Introduction: Mad Dog Robot
After seeing IBM computer Watson beat two former champions in Jeopardy earlier this year, I wondered if a simple robot could compete with people in more physical challenges.
Here's a DIY robot designed to compete in "Mad Dog" challenge as seen on NBC game show "Minute to Win It." In "Mad Dog," two Tic-Tac boxes are mounted to each end of a 12 inch ruler; contestants pick up the ruler with their teeth and have to shake out all the Tic-Tacs within a minute.
Any universal IR remote control which can produce Sony TV IR signals can control the Mad Dog Robot - either with individual functions or macros running pre-programmed command sequences.
Mad Dog Robot functions:  mechanical jaw opens / closes, and tightly holds the ruler,  simulated neck rapidly tilts ruler clockwise / counterclockwise about 45 degrees from horizontal, and finally  a powered platform moves robot forward / backward to pickup and replace the ruler.
Main components: Harbor Freight cordless electric drill motors (2), automotive wiper motor, Picaxe 18 M2 microcontroller, wood and metal components made from stuff available at hardware or home improvement stores. Part cost is approximately $125. Labor cost only $2 assuming I pay myself 5 cents an hour. Construction requires basic circuit building and wood and metal-working know how – mostly drilling and sawing – no welding or machining required.
You’ll notice a few extra holes here and there - that reflects the trial and error development process.
Hopefully this serves as a “starting point” to perhaps motivate makers and inventors to create even better robots to compete in entertaining physical challenges such as those presented on “Minute to Win It” game show.
Safety First – the robot throws Tic-Tacs at high velocity, stay out of harms way by always standing either in front of or behind the robot - never at the side of the robot.
Step 1: Overview and Parts List
See system overview diagram & photos.
I tried to make the parts list as complete as possible, but likely missed a few components, sorry about that.
Electronic components were purchased over several weeks from multiple suppliers – but in hindsight you can probably get almost everything from a single supplier such as Digikey.
The exception is Picaxe parts - I recommend USA Picaxe distributor Peter Anderson who provides quick order processing and low-cost shipping.
“Monster Guts” is the most viable windshield wiper motor source. Cordless electric drills from Harbor Freight.
My local Tractor Supply Center store (TSC) sells most nuts and bolts at $1.99 per pound - much cheaper than most hardware stores.
The universal remote control listed is what I actually used, but you probably already own a suitable remote control.
Step 2: Configure Remote Control
Let’s start with an easy first step …
Configure the universal remote control so that it can control a Sony TV. See photo for “Mad Dog Robot IR Remote Control Command Keys”
Step 3: Fabricate Basic Wood and Aluminum Components
Sketches 1-4 describe the components made out of ½ plywood, 2 x 4 stud, ¾ “ by 1 ½ hardwood, and 1” by ¼ “ aluminum bar stock.
There are few other components to make later on, but these are a good start.
Step 4: Basic Structure
Refer to sketch #5.
Following drawer slide kit directions - attach the roller part to movable platform (part A), and other half to hardwood drawer slide mounts (part F). Test everything together and then use ¼ inch hex head bolts and T-nuts to attach drawer slide mounts to the base (part C). Once you're sure that everything slides smoothly, slide out the movable platform away from the base.
Finally, using wood glue, two # 8 wood screws 2 ½” long, ¼ inch carriage bolt nut and washer, attach 2 x 4 upright to moving platform. See photos.
Step 5: Hack Drill Motors
See how-to link below for removing motors from electric drills. For this application I used an O-ring, rather than set-screws, to lock up the gear box torque limiter because it was cheap and simple.
Two additional modifications are required to the front “double D” black plastic section of the drill. First using Dremel tool or file remove semicircular rib at the top of one of the “double D” the sections. Second using Dremel tool or round file, cut 2 semicircular grooves on either side of “double D” section to accommodate the mounting bolts, see photos.
