Loki Crosses the Pond — Part 2
noise. Install two or three 1N4001 diodes in series with the
battery if you intend to use the 7.2V higher voltage battery
pack. A bypass cap is sometimes needed on the servo
battery line. Another possible addition is a seven-pin,
double row, straight solder tail header for
the optional LCD display (follow
instructions in CA1). An external 16x2
LCD display could also be used. In
this case, you might want to put the
connector on the top of the PCB.
Current software does not utilize the
LCD display; and the RE0 and RE1
pins were usurped for use by the IR
sensors. These PIC pins will need to be
re-assigned if the LCD is used.
The above parts are all added to
the prototype area of the QwikFlash
board. Wire these per the “Servos and
Sensors” diagram in Schematic 1.
There are hole positions for four
miniature toggle switches on Loki’s
body. I’m currently using only one for
servo power. There is already a toggle
switch on the QwikFlash board for 5V
power, but it is wired after the 5V
regulator chip. Builders might want to
add a switch in the power line to the
QwikFlash board, or for a board that
does not have its own power switch.
Electrical
The electrical system on Loki is simple. It consists of a
battery, switch, battery connector, and wiring. The free
ends of this wiring are to be terminated in the power
Parts List
ITEM/DESCRIPTION QT Y
QwikFlash board options
• Blank PC board only 1
• Parts kit for 452 demo board 1
-OR-
• Unassembled PC board and parts kit 1
• IC MCU Flash 32KX16 40 DIP 1
Available as programmed part from the author.
SUPPLIER/PN
Micro Designs Inc./QF-QFPCB3.1
Digi-Key/18F452-KIT-ND
Micro Designs Inc./QF-PARTS2
Digi-Key/PIC18F4620-I/P-ND
(un-programmed)
Additional parts for prototype area of QwikFlash board
• Rectifier GPP 50V 1A DO- 41 3 Digi-Key/1N4001DICT
• Conn Header .100” SINGL STR 36 POS 1 Digi-Key/S1011-36-ND
• RES 2.7K ohm 1/4W 5% carbon film 2 Digi-Key/2.7KQBK-ND
• RES 1.0K ohm 1/4W 5% carbon film 4 Digi-Key/1.0KQBK-ND
• Qty. 10 5” jumpers and 20 headers 1 SchmartBoard/920-0006-01
• Qty. 10 7” jumpers and 20 headers 1 SchmartBoard/920-0007-01
• CST-100 six-position connector receptacle 1 Digi-Key/A19494-ND
• Crimp CST-100 pins 6 Digi-Key/A19520-ND
• Conn 2.1 mm female plug 5. 5 mm OUT 1 Digi-Key/CP3-1000-ND
Sensors
• Devantech SRF08 ultrasonic rangefinder 1
• Sharp GP2D12 IR sensor 2
Super Droid Robots/TS-012-008
Lynxmotion/SIR-01
Cables
I used four 4” pre-made “jumper”
wires for the ultrasonic rangefinder
(cut two blue 8” lengths in half) and
six 6” yellow wires for the Bluetooth
transceiver. These are available from
SchmartBoard (the colors designate
the length) and have female pins for
.025” posts on either end. (These are
great for working on proto boards.)
The ultrasonic rangefinder cable will
need a CST-100 six-position connector
receptacle stuffed with six Crimp
CST-100s. A tool is available to crimp
the pins, or use a pair of needle-nose
pliers to crimp the pin on the wire
before inserting them into the
connector receptacles. You’ll also want
to solder in a five-position, single row,
straight solder tail header into the
backside of the ultrasonic rangefinder.
One of the other standard length
jumpers (red) would probably work for
the SMiRF, but I wanted a connector
body here. As an afterthought, I’d
have put one on the ultrasonic sensor
cable, as well.
Servos and batteries
• HS-475HB ( 76 oz in) standard servo
• 7.2 volt Ni-MH 1600 mAh battery pack
• Wiring harness — battery connector
• 2.4 - 7.2 VDC Ni-CD and Ni-MH universal
smart charger
4
1
1
1
Lynxmotion/S475HB
Lynxmotion/BAT-02
Lynxmotion/WH-01
Lynxmotion/USC-01
Bluetooth
• Bluetooth modem — BlueSMiRF RP-SMA SKU# 1
• Bluetooth USB module SKU# 1
• 2.4 GHz duck antenna RP-SMA SKU# 1
SparkFun/WRL-00158
SparkFun/WRL-00150
SparkFun/WRL-00145
Body parts
• 0.25” dia. standoff RND 4-40 .625”L alum 8
• 0.25” dia. standoff RND 4-40 .375”L alum 2
• 4-40 x 1/4” Philips head screws 8
• 4-40 x 5/8” Philips head screws 2
• 4-40 nuts 10
Digi-Key/1839K-ND
Digi-Key/2026K-ND
• Approximately 150 sq in. 1/16” double-sided
PCB board
• PCB copper clad 4. 5” X 7” two-side 3
• PCB copper clad 6 X 9” two-side 1
Digi-Key or surplus
Digi-Key/PC41-C-ND
Digi-Key/PC53-ND
• Approximately 25 sq in 0.0625” 5052 (H32)
aluminum plate
• Servo angle brackets bend up from 2
aluminum plate
• IR sensor mount 1/2” x 1/2” x 6” long 1
aluminum angle bend up from aluminum plate
-OR-
• IR sensor mount 1/2” x 1/2” x 6” long 1
aluminum angle
Onlinemetals or surplus
SERVO 07.2008 53