Random Thoughts arent they great ;)

Email i sent to don, just to give you some ideas of the things ive been thinking about lately

Hey Don,
This is chester, been a long time since we talked.
I am planning to make a digital clock that scanns back and forth, like the ones they have in some stores. I came up with an easy way to move the leds back and forth, very fast, the voice coil mechanism inside of a hard drive. I got one from a very old SCSI 1 gig hard drive from the 1980s it was from the universitys server and is huge, so is the voice coil mechanish that moved the 10 heads back and forth :)
It was meant to move very fast, and change directions rapidly, so i think this is just the right job for it.
I am taking a cpp course in high school right now, dont know much about assembly yet though.
I wanted to know if it would be easy to alter your code so that it scanned the time on the foreward and backward cycles ? I dont know what is involved in doing that, just seeing if it would be worth it or if just having it scann on the foreward cycle would be more practical ?
It might also be a little hard to get the timings right because the drive coil would be moving faster near the end of its swing, although if you put the leds on a long arm and just used the middle of its swing the speed would probably be farily uniform.
The drive coild doesnt move much, so either way its going to need to be on a long pole. This may be a good thing though, as long as it has enough torque to move it fast engouh, because the digits will be fairly horizontal and not curved.
Getting the timing pulse would be fairly simple, i plan on using some type of photo interrupt to sense when it gets to one side, and then reverse the direction the leds move, and start the leds scanning the time. Thats very simple to do because the coil has a center tap with the other sides wound in differnt directions, so it only takes two drive mosfets to get both directions.
I also hope to do more than just a clock with this display, like make some simple video game with it, maby even get 3 rows of leds and get a full color display with PWM brightness controll :):) hehe, i can dream.

Chester Lowrey

Chester's Electronics Lab

Email i (tried) to send to a programming mailing list, if you can help me with this problem please let me know

Hello everyone,

I have a quesion about interfacing my custom built light gun into programs i would like to make. I built the gun from scratch and it detects the light coming from the monitor, if light is sensed a pin on the parallel port goes high, another pin is used for the trigger on the gun.

I have already made a simple target shooting game in cpp that just cheakes to see if light is sensed, and as there is only one source of light on the screen this means that the target was shot, it also counts down the ammo and stuff like that.

What i would really like to do is be able to know where on the screen the gun was aimed, not just light/no light :)

The way the arcade games do this is by flashing the screen white when the trigger is pulled (or mabe the screen is bright enough so they dont have to do this, i think there is more than one way) and then when the gun senses light the software cheaks where the video card was scanning the electron beam across the screen, so it knows at exactly what part of the screen you shot. As you can see the timeing has to be fairly fast, my gun is fast enough, what i dont know how to do is get any information from the video card as to where it was scanning when light was sensed ?

I thought i could make some kind of timer start running when the screen was flashed, and then count the time it took to sense light, that would be a really crude way of telling where it was scanning, and probably not accurate enough to do anything with. But if the graphics card method is hopeless i may not have another choice.

If you can help me at all i would greatly appreciate it.

Chester Lowrey

Chester's Electronics Lab