Dial and Draw

Dial & Draw is my super sized version of the classic knob based kids toy we all knew and loved. In this Instructable we are going to create a robot capable of drawing wall sized murals with the just the twist of a dial. Were going to borrow some of the physics from classic polar or string plotters, but ours will be controlled with two dials that will rotate two stepper motors on either side of the drawing area. To make all of this work we will be utilizing the Intel Edison to process positional data from the two potentiometers and then turn that positional data into rotational motion which gets fed to the stepper motors.

This is a harder than average build that involves a lot of different skills, so take your time enjoy the process, and lets make an awesome super sized Dial & Draw robot!!!

All of the files needed to laser cut this project are attached to this step. I used an Epilog laser to cut out my 1/8" Acrylic. Before you begin assembly peal off all protective plastic on the acrylic. Then thread the button head screws through the bottom side of the main gantry plate and secure each screw with a nut. Then thread another nut onto each bolt until the nut is 0.50" away from the main gantry plate. Once you do this for all 4 screws, add the second gantry plate on top of the nuts and add another 4 nuts to retain the second plate.

Now add the two trapezoidal pieces and pen carriage plate to the main gantry plate. These pieces will all interlock nicely to each other and the main gantry plate and should be secured with some acrylic cement.

This tiny acrylic box fits on to the end of the relay to engage and retract the drawing utensil for the Dial & Draw. To assemble carefully inject some acrylic cement into the seams between the pieces of the box and wait for it to dry (30 seconds) before going on to the next piece.

Take the last piece of the pen carriage and thread the M2.5 screw through the hole and onto the solenoid. Use your syringe and acrylic cement to glue the other there sides of the pen carriage to the solenoid assembly and hold for 30 second to a minute while the glue dries. Finally secure the solenoid assembly to the main gantry with two M2.5 screws.

Add a gear to your stepper motor shaft and tighten down the set screw with a hex key. Then put washers to each screw and secure the stepper motor onto the face plate. After you can assemble the three retaining plates for the motor, they're the ones with the holes. Add the stepper motor which is now attached to the face plate and use your acrylic cement to keep everything in place.

To give our robot the ability to do motion in both the X & Y plane (to give it motion up, down, left and right) we're going to need two motors! Repeat the last step and you should have two enclosed motors when you're done :)

Lets make sure we are keeping everything nice and neat by braiding out stepper wire cables. To do this simply put the four wire ends inside the drill as though it was a drill bit, and then tighten the drill jaws around the wires until its tight. Hold the end of the wires and let the drill braid them all together into a neat twist. Be careful not to over twist the wires as they will break, and thats never fun.

After laser cutting the case, put the two front pieces on top of each other and thread the potentiometer through. The potentiometers come with a washer and nut that will go on the front side and keep everything in place. I didn't do it on my model but I recommend gluing the two front controller pieces together to make later assembly steps easier.

Using the laser cut living hinge, begin to wrap around it around the top and bottom controller face plates. This will take a little bit of cajoling here and there but eventually the living hinge wrap should fit into all of the slots on the controller plates.

Using the laser cutter I cut out two 50 tooth gears and smaller 10 toothed gears to make our knob to potentiometer gear ratio 5:1. This means that it'll take 5 full revolutions of the knob to drive the potentiometer one full revolution. This allows us to have much finer control over the position of the Dial & Draw.

Insert a washer into the potentiometer and large gear slot. Warm up your hot glue gun and squeeze out just enough to keep everything in place. If you have a creative way to cover up the glued washer you can do that here in this step.

Thread through the M4 screw from the back of the controller faceplate and tighten down a nylon locking nut. You don't want to tighten the nylon nut all the way because then the knob wont turn, just tighten it one turn before snug. Then place the small gear on top of the locking nut and tighten down another nut until the gear spins when you turn the screw. Grab your knob and loosen the set screw enough to be able to fit the remaining exposed part of the screw inside and tighten that down as well. You should now be turning the small gear when you rotate the knob.

Thread your belt though the top weight plate (the one with two rectangles) and secure it with a zip tie. Then simply stack all the weight plates to there slots are aligned and snap in retaining bracket.

Following the contours of the controller I drew a sharpie line of where I wanted to but the bread board to make sure that it fits when the living hinge is wrapped around. Using a dremel with the cutting wheel attachment on the highest speed, cut through your line on the breadboard, make sure to file away any sharp corners.

Grab one of your Big Easy Drivers and a pair of snips. Cut four 2 pin headers and one 3 pin headers and arrange them in the desired position in a breadboard. The breadboard will hold the pins in place while we solder on the headers. Next, grab your soldering iron and solder all pin headers into place.

Insert the Big Easy stepper motor driver into the breadboard and connect two wires to the ground Dir and Step pins on the board. Then connect the opposite end of those wires to pins 8 and 9 or your Edison Arduino breakout board. Next you want to connect the 4 wires coming out of the stepper motor to the 4 pins in the Big Easy board.

There is one slight catch here, you have to hook up the right pairs or wires to the board. To check which pairs go together you should grab a multimeter and set it to resistance mode. The two wires with the least resistance are a pair.

Finally, make sure your ground are connected and duplicate your wiring for the other board, so you have two stepper motor drivers. I used 4 and 5 for the other Dir and Step outputs.

To keep everything clean and to also avoid yanking out the cables from your bread board I used zip ties to do some cable management. Looping the cables around and then through the zip tie anchor ensures that a tug on the cables will be absorbed by the breadboard rather than the pins. I used a little hot glue as well to really hold everything down.

Solder on the power (red), signal (white) and ground (black) wires to the potentiometer. The signal wire will go to the A0 analog input pin on the Edison shield. Next, strip the power cables coming from the 12V wall wart and plug them into the power and ground pins of the stepper motor board. Finally, tie everything off with zip ties to keep it from getting yanked out.

After the design was finished I realized that it would be easier to not have to remove the Edison from the case every time I wanted to put new code on it. So I drilled a small hole, which I then turned into a connector sized USB cable rectangle.

Yay! You did it. Now go let your imagination run wild. I used a dry erase pen but this robot could paint with brushes, or spray paint!