August 20, 2008

Homebrew Cintiq

I've heard before that "necessity is the mother of invention", I knew what it meant, but man...never has it processed as it has now.

I present the homemade cintiq:


At the top is the usb powered ir-pen. I'll post links to schematics, materials, etc. at the end. At the bottom is my battery powered pen, not as powerful as the top one (I think output voltage may be 1.4 or has degraded over time), but...it kinda gets the job done.

This digital picture exposes the ir frequency of the led otherwise invisible to the naked human eye. Wanna see it yourself? grab your tv remote, push the on button and look at the tip of your remote through your digi-cam, you should be able to see the little led light up every time you press the button on your tv remote.

The wiimote points at the computer screen relaying information of the placement of the ir pen via bluetooth to the computer. With Johnny Chung Lee's program, the computer can register this signal as a HID device and allow for mouse-like functions, thus a cheap whiteboard, or...cintiq device. Not as great as real cintiq, but...for the price, this ain't bad at all.

Only critiques on this would be that if there was a way to be able to relay the position of the ir in space with two wiimotes coming together, that would make this system very efficient and accurate.

Materials:

USB Bluetooth Adapter
Momentary Switch
Bic Pen - love it because the led sits perfectly on top
USB cable from an old usb mouse -you can use any usb 2.0 cable (most are 2.0), I just ripped it from my old mouse because it stopped working...like most gigaware products I've bought in the past...
wiimote
tripod - anything works really, as long as you can mount your wii and adjust the angle of elavation. I taped together three acrylic paint tubes, and taped on one of those adjusting combs to lay the wiimote on.
solder - great gauge
wire - great gauge
iron - 15 watts is more than enough
electrical tape - insulate to prevent short circuits (most useful on the led legs)
rotary tool - dremel works too, I have the one in the link. Get one with variable speed, and a bit that can soften up the top of the pen. Then go in with your drill bit. This is to fit the momentary switch into the pen of course. Also to make a small hole at the bottom of the pen so that it leads out to power source.
ir led - make sure it's infrared frequency and not visible, I got mine from an old tv controller no on used anymore. The brighter, the better - remeber, the wiimote has a small webcam in it that needs to be able to pick up this light, if it can't, nothing registers on the pc.
Battery - if you're going to make a portable version, just attach the two wires from the led to the positive and negative poles of the batter. This can be done several ways, the most convenient I would say is to get a battery holder. Getting a single 1.5v battery holder is easier since it won't require any resistors and it's easier to replace once it runs out of power.

You can also just spiral the ends of the stripped wires and attach them to either end of each battery using electrical tape, just make sure the contacts are clean, and there's plenty of exposed wire making contact with the tips of the battery, or you'll get a weak and unsteady connection.

That's about all that's needed. Important links here:

Johnny Lee
USB schematics


Just in case:

R=(Vs-Vl)/I

where R= resistance, Vs= Voltage Supply, Vl- Voltage LED, and I is current (generally 20mA). Make sure you get a resistor in your circuit or else your LED won't last very much. To calculate how much you need, example for USB is given as:

R= (5v-1.5v)/.02

Resistor in series of the system should be: >=175ohms. This of course will give a bit less than it's max luminosity. So...I woul make the resistance a bit less, in my case I made mine way less with a 47ohm resistor, but...it works and LEDs last a long time anyway

Here's a video of it in action:

video

Overall impressions:

My main purpose was to use this as some sort of cintiq substitute or wacom (since I have neither the former nor the latter), but...it's just too inconvenient.

The wiimote needs to be able to see the ir frequency emitting from the led. If it can't, it's a no go. so...you can't block the wiimote's view at anypoint. Meaning...you need to place the wiimote in a very strategic location, or it's going to be uncomfortable. Also...the wiimote and white board cannot be moved AT ALL during use. If moved, you will need to recalibrate or it simply won't work well.

It's good for what it is, and if there was a way to some how mesh the singals coming from two wiimotes in regards to the ir's position in space, I am sure the accuracy would be perfect, and all issues would be resolved.

Maybe I just need a stronger ir led (I did get it from an old tv remote (early 90s). But ummm, yeah, I guess I'm going to have to get that wacom tablet, plus...this led substitution won't give you pen pressure or custom shortcuts =)