Dale's Homemade Robots

IR Bump Sensors

Front Infrared Emitters

The front of the vacuum robot is equipped with infrared emitters. There are three sets to cover areas directly ahead and to both sides. The reflected infrared pulses are picked up by the sensors on top of the robot show below. Each of the 3 sets has both high and low power emitters. The low power emitters are used to avoid obstacles. The high power units are used to send pulses up to 15 feet to the Homing beacon transponder . Also seen here are the left and right foam padded bump switch assemblies.

Top Mounted IR Sensors

The sensors are the type used in IR remote controls for VCRs and TVs. These are designed to respond to IR energy which has been chopped at a 40 kHz rate. Note there are both left and right sensors. These are used to guide the robot to the homing beacon as well as avoiding obstacles. Also seen here in front of the IR sensors is the top bump switch assembly.

Since there are only 2 IR sensors used for detection of 5 IR emitters and the homing beacon I had to devise a means of discriminating between all the sources. This is done with time slots. Each emitter is only active during it's assigned time slot of about 500 microseconds. The receivers know which emitters signal they are receiving based on the time slot value. The homing beacon's response pulse is delayed 3500 microseconds to make sure any false activaitons don't fall on any of the sensor time slots.

Beam Interruption Emitters

There are left and right emitters that are line of site to the top mounted IR sensors. When the robot attempts to roll under furniture at least one of these emitters will become hidden and the beam broken. The main control processor then issues a back out command.

• Source Code for PIC 16C73 IR sensor controller
• Schematic (gif image, 165K)