Robot tips, hints and suggestions

A collection of hints and tips provided by robot project alums in their "robot project reflection" assignment due after the show. Who knows, you may find a gem located here.


One handy construction tip that I learned was a quick and dirty, yet efficient way to mount a wheel on a motor shaft. The way that I found to be most effective for my robot was to use tubing that is used for RC car fuel lines and model airplane wheels. The diameter of the tubing was smaller than that of the shaft, but the tubing can expand, allowing it to fit snuggly onto the motor shaft. The tubing also expanded enough that it would fit snuggly inside of the hole for the airplane model wheels. The most useful parts for my robot were the chopsticks that I attached to the switches on the front and back of the robot. The chopsticks allowed the robot to run into an obstacle at a place different than the switch and still reverse directions. I got the chopsticks at Leann Chin and they were free.

Use a cam to smoothly depress and release a button with one revolution of a motor.

I found two cordless screwdrivers at Sears for $6.49 each. They are really easy to take apart, have pretty good motors and gearboxes, and the hex fitting on the gearbox output shaft for easy coupling to almost anything. No-load rpm is about 60.

For a set of wheels, tilt two gearmotors down towards the ground and run right on the shafts.

Hub Hobby has a large selection of motors with gear transmissions all-in-one. They are only $5-10. I also took apart a few R/C cars and they are only a few dollars at thrift stores.

Many people are tossing out their VCR's as DVD players take over. VCR's are full of gears, motors and levers.

Floppy disk drives have a nice stepper motor that can be extracted.

Hot glue is strong, flexible, easy to use, and cheap.

Have your electronics and mechanisms be accessible to make it easy to change and repair your robot.

Use the pulsing method to slow your motor (see the motor control document), but watch out for voltage spikes.

If you need a powerful spring with a trigger mechanism, use a mouse trap. Bend up the trigger to make it less of a hair trigger.

Use cardboard, plastic tubs and lids, nails, pens, pencils, and whatever else that is cheap.

Ax-Man is a great place to find stuff.

Secure your electronics. Fasten all the components down to a board, then connect with wires. You can even glue down your components with legs pointing up.

I used some Tupperware from Target and a hinge from the hardware store.

I used screw-in eyelets and string to run power around my robot. Easy and works great. Bought both from Kmart for about $1.00.

To cut plexiglas, score with a utility knife then break over the edge of a 2x4 or other strong straight edge.

J-B Weld is a great expoxy. Very strong.

For my spring-loaded catapult I used a door hinge, a spoon and a spring. I duct-taped the spoon to the hinge. I attached one end of the spring to the spoon and the other to a screw on the board. By turning the screw, I was able to adjust the strength of my catapult with great precision.

I used two of my stamp pins as both inputs and outputs by redefining them as INPUT, then later as OUTPUT in the program.

I am familiar with sewing supplies so elastic and thread were critical to my robot.

A paint roller makes a nice spool for a web.

Lots of parts came from an old turntable that I took apart.

To make a turn table move slowly, rim drive it with the motor. Put something with high friction on the motor shaft then just press it up against the rim of your turntable.

I suggest to anyone who will take this class to get an early start; no one should have to suffer like me.

Lubricate moving parts with soap, grease, petroleum jelly (vasolene). Vasolene makes a great lubricant. Just dab a little bit on your gear train or bearing and hear the noise go away.

I found a solenoid for $1 at Axman.

I used a carpenter's C-clamp as the main mechanism in my can crusher.

On paper, everything worked perfectly. In the shop it was a different matter.

Copper plumbing pipe and fittings are useful for robot construction.

Make your robot strong and sturdy. You don't want it falling apart during the show.

I completed my robot entirely on my own, and I built it in less than 24 hours after my initial robot broke down the evening before the Robot Show.

When using electrical tape to join a drive shaft to the motor, put down a layer of tape on each part first, then join together with tape.

I slowed down my motor using pulse width modulation. This was much easier than buying a resistor or building a transmission. Details for doing this were on the course web site.

For my ferris wheel, I used a small bike wheel. $1.95 at Axman.

