PICAXE Tutorial

11c. Musical Tunes

Music can be created by writing your own directly, using the Tune Wizard or by importing pre-made tunes (mono Ringtones). See Man 2, pg 242-9, Man 3 pg 11.
Tunes are produced using standard musical scales in three octaves similar to a piano. Different tempos can be set for 1, 1/2, 1/4, 1/8.
 
Command — Tune 2, speed, (note, note, ...)
 
2 — refers to output pin
 
speed — variable or constant (1 — 15) creating the tune’s tempo.
 
note — In note $70, 7 refers to Octave (5 — 7). Last number/letter refers to the note (C, C#, D ...)
 
'LetItRain
tune 2, 6,($70,$7C,$7C,$7C,$73,$7C,$7C,$73)
 
 
Import Tunes
 
Tunes can be downloaded from PICAXE
 
Download ZIP file in new folder and unpack
 
a). For TV and Christmas Downloads as file.bas
    1. Open PICAXE programme window. (no need to use Tune Wizard)
    2. Select Open > Select your tune.bas> Open
    3. Open in new window
    4. Play = Simulate
    5. Try altering speed. 1 is high
 
b).Mixed Tunes 1 — 3 Downloads as file.txt
    1. Open PICAXE > New > Wizards > Ring Tones Tunes > Tune Wizard
    2. File > Import Ringtone > select file.txt > open
    3. Edit > Copy Basic
    4. “Paste into main document” > Yes > Close Tune window
    5. Play and change speed
 
c). Download free Abba SOS
    1. Copy mono RTTTL Ringtone
    2. Open PICAXE > New > Wizards > Ring Tones Tunes > Tune Wizard
    3. Edit > Paste Ringtone
    4. Edit > Copy Basic
    5. Yes
    6. Play

12. Flashing LED’s using PULSOUT

Using PULSOUT to control the length of LED pulse and delay.
Only one pulse will be obtained so a pause is added to create the delay before looping back to start again.
 
main;
pulsout C.1, 500 ; output on pin C.1 (leg 6), pulse 5ms
pause 200 ; pause 20ms
goto main ; loop back
 
pause — Man2 pg 145 — value in ms, 0 — 65535. eg 5000 = 5 sec
pulsout — Man 2 pg 206 — value in 10usec units, 0 — 65535. eg 150 = 1.5ms

Newbury Harbour Lighthouse. Oc (2) G 15s
Occulting twice, Green, every 15s. Sequence 7s on, 2s off, 4s on, 2s off

13. Use of R/C transmitter/receiver as a source of input

Sailservo has researched servos and receivers and found most information supplied to be suspect. To get an idea of real torque values divide manufacturer’s values by three or four. You should not use motors below about 50% speed drop so use this value when initially choosing your minimum duty cycle.
 
There is no such thing as a standard receiver output PWM pulse value. It differs between channels and even similar receivers
920us was the lowest found during tests and 2140us the highest.
1100 to 1900us is an approximate average with a range of 800us.
 
The joystick central position is not what you expect at 1500/1510us.
My Spektrum Dx/5e + orange receiver gave 1410 to 1430 depending on which side you moved from. That’s a 20us variation.
Set the trim buttons for each channel at their central position so you can make fine adjustments later.
 
When you are changing your code for different situations you may have to overlap the values to get correct working. In one instance, the motor suddenly went to max revs when it should have been off.
 
if w1 < 125 then = if w1 is less than 125
if w1 > 115 then = if w1 is more than 115
100us overlap
 
Altering frequency from 4 to 16MHz increases accuracy
 
if w1 < 561 then
if w1 > 559 then
Overlap is 560 +/- 1 = 10us
 
Buy the Picaxe oscilloscope (£12) to see what’s happening. Can also be used to check voltages in your circuit.
To find accurate values goto Utilities — Measurements — Waveform measurements.
 
If you change transmitter or receiver, you may have to alter your coding. Sailservo’s EPA End Point Adjuster could help if you don’t have a computer transmitter.
 
I’m afraid, it is all trail and error. The coding has been made to be easily adjustable.
 

13a. Fixed inputs Ch5 switch

Simple circuit using the landing gear switch on the transmitter with the receiver outputing via Ch5. The pulse signal is feed into C.3 on leg 4. Two LED’s are feed from outputs C.1 & C.2.
Red led is on when switch @ 0 and green @ 1
Receiver power from Picaxe supply.
 

[CODE]
 
init: w1 = 0
 
main:
pulsin C.3, 1, w1                   'State 1 = low to high pulse starts timing
if w1 < 135 then redled        'if w1 is less than 135 then red LED
if w1 > 165 then greenled     'if w1 greater than 165 then green LED
 
redled:
low C.1            'leg 6 switch off green LED
high C.2           'leg 5 switch on red LED
goto main        'loop
 
greenled:
high C.1           'leg 6 switch on green LED
low C.2            'leg 5 switch off red LED
goto main        'loop
 
[/CODE]
 
Research carried out by SailServo has found that R/C receiver output pulses differ for all manufacturers, models and even channels.
 
