GI OCD is my current project to create a better LED controller for LEDs in the GI of WPC games. Similar to LED OCD (http://ledocd.com), it is completely configurable, allowing you to set the brightness levels for each string of GI independently. Other features will be revealed as I continue to work on it. For now, I just wanted to share a video of the basic functionality in action. There is still a LOT of work to do before I will be able to say if it can be made practical and affordable.

Note that I am controlling the backbox GI because it is easier to get to and change bulbs. The bulbs behind the plastics are still incandescent because I was too lazy to swap them out for now.

Yes, that's the main goal, actually. If you notice in the video, each of the 8 brightness levels that are controlled by the machine are interpreted by GI OCD, then re-driven as PWM'd DC to allow different output brightness, but in a smooth manner.

A little off-topic here, but... Obviously, mounting a board with screws will be more secure. That said, I've had a few installed in my machines using the sticky feet for about a year and a half, and none have come loose. I run the cables through the existing clips, so there's not much weight on the board itself. If this is a common problem, please let me know. I would be happy to remove the sticky feet from the kits and drop the price a buck if no one uses them.

Now, any thoughts on GI?

Sorry, I wasn't able to figure out what you meant by the harness comment.

It's all part of the challenge.

Right now, I have a board sitting on the glass with an oscilloscope attached just trying to make it work without burning the board up. The bridge gets pretty hot, even with the single string of lamps I'm currently controlling. I don't have a thermal probe handy (one is on order), so I don't know how hot it really is yet.

This (GI OCD) is only for GI, and for now, only for Williams WPC games. Luckily, however, LED OCD does work for LOTR's controlled lamps. I've sold a good number of those, and they work quite well.

... and then another peltier to cool the first one...

It wasn't getting as hot as I had thought, testing it by finger. It turned out to be around 55C. It would be even hotter by the time I start powering 5 full strings, though. I didn't have enough bayonet LEDs on hand, so I'm waiting on more to arrive before pressing further.

One option I'm looking into is a bridge that uses appropriately controlled MOSFETs rather than the standard diode bridge. To test this, I'll have to run another prototype PCB, though.

I did get one other feature working this weekend. It can detect whether the machine is being played by watching the coil activity. Using this, you can configure it to control lamps differently based on whether the game is being played or not. There's already a setting in the WPC ROMs that can be used for power savings, but this is more flexible. For example, you can control each string independently. Also, I am using it to reduce translite glare on the glass by dimming the backbox lamps while in play.

Yeah, I considered it. There's not much overlap, though, so there wouldn't really be much, if any, space savings. The board would be bigger, and you'd have to find space to mount one bigger board instead of two smaller ones. Plus, you'd be forced into buying both solutions rather than being able to choose. The price would end up being about the same as buying two separate kits.

If I'm understanding your question correctly, no, it currently lets me map 8 different duty cycles to each of the 8 WPC brightness outputs. It does this independently for each string. Once I get a game fully up and running, I'll be able to tell better if the smooth fading between levels is necessary.

Last night, I finally finished swapping out my playfield lamps with LEDs. I used a mix from Comet Pinball; mostly 1 LED SMT 5050 Frosted, with some 2 LED Faceted in the areas that could use some more light. They look really nice, and the machine is much cleaner looking than before.

Because the bridge/cap setup yields over 9V, I ran a test at 65% duty, which measured at 6.3VDC average on my DMM. This is still brighter than I prefer, but I wanted to see how much heat this generated. The bridge topped out at 71C. While this is hotter than I'd prefer, it's still well within what the bridge is rated for, and it's lower than I was expecting. I'm still a bit concerned about what would happen if a failure locked all the strings on, and I would rather not rely on the fuses to shut it down. I have already sent a new design for fabrication that will let me test the MOSFET bridge design.

Anyway, I'm loving the new look. I dimmed the LEDs to taste, and played a few games. Having the backbox automatically dim when I start playing is just too cool, and since I can map the playfield control signals to the backbox strings, it turns off when the playfield turns off rather than staying on all the time. The intro to Stiff in the Coffin is more dramatic with the backbox flashing, and "Turn out the lights" is extra cool as well.

I can't see any flicker until I get down to about 5% duty cycle. My wife has the eagle eye for detecting strobing, and she says she can't see anything bad either.

If you can't tell, I'm extremely excited. I wish I'd done this sooner.

I was a bit skeptical that this could be done without a really big board, a huge amount of capacitors, and pounds of heat sinks. It's coming together much better than I would have guessed. The current board is 6" x 2.75", and I could probably make it a bit smaller if necessary.