For the jaw opening mechanism motor you’ll need to reattach the drill chuck.
For the neck motor reattach the black cover disk. Use two #4 washers to move the disk from the end of the motor a little bit, see photos. Thread a 3/8-24 hex nut onto the motor drive shaft followed by driving link [part J], and lastly use a small washer and reverse thread screw to complete the attachment of the driving link to the motor shaft.
Modify the drill motor battery pack. Separate battery pack halves and with a multi-meter find the battery connecting strap providing +12 VDC output. Solder a 6 inch wire to this strap and cut a slot in battery housing to route the wire out.
I used a motorcycle type bullet nose quick-connect at the end of the 6 inch wire, but a 3/16 spade quick-disconnects are more readily available. See photos.
Save the battery pack horseshoe shaped electrical connector.
Step 6: Neck Main Shaft
The neck is a 6 inch long ½-13 carriage bolt coupled to the plywood disk [part b] with nut and washer. Two flange type ball bearings support it within the 1 3/8 hole bored in the main upright. Two additional nuts allow preloading of the ball bearings.
Step 7: Neck Drive Mechanism
Connect the aluminum main link [part K] to the plywood disk (part B) using a 1 1/2 inch quarter inch carriage bolt, 3/8 OD steel spacer, 2 to 3 ¼ inch flat washers, 2 to 3 3/8 flat washers, and ¼ inch nylock hex nut. The ¼ flat washers go on either side of the spacer, while the 3/8 flat washers position the aluminum link within the spacer.
Attach other end of aluminum main link to the motor driving link [part J] using 1 1/2 inch quarter inch hex head bolt, 3/8 OD steel spacer, 2-3 ¼ inch flat washers and 2-3 3/8 flat washers, and ¼ inch nylock hex nut. Use grease to lube the two joints.
Using motor mounting bars [part L] determine ¼ diameter hole locations in the moving platform so that the main link is vertical.
Although I used t-nuts and four-inch long screws, I later found it simpler to use four-inch long carriage bolts, nuts and washers, to create studs coming out of the moving platform. See photos.
Using nuts and washers on either side of motor mounting bars [part L], clamp and position the neck motor so the main link is vertical and moves without binding. Vertically position the neck motor so its centerline is 245 mm below neck main shaft centerline.
Re-bend a 1 ½ pipe clamp to better fit around motor rear section, add rubber padding to clamp inside surface. Use 4 inch long ¼ carriage bolts, nuts and washers, to attach pipe clamp to moving platform so it supports the motor, see photos.
Step 8: Jaw Mechanism
With the linkage mechanism now attached to the neck, rotate the linkage to determine the maximum clockwise and counterclockwise positions - then determine the center position which lies between the two. You can move the mechanism by hand although there's some resistance due to the gear friction. Mark top of the carriage bolt with a magic marker to indicate the center position. Install a half-inch coupling nut to the shaft so one of the flats lines up with center position mark. Using a 3/16 diameter drill, drill 5/8 of an inch from the end of the carriage bolt, drill the hole through both the coupling nut and the carriage bolt. Also drill a 1/8 hole 2 inches from the end - this will be for the actuating cable.
Cut a 50 mm length from the 1/4 by 1 inch aluminum bar stock. Drill a 3/16 diameter hole in the center of that member.
Remove the rubber covers from the handles of 2 Home Depot mini clamps; enlarge the handle holes to 3/16 inch diameter. Position the clamps at either end of 50 mm aluminum cross-member, and drill two 3/16 holes to attach the clamps. See photos.
Fabricate from 1/16 thick steel (electrical junction box cover), a connecting plate for the two lower clamp legs, see photos.
Attach the clamps to the aluminum cross-member and connecting plate using ½ inch long 10-24 button head internal hex socket cap screws and nuts. Use 1 ½ inch long cap screw to attach cross-member to coupling nut and carriage bolt.