Receiver output test. Checked with GWS MT1 Servo Tester.
 
Min/max range found was 920 to 2140us. (different receivers)
Max range 1149us.
 
Low values from 920 to 1320us.
High values from 1692 to 2140us.
 
Using 135 and 165 will cover all possible receivers as they are above and below all known values.
 

 
The pulse feed is directly from the receiver giving an amplitude of 3.3v. However, the positive pulse height is only 2.5v which is getting close to the minimum +2.0v for picaxe logic high. To avoid this problem a transistor is added between the receiver and picaxe. As the transistor reverses the polarity, the pulse is measured at the traing edge and the Pulsin state code has to be changed to a "0". Simlarly, change the button on the scope "Trigger - Polarity" to falling.
 

 

 
Prototype breadboard setup shows the Picaxe oscilloscope hardware costing £12. The pulse trace shows the high and low values which are similar to the more accurate meter readings
 
Spektrum Dx5e/Orange RX. Ch5 Gear switch = 1102 and 1849us.
 

13b. Variable inputs Ch3 throttle

In this test, the transmitter’s throttle joystick is used as it has no central point. Receiver is channel 3.
The circuit and code remains the same as the previous test 13a.
Red = 0 - 135 and Green = 165 - 190.
As expected, the section between 135 and 165 was being read as “0” pulse and the red led stayed on.
 
To solve this, new code was added to positively turn off both leds between 135 and 165.
 
if w1 > 135 and w1< 165 then noled     'if w1 is more than 135 & less than 165 then no LED
 
noled:
low C.1         'pin 6 switch off LED green
low C.2         'pin 5 switch off LED red
goto main     'loop
 
This caused a problem as both red and green leds flashed together at the change points.
The Picaxe reads the input pulse to the nearest 10us. The meter readings show that it is easy to position the joystick at the middle of the change position so it is neither or both resulting in both leds flashing on.
 
I have no experience to know if this happens in real life but is useful to know if you find both events happening at the same time at the change over position.
 

 
The point of change between on and off was a noticable 10us and could be found by moving the joystick. Both leds flashing

13c. Increasing frequency to improve accuracy

Frequency
The 10us pulse width is determined by the Picaxe’s 4MHz frequency so the test was run again with the frequency raised to 16MHz by adding code “setfreq m16”.
This gives a pulse width four times faster at 2.5us. The cut off point values have to be multiplied by four. The “pulsin” value is more than 255.
 
w1 not b1.
In previous coding b1 was used, b signifying a BYTE variable which can only hold integers/numbers between 0 and 255. w1 is a WORD variable holding 0 to 65535 and has to be used here.
 
[CODE]
 
init:
setfreq m16
w1 = 0
 
main:
pulsin C.3, 1, w1
if w1 < 540 then redled
if w1 > 539 and < 661 then noled       '1us overlap
if w1 > 660 then greenled
 
redled:
low C.1
high C.2
goto main
 
greenled:
high C.1
low C.2
goto main
 
noled:
low C.1
low C.2
goto main
 
[/CODE]

Increasing the frequency and overlapping the values by 1us appears to solve the problem. Moving the joystick does not pick up the flashing leds at the change point. The 2us flashing band is smaller than the joystick movement accuracy.
 
Remember that the code values are totally dependent on the receiver’s output. Trial and Error.
 
This increase in accuracy may be useful for certain applications.
 

13d. ch4 joystick centre

Servos need a central off position which has a narrow pulse width band called the “Deadband” which range from 4 to 7us. The manufacturers specify their servo central position to be 1500/1510us. Unfortunately in real life this value can vary from 1390 to 1590us. Again, trial and error will be needed.
 

A yellow led has been added to simulate the Deadband from C.4 and “noled” code changed to “yellowled”.
 
[CODE]
 
init:
setfreq m16
w1 = 0
 
main:
pulsin C.3, 1, w1
if w1 < 561 then redled
if w1 > 559 and < 581 then yellowled
if w1 > 579 then greenled
 
redled:
low C.1
high C.2
low C.4
goto main
 
greenled:
high C.1
low C.2
low C.4
goto main
 
yellowled:
low C.1
low C.2
high C.4
goto main
 
[/CODE]
 
Joystick movement about the central position is not accurate. If you let the stick spring back to the centre you get 1410us one side and 1430 the other so a wide deadband is necessary.
 
The critical thing is that the stick must always turn off the servo or motor. Again, trial and error. Set the joystick trim button centrally before you start then use it to fine tune the position at the end. 200us variation for throttle Ch3.

13e. ch4 motor control H Bridge

 
L298N is the H Bridge module which sends the correct voltage pulse to control the motor’s speed and direction. It also includes a series of diodes to stop the motor generating a back EMF when power is removed from the motor.
 
