PARTS LIST
ITEM ASSEMBLY SEQUENCE
❑ C1 3
❑ C2 9
❑ C3, C4 10
❑ D1 1
❑ D2 3
❑ DB9-F 11
❑H1* 7
❑H2* 7
❑H3* 7
❑ H4 7
❑ H5, H6, H9 7
❑ None 13
❑ H7, H8 8
❑ IC1 5
❑ None 14
❑ LED 6
❑ R1 2
❑ R2 2
❑ R3 2
❑ R4 2
❑ SW1, SW2 12
❑ VR1 4
* Optional (for use with breadboard)
PART
Capacitor, 0.01 μF
Capacitor, 47 μF, 50V
Capacitor, 100 μF, 50V
Diode, BAT85
Diode, 1N4002
DB9 conn., right-angle, female
Header, female, straight, five pins
Header, female, straight, two pins
Header, female, straight, four pins
Header, male, straight, 2x5 pins
Header, male, straight, three pins
Shorting jumper, two pins
Molex conn., straight, two pins
DIP socket, 14 pins
PICAXE-14M processor
LED, 5 mm, red
Resistor, 1/4 watt, 180 ohms
Resistor, 1/4 watt, 22K
Resistor, 1/4 watt, 10K
Resistor, 1/4 watt, 330
Power switch
Voltage regulator
DIGI-KEY P/N
BC1078CT-ND
493-1106-ND
493-1107-ND
568-1617-1-ND
1N4002RLGOSCT-ND
A2100-ND
S7038-ND
S7035-ND
S7037-ND
A26525-05-ND
WM6703-ND
S9001-ND
WM4200-ND
A9414-ND
NA
160-1705-ND
180QBK-ND
22KQBK-ND
10KQBK-ND
330QBK-ND
CKN5001-ND
7805 497-1443-5-ND
■ FIGURE 3
manufacture the Brain Alpha board. You may want to refer
to it as we discuss the steps involved in assembling the
board. When assembling any PCB, it’s a good idea to work
from the smallest to the largest parts — it makes it easier to
hold the parts in place as you solder. Just follow the suggested
sequence included in Figure 3 and you won’t go wrong.
As you are soldering components into the PCB, keep
in mind that several parts are polarized, so be sure to observe
the proper orientation when installing them. The cathode
(painted stripe) of both diodes should be to the left. Bend the
leads of the voltage regulator (VR1) so that when it is inserted
into the board, the metal tab lays flat on the board and the
hole in the regulator lines up with the hole in the PCB. Pin 1 of
the DIP socket (IC1) is up and to the left. (Don’t insert the
PICAXE-14M yet! Later when you do, be sure its pin 1 is in the
same position.) The cathode of the LED (shorter lead/flat
portion on the edge of the plastic lens) is to the right. The
raised plastic “key” of each of the Molex connectors (H7 and
H8) should be to the bottom. The negative lead of the three
electrolytic capacitors (C2-C4) should also be to the bottom.
If you are assembling the Brain Alpha without a
breadboard, you don’t need to include the three female
headers (H1-H3 in the Parts List). If you would rather use
a breadboard, solder in the three female headers and then
peel the backing off the breadboard and carefully affix it
to the Brain Alpha board so that its edge just touches H1
through H3 and its holes line up with the holes in the
header. That’s all there is to assembling the PCB itself.
Next, it’s time to add the two required battery packs: a
nine-volt battery to power the PCB electronics; and four AA
batteries to power the servo motors. There’s ample room
58 SERVO 09.2008
on the lower deck of the TankBot to mount the batteries.
You can use self-stick tape to hold both the nine-volt battery
and the AA battery holder included in the kit, eliminating the
need to drill additional holes in the TankBot. You can also
use the two polarized female Molex connectors (also
included in the kit) to attach to the battery pack leads so
they can be easily inserted into appropriate male molex
connectors on the Brain Alpha board. If you prefer, you could
just solder the battery wires directly to the PCB, omitting
the Molex connectors altogether. In either case, make sure
to observe the correct polarities as marked on the PCB.
Testing the Brain Alpha Board
Before we insert the PICAXE-14M in its socket, let’s
double-check that both batteries are wired correctly. With the
batteries connected to the appropriate header (9V to H7 and
6V to H8), slide both power switches to the “ON” position on
the right. Using a multimeter set to measure volts ( 10 or 20
volt scale), hold its “ground” probe on any one of the ground
pins on the left side of the H4 expansion connector (we’ll
discuss expanding the TankBot in future articles) and carefully
measure the voltages on the three lower pins on the right
side of H4. They should match the voltages shown in Figure
4. Be very careful not to short any of the pins on the right
side of H4 or you could damage the header. (If you have an
insulated pin probe, that’s even better.) Also make sure that
pin 1 of the IC socket is at +5V and pin 14 is at ground.
For the remainder of our discussion, I’m assuming that
you’re using a breadboard on the Brain Alpha; if not, adjust
your procedures accordingly. Once you have determined
