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With a PICAXE 08M2 microcontroller and a few servos the electrical part of the task is pretty simple. Basically two buttons (a ONES place button and a TENS place button) pull an input to the PICAXE high, causing a subroutine to be called and the appropriate servo to move. Adding wireless to the rig should be easy as well by re-purposing a cheap remote from a toy RC car to replace the two button/switches that cause the servos to move.
Adding the mechanical digits will not be completely trivial, by my buddy says he is up to the challenge.
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Short video of the rig in action.
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Schematic drawing of the build (click to increase size):
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PICAXE 08M2 Project Source Code. Very simple:
#rem
*******************************
***** www.WhiskyTangoHotel.Com *****
*******************************
Project Name: Walker Swim Heat Counter
Start Date: June 1, 2012
Program Rev History:
This version steps the a ONES digit Servo and a
TENS digit Servo in ten increments to "display"
the numbers 00-99.
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PICAXE PE Rev: 5.5.1
#endrem
#picaxe08m2 ' using PICAXE 08M2 uC
#COM11 'programming on COM11
'min servopos value = 75
'center servopos value = 150
'max servopos value = 255
symbol Ones_Button = pinc.4 'input button for Ones digit. Pull high to count
symbol Ones_Position = b0 'servo location var
symbol Tens_Button = pinc.3 'input button of Tens digit. Pull high to count
symbol Tens_Position = b1 'servo location var
'b2 is variable used for math in calculating both servo positons
'Init some stuff...
let dirsC = %11000111 ' define I/O of PortC. Not really required.
servo 1,150 ; initialise ones digit servo
servo 2,150 ; initialise tens digit servo
Ones_Position = 0
'Calculate and move Ones digit Servo to "display" 0
b2 = Ones_Position * 15 + 75
servopos 1, b2
Tens_Position = 0
'Calculate and move Tens digit Servo to "display" 0
b2 = Tens_Position * 15 + 75
servopos 2, b2
main: 'main loop continually checks if a button is pushed to move the Servos.
If Ones_Button = 1 then 'move servo for Ones Digit
gosub Change_Ones
endif
If Tens_Button = 1 then 'move servo for Tens Digit
gosub Change_Tens
endif
goto main 'loop and check for button presses
Change_Ones: 'Routine called when "Ones" button is pressed.
If Ones_Position = 9 then 'highest position is '9'. Wrap to '0'
Ones_Position = 0
else
Ones_Position = Ones_Position + 1
endif
'Convert the Ones_Position into the correct servo location
let b2 = Ones_Position * 15 + 75
Select Case b0
Case 0
servopos 1, b2
Case 1
servopos 1, b2
Case 2
servopos 1, b2
Case 3
servopos 1, b2
Case 4
servopos 1, b2
Case 5
servopos 1, b2
Case 6
servopos 1, b2
Case 7
servopos 1, b2
Case 8
servopos 1, b2
Case 9
servopos 1, b2
endselect
pause 500 'delay 500mSec to allow the servo to move
return ' Change_Ones
Change_Tens: 'Routine called when "Tens" button is pressed.
If Tens_Position = 9 then 'highest position is '9'. Wrap to '0'
Tens_Position = 0
else
Tens_Position = Tens_Position + 1
endif
'Convert the Tens_Position into the correct servo location
let b2 = Tens_Position * 15 + 75
Select Case b0
Case 0
servopos 2, b2
Case 1
servopos 2, b2
Case 2
servopos 2, b2
Case 3
servopos 2, b2
Case 4
servopos 2, b2
Case 5
servopos 2, b2
Case 6
servopos 2, b2
Case 7
servopos 2, b2
Case 8
servopos 2, b2
Case 9
servopos 2, b2
endselect
pause 500 'delay 500mSec to allow the servo to move
return 'Change_Tens
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