The central deadband is easy as everything is off. The motor speed increases either side so the coding is positive going forwards and negative for reverse.
 
The second consideration is that the motor should not be run below 50% speed drop. Below this can stall the motor and increase the current drain.
For example servo Acd1 % speed drop is;
No load 0% = 0.2A. 10% = 0.5A. 30% = 0.7A 60% = 1.0A 100% = 2.2A stall
 
H Bridge setup
12v Jumper. Only remove if using over 12v. (Note, voltage supply specified as 12v on the PCB)
EN Jumpers. Remove. (only used with stepper motors)
 
It is possible to alter the rate at which the motor speed increases from a linear straight line to a curve between 0 and max. Starting very slowly and then rapidly increasing.

13f Ch4 Motor controller

These two tests use previous codes but with Ch4 Rudder as it has the central off position.
 
This test uses a 14m2 Picaxe with a dual L298N H Bridge module to control a single motor from a Tx/Rx receiver. The frequency is left at 4MHz to reduce complications.
 
Picaxe Oscilloscope is used to check and calibrate the receiver input into pin c.3. It is possible to measure the pulse width in msec from the bottom tool bar. It can also be used as a volt meter to check outputs.
 
6.2v battery is used to supply the motor via the H Bridge driver with 5v supplied to the Picaxe and receiver from its onboard voltage regulator.
Normally the receiver will be used to control other servos and will be supplied by its own source. In that case, the red +ve supply in the receiver/picaxe cable must be cut at X.
 
The PWM pulse from the receiver into the Picaxe is significantly different to the PWM pulse from the Picaxe to the H Bridge drive. (See below).
Receiver PWM has a pulse from 1.0ms to 2.0ms repeated every 20ms. (approx).
H Bridge outputs a regular pulse with its width controlling the motor speed. At half power the pulse is only on for half the time.
 
H Bridge setup
12v Jumper. Remove if using over 12v. (Note, voltage supply specified as 12v on the PCB)
EN Jumpers. Remove. (only used with stepper motors)
 
Dirs
The ports on the 14m2 have to be specified as in or outputs. The two PWM outputs to the H Bridge showed correctly working voltages but the motor would not run. It did when I set pin b.1 enable to an output
 
dirsb%00110011,   0 = input and 1 = output. Port numbers run 7,6,5,4,3,2,1,0
b.0, 1, 4, 5 are outputs. Ports 2 and 3 are not used so either 1 or 0 is correct
c.1, 2 are outputs and c.3, 5 inputs. c.0, 4 not used = 00000110
Port numbers not on picaxe are 0
 
Waveform
This shows the input and output waveforms with the joystick just on forwards at 1600us and just before the output goes high at 1800ms. The input waveform goes downwards because transistor between the receiver and Picaxe inverts the input signal. The signal is measured from the trailing edge.
 


 
Symbol names may remain black when you write them. Just check your code and they should turn blue.
 
If you have previously used the USB cable for the oscilloscope you might find you cannot upload a programme if the cable is installed. Odd.
 
I found that you could not uses word variables above w13. Odd.
 
w1 < 100 — less than 100
w1 > 100 — more than 100

13g. ch4 3 position motor control

This test is to make a motor run slowly, medium and fast in one direction with three joystick positions. Left, centre, right.
 
Motors may not turn with a duty cycle below 50%. This minimum value can be found by trial and error.
 
It becomes confusing when you start to use a lot of pin numbers c.2, b.5, so we replace the number with a name and use “symbol”
 
e.g. Symbol redled = b.4
 
Many pins can be used as either inputs or output but in certain cases they must be specified. This programme would only work if b.1 enable was made an output
“dirs = %00000000” sets the pins to input/output. Remember that 0 is input and 1 is output. See code below>
 
Only one pwm output c.0 or c.2 can be used at one time. c.0 makes the motor clockwise and c.1 backwards. Servos are specified as either cw or ccw so you may have to swap outputs.
 
pwmout c.2, 99, 0 sets the period at 99 and duty cycle at 0.
 
This information come from the Picaxe — Wizard — pwm calculator.
Leave the frequency at 10000Hz and clock to 4Mhz. Change PWMOUT pin to your output pin.
 

 

 
[CODE]
 
init:
 
symbol enable = b.1
symbol redled = b.4
symbol greenled = b.5
 
dirsb=%00110011     ; x, x, out, out, x, x, x, out, 1 = output 0 = input.
dirsc=%00000100    ; x, x, in, x, in, out, x, x
 
w1 = 0
 
pwmout c.2,99, 0
 
main:
 
pulsin c.3, 0, w1
if w1 < 135 then slo
if w1 > 135 and w1 < 165 then med
if w1 > 165 then ful
 
slo:
high enable
high c.2
hpwmduty 240    ;duty 60%, stall @50%, h has to be added to pwmduty
 
high redled
low greenled
goto main
 
med:
high enable
high c.2
hpwmduty 320    ;duty 80%
 
high redled
high greenled
goto main
 
ful:
high enable
high c.2
hpwmduty 400    ;duty 100%
 
low redled
high greenled
goto main
 
[/CODE]
 
H Bridge input pulses at three fixed positions
 

 
The upper continious red line is maximum power/voltage being delivered to the motor. It is a straight line at 100%. At lower duty cycles continious power is replaced by pulsed votltage until at 50% it is a continiously pulsed. At this point the motor is getting insufficient power/voltage to turn.
 

