Parallax 29158, 29157 User Manual

599 Menlo Drive, Suite 100
Rocklin, California 95765, USA

Office: [phone]
Fax: [phone]

General: [e-mail]
Technical: [e-mail]
Web Site: www.parallax.com
Educational:
http://www.parallax.com/html_pages/edu/

BASIC Stamp HomeWork Board

#29158 10-pack of Breadboard version
#29157 10-pack of Through-Hole version

Introduction

It’s not often that we start technical documentation with a bit of marketing punch. If you like the low cost of a
BASIC Stamp Rev. D (retails ~$34) and the idea of a half-price BASIC Stamp 2 / Board of Education (retails
~$109) then the BASIC Stamp HomeWork board is the ticket for your class. This is the least expensive way to
get a large educational group started with the BASIC Stamp.

The HomeWork Boards were created exclusively for educators to send home with students with these uses in
mind:

• BASIC Stamp-related homework assignments

• Dedicated science-fair, contest or hobby projects

• Students who express personal interest in further developing their BASIC Stamp projects but can’t have

their own Board of Education / BS2 due to it’s higher cost

Since it’s less expensive than the Board of Education / BS2 module, can the board be used for Stamps in Class
experiments? Possibly, with the following considerations:

• Servo connection ports for robotics are not included on the HomeWork Board. It’s possible to use

male/male headers for servo connections with a second power supply jumpered to the HomeWork
Board to control servos.

• 220 ohm resistors are built into each of the 16 I/O pins for current protection so the PBASIC interpreter

cannot be easily damaged. This protects the BASIC Stamp from over-current conditions but also
slightly changes the behavior of the Stamps in Class experiments if used on this board based on the
command being used.

• Stamps in Class circuit pictorials do not match the HomeWork Board. Again, minor workaround once

you understand the difference between the power supply options.

• Power supply is from a 9V battery, not the wall pack.

• Current supply from the on-board regulator is limited to 50 mA versus the Board of Education’s amp or

more.

However, these cost-reducing limitations do not limit the use of the HomeWork Board for other projects. In fact,
the minimalist design is simple to use and entirely flexible for most projects.

Parallax, Inc. • BASIC Stamp HomeWork Board ver 1.1 Page 1

Package Contents

The BASIC Stamp HomeWork Board is sold only in quantities of 10. The reason for this is that the board is
intended for the educational market only, to be purchased by educators for use in their classrooms. The kit
includes only the boards – nothing else.

BASIC Stamp HomeWork Board Hardware Design

BASIC Stamp HomeWork Board uses the BASIC Stamp 2 surface-mounted directly to the printed circuit board.
The BASIC Stamp 2 has a wide variety of available support hardware, code examples and applications. Further,
it performs most of the same functions of the newer BASIC Stamps though with less speed and memory. The
BASIC Stamp 2’s technical specifications are shown below (Table 1). Also review the hardware (Figure 1) and
schematic (Figure 2).

Table 1

BASIC Stamp

HomeWork Board

Specifications.

Microcontroller: PIC16C57 surface mount
Speed: 20 MHz / ~4,000 instructions per second
EEPROM: 2K bytes (program and data)
Program Length: 500 lines of PBASIC
RAM (variables): 32 bytes (6 for I/Os and 26 for variables)
Input / Outputs: 16 (up to 17 RS-232 communication ports)
Source / Sink Current: 50 mA / 50 mA
Serial Communication: 300-50K baud I/O
Current Requirements: 7 mA running, 50 uA in sleep
PC Interface: Serial port

Power Supply:

Environment:

HomeWork Board Size: 3” x 4”
Project Area: Built-in breadboard on StampLab
Microcontroller: PIC16C57 surface mount
Speed: 20 MHz / about 4,000 instructions per second
EEPROM: 2K bytes (program and data)
Program Length: ~500 to 600 lines of PBASIC

5 V through an LM2936 regulator from a 9V
transistor battery
32 to 158° F (0 to 70° C), 70% non­condensing humidity

Parallax, Inc. • BASIC Stamp HomeWork Board ver 1.1 Page 2

Figure 1

B

StampLab printed

circuit board keyed

with part

identifications.

