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Robot Building for Beginners

A beginner’s book on how to build a robot, from the author of Robot Room.
Contains tricks, tips, and advice on getting started creating your own robots
from scratch. THIRD EDITION!

Intermediate Robot Building

Learn how to make a robot power supply, compare motor driver circuits, create an
infrared obstacle / wall / opponent sensor, play music, and much more. SECOND
EDITION!



WHAT’S NEW? (FOLLOW @ROBOTROOM ON TWITTER)


New Articles on Patreon
There are at least 30 new Robot Room articles available for patrons. Click here
to check them out:




Goodbye Google Adsense!
I've removed Google Ads from Robot Room. Why?



5V Regulator Cap for 9V Battery
For quick portable projects and temporary hacks, it is often faster to reuse a
simple 5V regulator circuit than to integrate a power supply into the device
design. My toolbox has an LED tester and magnifier light, so why not add a
convenient 5V regulator cap to the collection? There are nicer ones on the
market that have surface mount components, but half the fun of an electronics
hobby is creating something basic in your own style. This double-decker board
with flashing LED power indicator allowed me to experiment with flush battery
snaps and board interconnects.



Mercury Battery Replacement Regulator
Several decades ago, mercuric oxide button cells were common consumer power
sources. Mercury was phased out due to environmental concerns, leaving behind
vintage photographic equipment and watches that were incompatible with
alkaline's wide voltage change or silver-oxide's slightly higher nominal
voltage. Tinkerers have come up with a variety of solutions for many devices.
Perhaps modern technology can address a few more with an itty-bitty 1.35V
low-dropout linear regulator.

3D Printed Spool and Wire Soldering Holder
Buying new wire begs the question of what type of insulation to choose. PTFE is
selected since it doesn't tend to melt back as common PVC wire insulation does.
The new wire arrives without a spool, which necessitates printing a spool on a
three-dimensional printer. The spool is easy enough to model but consumes the
day with a six-hour print time. Soldering the newly acquired wire to another
wire is frustrating with the classic misaligned 'helping' hands tool. Thus,
old-fashioned wooden clothes pin attached to a base become the project being
worked on rather than whatever I needed that wire for in the first place.

Generating Waveforms with Paper Discs
In a pinch, you can generate square, sawtooth, sinusoidal, triangular, and
noisy/static waveforms by playing a patterned disc on a record player or spare
motor using a light sensor. An LED illuminates the paper disc, which reflects
varying amounts of light into the light sensor as the disc rotates on the
turntable (see the video for a demonstration.) The circuitry is fairly simple
and uses commonly found parts. Can you guess the waveform generated by the
thumbnail image?

Resistor Forming Tool
Who hasn't looked at a classic red resistor lead forming tool and exclaimed "I
could 3D print this!" I took a shot at designing and printing a few variations.
The end result is a functional tool with a couple of improvements, but not as
crisp, due to the limitations of home fused-filament resolutions.

Upgrading Magnifying Desk Lamp to LEDs
Circular T9 LED bulbs are available to replace fluorescent bulbs in desk lamps.
LEDs provide a broader spectrum of light, which is particularly important if you
are shooting macro photographs, but is also easier on your eyes if you're
soldering or inspecting boards. Unfortunately, the commercial LED bulb I
received was defective and had a flickering power supply. Hacking in six
additional smoothing capacitors and replacing a missing LED solved the problem.

Identifying Bad Capacitors
If your consumer electronic device is failing, it is often caused by old,
overheated, or defective capacitors. If you open up the case and inspect the
capacitors, you may find some that are bulging, crusty, or are lifting off the
PCB. Here are some photographs of damaged CapXon brand aluminum-electrolytic
capacitors found inside failing Samsung LCD monitors. Also included is a photo
of a good capacitor that has beneficial goop surrounding it.

How *Not* to Cast and Machine Bismuth
Bismuth is a high-density non-toxic metal that forms beautiful crystals. Well,
supposedly it forms beautiful crystals, just not for me. See examples of clay
casting failures and chipped surfaces as I muddle my way through trying to make
anything out of bismuth.


Sun Tracker Failed Project
Sometimes you gotta know when to walk away -- which was eight years ago. I dug
up this robot that was supposed to emulate a sunflower tracking the sun. Due to
a design flaw in an overly complicated analog sensor bus, and general ugliness,
this project got literally shelved. Now it sees the light of day, if only to be
a lesson to others.