14. Throttle Ch3 controlling motor speed in one direction

These two tests look at controlling the motor speed increase either in a straight line (linear) or a curve (non – linear). The latter allows for greater control at low speeds but requires a lot of coding to make changes. Linear only requires min/max input values and min/max duty cycles.
Ch3 Throttle is used as it has no sprung central off position.

14a Ch3 Linear speed increase. Off – max forwards

With this code, the motor speed increases is linearly and can be easily altered to suit different receivers.
 

 

 
[CODE]
 
; Ch3 throttle output 1203 to 1898
; b1 enable
; b.4 redled
; b.5 greenled
; c.0 reverse direction
; c.2 forwards direction
 
init:
 
dirsb=%00110011
dirsc=%00000100
 
pwmout c.2, 99, 0
 
w1 = 0        ; variable input
 
main:
 
pulsin c.3, 0, w1
 
w2 = 120        ; min speed joystick position
w3 = 180        ; max speed joystick position
w4 = 150        ; min duty cycle
w5 = 400        ; max duty cycle
 
w6 = w5 - w4        ; 400 - 150 = 250
w7 = w3 - w2        ; 180 - 135 = 45
 
w8 = w6 / w7 * 10        ; 250/45 x 10 = 56, x 10 variables ignore decimal part of value
 
w9 = w1 - w2               ; 157 - 135 = 22 ; 157 test value
w10 = w9 * w8 /10      ; 22 x 56 / 10 = 123, /10 to remove previous x 10
w11 = w10 + w4          ; 224 + 150 = 273. mid point = 275
 
if w1 < 120 then fwdoff
if w1 > 110 and w1 < 185 then fwdon
if w1 > 180 then fwdfull
 
fwoff:    low b.1 : low c.0 : low c.2  : pwmduty c.2, 0     : high b.4 : low b.5 : goto main  
fwdon:  high b.1 : low c.0 : high c.2 :pwmduty c.2, w11 : low b.4 : high b.5 : goto main  
fwdfull: high b.1 : low c.0 : high c.2 :pwmduty c.2, 400 : high b.4 : high b.5 : goto main
 
[/CODE]

14b. Ch3 Linear speed decrease. Max reverse – off

; variable reverse
; Ch3 throttle input 1003 to 1898
; b1 enable
; b.4 redled
; b.5 greenled
; c.0 reverse direction
; c.2 forwards direction
 
init:
 
dirsb=%00110011
dirsc=%00000101
 
pwmout c.0,99, 0     ; reverse
pwmout c.2,99, 0     ; forwards
 
w1 = 0        ; variable input
 
main:
 
pulsin c.3, 0, w1
 
w2 = 135        ; min speed position
w3 = 180        ; max speed position
w4 = 150        ; min duty cycle
w5 = 400        ; max duty cycle
 
w6 = w5 - w4        ; 400 - 150 = 250
w7 = w3 - w2        ; 180 - 135 = 45
 
w8 = w6 / w7 * 10    ; 250/45 x 10 = 56 No decimal variables
 
w9 = w3 - w1              ; 180 - 157 = 23 ; 157 test value mid point
w10 = w9 * w8 /10   ; 23 x 56 / 10 = 129
w11 = w10 + w4         ; 129 + 150 = 279 ; mid point = 276
 
if w1 < 135 then revfull
if w1 > 135 and w1 < 180 then revon
if w1 > 170 then revoff                    ; 10 overlap
 
revfull: high b.1 : high c.0 : low c.2 : pwmduty c.0, 400 : high b.4 : high b.5 : goto main
revon: high b.1 : high c.0 : low c.2 : pwmduty c.0, w11 : low b.4 : high b.5 : goto main
revoff: low b.1 : low c.0 : low c.2 : pwmduty c.0, 0      : high b.4 : low b.5 : goto main
 

15. R/C controlling motors

This uses previous coding and the L296N H Bridge motor control module to drive a motor as a servo. This introduces positive feedback.
 
My objective is to control the main sail sheet of my very large 1/10 scale French Pilot cutter the Jolie Brise. The sheet travle is 600mm and its load is about 4kg. There is nothing on the market or incorporates “Captive Drum Technology”.
 

 
The yellow slotted disc is to optically count the number of turns to provide fully in to fully out control. About 7 turns.
 
A 10:1 geared 5k variable resistor may be used to provide postional feedback.
My original intention was to use the slotted disc for this function to simplify the design doing away with the gearbox and all its supports and wiring.
 
