Old Foot Pressure Sensors Page

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When I first got a Bioloid kit to play with, one of the first things I noticed was these strange, keyhole-shaped indents in the bottom of the feet. It wasn't clear at all what these indentations were, but after I got my hands on some FSR pressure sensors, it became clear.

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This page is going to detail how to add pressure sensing to the Bioloid's feet. Each foot has four indents, and the four pressure sensors on each side will feed into a custom ATmega168 board that becomes a bus sensor.

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This is the real (tiny sized) prototype foot pressure sensor board, mounted on one of the feet... The board is 1" long by 3/4" wide.

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Here's a prototype of the ATmega168 board:



You can see the bioloid bus connector on the bottom left. Next to it is a 9-pin SIP header, which allows me to plug my USB -> TTL converter into the board, and talk to the ATmega168 directly from my PC over the hardware UART. The two-pin header above the bus header is for a jumper, which ties Tx and Rx together for when it is plugged into the bus.

This ATmega168 is running at 8 MHz, because I need to be able to run it at 3.3 volts. The voltage regulator for the board is (for now) a 78L05. I put it in a SIP socket so I could replace it with a 3.3 volt regulator once I get my hands on one.

The six 3-pin headers at the top center are hooked up to the six A/D ports of the chip. The other two pins in each 3-pin header has Vcc and ground.

Finally, the programming header (6 pins) is on the top right.

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This is the circuit board (3/4" x 1") that the four FSR sensors will plug into. It will be a bus sensor, and will plug into the spare jack on the AX-12 in the foot that controls foot pitch.

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