Mounting an iPad for Desk-Based YouTube Videos
For many hobbies, an overhead shot of your desk or workbench is the ideal view
for your videos. This is unwieldy for tripods, but suitable for a desk swing
arm. Similar to a desk-mounted magnifier light, the camera can be quickly
positioned at various distances, and can be swung away when not in use. The
single arm does not tend to block room lighting. Take a look at my tablet-mount
setup, and see how the arms were extended to fit a larger form factor.

Macro Photo vs Microscope
Fifteen years ago, I proudly photographed a PCB using an Intel QX3 toy
microscope. How well does that old microscope compete against a modern 16
megapixel camera with macro lens, extension tubes, tripod, linear table, linear
slide, remote shutter, 28 LED ring light, and stacked photography software? Can
such a photo setup match the microscope's 200x magnification? In fact, exactly
small of details can we clearly see with a modern rig? Would you believe 10 µm?

3D Printed Trimpot Thumb Dial
Create your own colorful finger-friendly dials for common trimmer
potentiometers. With a little slot that press-fits into the screwdriver slot,
and a dab of emblem adhesive, these home printed dials will make your projects
much easier to adjust.

LED Tester with Display
Throw away your multimeter and spreadsheets, here is a self-contained
current-limited LED tester that displays LED voltage drop, current, and
recommended resistor. With about $10 in parts and a 9V battery, this
indispensible tool is tailored for the everyday tasks of the electronics
enthusiast.

The TGIMBOEJ Curse
Remember that thing you were going to get to? Well, it took me seven years to
ship a package. No kidding. What's inside? Are there more like that? (Yes, 144)
Come closer to hear the tale of The Great Internet Migratory Box Of Electronics
Junk.

Replacing Broken Tip of IC Hook Probe
Arg! The multimeter measurements are wrong because the probe detached from the
circuit because the IC hook tip broke, again! I go through far too many broken
IC hooks to keep throwing them away. Is it possible to 3D print a replacement
tip? Is this an opportunity to improve the tip to be more robust?


Leveling A 3D Printer
How to accurately set the extruder nozzle height above the print bed when
leveling a 3D printer. Use a thickness gauge, magnet, and a multimeter in
continuity mode to beep when the print head makes contact. Includes a trick to
clean the tip of the nozzle by scraping it with the zinc interior of a penny.


Printed Circuit Board Survey
What features do hobbyists, students, and small shops look for in a PCB
manufacturer? Do people care about lead free? What about board shape and
internal cutouts? Is board color important enough to offer as an option? Find
out the results of the PCB survey...


PCB Motor Mount
If you don't have a home machine shop or 3D printer, you can make a motor
mounting bracket from a PCB. Printed circuit boards are strong, lightweight,
precise, and are easily manufactured. The PCB bracket can then be attached to
your project using screws, straight solder, right-angle headers, or dual-row
headers. The video in the article shows you the process step-by-step, including
how to make the board non-rectangular and how to place screw holes at angles.


Better Etching of Homemade PCBs
You consistently create homemade PCBs with traces as fine as 6 mil traces, using
common household objects, such as sandpaper, cleanser, aluminum foil, and a
clothes iron. I test various chemicals, temperatures, and pressures to determine
how to make circuits with minimal voids, distortion, and fills.

PCB Hole Sizing
How big of a hole do you need drilled in a printed circuit board to fit a part?
Don't just measure the part with calipers and use that for the hole size! You
must make the hole larger to account for the tolerances of the part and the
circuit board manufacturer. Of course, that brings up the question of how much
can you trust the size of the holes the manufacturer is drilling. Let's see what
pin gages say about some of the boards laying around the robot room.

Hamming ECC
Error correcting code (ECC) is superior to ordinary checksums, in that is can
both detect and correct errors in data storage and transmission. Learn how
Hamming codes work. Fully working C library included.


Thermal Imaging
Infrared pictures and images can reveal energy waste, health issues, security
codes, animal behavior, and circuit board flaws. It is also a great way to cheat
at hide-and-go-seek. Take look at a gallery of fascinating thermal images taken
with the Flir E4 infrared camera. Additionally, there is a video of a
power-supply heating up, as well as desoldering wires.


Rocket Ignition System
The problem with most model rocket launch controllers is that the battery is
located with the operator, far away from the launch pad. This requires thick
cables and wastes significant energy. By locating the battery near the rocket
engine and using a remotely-controlled relay, the improved launch system is more
efficient but can still be built at home. Includes complete schematics, the pcb
layout, and source/object code.

Back And Forth Mark II
The single motor drive train on the original Back And Forth robot was unique but
a failure. To overcompensate, the next generation is four wheel drive and six
switches just to move forward and move back, repeatedly. There are some nice
mating parts that may be useful in your next project. And, you'll be surprised
to see what's inside the half-height batteries.