Motor spec
Motor MFA919D. 100:1. 6kg.cm. 119rpm at 9v. Drum 15mm dia. 47mm circumference. 8kg sheet load. 1.1sec/100mm. 600mm sheet travel @ 6.6sec. Average PWM input pulse 1.1 to 1.9ms = 0.8ms.

15a. Ch4 Linear speed forwards - central off [half code]

; Ch4 throttle input 116 to 155/157 to 190
; b1 enable
; b.4 redled
; b.5 greenled
; c.0 reverse direction
; c.2 forwards direction

 
init:
 
dirsb=%00110011
dirsc=%00000101
 
pwmout c.0,99, 0
pwmout c.2,99, 0
 
w1 = 0 ; variable input
 
main:
 
pulsin c.3, 0, w1
 
w2 = 157
w3 = 180
w4 = 150
w5 = 400
w6 = w5 - w4
w7 = w3 - w2
w8 = w6 / w7 * 10
w9 = w1 - w2
w10 = w9 * w8 /10
w11 = w10 + w4
 
if w1 < 157 then fwdoff
if w1 > 157 and w1 < 185 then fwdon
if w1 > 180 then fwdfull
 
fwdoff:  low b.1 : pwmduty c.0, 0 : pwmduty c.2, 0      : high b.4 : low b.5  : goto main
fwdon:  high b.1 : pwmduty c.0, 0 : pwmduty c.2, w11 :  low b.4 : high b.5 : goto main
fwdfull: high b.1 : pwmduty c.0, 0 : pwmduty c.2, 400 : high b.4 : high b.5 : goto main

 

 

15b. Ch4 Linear speed reverse - central off [half code]

; Ch4 throttle input 116 to 155 / 157 to 190 ; b1 enable
; b.4 redled
; b.5 greenled
; c.0 reverse direction
; c.2 forwards direction
 
init:
 
dirsb=%00110011
dirsc=%00000101
 
pwmout c.0,99, 0
pwmout c.2,99, 0

 
w1 = 0
 
main:
 
pulsin c.3, 0, w1
 
w2 = 120
w3 = 155
w4 = 150
w5 = 400
w6 = w5 - w4
w7 = w3 - w2
w8 = w6 / w7 * 10
w9 = w3 - w1
w10 = w9 * w8 /10
w11 = w10 + w4
 
if w1 < 120 then revfull
if w1 > 130 and w1 < 150 then revon
if w1 > 145 then revoff
 
revfull: high b.1 : high c.0 : low c.2 : pwmduty c.0, 400 : high b.4 : high b.5 : goto main
revon:  high b.1 : high c.0 : low c.2 : pwmduty c.0, w11 :  low b.4 : high b.5 : goto main
revoff:  low b.1 :   low c.0 : low c.2 : pwmduty c.0, 0     : high b.4 :  low b.5 : goto main

15c. Ch4 Linear speed reverse – central off – forwards

Combination of codes 15a & b
 

[CODE]

; Ch4 throttle input 116 to 155 / 157 to 190   symbol enable = b.1
symbol redled = b.4
symbol greenled = b.5
symbol rvsduty = c.0 ; reverse direction
symbol fwdduty = c.2 ; forwards direction   init:   dirsb=%00110011
dirsc=%00000101 pwmout c.0,99, 0 : pwmout c.2,99, 0
w1 = 0   main:   pulsin c.3, 0, w1   if w1 < 100 then revfullon
if w1 > 95 and w1 < 145 then revvariable
if w1 > 140 and w1 < 160 then revfwdoff
if w1 > 155 and w1 < 205 then fwdvariable
if w1 > 200 then fwdfullon   ;------- REVERSE FULL ON-------------   revfullon:
high enable : pwmduty rvsduty, 400 : pwmduty fwdduty, 0 : low redled : high greenled : pause 100 : goto main   ;--------REVERSE VARIABLE -----------   revvariable:
w2 = 120 : w3 = 155 : w4 = 130 : w5 = 400
w6 = w5 - w4
w7 = w3 - w2
w8 = w6 / w7 * 10
w9 = w3 - w1
w10 = w9 * w8 /10
w11 = w10 + w4
high b.1 : pwmduty rvsduty, w11 : pwmduty fwdduty, 0 : high redled : low greenled : pause 100 : goto main   ;---------- OFF -----------------   revfwdoff:
low enable : pwmduty c.0, 0 : pwmduty fwdduty, 0 : high redled : high greenled : pause 100 : goto main   ;---------- FORWARDS VARIABLE --------   fwdvariable:
w2 = 157 : w3 = 180 : w4 = 130 : w5 = 400
w6 = w5 - w4
w7 = w3 - w2
w8 = w6 / w7 * 10
w9 = w1 - w2
w10 = w9 * w8 /10
w11 = w10 + w4
high enable : pwmduty rvsduty, 0 : pwmduty fwdduty, w11 : low redled : high greenled : pause 100 : goto main   ;------------- FORWARD FULL ON ----------   fwdfullon:
high enable : pwmduty rvsduty, 0 : pwmduty fwdduty, 400 : high redled : low greenled : pause 100 :goto main
[/CODE]

15d Ch4 Non linear speed increase. Off — max forwards [half code]

In this test, the throttle varies the motor speed from zero to maximum in one direction with an initial off deadband.
The principles of the last test are used with small steps and the duty cycle length increases gradualy from zero upto max.
I had to go back and increase the frequency to 16MHz and overlap the values.
It worked without glitches between the individual steps. More steps can be added to make the speed increase smoother.
 