As you'll see, it looks great in SS, but I really think it will be awesome for the shields in STTNG. As far as I'm aware, there is no good solution for that right now other than leaving incandescents in there and having the inserts look green.

Thanks for all the kind words, guys. Here's some video. Like all lighting, it is difficult to capture accurately in video or pictures, but I think this gets the point across. I tried to add some inline comments, but my video editing app kept crashing, so I bailed on that.

You'll have to look closely to see the backbox dimming when the first ball is kicked out.

The backbox lighting is normally always on, but I have it configured to use the playfield inputs, similar to the blackout mod for AFM. That works well in almost all cases, but it goes dark when it's time to "stop the spider".

At around 2:30, you can see the dimming working a good bit during the intro to Crate multiball and when Jackpots are collected.

At 6:00, the start of Stiff in the Coffin is especially cool with the backbox lighting flashing.

The flashing you're seeing at the start of Coffin multiball is intentional. It is programmed that way, and it does it with incandescents. The unintended effect is like what you see at the beginning of the video in the first post.

I might add fading between brightness levels, but it is not a top priority. It would smooth out effects like what you see at 1:17 when the ball drains. It goes from B8 to B2 in steps that you can see if you're ultra picky.

My next priority is to manage the heat. Hopefully, the MOSFET bridge will work out. If not, I may have to settle for a better heat sink.

OK, so after thinking about this some more, I realized you were probably not talking about LEDs flickering as much as having sharp on/off transitions. That is something that I do plan to work on at some point. It's still low priority, but is on the TODO list.

Crash was right!

I had some unexpected free time this weekend, so I added a configurable delay that controls how fast it switches from one brightness to another, pretty much the same thing as in LED OCD. It "rounds off the edges" quite nicely. You still get the flashing effects like at the start of Stiff in the Coffin, but it's "softer" flashes.

It will be another week or so before I receive the updated boards, but I did some more temperature testing with the diode bridge. I gradually increased the duty cycle while monitoring temperature, and by the time I got to 100% duty, it settled at 90C. That's still within the operating range of the bridge, but it's pretty darned hot. You really shouldn't be running it that way, because it runs the LEDs at a constant ~9V.

The rest of this gets pretty nerdy, but it seems to help me straighten out my thoughts by putting them in writing.

The heatsink I have now is no slouch (10C / W), but I have a better one on order. It's too hard to tell how much it will help since it depends on airflow, ambient temperature, etc.

There are drawbacks to the MOSFET bridge approach as well. The most obvious is cost. It would be about $12 in parts vs $5 for the old school bridge and heatsink.

It's also more complex, and the controller is a tiny SMT chip with a GND pad in the middle, making it something that most pinheads won't want to work on themselves.

It will output a higher DC voltage, meaning you'll have to run at a lower duty cycle for the same brightness, effectively reducing dynamic range.

Finally, the DC voltage HAS to stay above 9VDC for the controller to run properly. There is a tradeoff between LED current, the amount of capacitance, the voltage ripple, etc. It's a lot to think about.

A pony?

I'll take video when I can.

My board has a diode bridge rectifier on it to convert the AC supply to DC. All of the current for all of the GI has to go across two diode drops. It adds up to about 1.4V drop at around 5A when using typical LEDs.

In the original design, they use TRIACs to turn the AC on/off directly, and they have separate heatsinks on each string. In WPC95 games, they decided to make two strings always on, and early games, they included diodes to account for the same voltage drop (so that those strings wouldn't be brighter than the others). Those diodes cook the boards, so you'll see a black crispy area under them.

The short answer is that the heat has always been there, and I'm just concentrating it all in one spot.

Once I have DC to work with, the PWM'd MOSFETs run nice and cool.

That would work, but it would be more expensive.

It's worth thinking about. If you include the smoothing caps, the parts on my current board add up to about $10 - $12. Do you have a $10 supply you could recommend?

9V is OK, but 7.5V would be better.
Capable of 6A at an absolute minimum, 10A would be better.

I'm really not thinking that far ahead just yet.

Exactly. It's extra work for me now, but it pays off in the end. The less expensive I can make it, the lower I can set the price if/when I decide they're feasible.

LOL! There are a lot of possibilities for cooling. I will avoid fans at all cost. They're too unreliable.

Well, as long as we're designing by committee, here's what I'm testing with the new board design:
http://www.linear.com/product/LT4320

Watch this video:
http://www.linear.com/docs/43277

Now, you guys had better not steal my idea.