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Rotating monitor construction *Project finished*
DaOld Man:
Thanks Bfauska.
I have been thinking about this tonight. I thought maybe a transistor, capacitor and resistor set up as an "on delay timer" (On delay timer would pass current to the interface after a time delay, say 30 seconds after power on, hence on delay).
But for this application, since all outputs are turning on at once during boot up, I thought the simplest approach would be one transistor and one resistor.
Look at the attached print.
I added a PNP transistor right below the printer plug.
I tied the base of this transistor through a 470 ohm resistor to pin 6, which is the fifth output. Since we wont be using the fifth output in our project, I thought this would work. I added it to my test breadboard circuit and it does work.
Here's how:
On computer bootup, all output pins go high.
A PNP transistor passes current from its Collector (C) to its Emitter (E), only when current flows from its Base (B) to its Emitter. (In other words, the base has to be negative or ground).
So when all outputs are on, pin 6 is high, or positive. No current flows from base to emitter, so no current flows from collector to emitter, so, the LEDs do not light.
But when pin 6 is turned off (Low or negative), current flow from base to emitter, so current flows from collector to emitter, powering the LEDs.
In short, if pin 6 is turned on, the leds are turned off.
This works on my test bread board, so I am going to implement it into my interface circuit.
Now, this method will not work on applications that require pin 6 to be turned on when pins 2 or 3 are on. But we dont need pin 6 in our project, so we should be good to go.
I used the 470 ohm resistor to limit current flow through the transistor. transistors have a maximum current flow before they self destruct. I first tried a 4900 ohm resistor, but the leds seemed pretty dim, so I tried the 470 ohm, and they look good.
Please note that I adhere to the principal that current flows from negative to positive, some folks will highly disagree. If you buy into the positive to negative theory, just reverse the current flow in your mind, and it should be A-Ok..
theCoder:
Man, this is good stuff. I love the way you got past the boot issue with just 2 components. I would have been tempted to do something with a 555 or PIC. Those opto's are great to work with. Simple & safe.
Make sure to post a short video when you have it all integrated and working.
DaOld Man:
Thanks theCoder!
I will try a video, I havent done that before, so it might be even crappier than my paint pictures, but we shall see..
I had to make a change on the circuit.
I double checked Koz319s website, and I see he is using pin 6 for the degauss circuit, so Im moving my pnp transistor from pin 6 to pin 4.
Hopefully I wont need the degauss circuit, Im hoping the monitor will degauss when it turns on (man, I need to test that!). I intend to turn the monitor off while rotating.
But I need to leave that output alone, just in case someone else wants to use it for degauss.
The next drawing of the interface I post will have the change on it.
koz319:
In regards to the parallel port pins going high on startup, I did not implement any type of bypass on my cab, it's just the h-bridge straight to the parallel port.
For my particular set-up, the only negative has been the degauss circuit being repeatedly activated at boot. The degauss coil in the monitor has thermal protection built in, so it can only be activated every so often (say 30 seconds or so). If it is triggered at boot (which happens on occasion), and then I go straight into a game which requires the monitor to rotate, the thermal protection on the degauss coil keeps it from degaussing completely when rotation is finished, and the colors are off a little. I't falls into the occasional annoyance category.
I actually want to do pretty much the same thing as DaOld Man drew up and just haven't gotten to it. (probably because it will take me about 40 minutes to clear out a space and move the cab out from the wall so I can open it up to implement a 2 minute fix :) )
I would definitely recommend implementing this from the get go.
Gotta go, looks like theres a woot-off going on!
Koz
bfauska:
Turning off the monitor would certainly be a clean solution, but if you want to draw focus to the cool rotating monitor in your setup, could you have the front end play an animation while the monitor rotates before a game starts? Like a spinning spiral, or a bunch of gears that look like they are doing the work. The sign at the Wynn in Las Vegas has a part that moves over a huge monitor and when the movement is happening they have all kinds of animations that play with the movement to interact, it looks really cool.
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