Advantage: The rate of speed change can be varied to give more control at slow speeds.
 
[CODE]
 
init:
 
init: setfreq m16
 
symbol enable = b.1
symbol redled = b.4
symbol greenled = b.5
 
dirsb=%00110011
dirsc=%00000100
 
w1 = 0
 
pwmout c.2,99, 0
 
main:
 
pulsin c.3, 0, w1
 
if w1 < 520 then stp1                            ;0
if w1 > 519 and w1<541 then stp2       ;200 duty cycles
if w1 > 539 and w1<561 then stp3       ;208
if w1 > 559 and w1<581 then stp4       ;220
if w1 > 579 and w1<601 then stp5       ;232
if w1 > 599 and w1<621 then stp6       ;244
if w1 > 619 and w1<641 then stp7       ;260
if w1 > 639 and w1<661 then stp8       ;276
if w1 > 659 and w1<681 then stp9       ;296
if w1 > 679 and w1<701 then stp10     ;328
if w1 > 699 and w1<721 then stp11     ;360
if w1 > 719 then stp12                         ;400
 
stp1:
low enable
low c.2
hpwmduty 0
high redled
low greenled
goto main
 
stp2:
high enable
high c.2
hpwmduty 200 low redled
high greenled
goto main
 
Steps 3 to 12 similar to stp 2 except for the changing duty cycle.
 
[/CODE]

15e. CH4 Non – linear speed. Max reverse – off – Max forwards

Extension of 15d
 
init: setfreq m16
 
symbol enable = b.1
symbol redled = b.4
symbol greenled = b.5
 
dirsb=%00110011 : dirsc=%00000100
 
w1 = 0
 
pwmout c.2,99, 0
pwmout c.0,99, 0
 
main:
 
pulsin c.3, 0, w1 pause 100
 
if w1< 417 then rv6
if w1 > 415 and w1<441 then rv5
if w1 > 439 and w1<465 then rv4
if w1 > 463 and w1<493 then rv3
if w1 > 491 and w1<517 then rv2
if w1 > 515 and w1<541 then rv1
if w1 > 539 and w1<621 then stpoff
if w1 > 619 and w1<633 then fr1
if w1 > 631 and w1<646 then fr2
if w1 > 643 and w1<657 then fr3
if w1 > 655 and w1<668 then fr4
if w1 > 667 and w1<681 then fr5
if w1 > 679 then fr6
 
rv6: high enable : low c.2 : high c.0 : hpwmduty 400 : high redled : low greenled : goto main
rv5: high enable : low c.2 : high c.0 : hpwmduty 360 : high redled : low greenled : goto main
rv4: high enable : low c.2 : high c.0 : hpwmduty 320 : high redled : low greenled : goto main
rv3: high enable : low c.2 : high c.0 : hpwmduty 280 : high redled : low greenled : goto main
rv2: high enable : low c.2 : high c.0 : hpwmduty 240 : high redled : low greenled : goto main
rv1: high enable : low c.2 : high c.0 : hpwmduty 200 : high redled : low greenled : goto main
 
stpoff: low enable : low c.2 : low c.0 : hpwmduty 0 : high redled : high greenled : goto main
 
fr1: high enable : high c.2 : low c.0 : hpwmduty 200 : low redled : high greenled : goto main
fr2: high enable : high c.2 : low c.0 : hpwmduty 240 : low redled : high greenled : goto main
fr3: high enable : high c.2 : low c.0 : hpwmduty 280 : low redled : high greenled : goto main
fr4: high enable : high c.2 : low c.0 : hpwmduty 320 : low redled : high greenled : goto main
fr5: high enable : high c.2 : low c.0 : hpwmduty 360 : low redled : high greenled : goto main
fr6: high enable : high c.2 : low c.0 : hpwmduty 400 : low redled : high greenled : goto main
 

Copper Strip Prototype Board Top
 

Copper Strip Prototype Board Copper side
 

 

 

---

---

16. Servopos output to Servo

servo and servopos are used to output a PWM signal to a servo.
 
Values used are 80 to 220 = 0.8 to 2.2ms. If you go outside these values you can damage the servo either by hitting the end stops (90 deg arm servos) or by running continuously (drum servos).
The average receiver outputs 110 to 190 = 1.1 – 1.9ms = 0.8ms range.
 
pause is added to allow the servo to move to the next position. The 5sec pause used here is because the drum servo turned slowly.
 
servo is used to start the timer and create the correct 20ms frame rate.
 
