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Akit-BASIC Stamp2SX : BASIC Stamp2SX Activity kit
4.3 Sound driver
AX-2SX board provides a 100mW 8
W
speaker and connect with P12 of i-Stamp. i-
Stamp can out the audio signal couple via C2; 10mF capacitor to drive this speaker. This
circuit demonstrate the i-Stamp’s performance about driving a small speake without
external amplifier circuit
4.4 4-Input switches
At P8 to P11 are assigned to Input ports. They are connected 4 of push-button
switches and connected 4 pull-up resistor to define logic “HIGH” in normal state. If any
swith is pressed, that port will be connected to ground. Logic “0” will applied at that port.
i-Stamp can read port’status with programming.
Addition at P8 to P11 has limit-current resistor 220
W
(R9 to R13) for protecting i-Stamp’s
port. Normally i-Stamp’s port can connect to Ground directly but must set to INPUT only.
The R9 to R13 are used to protect port destroy in case setting any port to output and
switch is pressed. If not protected, i-Stamp’s port will be destroy.
4.5 Relay driver
P13 of i-Stamp is connected with ULN2003 input (pin 7). Output of ULN2003 (pin 10)
is connected with 12V relay. i-Stamp can active the relay operation with send logic “1” to
pin 7 of ULN2003. ULN2003 will invert logic to activate relay. Relay’s coil have current
draw. LED9 lights up to indicates the operation and relay contact will switch from NC to
NO. Relay contact rating is 220Vac 5A and suitable to drive 600W electric load. User can
connect the electric appliance load to controlled by i-Stamp.
4.6 LDR circuit
One feature of i-Stamp is the simple analog signal processing with special command;
RCTIME. This command concept is RC time constant operation. In AX-2SX board, use LDR
(Light Dependent Resistor) and 0.1uF capacitor. They are connected to P14 of i-Stamp.
R14 resistor is connected with P14 in series for 2 purposes. One is assistance the RC
operation start. Another function is current limitation from reverse current of capacitor
rechageing.
4.7 Serial interface port
AX-2SX board assign P15 of i-Stamp to serial communication port to extension. The
external device that connect at this port must have serial communication such as the
Serial LCD, Serial keypad or Serial Real time clock module. Serial interface connector use
3-pins header. The assignment port from left is +5V, P15 or signal and Ground. Same any
previous port, P15 has a current-limit resistor for protection.
