5-motor walker circuit

Posted on Feb 5, 2014

The P5 design uses only eight 74HC/AC240 chips which are all octal inverting buffers. Each 74HC/AC240 chip has two groups of four inverters each controlled by a tri-state enable pin (pin 1 and 19). The 74AC240 chips (U1-U5) are used as H-bridge style motor drivers since they have almost double the drive current compared to 74HC240 chips. These mot

5-motor walker circuit
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or driver chips are permanently enabled by grounding control pins 1 and 19. The two groups each have four inputs connected in common to a bicore output and the four outputs are connected in common to one motor winding terminal. Since each bicore has two complementary outputs the voltage across the motor winding causes the motor to rotate back and forth. The 74HC240 chips U6 and U7 are each used to form a master - slave bicore pair with reverser. The inverters used for the bicore s are permanently enabled by grounding pin 1. The inverters used for reversing are turned on or off with the tri-state enable pin 19. Only 2 of the 4 tristate inverters are used conventionally for reversing the phase of the slave bicore s while the other two are put to a novel use: one inverter is used to provide positive feedback to the enable pin and the second spare inverter is used to turn on a RED flashing LED when the reverser is active. The flashing LED also provides diagnostic visual indication of the operation of the slave bicore. The 74HC240 chip used for U8 provides a reverser and a slave bicore for the waist motor as well as a monocore (a. k. a High Low Oscillator) photobridge comparator which controls the phasing of the front and rear motors. I) The photobridge comparator uses 2 inverter s from U8 connected in series as an voltage controlled oscillator with complementary outputs to generate three states : If the left photodiode gets...

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