This program directly controls the servo movement.
 
servo    —   Man 2 pg 204
servopos — Man 2 pg 206
 
init:
servo 1, 100           ; initialises timer and sets servo to 100 = 1000µsec = 1.0ms
main:
servopos 1, 100     ; sets servo to 1000µsec
pause 5000           ; pauses for 5 sec
servopos 1, 150
pause 5000
servopos 1, 200
pause 5000
servopos 1, 150
pause 5000
goto main

16a. Joystick output to Picaxe

In this section I wanted to stop using a transmitter/receiver and directly control the motor with a centrally sprung joystick taken from a redundant transmitter. The 08m2 chip is used to convert the voltage produced by the joystick’s Variable Resistor into a PWM pulse to control a motor.
 


Red led shows when the joystick is in reverse mode and green in forwards. Both leds on in neutral.
The 10K resistor grounding "Serial In" was added as I was having problems getting a stable output. It would take 30 seconds to connect and then flick on and off.
There were still problems getting a steady output pulse without the signal momentarily going to zero making the motor stutter. I tried all sorts solutions such as changing the wire and component positions in the prototype board as there can be continuity problems. Picaxe, power source, variable resistors and pulse meters were tried with no effect. Removing the Led's and its coding made no difference.
A collegue suggested adding smoothing capacitors. 1uF capacitors were added to smooth the power supply and voltage into the acd input c.4. I tried values up to 200uF. Somebody suggested placing a 1N4148 diode in the +ve supply line to demove -ve spikes. None of these solutions worked.
 
Then I posted a message on the Picaxe forum. hippy's solution was to add a PAUSE 100. This worked. Also suggested, for good practice, was to set the servo initial value to something other than 0, I used the joystick central position 158.
 
[CODE]
 
init:
b1 = 0
servo c.1, 158
 
main:
readadc c.4, b1
servopos c.1, b1
pause 100
 
if b1<148 then redled
if b1 > 143 and b1 <165 then redgreenled
if b1 >158 then greenled
 
redled:
high c.2
low c.0
goto main
 
redgreenled:
high c.0
high c.2
goto main
 
greenled:
low c.2
high c.0
goto main
 
[/CODE]
 
The original circuit had no resistors either side of the joystick Variable Resistor. Unexpectedly, the 08m2 gave an PWM output on C.1 of 0.26 to 2.1ms .
 
Various resistors were added to see what happened and the values chosen that gave a 1500us central position and 930us range which suited the previous coding for the motor controller.
 
Joystick VR spec.
45 deg movement. Usable 2.54K, Range = 1.12 to 3.66K, Trim = 0.4K +/-, red/orange/black.
 
Joystick positions:
Minimum   1050ms PWM pulse. 1.98 volts on c.4
Central      1500ms. 2.86 volts on c.4
Maximum 1980ms. 3.76 volts on c.4
 
Use 5K preset variable resistors for more accurate setting.

16b. Joystick and variable resistors control circuit

Varying resistance of input devices showed a range between 4.37K and 5.24K. Existing circuit could not output a consistent PWM pulse to feed into the motor control circuit.
 
The circuit was changed by adding 5k preset variable resistors either side of the joystick/potentiometer. Two fixed resistors 1k5 and 4k7 have been added to avoid current overload if input resistance went to zero.
 
Various fixed and variable resistors were tried to produce a PWM pulse of 1s to 2s. The motor circuit will have to be altered to give the motor linear forwards and reverse speed over the full range.
 

On thr right is a joystick made from CH3 transmitter throttle 4R3. In the middle is a small joystick used with PCB's 4K6. At the top is a standard 5k potentiometer in a housing 5k3,
 

16c. Joystick controlling motor

Combination of two circuit boards
 
14m2 Motor Control PCB CODE

pause 100 has been added to remove glitches when changing speed.
 
symbol enable = b.1
symbol redled = b.4
symbol greenled = b.5
symbol rvsduty = c.0 ; reverse direction
symbol fwdduty = c.2 ; forwards direction
 
init:
 
dirsb=%00110011
dirsc=%00000101 pwmout c.0,99, 0 : pwmout c.2,99, 0
w1 = 0
 
main:
 
pulsin c.3, 0, w1
 
if w1 < 100 then revfullon
if w1 > 95 and w1 < 145 then revvariable
if w1 > 140 and w1 < 160 then revfwdoff
if w1 > 155 and w1 < 205 then fwdvariable
if w1 > 200 then fwdfullon
 
;------- REVERSE FULL ON-------------
 
revfullon:
high enable : pwmduty rvsduty, 400 : pwmduty fwdduty, 0 : low redled : high greenled : pause 100 : goto main
 