Maximum Sampling in Software
When sampling at the maximum software rate, the signal itself may affect the
software, resulting in inaccurate readings. Here is an example of how I debugged
an issue and doubled the rate.

Yummy Candy Tin Robot
Yummy is a line-following robot made from an m&m's candy tin, in homage of
Sweet. Yummy features a light sensor for detecting when the candy tin has been
closed, to delay starting the motors as long as necessary. The rear tail lights
use 10 mm red LEDs with Fresnel lenses.

Cleaning a Mouse Scroll Wheel
The scroll wheel on the Microsoft Wireless Mouse 5000 can stop working over
time. As you'll see, the scroll wheel is a classic interrupter encoder wheel
that can be fixed by cleaning. The difficult part was figuring out how to open
this mouse, which ended up being held together with four T6 torx screws hiding
underneath the glide strips.

Removing Solder from PCB Holes
Excess solder can clog circuit board holes due to overzealous soldering or when
desoldering to remove a part. It can be annoying to try to get the solder out of
the hole, but these methods and tools can help. Article also describes how to
make your own Teflon desoldering tips.

Sturdy Attachment of a Lego Wheel to a Gearmotor
Nothing is more pathetic than a robot that has lost a wheel. Couplings based on
the standard mating cross axle have a habit of sliding off. But, the peg holes
present in larger wheels provide opportunities to securely attach the hub with
screws. Using a lathe, milling machine, digital readout, magnets, PVC plastic,
and a carefully-drafted layout can produce a rugged Lego coupler. Ah, an article
on math and machining; what could be more universally appealing?

Replacement Battery Pack from AAA Cells
When a consumer device stops working because of a proprietary battery pack, you
may be able to repair it by replacing the batteries with off-the-shelf
rechargeables. If necessary, it is possible to solder together your own battery
pack so long as you wear safety equipment, have a solder gun, and clean the
terminals. Of course, this assumes you can find cells that match in size,
voltage, and chemistry.

Afterthought Cake Robot
A pleasant robot that doesn’t do much consists of a collection of interesting
parts assembled together because they didn’t fit any other robots. The robot is
a successful experiment in making couplers shorter, employing escap rectangular
motors, detecting distance moved with an interrupter infrared encoder, and a
cube of multiple smaller PCBs. Powered by a single 180 mAh lithium polymer cell
without a voltage regulator. Motors driven using low-voltage high-current Zetex
bipolar transistors. Includes lots of big pictures and a descriptive
demonstration movie.

Replacement for PNA4602M
The Panasonic PNA4602M 38-kHz infrared detector was a very popular electronic
part for obstacle and wall detection. Unfortunately, the PNA4602M is
discontinued and similar modules can’t handle continuous signals. Good news! The
new Vishay TSOP4038 is an excellent substitute. Tests compare detection
distance, false pulses, and detection time. Also included is the relevant source
code to variable-frequency duty-cycle measurement.

Serial Communication
A very popular method of sending and receiving data between devices and
computers is good old asynchronous serial communication. See traces of
characters being transmitted. Learn how far timing can be off before introducing
errors. Includes a table of popular crystal frequencies and baud rates, as well
as machining information and a source code snippet for an automatic bps
detection tool.

Digital Indicator
Reuse is a good thing. In this case, a unique surplus item that appears to be a
digital caliper is actually a digital indicator based on the caliper body and
circuitry. The data port pinouts, mounting screw sizes, and example output
analysis are posted, along with a cheap way of powering the tool from a 'AA'
cell.

Repairing a Model Rocket
A rocket found in a tree had loose and missing fins, a broken parachute, and a
lifeless shock cord. Replacement fins can be made from balsa wood, using a pen
and a hobby knife. After sanding, they can be reattached with two kinds of glue.
Simple repairs and replacements make the rocket flight capable again. After all
that work, an overzealous choice of a rocket motor sealed the rocket’s fate.
Where do you think the rocket (and “Lego Major Tom”) ended up?

Machining Magnesium for Elemental Density Comparison
To demonstrate the massive difference in densities of naturally-occurring
elemental metals, a large magnesium ingot is machined down to a precise cylinder
using a hacksaw, milling machine, and lathe.

Long Exposure Photography
LEDs create beautiful and informative light trails when a robot is photographed
in a dark place with the shutter open. This approach captures the exact
movements and behavior in a single photo, as opposed to replaying a movie over
and over. Use a tripod, remote control, and experiment with lighting conditions
for best results.

