St Albans Robots

http://www.picaxe.com/BASIC-Commands/

http://www.picaxe.com/docs/picaxe_manual2.pdf

Watch video https://www.youtube.com/watch?v=ewokFOSxabs

Play game https://studio.code.org/projects/applab/iukLbcDnzqgoxuu810unLw

(see above for example)

Setting pins

Toggling pins

If statements

Reading analogue values

Pause

Playing sounds

Reading switch

Piezo sounder

Infrared receiver

LDR (Light sensor) -  Analogue reading

Touch sensor

BASIC

PYTHON

Assignment

let pins = %10101111

pins = %10101111

Comparison

If statements (selection/decisions)

if condition then

    *do this*

end if

if C.1 > %10101111 :

        b7 = 500

If… else

if condition then

    *do this*

else

    *do this*

end if

if condition :

     *do this*

else:

     *do this*

If… elseif… else

if condition then

    *do this*

elseif condition then

    *do this*

elseif condition then

    *do this*

else

end if

if condition :

     *do this*

elif condition :

     *do this*

elif condition :

     *do this*

else:

     *do this*

Select case statements

For loops (count controlled)

for i in range(1,20):

      if pinC.1 == 1:

            break

While loops (condition controlled loops)

while pinC1 == 1 :

      *do this*

Forever loops (infinite loops)

while True:

     *do this*

Exiting from a forever loop (the exit command)

while True:

     *do this*

     if condition  :

           break

Subroutines

flash()

flash()

def flash():

     high B.1

     pause 500

Delay

import time

time.sleep(1000)

1: Light  LED with pauses.

LED on/off pin B.3  (there's also an LED on B2)

(flash on / off - pause)

Choose pause time.

BOT115 example 1 page 16, flashes 2 LEDs alternately.

http://www.picaxe.com/docs/bot115.pdf

2: Push button + LED

See BOT115 example 2, Page 17.

- LED on/off pin B.3

- if pin c.1 =1  (decision)

- push for on, push again for off

- long press for flash.

Extension : detect long press, and give slow flashes.

http://www.picaxe.com/docs/bot115.pdf

3:  LDR + LED

Read analogue voltage

- debug LDR on B.1

- flash LED with speed depending on LDR ( pause length)

- potentiometer on C.2 - > debug.

  Use potentiometer to set threshold for light alarm.

  readadc B.1,B0

  readadc C.2,B1

  if B0 > B1 then .....

4 Piezo  B.5

- "sound" command with pitch/duration.

- "play" command (4 tunes built-in)

- piezo pitch depends on LDR light level.

Extra 1: make piezo play by manually pulsing high, then low.

See what toggle does with no delays on loop.

Extra 2:

Simple loop with toggle. BUT. Run with different processor speeds!

Use setfreq m4 for normal, up to setfreq m32. 8 times faster.

5 TV remote + piezo.  B.0

- select tune to "play" based on digit pressed.

- enter 2 digit number for "sound" command.

6 Virtual pet

If you cuddle it, it purrs (buzzer)

- temp sensor to detect cuddle  C.6

- pulsed buzzing for purring.   B.4  purr purr....purr purr....purr purr....purr purr....

7 Fridge alarm

- temp sensor  C.6

- LDR          B.1

- buzzer.      B.4

Buzzes if it gets too warm.

Buzzes if door open (light) for too long.

8 Parking distance sensor

- Sharpe single analogue input.   C.2

- sound buzzer more quickly as you get closer.   B.4

- sound continuously when too close.   B.4

Use analogue signal to calculate distance in cms.

Dist = 13 / signal voltage in volts.

See

https://www.smart-prototyping.com/blog/Sharp-Distance-Measuring-Sensor-GP2Y0A41SK0F-Tutorial

Use maths to calculate pauses, and a decision as to when to make it continuous.

9 Debug techniques.

- send message back up the download lead on power up

   sertxd("This is BOT115 example 2a",13,10)

- debug screen to see all your data items

   debug

10 Stationary Line Follower

Control 1 motor using pins B.6,B.7

Read a line position sensor on C.2.

Mount the motor and the line sensor so that the rotation of the motor shifts the sensor sideways.

Your program should stop the motor if the sensor is central (120) within a margin of +- 20.

If > 140 then drive the motor forwards.

If < 100 then drive the motor backwards.

OR maybe the other way round, depending on the electrical connection to the motor, or mechanical arrangement.

Enhancement:  make the line signal be corrected according to speed of change (or Derivative)

Corrected = (this reading - previous) *

Constant + this reading.

Then use corrected signal instead of this reading.

So that it stops earlier if it's already heading towards the centre.

Use a mechanical linkage to drive it nearer/further from the wall.

