Ramsey Electronics Walking Electronic Bug WEB1 - Manual (Page 4)

WEB1 • 4
INTRODUCTION
Here is a very unique little kit that’s great for kids. The WEB1 is a little robot
made completely out of electronic parts and wire. It’s pretty easy to build, and
once it’s adjusted properly, it will entertain for hours. It has little pager motors
in it that vibrate and propel it on its little wire feet. How fast it goes is
adjustable by bending its feet and also by a pot that controls motor speed.
When it approaches an obstacle such as a wall, it turns to avoid it. It does
this with a second little pager motor.
WEB1 CIRCUIT DESCRIPTION
This is a fairly simple circuit, and easy to follow even for a beginning kit
builder. The kit uses a 555 timer U1 to pulse the two pager motors. The 555
timer does not directly drive the motors, but instead turns them on through
transistors Q1 and Q3. This is done because although the motors don’t draw
much current on average, they do when they initially start spinning. The 555
objects to these big current spikes, so the transistors take the beating
instead. Normally only one motor is running and the WEB1 moves in a
straight line. In this state, U1 is pulsing Q3 which drives the motor attached to
pad P1. This motor’s speed is adjustable via R2. When the WEB1 gets close
to an obstacle, infrared light emitted from D1 bounces off the object and into
the infrared phototransistor Q2. Then Q2 switches on and turns on transistor
Q1 which drives the motor attached to pad P4. This motor causes the WEB1
to turn aside from the obstacle. The sensitivity of phototransistor Q2 is
adjustable through R5. Without this adjustment, sometimes room lights would
turn Q2 on and make the WEB1 turn all the time. Okay, let’s get building.