RTFTechnologies Basic Stamp 2 Robotics Control System

Basic Stamp 2 Control System

Overview:

The Basic Stamp is a micro controller designed for robotics applications. However for use in most modular and large scale robots, the basic stamp requires physical and electrical protection, as well ar a power source and programming port (serial, RS-232). This system includes a 900 MHz radio link (>1000ft range) as well as an 8 channel PWM output and joystick input.

Processor Module:

The Basic Stamp 2, by Parallax-inc, is enclosed in a radio-shack project box and assembled on a radio shack circuit board. The bs2 is mounted in an IC socket for easy removal or upgrade. My present design will work with the BS2, BS2SX, PS2E, and BS2P24. It used MAX367EPN over-voltage / surge suppressor chips, available as free samples from Maxim IC, to protect the bs2-ic from voltages outside the TTL/CMOS range. The MAX367s are run at 5v, restricting the voltage into the inputs to 5.25v to -0.25v and can handle inputs of +- 40v. I/O live 0 is dedicated to an input button. I/O lines 1-3 (external audio connectors) are over-current protected by a series 1K-ohm resistor. I/O lines 4-15 can be connected to via an external DB-15HD connector, available at radio-shack. Between the bs2 and the MAX367s are test points, similar to a breadboard, as well as sockets for pull-up and pull-down resistor packages. Power is regulated via a 7805 5v regulator, that is connected to the BS2's 5v live and the MAX367 V+ lines.

These are pictures of the Processor assembly during construction. The 9 pin sockets next to the stamp are for pull-up or pull-down resistor blocks. The 24 pin sockets can be used as test points or for jumper wires. The pin headers go to the DB-15 connector(not shown).

Electrical Diagram:

The MAX367s connect to gray rectangles denoting the pin headers. These connect to the DB-15f connector on the processor module.

Different colored lines that cross do not connect.

Processor Module I/O Table.

Serial hook-up table		I/O line hook-up table

DB9-f pin	BS2-ic pin	DB15-f pin	BS2-ic
1	nc	1	v+ in (before the 5v regulator)
2	1	2	ground
3	2	3	nc
4	3	4	I/O 4
5	4	5	I/O 5
6 , 7	loopback	6	I/O 6
8	nc	7	I/O 7
9	nc	8	I/O 8
		9	I/O 9
		10	I/O 10
		11	I/O 11
		12	I/O 12
		13	I/O 13
		14	I/O 14
		15	I/O 15

900 MHz Telecommand System:

Utilizes the HP-2 series RF modules (pin compatible with the newer HP-3 ) from Linx Technologies .

Although encased in plastic enclosures, each module has a copper foil ground plane at the bottom of the box which increases the performance of both the RF module and antenna. During operation the antenna is normal to the ground plane (horizontal during scan). Multiple channels from 902-928MHz are selectable via the DIP switch. The modules are capable of transmitting audio or serial data up to 50,000bps, however operation with the basic stamp has only been tested at 9600bps.

Transmitter:

Linx TXM-900-HP-II transmits raw data from the bs2 module at the telecommand station to the receiver on the robot.

Transmitter Module I/O Table.
DB9-f pin		Function
3		Serial data in
5		ground
6 , 7		loopback
9		v+ in

Since the module is designed for 0-3v logic levels, a 2.2k series resistor is necessary to operate the module at the 0-5v logic levels generated by the basic stamp. The 5.1v zener diode protects the module from negative and over voltage on the data input.

Receiver:

Linx RXM-900-HP-II receives raw data from the transmitter at the telecommand station and outputs it to the bs2 module on the robot.

Receiver Module I/O Table.
DB9-f pin		Function
2		Serial data out
5		ground
6 , 7		loopback
9		v+ in

Code:

Test code for robot and transmitter

Basic Stamp code editor and manual

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