Test fit the mini clamp subassembly to the coupling nut, you'll notice a distinct upward tilt to the clamp jaws, to reduce this tilt, grind a bevel in the bottom side of the coupling not, see photos. Under the 1 ½ cap screw head use a ¼ inch OD spacer with a beveled end to provide an even clamping surface.
Step 9: Jaw Drive Mechanism
Cut the head off a 3 inch long quarter-inch bolt, and clamp it in the chuck of the jaw drive mechanism motor so about 2 1/4 inch sticks out beyond the end of the chuck.
Using drill motor mounting bars (part L), quarter-inch carriage bolts, nuts and washers, attach the motor to the lower right-hand side of the moving platform. You'll need to add a couple flat washers under the bottom mounting bar so that the chuck is elevated above the surface of the platform so it’s not dragging on the movable platform.
Attach a quarter inch turnbuckle to the threaded shaft, screwed it on so thread engagement is about a ¼ inch. Drill a hole in the moving platform in line with the center slot of the turnbuckle and about 1/2 inch ahead of the end of the threaded shaft.
Create a turnbuckle guide using carriage bolt, nuts, washers, and nylon quarter inch nuts and washers as shown in the photos.
Position the cable mount wood block (part G) sit it aligns with the opposite end of the turnbuckle. Create a stepped diameter hole to hold actuation cable in this mounting block. Attach the mounting block to the moving platform with T-nuts installed the platform and hex head cap screws, see photos.
On the right-hand side of the turnbuckle using 1 inch long # 6 sheet metal screws to attach the wooden microswitch mounts [part I]. Position them so the front and rear microswitches limit turnbuckle movement as it moves from jaw open to jaw closed positions. That is, the N.C. microswitches need to trip (open) before the turnbuckle bottoms out on anything solid. Number 4 sheet metal screws one half-inch long can be used to mount the microswitches.
Cut actuating cable outer casing 15 ½ inch long and inner cable 22 inches long. Thread the inner cable through the front turnbuckle hole and then thru the mounting block. Install the outer casing and then thread the inner cable through a 1/8 flanged nylon bushing in the mini clamp connecting plate and finally through the 1/8 hole in the ½ carriage bolt. Make a cable clamp by drilling a 3/32 hole in the center of a 10-24 coupling nut and then use a 10-24 screw to clamp the cable within the coupling, see photos.
Step 10: Moving Platform Mechanism
Using 1/8 thick, half-inch wide aluminum bar stock; fabricate the inverted U bracket as shown in the photo. With the inverted U bracket centered within the three-quarter inch wide slot of the moving platform (part A), position center of U bracket vertical slot 6 inches from the rear edge of the main base. Drill two 5/16 mounting holes in the base (part C) and install T-nuts in those holes, and then attach U bracket using ¾ long hex head cap screws.
Fabricate from 1/16 thick steel (electrical junction box cover), an L bracket to mount the wiper motor, see photos.
Using wood glue mount the wiper motor elevation platform [part D] the as shown in the photo. Install wiper motor to L bracket and position the ball ended arm at three o'clock - the full forward position. With the ball engaged within the inverted U bracket and the movable platform fully rearward, mark the location for the L bracket mounting holes. Using 1 1/2 inch long quarter-inch carriage bolts, nuts, and washers attach the L bracket to the movable platform, see photos.
Using sheet-metal, fabricate an L bracket which attaches to the rear of the base (part C) such that it catches a microswitch mounted at the rear of the movable platform, see photos. The microswitch should trip as it contacts the L bracket mounted to the base.
Step 11: Microcontroller PCB
Assemble the Kiwi Patch PCB kit per the general instructions. See Picaxe 18M2 chip pinout diagrams in Picaxe Manual 1 for chip specific power, ground, and serial in/out pin connections. See links below.
