36 January 2016
microcontroller-based devices over ZigBee!! They even
have an Arduino shield you can use to hack together a
prototype.
It was the perfect storm. I had an open platform
(Smart Things), an open protocol to talk to it (ZigBee), and
years’ worth of awesome Propeller-based devices that
could take advantage of it. So, last April, I created a
standards-based ZigBee object for the Parallax Propeller
that allows my devices to communicate based on the
ZigBee HA public profile. It opened a huge door of
opportunity for my devices. Now, I can make a device,
connect it to the Smart Things hub over ZigBee, and
control it with my iPhone. All this and I don’t have to write
one line of code that runs on the iPhone!! My device
identifies itself to the Smart Things hub, tells it what it is
capable of, and the Smart Things hub then determines how
to control it.
Recently, one of my ZigBee HA projects — the
CoopBoss (Chicken Coop Door controller) — won Best in
Show at Smart Things and it’s on its way to becoming a
commercial product. They did a nice write-up on the
CoopBoss; if you’re interested, you can check it out at
http://blog.smartthings.com/stories/a-smart-chicken-coop.
The CoopBoss was a project I put together after my
wife lost three of her best hens in a
mink attack one night last spring.
We forgot to close the coop door
and a mink got inside and just
ripped three of her five chickens
apart. She was heartbroken. Her
chickens had been with us for
three years supplying my lunch
three times a week.
The CoopBoss is a custom
printed circuit board (PCB) that
drives an off-the-shelf 12V actuator
to push the coop’s sliding door
closed at sunset and open at
sunrise. My wife is able to control
it with her smartphone, and can open or close the door
anytime, anywhere she has service.
Figure 1 shows the ports to connect the CoopBoss to
the real world. They are the following:
Motor Connection: Connects to a 12V DC linear
actuator to push and pull the coop’s door. The motor
control circuit has been tested with Progressive
Automations’ 12V actuator model number PA-14-12-35.
However, just about any 12V DC four amp or less
actuator should work.
Main I/O Header: This header is connected to two
thermistors, one photoresistor, and two normally-open
pushbuttons.
DC In: 12V DC power in and five amp fuse holder.
Aux Port: Auxiliary port for future expansion.
Antenna: XBee antenna connection.
Figure 2 highlights the CoopBoss’ onboard modules
which include:
Motor Control: Based on IXYS Integrated Circuit’s
CPC1709J solid-state relays. The motor control circuit uses
four optically coupled solid-state relays arranged in an H-bridge to drive the 12V DC
actuator motor forward and
reverse. It is connected to the
microcontroller (H) with four I/O
pins.
Object Detection: Motor
current monitoring is based on the
Texas Instruments’ INA219BIDCNT
bi-directional current/power
monitor chip. If the door bumps up
against an object during a close,
this circuit will detect the small
increase in current and quickly
relay that to the microprocessor
(H) over an I2C bus. The
FIGURE 1. CoopBoss Ports.
FIGURE 2. CoopBoss Modules.
