Table of Contents

Summary of Changes to Sumovore and Brainboard 2

by Dan Peirce B.Sc. March 18, 2010 (rev. Nov. 2014)

In 2014 a significant modification was made to the Richmond campus robots in that that now use four AA lithium batteries. Before 2014 six AA alkaline batteries were used.

The Purpose of the Modifications

The purpose of the modifications listed on this page are each for one of the following reasons:

  1. To make the robot hardware more reliable. Reliability is essential. It is virtually impossible for the students to have reasonable success modifying their programs in a resonable amount of time if the robot hardware does not behave consistently. The PIC has now being configured to watch for out for low voltage conditions.
  2. To make in circuit programming with the PICkit2 possible.
  3. To make the robots as interchangeable as reasonably possible. A program should work equally well on any of the robots (to the extent reasonably possible).
  4. To simplify the task of building the robots (i.e. leaving off unnecessary components the robot was designed for the mini-sumo event and doubles for line following as a secondary purpose. We only do line following because it is a better programming task. Also, the florescent tube lighting and electronic ballast used in our labs can interfere with the IR opponent detectors [IR DET1, IR DET2] as the florescent tubes age).
  5. To use long lasting Lithium batteries.
    1. The voltage from the lithium batteries is more consistent than from alkaline batteries.
    2. The robot speed is also more consistent.
    3. This means the time of travel is more consistent.
    4. The motors are actually rated for six volts not nine volts. Using four lithium batteries should extent the life of the motors.
  6. The use of a smaller main battery voltage requires a regulator for the digital electronics that can maintain a regulated output even when the battery voltage drops below six volts. This is why the DC-DC converter is used in place of the linear regulator.
  7. To avoid damaging the track electricians tape covers the bottom of the scoop.

Robot 1.1

Require new image since two cell battery pack is removed and linear regulator has been replaced with DC-DC converter

This image shows parts that I am not installing when building the new version 1.1 robots.

  1. IR DET1, IR DET2, LED1, LED2 not needed saves build time LED1 and 2 only confuse our students and waste battery power.
  2. IC1 removed because it interferes with changes for dynamic braking. I leave the socket off to save build time. This IC is essential if one were to use the discrete brain board that comes with the sumovore but we don't use it. I save those parts for other things.
  3. C2, C3, R3, R4 without IC1 they don't do anything I leave them off to save build time
  4. Linear regulator replaced with DC-DC converter board. add details
  5. Two cell battery pack from top of main board is removed and replaced with a wire short.
  6. Test point added to main board to check battery level .

This image is actually of main board 1.0 but the position of Diag1 is about the same on version 1.1 board (just slightly farther from switch and the Ziptie ref. no longer exists on the newer board)

Sensor board on version 1.1 robot

Note most of the parts left off.

All copper is coated with solder to avoid oxidation. Note IC4 does not do anything good for us. It just creates some EMI that could possibly cause spikes on the sensor outputs. LED4 and LED5 just waste battery power. TP1 is for adjusting 555 frequency and is not needed.

Robot 1.0

  1. Replaced linear regulator with DC-DC converter.
  2. Two cell battery pack from top of main board is removed and replaced with a wire short.
  3. IC1 removed from socket. removed because it interferes with changes for dynamic braking
  4. test point added to main board to check battery level

Sensor board on version 1.0 robot

PIC Brainboard #2

  1. PIC16F877A is replaced with a PIC18F4525

    1. PIC16Fxxx components are not optimized for C while the PIC18Fxxxx components are
    2. PIC16Fxxx components have only a 8 level hardware stack while PIC18Fxxxx components have a 32 level hardware stack. this makes the PIC16Fxxx components much more prone to hardware stack overflow problems which is bad when one is encouraging students to create functions. Also the printf() function itself is a wrapper that calls functions that call functions (all in the stdio module). It is easy to exceed 8 levels of function calls.
  2. Resonator not installed we use the internal osc

  3. I2C connector not installed. we don't use it

  4. Reset switch not installed instead we use the two holes for our programming adapter board see below

  5. In Richmond I change 5 resistors (under the PIC) so that the sensors do not go into saturation even above white paper (resistors chosen in an attempt to get same response to grayscale for each sensor).

  6. Two jumpers added for dynamic braking. E1 to p13 of P2 and E0 to p15 of P2.

  7. a header with wires attached is hot glued under the PIC board to provide a connection for programming.

    There are four connections between the two boards (see four pins). The two pins that are 0.4 inch apart fit into the holes where the reset switch would have been. The two pins close together fit into the holes for B6 and B7. Those four points are indicated in the image below.

New image required since two cell battery pack has ben removed.

All Robots

Tape sensor board to front scoop.

Layer #1 folded over bottom edge of scoop Layer #2 wrapped around scoop from end to end to keep layer #1 from lifting Layer #3 wrapped around sensor board and scopp from end to end to keep sensor board tight against scoop and to try to keep sensor board from moving.

Close up from end showing tape wrapped around bottom edge of scoop (upside down)

New passive cable to be used with version 2 brain board A simple passive cable is needed to connect between the robot and the PC COM1 port. Page 13 of the PIC brainboard V 2.0 manual PIC brainboard V 2.0 manual shows the connections between the DB9 connector and pins that fit into the brainboard. As suggested I used a cable from a dead serial mouse for the connector and cable.