Capacitor Leakage
When power is disconnected from a circuit, the capacitors on the board are
discharged by the electronic components until no voltage remains. That’s fine.
But, did you know that if you charge a capacitor on its own, it will slowly
discharge through itself? More surprisingly, some capacitors become leakier with
time, but can be healed through usage. I was shocked to discover how difficult
self-discharge is to measure.

Industry-Standard LCD Modules
A blowout price on a 2x8 LCD module without specs leads to a bargain on
industry-standard 14-pin alphanumeric LCDs. Demonstrates simple techniques for
determining connector pins. Ultimately, the datasheet is found, and the contrast
and backlighting pins are covered as well. Includes an example of writing custom
bitmap characters.

Color Printed Circuit Boards
Green is so boring! Finally, your electronic devices can have beautiful red,
black, and blue color circuit boards. The example shows an exposed-PCB Sandwich
robot that starts with colored copper clad boards. The PCBs are etched at home
with a peristaltic pump, after including an image of my dog and dealing with
government-coded dots. The project is rounded out with a clear DIP socket and a
shrouded battery cap.

Trimpots
A visual guide to breadboard-friendly trimpots (small variable resistors) that
appear in nearly every hobbyist electronic project. The article features
comparison pictures and part numbers of 3/8-inch and 1/4-inch square single-turn
and multi-turn trimmers. Even more interesting is the cutaway close-up
photographs of the inside gears and brushes of these tiny potentiometers.

Back-And-Forth Robot
A robot that drives forward to a wall and returns is a popular contest and
student project. Surprisingly, this robot can be made with an off-the-shelf
8-pin motor chip, a couple of resistors, and a couple of chips. The article
provides a complete walkthrough of the schematics, along with an animation of
the changing states and a video.

Minifigure Multimeter
Have you ever had a pile of assorted resistors that you wish to quickly
organize? Place each resistor in the hands of the electrified Lego minifigure to
see and hear the nearest standard resistance. This practical meter includes both
an ohmmeter for resistance measurement as well as a voltmeter for battery
measurement.

Weatherproof Project Box
Modifying a Pelican micro-case for a dustproof, waterproof, and bugproof outdoor
electronics container. Tips on punching a rubber liner and connecting external
wires through a PVC pipe, or hacking a seal with poster tack.

Safe Sync for External Flash
Digital cameras have a relatively low voltage limit on their sync hot shoe,
compared to mechanical cameras. This makes modern cameras susceptible to damage
from higher-voltage external flash units, which consumers and hobbyists may
attempt to reuse from previous generations. The circuit described in this
article is a classic solid-state level-shifter often used to interface DC
circuits to AC appliances.

Electrolysis Rust Removal
There’s nothing more depressing than to see corrosion on your precision tools or
antique hardware, particularly if the rust is in a hard to reach area.
Fortunately, there’s an electrical technique to reverse oxidation without
harming steel or iron the way abrasives or harsh chemicals can. Includes results
of testing a graphite electrode for the anode.

How to Measure Low Resistances
Occasionally you'll run across electronics such as relays, cables, igniters,
switches, or current-sense resistors that have resistances less than one ohm.
Few multimeters accurately measure less than 1 Ω, but most have a millivolt mode
that can be combined with a 5 V source, a fixed resistor, and some simple math
to determine milliohm resistances.

PCB Layout Tricks and Tips
A few extra holes, wider pads, and copper fills can greatly increase the
versatility, solderability, and ease of testing of the printed circuit boards
you design.

Solar Recharging
A small solar panel or series of solar cells can power an electronic device
during the day, as well as recharge NiMH batteries to power the device at night.
This simple recharger uses diodes for reverse-power protection and so that the
project can measure the power source voltages. Includes schematics and graphs.

Multimeter Reviews
A digital meter is an essential tool for all robot builders and electronic
hobbyists. If you’re just starting out, can you buy the least expensive model
and still get accurate results? How much do you need to spend to get a decent
mid-range model? A dozen multimeters are tested and compared.

Previous articles are moved into the categories below. To be automatically
alerted to new articles when they are posted, subscribe to the Robot Room RSS
feed.


ALL ARTICLES



Robots
All robots

Line-Following Robots
Including maze solving

Mini-Sumo Robots
Plus ring making and rules

Solar Robots
BEAM and microcontroller

Motors
Mounts, couplers, H-bridge, PWM

Machining
Milling, drilling, and lathe

PCBs and Breadboards
Solderless and printed circuits

Tachometers
Also counters and encoders

Electronic Projects
And various electronic parts

Sensors
Infrared, photo, and distance

Inside Toys
Reverse-engineering

Calculators
Ohm’s law and resistor bands

Miscellaneous
Multimeters and more

Obsolete
Scrapyard of old articles


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