I made a spray painting gondola, see step 11 for information. This ends up being a nice upgrade since you can only write with a marker on certain walls, but you can spray paint on any wall (brick, cement, etc.) ;). I've also added a video below
When I thought about what making something on a computer real one of the first things that came to my mind was Facebook wall posts. Wouldn't it be cool if I could post them on a real wall. Well now I can!
This robot draws posts to your virtual wall in Facebook, onto a physical wall. To do this I looked at various drawbots that used two steppers and a pen to create large drawings. You could easily do this with an Arduino, but I wanted to see what I could do with the EiBotBoard that came with my Eggbot. I also harvested the motors off the Eggbot to make this happen. Since I don't have a 3d printer yet (hint hint . . .) I made this with parts that don't need to be printed, but it could be improved on with a few 3d printer parts.
You could draw directly on the wall. Since I'm married I'm not allowed to do that though so I have mine draw on a white board mounted to the wall ;). The frame is portable so you can easily move it somewhere else, plug it in and go. It supports multiple fonts (stolen from the Eggbot Hershey Text plugin for Inkscape)
Since this drawbot basically just draws text, it doesn't have to be from Facebook, any text you want it to render would work as well.
Step 1: Drawbot Basics
The length of the string is "c". "a" is the distance from the motor down vertically to where you want to be (the Y coordinate). "b" is the distance from the motor to where you want to be (the X coordinate). Doing this calculation for both of the motors gets you the distance you want each of the two string to be to land on a certain point. You want your frame to be much bigger than the area you're drawing on, because certain places are difficult to reach if it's not. In the picture attached to this step you'll notice there are two triangles, one with A1, B1, C1 and the second with A2, B2, C2. So:
A1² + B1² = C1²
A2² + B2² = C2²
And solving for C (the length of the string) we do:
C = square root of (A² + B²)
A decent write up on this can be found here http://www.marginallyclever.com/2012/02/drawbot-overvie/
Step 2: Parts
- I used 1/2 inch PVC, but almost any size should work. I wanted mine to be adjustable, so I used two foot sections of PVC then used couplers to attach them (I didn't use glue so I could pull them apart to change the size if I wanted to ). For the frame in the picture I used about 28 feet of PVC.
- 2 PVC Elbows, one for each corner
- Several Couplers (depending on the size of the frame and the length of your sections of pipe).
- Rubber feet, I couldn't find any that fit on a 1/2 pipe, but they had some 1 inch feet at Home Depot that fit over the coupler to join two 1/2 pieces of PVC.
- I used the clear piece of plastic that comes when you buy a stack of CDs. Anything about that size and flat should work. Clear is nice because you can see what it's drawing, but it's not required.
- Office supply clips. I used two of these, a small one to hold the pen to the gondola and to tie the strings on from the motors. I used a second one the the pen to weight it properly, so the gondola was flat against the wall.
- Shaplock for some customization. I needed something for the clip to clip onto, so I made it out of Shapelock, which is basically a bag of little plastic beads that melt in hot water so you can form then into whatever, then they harden when they cool.
- I found string at the hardware store. I wanted spools that were deep and I couldn't find anything so I made my own. I used some tubing the fit over the stepper shaft tightly, then I glued a couple of pieces of cardboard to it for the sides.
- I use some electrical box blank covers. The hole in the middle of them fits the stepper motor perfectly (after you pop out the piece of metal).
- This is how I connected the motors to the EiBotBoard. Using Ethernet connectors and cables I could use longer cables for bigger frames.
- Almost anything will work, these don't have to be particularly strong. I used the ones that came with my Eggbot
- This is used to lift the pen or marker off the board, almost any servo should work.
- EiBotBoard - This is a cool board, it's able to control two steppers and several servos at the same time. Again, you could easily replace this with an Arduino (and I'll probably make an Arduino version as soon as I can find my Motor Shield).
Step 3: Building the Frame and Mounting the Motors
Step 4: Stepper Motor Mount
Step 5: Spools and String
Step 6: The Gondola
Step 7: Connecting the Motor Controller
To connect the server I used really light weight wire I found at Fry's. That way the movement of the gondola isn't hampered by wire that's resisting the movement. The is important since this is heavily reliant of gravity an the length of the two strings to get it to work accurately, other forces shouldn't be involved.
Step 8: Communicating with the EiBotBoard
"EM,1,1\r" - enables the motors
"SC,4,[some number]\r" - sets the minimum value on the server (for pen down)
"SC,5,[some number]\r" - sets the maximum value on the server (for pen up)
"SP,1,100\r" - lifts the pen
"SP,0,100\r" - lowers the pen
"SM,[time to move],[motor 1 steps],[motor 2 steps]\r"
Step 9: Getting Your Facebook Wall Posts
Step 10: Drawing the Text
Step 11: Spray Painting!
I took an empty large can of olives and cut the bottom off and cut arches on opposite ends with tin snips (watch out, the metal is sharp after you cut it). Then I drilled a hole near the top to put a bolt through to hook the arm on to push the sprayer down on the spray paint can valve. i used Shape Lock to form the plastic holder that the bottom of the paint can clicks into. I tried this first with full sized paint cans, but it was too heavy for my steppers.
The curved arm that pushes down the spray paint valve is also made out of Shape Lock. There are several other ways to make the arm including using a hanger, like this silly string shooting Instructable. There are also plans for 3D printed versions of this, but alas, I have no 3D printer to print them on (wink wink).
As you can see I had to make the frame wider, I just added 6 feet of pipe. I also made the letters bigger, since small letter in spray paint just look like a blob of nothing readable.
The rest is the same as before, the steppers move the spray painting gondola around and the servo with the arm turn spray paint where it's needed..