Added to Kiwi board are 3 signal wires to MOSFET Board, interface circuits and connectors for: front and rear movable platform microswitches, IR sensor, Opto sensor, DPDT relay coil power, “time-out error” red LED, and green “power on” LED, see diagrams and photos for details.
Step 12: MOSFET PCB
I used a 2” by 2” piece of stripboard for the MOSFET board; link below is a good how-to for stripboard circuit construction.
You could also use perfboard and point to point wiring. See diagrams and photos for details.
Step 13: IR Receiver and Opto Sensor PCBs
IR Receiver PCB:
The IR Receiver PCB board is constructed on stripboard 3/4 inch wide and 1 1/2 inches long. See the circuit diagram and photographs.
Velcro mounts the PCB board to the top of the 2 x 4 upright. Using three wires of a four wire telephone cable make a connection cable to 18M2 PCB board.
Opto Sensor PCB:
The Opto Sensor PCB board is construction on a piece of stripboard 5/8 inches wide and 3 inches long. See the circuit diagram and photographs. Below is a link to the datasheet for the Opto sensor.
The Opto Sensor PCB board is attached to the main upright with Opto Sensor Mount (part H). Two #6 sheet-metal screws 1 ½” long will attach the mounting block to the upright and two #4 sheet metal screws half-inch long will attach the PCB board to the mounting block
A “sensing hole” is required in the plywood disk for the Opto sensor to detect the neck center position. Place a ruler in the mechanical jaw and rotate the neck so the ruler is horizontal, drill a 3/16” diameter a hole at the three o'clock position, see photos. Using three wires of a four wire telephone cable make a connection cable to 18M2 PCB board.
Step 14: Jaw Mechanism Wiring Harness
The jaw mechanism wiring harness includes a DPDT relay to allow reversing MOSFET PCB current polarity so jaw motor can run clockwise or counterclockwise. Two normally closed microswitches cut off the current to the motor when the turnbuckle reaches either forward or rearward travel limit. See circuit diagram.
For quick disconnects I used motorcycle style bullet nose connectors, but 3/16 spade quick-disconnects are more readily available at most hardware stores.
Polarity of jaw motor connections should be such that with the coil of the DPDT relay not energized the motor turns in the direction that moves the turnbuckle moves away for the chuck. An easy way to determine correct connection is by using jumper wires to test the connection between the motor and drill battery.
Step 15: Main Wiring Harness On/Off Switch and Battery Mounting
Using a short section of 1 by 1 by 1/16 thick aluminum angle stock mount the on/off switch to the left hand side of the rear movable platform using ½” long #4 sheet metal screws. See photo.
Using two strips of adhesive backed Velcro mount the battery to the left hand front corner of the movable platform see photo.
See Circuit diagram for wiring details. Use 18 gauge stranded wire for power lines and 26-24 gauge solid core for most digital lines.
Telephone cable was used for IR Receiver and Opto sensor lines. These lines were secured using zip-ties stapled to moveable platform and main upright.
For quick disconnects, I used motorcycle style bullet nose connectors, but 3/16 spade quick-disconnects are more readily available at most hardware stores. Female 3/16 spade connectors work for making connections to the wiper motor. See photo for wiper motor pinouts.
Step 16: Programming Microcontroller
Download the PICAXE Programming Editor from the link below.
Download file “Mad Dog Robot.bas” to your computer.
Buy either a Picaxe USB or Serial (RS-232) download cable. Recommended USA source…
Connect the download cable to the Kiwi board and your computer. Assure the Kiwi power is powered up.
Open the PICAXE Programming Editor.
Click View Menu and selection Options.
Under Options tab Modes, select "Picaxe-18M2".
Under Options tab Serial Port, select the com port you connected the download cable to.
From Open menu select the file Mad Dog Robot.bas.
Click the Program button to download code to Picaxe chip.
Step 17: Prepare Tic-Tac Ruler
Buy a good quality 12 inch wooden ruler, look for a ruler with nearly rectangular cross-section; beveled edges compromise the clamps ability to firmly hold the ruler.
