Auger front end.
allowed around the rear wheel mechanism. Because the
bright green plastic design is inviting, it’s a good idea to
treat this as you would any of your power tools — up and
away from children.
THE TEAR DOWN
Dimensions 15. 5” L x 3. 25” W x 2.2” H
Drive Rear (opposite end of auger)
Tread Rubber, one piece, 1/2” wide
Length, auger tip (total) 1.9”
Dimensions, square auger shaft 1.2” L x 0.3” square
Length, antenna 13. 5”
Weight, body (no battery) 23 oz
Weight, NiCad pack 12 oz
Charger 9 VDC wall module, 150 mA
Speed (forward/reverse) 9 in/second
Control range, outdoors 57 feet
Control range, indoors 30 feet
Battery 7.1V NiCad; capacity not listed
Drive only — 300 mA
Current drain 7.1V Auger only — 500 mA
Auger and drive — 800 mA
RC frequency 49. 86 MHz
Controller weight (no battery) 5 oz
TABLE 1. Looj robot specifications.
The rubber tread peels off easily, and the rear wheels
are attached with Phillips head screws. After that, peering
inside the Looj takes a bit of work. Unfortunately, iRobot
elected to glue the cover in place. I used a sharp
screwdriver to break the seal and then remove the cover.
The most challenging section of the cover is over the thin
bridge framing the battery compartment.
Once the cover is removed, the electronics and drive
assemblies are readily accessible. The front auger motor
and gearbox are easily extracted without tools. The rear
compartment is more complicated. The electronics —
located adjacent to the rear drive gearbox — are also easily
removed with a gentle tug. Fortunately, connectors are
used for power, motors, and the on-off switch. The antenna
is the only wire that must be cut or unsoldered to extract
the electronics unit.
The electronics assembly consists of a motherboard
and two solder-on boards. The motherboard appears to
be primarily for power management and input/output.
One board is obviously the RF receiver, given the RF
coils and the antenna connection. The other board is
apparently the motor controller. One of the two 14-pin
chips on the controller board
is a 74HC74D flip-flop and
the other is an LM339DG
quad comparator. The
balance of semiconductors
are three-lead devices and
The rear drive motor
assembly is best left inside
the Looj body. The axel runs
through the gearbox and out
of the Looj body, making
extraction problematic. I
used modest force in an attempt to drive the axel
through the gearbox, but encountered stiff resistance.
Instead of possibly destroying the gearbox, I used a
Dremel to saw through the body of the Looj to release
the gearbox. The complete electromechanical system is
Looj body cracked open showing
expansive empty battery compartment.
SERVO 05.2008 29