For neat wiring, use the "dead bug" approach. Glue your components (transistors, resistors, integrated circuits) down on their backs to a backing board (cardboard, thin wood) with component legs sticking up (thus the term "dead bug"). Trim long legs then connect with wire.

I turned to my family and friends for ideas and for help. A great resource.

Double corrugated cardboard is much stronger than regular cardboard. Find someone who just moved their house and ask if they have any "dish barrel" boxes.

If you use carboard, fold into triangle column shapes to add structural rigidity.

Sketch all your ideas in your sketchbook.

Hang around Ax-Man and ideas will come to you. Bring a 9 V battery so you can try out motors on the spot.

Use www.howstuffworks.com to figure out how lots of robot components work (gears, motors, LED's,...).

Hot glue is the most versatile bonding method.

To fasten a shaft to a motor, use the tube from a Bic round Stic pen. It's just the right diameter to slip over the motor shaft. Hold everything in place with epoxy.

Use stuff from the videocassette you dissected. The spools make great robot parts and you can make a belt from the tape.

I used a hinge from Home Depot to make a joint. Nice and cheap.

Make sure you have a robot that works.

To attach string to a motor shaft for winching, wrap the string a few times around the shaft then secure with a layer or two of duct or electrical tape.

Have a mom or dad who is good with tools.

Lay out your circuit on a piece of cardboard. Use a pen to mark where the wires go.

Pay attention to the deadlines.

To index a rotating platform, make bumps or indentations around the edge of the platform that slide against a microswitch. Then program the stamp to see changes in the switch as it slides into the notches or over the bumps.

Use two pulleys connected by a rubber band to gear down your motor.

Here's how one student described where his idea came from: "Then my mom said something about a robot peeing, and a college guy can work with that."

If people smile when they see your robot, you are doing well.

Make sure your robot is durable so it can handle repeated abuse at the show. If you are the only one who can push the button without breaking the robot, perhaps a redesign is in order.

K.I.S.S (Keep it simple, stupid)

Windshield washer pump from U-Pull R-Parts auto junkyard in Roseville.

Clean your connections before you solder so that the solder flows and doesn't just ball up.

Use cotton rope for a belt. Have a method to adjust the tension as the belt stretches.

HobbyTown USA has a kit with two small motors and a gearbox. $11.50

Coat hangers are a good source of stiff wire.

A 3V motor (check Ax-Man) is great for small battery drain.

A paper towel roll with plywood rounds glued to either end makes a good roller.

Use plastic tie wraps (electrical section of any hardware store) are great for holding down motors or other components.

Cardboard is free, rigid, and easy to modify.

The hardest part was finishing my robot on time. I set a goal to finish my robot one week early. This was the best planning decision I have ever made because it gave me time to fix the tiny details.

Eye hooks work much better than pulleys for redirecting the path of string or fishing line. Cheaper too.

Buy a circuit board from Radio Shack (like the ones used in the EE lab) for mounting components. This makes life MUCH easier.

A gate latch (available at any hardware store) makes a great trigger mechanism.

If you have something sliding up and down on a pipe or rod, have the thing that slides be long to keep it from binding.

PVC pipe is great building material.

Make a shaft coupler from a short length of 3/8" dia. aluminum bar. Drill a hole in each end (use a lathe if you have access to one), then drill and tap holes in the side for set screws.

Threaded rods are good for making lead screws.

I learned from this project that I really could pull an all nighter.

I great spool for a belt drive or winch is to glue a spool of thread onto the motor shaft.

I was able to get a mannequin head from the Aveda Institute for no charge. I just asked nicely.

Use a drawer slide for linear horizontal or vertical motion. It is strong, friction-free, and won't bind.

Use a paint roller for a spool.

No matter how much you are encouraged not to procrastinate, you still do.

Magnets found in broken hard drives are really strong.

Using threaded rod and nuts allows for quick adjustments.

To attach the motor to a drive shaft, use a small wood dowel. Drill a hole in each end then hot glue the motor into one end and the drive shaft into the other. Drill the holes centered and straight. A lathe helps here.

"Measure twice, glue once."

Hub Hobby has sets of plastic gears that work great.

