Let's Make Robots!

Edwards circuit board

I got some questions from Adobi123 on the design of the board I built for Edward. I dont have any schematics cause it was done on the fly by laying the components on the board and trying out which locations would fit best. Anyway; I made a description of the components I used and I'll link some of them to relevant pages with documentation.

The board

  1. V2 Power connector (7.2V)
  2. Diode (on Voltage line) to protect the board when power is connected the wrong way. (Has been removed to get more volts to the motors)
  3. Powerswitch header. In the picture connected with a jumper, in edward it's connected to a switch
  4. 10uF cap
  5. 7805 Voltregulator (5V)
  6. V1 connect header. When closed with jumper: logic circuits and inputs are powerd by the regulated 5V
  7. 0.1uF cap
  8. 5V power out + Gnd or, if jumper 6 is removed, V1 power connector
  9. V2 power LED
  10. V1 power LED
  11. Reset button header
  12. LED1 (connected to 28X1 output pin 3(?)
  13. LED2 (connected to 28X1 output pin 4(?)
  14. Right IR sensor : SHARP GP2D120 (analog pin 1)
  15. Left IR sensor : SHARP GP2D120 (analog pin 0)
  16. Capacitator 0.1uF for right IR
  17. Capacitator 0.1uF for left IR
  18. I2C jumper to connect the 22K pullup resistor. Remove if another I2C device already has a pull up resistor
  19. Mem chip1: 24LC256 /32KB :  address=%10100000
  20. Two I2C connectors for other I2C devices such as the LCD. (V1, SCL, SDA, Gnd)
  21. Mem chip2: 24LC256 /32KB:  address=%10100010
  22. Connector for SRF05 (V1, output pin 0, input pin 0, Gnd)
  23. Push button connector (input pin7)
  24. Head Servo (up/down) connector (output pin 6, V2, Gnd)
  25. Neck Servo (left/right) connector (output pin 7, V2, Gnd)
  26. Motor connector (A1, A2, B1, B2)
  27. L293D motor driver chip
  28. PicAxe 28X1 CPU



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On the fly layouts, thats the best...never sure how they end up working in the end espeically when they are larger projects...but somehow they do!  :)
Still having problems with the display resetting. I'm going to open up edward to see of a larger (4.7uF or 10uF) cap on the power and GND will do the trick.
We are not quite sure why you added the .1 compactors for the IR sensors. We couldn't find out why on the online schematics for the sensors?

Thats what they say, anyway. Put a capacitor on every power and ground right next to each device. If you google the stability issues on the IR sensors you find the SHARP actually recommends putting a cap there. also read this. I put caps all around the board. Just in case. Can't hurt either.


Thank you! This has been super helpful, thanks again.