11:Stationary Wall Follower

Control 1 motor using pins B.6,B.7

Read wall distance sensor on C.2.

Line following techniques

Line Following Techniques

=======================

There are a large number of engineering considerations involved in Line following.

Sensor options

   TCRT5000, (height control above baseboard)

   Hamamatsu sensors (4 digital)

   Adjusting Hamamatsu LEDs

   QTR sensors ( 4 gang, 6-gang)

1 Digital sensor  (Crossing problem/ 2 zones)

2 Digital sensors (inside / line, 5 zones)

3 Digital sensors (7 digital zones)

"Weighted Average" analogue position calculation.

Analogue sensor dark/light calibration.

Intelligent sensor.

  3-zone (2 decision thresholds to set motor speeds)

  5-zone (4 thresholds) "select" in BASIC.

Use of High, Low, and Toggle BASIC.

"Fallen-off" detection /options

Variable speed motors ( 32 zones)

Maths to calculate motor speeds

Proportion

Derivative

Speed controlled by curvature (sensor reading/zone)

Speed reduction (/zero) on fall-off

Sensor position - distance ahead of wheels

TV remote to tune values

Tuning on the fly

EEPROM store for data

___________________________________________________________

Details:

TCRT5000

   a small infra-red LED/ IR receiver that senses

   white insulating tape against a blackboard paint background.

   It provides an analogue output reading from 50-60 for black,

   to 230 odd for white at a distance of 9mm. BASIC "readadc"

   The reading needs the backgrond value (black) subtracted from the value,

   before it can be used in weighted-average calculation of line position.

It is simpler to simply use it as a digital sensor: on the line or off.

Hamamatsu

   this is a white light optical sensor that also controls (modulates)

   the illumination LED(s).

   It correlates the sensor reading against the illumination pattern

   to give positive indication of "white"

   Digital only, but can be used with a single sensor and multiple LEDs to

   provide up to 6 detection zones. It can only give a digital yes/no,

   and requires extra hardware and some software/ output ports, to run with multiple LEDs.

   Used in original Wham! robots. BASIC : complex subroutine.

Intelligent sensor

   this uses 3 TCRT5000 sensors spaced 10 mm apart to detect

   the position over a 19mm white tape.

   It uses an 08M2 Picaxe chip to process the 3 analogue signals

   to a single analogue output. 

   It uses the reducing analogue outputs profile as each sensor passes over the tape

   to calculate a number in the range 0-31.

   The DAC output from the 08M2 restricts the granulatity.

Proportion

   The speeds for each motor are calculated from the formulae:

   BaseSpeed + Kp* (sensorPosition- centre value)  (right motor)

   BaseSpeed - Kp* (sensorPosition- centre value)  (left motor)

   where Kp is the proportional coefficiant

Derivative

   This is intended to increase stability.

   The instability is caused by the time delay between sensing the position over the line

   and the speed changes actually resulting from the changes in motor voltages.

   The technique requires storing the sensor reading from a previous sample

   (10 ms or so) and combining that with the current reading, to calculate a future reading.

Mr Fisher

12/11/2019

Intelligent line sensor

About the intelligent sensor.txt

This sensor uses 3 Infra Red detectors (TCRT5000) to measure its position on a white line.

It produces an analogue value (in the range 0 - 230) to show where it is.

----

0 is at the very left, or fallen off the left hand side.

230  is at the very right, or fallen off the right hand side.

110 is the middle of the line. (approximately)

----

The sensor has 3 connections, Ground, Power and Output.

The connector has 5 pins pointing downward. From the left hand side;

1: +5 volts power

2: not connected

3: not connected

4: Output 0-5volts

5: Ground 0 Volts.

----

When you switch on, you should "show" it the line.

It needs to measure the blackness of the background, and the whiteness of the line.

Switch on with the sensor to the left of the line.

Slowly drag the sensor across to the line, and continue till it is to the right of the line.

You can use the Analogue Output to steer your robot so that it follows the line.

Subtract the center value (110) from the Output and you have a number that is zero in the middle,

positive to the right, and negative to the left.

You need to multiply this number by a fraction - say 10/50 to reduce it so that the robot doesn't over-steer.

Then add this to the speed of the right wheel, and subtract it from the speed of the left wheel,

 and the robot should steer appropriately.

WARNING: Picaxe basic doesn't do negative numbers. So do the *10/50 on the reading, before subtracting 110 * 10/50 (=22) from the result.

Actually it does do negative numbers but they are indistinguishable from large positive numbers. Effectively it adds enough 256s to bring it positive again.

Consider:

7-9 gives  254  which is 256-2.

254 works as -2 when you add it to something.

10 + 254 gives 8. That's because, if the answer is greater than 255 it subtracts 256 until it is <256.

Look up "modular arithmetic"