Try plywood. Strong and easy to cut. You might be able to get some scraps for free from a lumber yard or Home Depot.

Look for gears and other parts in old toy cars.

I found a great Frankenstein mask at Target.

Isolate the high current (motor) paths from the low current (Stamp signal) paths.

To mount the start switch, I drilled a hole in the center of a plastic 2-liter pop bottle cap. The switch mounted perfectly and was very sturdy.

I used PVC pipe from a hardware store as the tube for my marble to roll down.

Make a structure sturdy enough to hold the robot steady.

To connect the motor to a shaft, find a short piece of soft tubing and slide it over both shafts, then use hose clamps to secure.

Foam padding is great because it can be cut into all kinds of shapes.

I used a 3 foot long, 3/8 inch diameter threaded rod and cut it into the lengths I needed.

Sketch all your ideas and bring your notebook everywhere you go.

To detect when the ball dropped down, I had it fall on a microswitch.

At www.howstuffworks.com I learned about motors, gears, circuits, relays, LED's, transistors, and much more.

I screwed my Stamp board to a small piece of plywood (or you could attach it to cardboard), then used velcro to attach the plywood to my robot. This way, I could easily detach the board for reprogramming or repair.

The most useful construction tip I learned was to start early.

I used a breadboard (protoboard) for constructing the electronics. No soldering and easy to make changes.

I made my folding arms from the frame of an old umbrella.

I used a flower pot that I found by the side of the road.

Reinforce things more than you think is necessary.

For assembling my structure, I used angle irons from Home Depot, $4 for a bag of 5.

Repeat to the class the evils and pangs that come from procrastination.

Aluminum foil is a great decorating tool.

For a moving platform, I had two wheels in the back and a furniture glide in the front. No need for a caster.

I got some ideas by watching "Junkyard Wars" on TV.

A fluorescent light bulb cover makes a great clear tube.

My piston wasn't strong enough to crush a can, so I just crushed paper instead. It was still pretty cool.

To turn a motor on and have it go until a switch was hit, I used this code:

   high 3                            'motor on
   wait: if pin4 = 1 then wait       'wait for switch
   low 3                             'motor off

I made a pulley and secured it to the motor shaft with a setscrew.

Hot glue was great for attaching my robot parts to my cardboard base.

Start early, give the best you can, and you won't regret anything.

Use the multi-meter to debug electronics problems.

To brainstorm on robot ideas, I made two lists. The first had robots I thought would be very cool, but probably too hard to make. The second had robots I knew I could make. I tried to pick something that combined ideas from both lists.

Keep the electronics and wiring neat and clean. That was my biggest headache. I had wires all over and they were hard to follow.

When running a new electronics circuit for the first time, put you fingers on the transistors and Stamp. If they get too hot to touch, disconnect the battery right away.

I built an electromagnet from a straw, a nail and 30 gauge, lacquer coated magnet wire (Radio Shack). I got this idea from the Getting Started in Electronics book. Turn the magnet on and off with a TIP120, just like controlling a motor.

I used a belt from a vacuum cleaner to connect two pulleys.

I made a sliding bearing from a dowel, two electrical boxes and a lot of hot glue. It worked great.

I put lots of labels in my stamp code so that I could quickly identify various parts of the program.

I built a Row-bot....get it?

I thought I had 10 hours of work left but it turned out to be more like 20...

I found two great gear motors from a machine that was being thrown out where my friend works.

When attaching gears to the motor, use a set screw to keep the gear from slipping.

I used juice cans in my robot. Cost = $0.

Fishing line is stronger than string.

Dental floss makes a great winch line.

Upholstery thread is strong.

Don't be afraid to ask the professor and TA's for help.

I used a chopstick for a drive shaft, carefully taping it to the motor shaft.

When soldering to the transistor, solder at the end of its legs to prevent the transistor from frying.

Use a DPDT relay to get the motor to turn in two directions. See the How to Control a Motor notes on the web for how to do this.

Spread apart the legs of the TIP120 to make them easier to get to.

If the tab to your motor has broken off, solder a wire to what's left.

When attaching a shaft to your motor, make sure it is aligned.

At the Ax Man store, I found a gear complete with set screw that made it easy to attach to the motor.

