweak the resistor accordingly on the blow channel.

6. The threes are almost worth the globe and gasket alone. Considering that get 60 of them per tree + a water resistant housing for $50...not sure if I oost out even with a "poor tree". I have also through about making my own board and putting something like a phirana flux LED in it ;)