S

T

A

M

P

i

n

S

C

L

A

S

S

A

P15
P14
P13
P12
P11
P10

H

Power

GG

Reset

F

BASIC Stamp HomeWork Board



P9
P8
P7
P6
P5
P4
P3

E

P2
P1
P0

[phone]
www.parallaxinc.com
www.stampsinclass.com

C

Vdd VssVin

X3

X4

D

© 2002

Rev A

A. BASIC Stamp 2 Module. The BASIC Stamp is comprised of several components: PIC16C57-20/SS

- a Microchip 2K 8-bit microcontroller programmed with the the BASIC Stamp “Interpreter” that runs
the Parallax BASIC Stamp code like a mini operating system; the 24LC16B EEPROM - a Microchip
2K EEPROM (electrically erasable programmable read-only memory) with a user-modifiable read­only memory (ROM) that can be reprogrammed with your BASIC Stamp code; a 20 mHz resonator
to provide an accurate clock source for the BASIC Stamp; 220 Ohm resistors across the I/O pins to
provide current protection for mistake wiring; an LM2936 voltage regulator which provides 50 mA for
the BASIC Stamp and your circuits powered from the breadboard’s Vdd connection.

B. DB-9 Female. The DB-9 port connects via serial cable to your PC’s serial port. This port is used to

download programs to your BASIC Stamp and for the BASIC Stamp to send data back to the PC.

C. Power and Ground Connections. Vdd is regulated 5V, Vin is 9V from the transistor battery, Vss is

ground.

D. Breadboard. Two areas of 5 column x 17 row breadboard project area. Connections are horizontal

separated by the trough.

E. Power Button. Illuminated when the BASIC Stamp is running a program only.

F. Reset Circuit. Reset the BASIC Stamp by pressing this button.

G. Battery Tie-Downs. If using the HomeWork Board Through-Hole Version for projects involving high-

vibration (on R/C airplanes, robots, etc.) a “zip-tie” can hold the battery firmly to the board if looped
through these holes.

H. Power Supply. Accepts a 9V battery.

Parallax, Inc. • BASIC Stamp HomeWork Board ver 1.1 Page 3

Figure 2

BASIC Stamp

HomeWork Board

Schematic

Vin

Vdd

20 MHz

N/C

Vdd

A0A1A2

R1

R2

RN1-2

Dat

Clk

24LC16B

Vss

Vss

13
12
11

10
9
8
7
6
5
4
3
2
1

X3

X4

16

Vss

P9

P10

P11

P12

P13

P14

P15

Ω

10k

Ω

100

D2

0Ω

Ω

PowerLED

4.7k

P15

26

Vss

RC7

OSC1

OSC2

U1

VSS

RTCCI2VDD3VDD

1

4

Vdd

0Ω

RN5

RN4

22

22

P8

P9

P10

P11

P12

P13

P14

RC0

RC1

RC2

RC3

RC4

RC5

RC6

(PBASIC2/SS)

PIC16C57-20/SS

RA05RA16RA27RA38RB09RB110RB211RB312RB4

P0P1P2

Vss

Breadboard

123456789101112131415

P0P1P2P3P4P5P6P7P8

0Ω

RN3

22

P4

P5P6P7

15161718192021222324252827

RB5

RB6

RB7

VSS

13

14

Vss

P3

0Ω

RN2

22

µF

C1

10

+

Vdd

3

VOUT

VIN

VR1 LM2936

1

Vin

9V Transistor

Ω

RN1-4

4.7k

Ω

4.7k

RN1-3

Vdd Vdd

Ω

10k

Ω

10k

Vdd

2

VSS

Battery

PB1

Reset

1/2 UM11TN

DTA114EETL

1/2 UM11TN

Ω

RN1-1

4.7k

162738495

Vss

Vss

Vss

Ω

10k

Ω

10k

Ω

10k

Ω

10k

Vdd

U2

Vss

µF

µF

C4

C3

0.1

0.1

J2

DB9 Female

Power Consumption and Battery Life

Parallax normally designs BASIC Stamp boards with power jacks for wall transformers. Wall transformers provide
plenty of power but they are not as portable for science fairs, robots and environmental datalogging. Considering
that the BASIC Stamp draws only small amounts of current it could be deployed in a remote location and run
from a battery for a long time.

The BASIC Stamp has commands for reduced power consumption, but what about the power indicator LED? It
could drain the battery in a day or two by itself if being used to indicate a power supply! LEDs consume current,
typically 10-12 mA. Removing the LED wasn’t an option since it discloses the common technical support problem
of a missing power supply.

The solution was to connect BASIC Stamp HomeWork Board’s power LED to the “clock” line of the BASIC
Stamp’s EEPROM. The EEPROM’s clock line is active only when the BASIC Stamp is actually running a
program. Moreover, the BASIC Stamp HomeWork Board’s power LED is a low current LED consuming only
about 2 mA.