Have your robot pause for 5 seconds after pushing the start button. This will make it more interesting.

My robot did everything in 20 seconds so I added a few pauses here and there which stretched out the time and made it more interesting.

A sink stopper makes a great plug. Pull it out with a motor and string to release water down a tube.

From Ax Man I found pulleys with teeth and a belt to match. Very useful.

Space out your electronic components enough so there is no danger of them touching each other and shorting out.

I started on my robot two weeks before the Robot Show. It was then that I found out that building a Robot was not as easy as it looked.

The gear motor has much more power than the small motor so use the gear motor if you have to move something heavy.

Build the frame of your robot with angle iron. It is very strong.

Looking at toys gave me lots of ideas for robots.

I found a perfect belt for my robot by taking apart an old printer.

I was surprised how useful it was to put everything in my sketchbook.

I used a high-wattage potentiometer that I found at Ax Man to control the speed of my motor.

Roller blade bearings are very high quality.

I made a spool out of wood and filed spiral grooves into it so that after a few revolutions, the string came off the end which is just what I needed for my robot.

I made bidirectional action by starting with string wound up on the motor shaft and attached to a spring-loaded slide. When the motor turned on, the string unwound and the slide moved away. Then the string wound up the other way and pulled the track back. The nice thing about this method is that the motor only has to turn in one direction.

Boot laces are flexible and strong.

Paper clips are beautiful construction material. Light, strong, easily shaped.

I made my robot so that it was easy to transport and I'm glad I did.

The pushbutton fits nicely into an 11 mm socket from a socket wrench set. Secure with a bit of hot glue and you are all set.

A small hamster ball housed all my electronics. $3.99 at Petco.

I used a cole-slaw tub to house my electronics. Cost = $0.

I carved a cam from wood.

I used a 0.1 uF capacitor that kept my robot from going off into la-la land from voltage spikes which it used to do about once every ten runs before I installed the capacitor.

Angle brackets and screws make a stronger robot than one held together with tape.

An embroidery hoop (about $0.69 at a crafts store) makes a great ring.

I bought a larger motor at Ax Man to make sure I had the right power and torque. However, the motor I bought drew far too much current and burnt out many electrical components. I finally was able to control it with a high current 12V relay, but the motor was still very hard on my battery.

I used a truck, six bearings and a wheel from my old skateboard.

Wood is a great construction material.

To make a drive belt, use some rubber tubing cut in half to make a giant rubber band. For a really long drive belt, cut up a bicycle inner tube.

The deadlines were a hinderance because they forced me to finish things more quickly than I would have liked.

Make a drive belt from cloth cut into strips about twice as long as you need. Cover each side with window caulk then wrap around a drum whose circumference is about right for the size belt you need. Squeeze with Saran wrap to remove any air bubbles, then let dry. Trim to correct width with scissors.

Make your wires a bit longer than necessary to allow for changes.

A 10 cent 0.1uF capacitor across my motor saved me from the voltage spikes that were causing my stamp board to go haywire when my relay changed motor directions.

A used a roller-arm micro switch from Radio Shack ($1.29). The roller could run up and down along my wall without catching on anything.

To attach two shafts, shove them into a piece of rubber hose. If the hose is a bit too big, glue the shafts in place or use a small hose clamp.

I bought an Eagle Claw bait casting reel at a garage sale for $2 and used the line guide mechanism to move my skier back and forth.

Use a squirt bottle to dispense water.

I looked at the mechanisms in a real dump truck to figure out how to design my robot.

Use cardboard and chopsticks to build your robot. You can make a nice, strong truss structure with chopsticks.

I added a switch in series with my motor battery so that I could kill the power quickly if something went wrong. I used a knife switch but any kind of switch would do.

I used my knowledge of physics to calculate the amount of force required to open a can of pop.

In the end I realized I could go complicated with the things a knew how to do, but should stay simple with the things that were new to me.

Wire several microswitches in parallel. If any one is pressed, the stamp pin will go low. This is how you can have lots of switch sensors while only using one stamp pin.

My robot had a modular design that made it easy to take apart and transport.