Attach two boxes of Tic-Tacs to either end of the ruler using 4-40 machine screws half-inch long along with nuts, flat washers, and lock washers, see photos. Cutting down the Tic-Tac tops as shown with reduce likelihood of Tic-Tacs jamming together as the robot tilts the ruler rapidly back and forth.
Step 18: Initial Operation and Testing
The basic idea is to build the support stands under the Tic-Tac ruler as it is clamped in the mechanical jaw with the movable platform fully forward and the neck centered.
Mad Dog Robot commands are: press volume up key to move the platform forward, press mute button to center the neck, press channel up key to open the jaw, manually insert the ruler in the jaw, and finally press channel down key to close the jaw. The ruler should now be in the proper position to allow us to locate the support stands.
Using two 3” long sections of 1 by 1 by 1/16 thick aluminum angle stock, attach 11 ¾ long Home Depot large wooden paint stirring sticks to the robot plywood base. The support stands go under the ruler and about 2 inches to either side of the neck main shaft centerline (4 inch span between supports). Mounting hardware: ¼ nuts, washers and 1” long hex head bolts (paint sticks to aluminum angles), 1/4 carriage bolts (angle sections to plywood base).
Clamp the two sheet metal support plates (see Sketch #6) to the paint stirring sticks with small clamps – office binder clips work well. The sheet metal support plates should be 2-3 mm below the bottom of the ruler, so the rule drops down when the jaw is opened. Test the positioning by pressing the channel down key to open the jaw and then volume down to move platform backward. The ruler should stay on the stand – if not adjust bracket positioning as needed.
Run several trials picking up and dropping off the ruler. After you’re satisfied the positioning is correct, unbolt the paint sticks from the aluminum angles while leaving the support plates still clamped to the paint sticks. Drill two 1/8” holes thru both bracket and paint stick and attached one to the other with 4-40 ½” long machine screws, nuts, flat and lock washers. The paint stick & bracket sub-assemblies can now be reattached to the aluminum angles. Run a few more pickup and drop off trials to verify position is correct.
Step 19: Final Test
Press remote 3 key to move robot into the “ready mode” position. Place the ruler with Tic-Tacs on the support stands.
Press remote key 4. The Mad Dog Robot should move forward, close the jaw around the ruler, move backward and begin rapidly tilting the ruler side to side to shake out all the Tic-Tacs.
After about 20 seconds of shaking, with all the Tic-Tacs now hopefully shaken out, the robot with re-center the neck, move forward and return the ruler to the support stands. Job well done!!!
Step 20: Final Thoughts
While the Mad Dog Robot is an adequate proof of concept prototype there are still a few areas for improvement.
The neck tilting mechanism can tilt the ruler back and forth very rapidly – but, when Tic-Tac boxes are nearly full, this very rapid movement generates high enough inertia forces such that Tic-Tacs can become jammed. To address this problem, the program initially runs the neck mechanism at rather slow speed when Tic-Tac boxes are full. A second compensating measure is cutting down Tic-Tac box tops which also reduces jamming.
Secondly, the next centering mechanism is not precise. Due to coasting, the neck does not always stop where it should. For this reason, the centering hole is larger than would seem necessary so “leading edge” light shuts the motor off early so the neck hopefully coasts to the proper position. It is desirable to move the neck at the slowest possible speed, but this can cause stalling when the battery charge state is on the low side. So, the program initially begins with a high pulse width modulation duty cycle and then every time it misses or overshoots, the next attempt is at a lower duty cycle thus going slower and decreasing overshoot likelihood.
On the things that work well list: the wiper motor and drawer slides provide quite and smooth movement of the platform, the mechanical jaw holds the ruler very firmly, and the mechanical jaw mechanism pulls the actuation cable with plenty of force and sufficient length of travel.
We have a be nice policy.
Please be positive and constructive.