Parallax, Inc. • BASIC Stamp HomeWork Board ver 1.1 Page 4

MilliAmp hours is a statistic measuring the amount of energy stored in a battery. For
example, if you have a 1 mA-hr battery and a project drawing 0.5 milliamps, the battery
will last for two hours. A typical 9V Duracell alkaline transistor battery provides about
565 milliAmp hours of energy.

If the BASIC Stamp is being used in a project where at least some small amount of time is spent doing nothing
you can put it in a low-power mode to extend battery life using the SLEEP command (Table 2). The duration
which you put the BASIC Stamp to SLEEP is accurate to ± 1% at 75° F and can ranges from 2.3 seconds to 18
hours (you can “wake up” and go back to sleep after 18 hours). By comparison, the PAUSE command is simply a
delay in a PBASIC program yet the BASIC Stamp continues to draw full operating current. See the BASIC Stamp
Windows Editor on-line help for all the details on the SLEEP and PAUSE commands.

Table 2

BASIC Stamp 2
and Power LED

current draw

during different

modes of

operation.

Note: 1 mA is 1/1,000th of an Amp. 1 microAmp (µA) is 1/10,000th of an Amp.

PAUSE Mode

SLEEP Mode 40 µA 0 mA (565 mAh/(40 µA/1000

BASIC
Stamp

Current

Draw
8 mA 2 mA (565 mAh/10 mA)

Power LED

Current

Draw

Possible Battery Life

= 56.5 hours

mA) = 14,125 hours

Maybe putting a BASIC Stamp to SLEEP permanently only demonstrates that a 9V battery can last almost two
years if you wake the BASIC Stamp once in a while. In reality, projects need to wake up and provide current to
“loads” like LEDs and other chips used in your project. If you know the current draw of the individual components
and how long they are activated you can make an educated guess at total current consumption and battery life. If
you’re only visiting your North Pole weather station annually even a small battery can provide a long lifespan for
the BASIC Stamp, not to mention larger batteries with more milliamp hours.

To clarify the BASIC Stamp’s different power consumption operating scenarios and their effects on battery life
review the following two programs in conjunction with Table 2. Downloading and understanding these programs
will require a look ahead to future chapters, so be prepared to re-visit this section.

Both programs have the same result. The BASIC Stamp will send numbers to the BASIC Stamp Windows Editor
debug window and then go into a period of inactivity for a second. With the PAUSE example the power LED
remains on because the EEPROM is still communicating with the BASIC Stamp interpreter chip, but with the
SLEEP example the EEPROM is shut down and the power LED is off.

With this example the Power LED remains on when the PAUSE command is executed. Current consumption
remains at 10 mA.

' POWER DEMO - PAUSE.BS2
' Demonstrating the power LED with SLEEP command
' {$STAMP BS2}

' I/Os, Constants and Variable definitions
loopCounter VAR Byte

' Main Program
Start:
FOR loopCounter = 0 to 99
DEBUG Home, "loopCounter =", dec loopCounter
NEXT
PAUSE 1000
GOTO Start

Parallax, Inc. • BASIC Stamp HomeWork Board ver 1.1 Page 5

With the SLEEP example the Power LED turns off when the SLEEP command is being executed because the
EEPROM is inactive. Current consumption is 10 mA while the loop is being executed but drops to 40 µA during
the SLEEP command.

' POWER DEMO - SLEEP.BS2
' Demonstrating the power LED with SLEEP command STeve
' {$STAMP BS2}

' I/Os, Constants and Variable definitions
loopCounter VAR Byte

' Main Program
Start:
FOR loopCounter = 0 to 99
DEBUG Home, "loopCounter =", dec loopCounter
NEXT
SLEEP 1
GOTO Start

Precautions

Be alert to static sensitive devices and static-prone situations. The BASIC Stamp, like other integrated circuits,
can be damaged by static discharge that commonly occurs touching grounded surfaces or other conductors.
Environmental conditions (humidity changes, wind, static prone surfaces, etc) play a major role in the presence of
random static charges. It is always recommended to use grounding straps and anti-static or static dissipative
mats when handling devices like the BASIC Stamp. Since you don’t have a dissipative mat, touch a grounded
surface after you have approached your work area. This isn’t as critical as you might think but being prudent only
protects your hardware.

Before building circuits, disconnect the battery.

Parallax, Inc. • BASIC Stamp HomeWork Board ver 1.1 Page 6