I used plexiglas from the scrap bin at Home Depot.

Hobby putty is great for temporary connections. I used to to attach my stamp board and battery to my robot.

Binder clips for holding stacks of paper make great robot parts. Cost = $0.

Axman surplus is the coolest store on the planet.

I used a solenoid to toss a coin. A spring-loaded mechanism triggered by a motor would also work.

I took apart a Big Mouth Billy Bass which has lots of neat robot parts inside.

I found a cheap, used tape player at Goodwill

Use hot glue to tack down electronic components and wires.

Use a 100 ohm power rheostat to slow down your motor. About $3 at Radio Shack.

I found a 12V, 4800 rpm motor from Axman that cost about $3.50.

The heart of my robot was a $1 spring that I found at Axman.

I know my robot would have worked if only I had a higher speed, higher torque motor.

Two-part expoxy will bond anything to anything.

I was most proud of my robot working perfectly at the Show. The day before it did not.

When you go to Axman to find a motor, bring your 9V battery and try them out on the spot.

I hot-glued a penny on the end of my motor shaft to keep the winch line from falling off the end of the shaft.

Use screws rather than nails.

Bend up used CD's with a heat gun then glue together with a hot glue gun to make a structure.

For a nice long slider, use a 1-1/2 inch pipe over a 3/4 inch pipe. Also works well for a hinge joint.

Use a door hinge for a rotary joint.

I used an old set of windshield wiper blades from my car.

To make a rotary bearing, align two washers and glue to the ends of a piece of wood. Run your shaft through the washers.

To attach something to the motor shaft, drill a larger hole than needed, then fill with hot glue. Drill a small hole in the hot glue than jam in the motor shaft.

An old battery powered screwdriver makes a great low-speed, high-torque motor.

Seemingly simple ideas can be surprising difficult to implement.

Dental floss is cheap and strong.

I used the motor eject mechanism on a dead CD-ROM drive.

Some pretty cool things can be built with junk if you just try.

For the longest time all my parts just at in my room looking at me, saying you have 4 weeks left, you have 3 weeks left, don't you think you should start on me?

Spray paint melts Styrofoam.

If your robot has to do the same thing many times, use a subroutine and the GOSUB statement.

I used caster wheels off the bottom of a chair.

To move water, I used a 12V windshield washer pump from an automobile. I bought it at a junkyard for $5. It worked great.

I found a push-action solenoid from an old door chime.

I found a gear at Axman that exactly fit the gear that was on my motor.

Twenty-five pound test fishing line can be used lots of places on your robot.

Use the loop on a binder clip to guide string being used on a winch. Position just before the motor shaft. Or, use a screw eyelet to do the same thing.

To couple a shaft to the motor, I drilled holes in each end of a round metal bar. Then I drilled and tapped holes perpendicular to these. The motor and shaft when into the end holes and were tightened down by a screw in the perpendicular holes.

Sewing machine bobbins work great as pulleys. Available at Target, Walmart, ...

I used old, slightly bent aluminum arrows for my elevator shafts.

I found a 14-pin adapter connector at Axman that fit right over my stamp pins which made if very easy to connect and disconnect the stamp board. An IDE cable from a disk drive can also be used.

To slow down the motor, put it in a loop with on and off times. The smaller the ratio of on to off times, the slower the motor will go.

I got a box of craft (Popsicle) sticks from Dick Blick Arts and Crafts. Cheap, strong and you get a ton of sticks in the box.

Use sensors rather than timing to control motors.

Fom-core board makes a great building material.

Because there is no ventilation in my rom, the fumes of the hot glue gun also contributed to my nice work pace ensuring completion. The more I hot glued, the more relaxed I became, which made working on my robot a joy.

I used an upside down pizza pan as a turntable. $1.99 at Wal Mart.

Solder all the wire connections. Electrical tape is not a reliable solution.

You can make a hinge joint by bending coat hanger wire into a springy looking kind of thing and then running a rod down the center.

I didn't follow my Gantt chart. It stressed me out to look at it because it reminded me that I was running out of time.

A few of the employees working at Home Depot became ingrigued by my robot and offered much advice on the design.

