Introduction
Arduino BT is an Arduino board
that already have built in Bluetooth module. This simplify hardware
interfacing. When it is up and running it simply act as normal
Bluetooth device. Pair it with a PC or notebook, and it is ready to
talk to Arduino IDE for programming. As simple as that.
There
lies the catch. The "When it is up and running part". Arduino BT is
using Bluetooth connection. It has no built-in port to accept USB. The catch
is that, it is not as easy to power up. Compared to Uno or Duemilanove which
is USB powered.
So how
do we power it up. Arduino BT does come with +ve and -ve terminal. In this
article. I am going to demonstrate how to use this terminal to power up
Arduino BT using AA batteries. Test it by uploading LED Blink sample program and highlight some possible
issue and pitfall along the way.
However,
please note that this article is not a complete replacement to Arduino BT
hardware page. The most important being hardware specification such as maximum
voltage. So, do check the page and base your design upon the specification given there.
A good
advice at this point is to understand that, unlike other board, Arduino BT
maximum voltage is specified as 5.5V.
So it is very critical to be careful with the power up stage. It is a
good idea to use multi meter and double check that batteries or adapters +ve
and -ve terminal voltage did not exceed 5.5V.
A good
point to think about is that power adapter (or wall warts) voltage under load
should be lesser than the voltage measured by multi meter on the terminals
without any load. But at this moment I'm taking "it is better to be safe
than sorry" stance. Will revisit this in the future. Perhaps continue with another article on powering Arduino BT using power adapter.
In
Malaysia, AA battery is commonly rated at 1.5V. Having 2 batteries in series give
about 3V. Which is enough voltage to power up the board and within spec. However this say
nothing about the amount of charge hold by the battery or how long will it
last. So here is our first pitfall of the day. And I am a pitfall magnets.
Personal
experience. Run down 6 AA batteries to death in the half day of troubleshooting. The reason being using normal grade batteries! So
dear readers, please use Alkaline
batteries. Better yet, use rechargeable
batteries!
With
that said, after initial test is done. I did use 4 AA rechargeable batteries
in series . Each of the battery rated at 1.2V with 2100mAH charge capacity. Do
be careful not to use 4 AA battery with 1.5V rating. That is 6V and possibly
may damage the built in and soldered micro controller. Definitely not user
replaceable. Unless the user is very skilled in soldering and desoldering
surface mount chip with many small pins.
Tutorial
Step 1
Assemble
the simple circuit. Note that diode is to prevent reverse polarity. Still, be
careful not to reverse polarity when connecting the second terminal header to
Arduino BT.
At this
point we are not using the LED yet. So leave it unconnected.
Good
idea to double check the battery voltage using multimeter before going to next step.
Step 2
Connect
the circuit +ve terminal (red wires) to
Arduino +ve terminal. Connect the circuit -ve terminal (black wires) to Arduino -ve terminal. Battery holder
without On/Off switch (as the one used in this article) means that the board
will be powered up when both terminal is in contact. Be careful!
Step 3
The
board is powered up. There is two on board LED. One is power LED which should
be steady on after power is up. The other
one is Low Battery LED which will light up when battery is low.
Step 4
Next we
are going to pair Arduino BT with a PC or notebook. Simply do the normal
platform specific ways to pair Bluetooth device. I am using a notebook with 64
bit Windows for this test. So in Bluetooth panel, click Add Device and wait
for it to detect. Initially it will detect it as Other Device. Select it and
click next an follow the instruction. A driver will be automatically
installed. Hence forth it will be shown as Arduino BT.
Important: The pairing must be done from PC or
Notebook since pass phrase need to be entered. When asked enter 12345 as the pass phrase.
Step 5
After
driver installation is successful and pairing is done. Verify
the COM port number. Simply double click the newly added device to look at its property page. Select the
hardware tab. The comport number should be displayed.
Step 6
Launch
Arduino IDE and open up the Blink
sample. After that, verify or do the following setting:
- Menu : Tools > Board and
choose Arduino BT with the correct microcontroller. In my case it is
Arduino BT w/ ATMega328.
- Menu : Tools > Serial
Port and select the correct COM port.
Step7
Since we
already open the Blink sample. Simply upload the code to Arduino BT.
Important: If the upload is not successful
with the following error:
My theory; the error is due to
on board Bluetooth module on Arduino BT actively communicate with Arduino
microcontroller using RX and TX pin.
Arduino IDE also use this RX/TX as serial port to program the
microcontroller chip. Hence the error. Apparently
not everyone suffer this problem and base on internet search, some manage to
solve it by replacing Bluetooth adapter on the PC/Notebook side.
Fear
not! The work around is to press Arduino BT reset button, release it and
immediately (within 2 second) press the upload button in the IDE. Works like a
charm!
The
reason being, boot-loader programmed into the micro controller wait for 5
second for programming serial communication before continuing with other function.
Step 8
Upload
is completed, the board reset itself and is running, but where is the blinking
LED!
Don't
panic! Unlike Arduino Uno or Duemilanove. Arduino BT does not come with
onboard LED connected to digital I/O pin 13.
This is
the time to connect LED black wire to GND and yellow wire to pin 13 on the
Arduino BT board.
Step 9
If
everything goes well, enjoy the blink!