;--------REVERSE VARIABLE -----------
 
revvariable:
w2 = 120 : w3 = 155 : w4 = 130 : w5 = 400
w6 = w5 - w4
w7 = w3 - w2
w8 = w6 / w7 * 10
w9 = w3 - w1
w10 = w9 * w8 /10
w11 = w10 + w4
high b.1 : pwmduty rvsduty, w11 : pwmduty fwdduty, 0 : high redled : low greenled : pause 100 : goto main
 
;---------- OFF -----------------
 
revfwdoff:
low enable : pwmduty c.0, 0 : pwmduty fwdduty, 0 : high redled : high greenled : pause 100 : goto main
 
;---------- FORWARDS VARIABLE --------
 
fwdvariable:
w2 = 157 : w3 = 180 : w4 = 130 : w5 = 400
w6 = w5 - w4
w7 = w3 - w2
w8 = w6 / w7 * 10
w9 = w1 - w2
w10 = w9 * w8 /10
w11 = w10 + w4
high enable : pwmduty rvsduty, 0 : pwmduty fwdduty, w11 : low redled : high greenled : pause 100 : goto main
 
;------------- FORWARD FULL ON ----------
 
fwdfullon:
high enable : pwmduty rvsduty, 0 : pwmduty fwdduty, 400 : high redled : low greenled : pause 100 :goto main

17. Photo Interrupter

The first problem I encountered was finding out how to connect it into the circuit. It appears others have the same problem. In the end I ignored the dirgram in the data sheet and went back to a basic principles of LED’s that their legs have different lengths.
 
PLANS = Positive is Long and Negative is Short.
 
The infraRed led is marked with +/E or diode sign. The Long leg goes to Positive rail through a 330R resistor. Short leg goes directly to negative rail.
 
The InfraRed sensor is marked with D/+ or C/E. The Long leg goes to Positive rail through a 470R resistor and the High/Low output signal to Picaxe. Short leg goes directly to negative rail.
 
The additional led and resistor were used to test the circuit. The led goes on (high) when there is nothing in the gap.
 
KTIR0221DS & KTIR0621DS (Darlington) with Power supply = 4.2v.
R1 = 330R, 2.98v, 9ma.
R2 = 470R, 3.29v, 7ma.
R3 = 470R, 1.44v, 3ma.
D4 = 1.15v.
D5 = 2.42/0.83 off/on.
D6 = 1.85v.

18. Slotted disc turn counter. TBA

The joystick code above is added to the motor driver code 14d.

19. Variable resistor feedback loop. TBA

20. Metronome for Tai Chi

Breathing is one of the features of Tai Chi as it requires a steady rhythm of breathing in and out to match the sequence of movements. Think of Tai Chi as slow ballet.
 
Metronome set their “Beats” in beats per minute BPM, commercial metronomes only go down to 30 bpm.
 
I need to measure the time in seconds for one single breath either in or out. Studying clips of “18 step Shabashi” and others on You Tube gave me a wide range of times from 2.5 to 5.5 sec. This corresponds to 24 to 11bps. I also timed the beats in music used for Tai Chi and found 16bpm was the common number.
 
YouTube 18 Step Shabashi
 
Online Metronome giving 20 to 11 bpm
 
The times are set by a 6 pole rotary switch (break – make – break), 3.0, 3.5, 3.75, 4.0, 4.5, 5.0sec.
Each leg goes to variable resistors making one side of a potential divider with a fixed 4k7 resistor to ground. C.4 is the Readadc input. The table below sets out the calculations.
 

No	BMP	Breathe in or out	READADC	PIN3 v	VR k	Pin3 k	Pause
1	12	5.00	240/230	4.98	5k0	9k7	4950
2	13	4.61	200/190	4.15	4k2	8k9	4450
3	15	4.00	150/140	3.33	3k3	8k0	3950
4	16	3.75	110/100	2.49	2k5	7k2	3250
5	17	3.53	55/50	1.66	1k2	5k9	3450
6	20	3.00	27/17	0.82	0k8	5k5	2950

 

[CODE]
 
init:
b1 = 150
 
main:
readadc c.4, b1
pause 100
 
if b1 >17 and b1 <27 then beat20
if b1 >55 and b1 <55 then beat17
if b1 >110 and b1 <110 then beat16
if b1 >150 and b1 <150 then beat15
if b1 >200 and b1 <200 then beat13
if b1 >230 then beat12
 
beat20:
sound c.1, (50, 50)
high c.2
pause 2950
goto main
 
beat17:
sound c.1, (50, 50)
high c.2
pause 3480
goto main
 
beat16:
sound c.1, (50, 50)
high c.2
pause 3700
goto main
 
beat15:
sound c.1, (50, 50)
high c.2
pause 3950
goto main
 
beat13:
sound c.1, (50, 50)
high c.2
pause 4560
goto main
 
beat12:
sound c.1, (50, 50)
high c.2
pause 4950
goto main
 
[/CODE]

November 2015, October 2018, January 2019, May 2020