8 SERVO 08.2017
Q. I’ve built several robots from kits, starting with simple line followers and most recently a robot controlled by an infrared remote. Next, I’d like to
add Bluetooth control so I can drive it with my phone. How
hard is that?
— James Hull
A. What a terrific and timely question since I discovered a neat little kit recently. A column or two ago, we hacked the $5 line following D2-1 “smart car” kits on
eBay from China. These use an
LM393 hardware comparator to
control two DC gear motors to
follow a line. The PCB (printed
circuit board) is the chassis, and
the front skid is an acorn nut.
Very simple, but it works.
Of course, all this robot can
do is follow lines. (Okay, with
some rework it could also track
towards a flashlight or other light
source, but that’s another
That bot’s “big brother” is the
D2-6 version (Figure 1), which is
microprocessor-controlled and has
three modes: line following, free
roam with obstacle avoidance,
and Bluetooth remote control. The entire robot kit costs just
$12-$16 (search “D2-6 Smart Car” on eBay, Banggood,
ICstation, or Aliexpress), and (IMHO) is a tremendous value
and a great way to start with Bluetooth.
You can drive the robot using the touch screen or by
tilting the smartphone/tablet — pretty nifty! What you learn
here can be ported over to another robot if you like. Only
two caveats: First, there is some surface-mount soldering
involved. I’m no SMT pro, but I did a passable job that
worked the first time. There are many great online SMT
soldering tutorials, such as https://www.youtube.com/
watch?v=5uiro WBkdFY. The pros make it look so easy!
If your SMT soldering confidence needs a boost, here’s
a nice $1 kit to practice your mad skilz with:
www.ebay.com/itm/162141836942. Blinking LEDs rule!
The second caveat is that the app provided is Android
only, so iPhone users need access to an Android phone or
tablet. Fortunately, both are cheap. Anybody in the market
for a great little 7” tablet should grab a 16GB RCA Voyager.
Walmart.com sells the tablet alone for $40, or $45 with a
detachable keyboard (Pogo pins).
Solving the D2-6 Mystery
Although this kit is available from numerous sellers, I
found little information available for it. No instructions; only
mixed cryptic reviews on Banggood. Banggood’s own
description is less than encouraging:
“If you need to learn
microcontroller programming or
re-download the program, please
use your own downloader, we do
not provide tutorials.
It is assumed that users have
soldering skills and
troubleshooting skills to assemble
this kit. Buyers are advised that
due to skills of user involved in
assembly it is not guaranteed
every kit will end up being a
working device. But we will make
as much efforts as we can to
approach that goal.”
My You Tube search on “D2-6
robot” only turned up one poor
Russian fellow who indeed
couldn’t get it working: https://www.youtube.com
I thought it was tragic to allow this potentially neat
little kit to remain in the shadows, wallowing in obscurity. I
love a good mystery and challenge, so I ordered one. (Okay,
three.) After poking around Banggood’s web page, I found
a less-than-obvious link ( http://files.banggood.com/2016
/11/SKU503908.zip) which downloads a zipped folder
containing numerous files.
The two we need are the D2-6 Instructions PDF (in
English, hooray!) and the “MagicCar” app in the aptly-named folder, “Android mobile phone Bluetooth remote
control software” (Figure 2). It’s the small (168 KB) APK
file you can store on a micro SD card and sideload onto
your smartphone/tablet. This is Beta version 1.0.2 and
although it’s nowhere to be found on the Google Play
store, you can download the app and instructions from the
by Eric Ostendorff
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