I learned that it is bad to procrastinate.

I used the metal box of an old boom box that my friend was throwing out. It created a professional looking housing for my robot.

I cut up 2-liter pop bottles to make the body segments for my catepiller.

If your motor wigs out and does its own thing indefinitely than you need to add a 0.1 uF capacitor in parallel with the motor to damp out the voltage spikes.

I am most proud that my robot was reliable. I was able to carry it from my dorm room to the show in a high wind and it still worked.

I used a plastic whipped cream tub. The plastic can be easily cut and drilled and the lid fits perfectly. Cost = $0.

When drilling, use a center punch (or a nail) to make a prick mark where you want the hole to be.

Use the SOUND command to get tones out of your Stamp. Hook up the speaker as shown in the Stamp manual under the SOUND command.

If you don't have access to tools, make friends fast with someone who does.

Don't worry about the decorations until you are completely done.

Never mount your Stamp board to a metal surface.

A hot glue gun can do wonders.

I used a windshield wiper motor out of a 1982 Mazda.

A small pipe clamp is handy for holding down a motor.

I used an empty peanut butter jar. Cost = $0.

I used two pop bottle caps for wheels.

A belt sander belt can be used for a conveyer belt.

When tying string to the motor shaft, hot glue in place.

To make a large diameter hole, cut a series of 1/4 inch holes around the perimeter, then use a file or a tiny hand saw to connect the dots.

Layout your electronics on a piece of cardboard, first drawing the locations of all components. Glue or tape the components to the board. Poke holes in the board and "stitch" everything together on the backside using the wire.

I used plumber's brackets (also known as a "row of holes") Great for attaching motors to the board.

Hold your motor down with a tie wrap (zip strap). Drill holes in the board on either side of the motor and run the tie wrap up through one hole, around the motor and down the other hole. Pull it tight. use two wraps spaced as far apart as possible.

I found wheel collars with set screws at Hub Hobby.

I used a sliding drawer track that I found at Axman. Strong and very low friction.

Draw out your schematic prior to wiring the circuit.

I used a light fixture metal pull-cord (same thing used to hold dog tags).

To slow down a turntable, have the motor in direct contact with the edge of the turntable. Glue rubber bands flat against the edge of the turntable to increase coupling friction.

I used a volume knob from Radio Shack to make a drum on my motor. The knob fit perfectly on the 1/4 inch motor shaft and even came with a set screw.

Hobby stores have 7", 8" and 98" rubber bands. Great for drive belts.

I found thin brass tubing at Hub Hobby. I used the size with a 1/4 inch ID to make a drive shaft for my motor.

To check if your motor is wired properly, briefly short out the collector and emitter pins of your TIP120 (the center and rightmost pins) with a screwdriver, paper clip or other conductor. The motor should then turn on.

To increase traction, wrap a rubber band around your pulley or wheel.

Broken printers and fax machines are great sources of robot parts.

Sometimes your code will be easier to read if you put multiple statements on one line. Use a colon to separate. For example:

   high 0 : pause 1000 : low 0 ' run motor for 1 second


Use a rubber band for a spring loaded catapult. Or, just a flexible ruler.

For triggers, eliminate binding by having load outside of the trigger pin supports.

On the Stamp boards, the row of holes right next to the pins are directly connected to the pins, so don't stick components through them.

Use an IDE cable from your computer to connect the stamp board to your circuit. The socket on the IDE cable will fit right over the stamp pins.

If you are building a linear slide with a cart that rides on two rails, have the slider bearing be long compared to the diameter of the rails and have the fit on one of the rails be loose.

If you solder wires to your motor, bend them back and tape tightly to the motor body. That way if you tug at the wires, they won't stress the solder joint.

Need a transmission? The cheapest, $5 Zebco fishing reel will have an excellent 4:1 or 5:1 transmission. Plus, fishing reels have some great bearings.

If you can find a junkyard battery screwdriver or battery drill, it will have a very nice motor and gear train in it.

To add interest to your robot, put in appropriate delays. For example, it will be much more interesting if it starts 2 seconds after you push the start button, rather than starting right away.

Take some pictures of your robot before the show. Even better take a video.