I built a simple watch-winder to keep automatic watches fully wound when not being worn. Mainly as a small project to play with a pyBoard and a servo motor.

A short piece of microPython makes the servo turn, first one direction, then then other, then a pause, at a speed that makes sure a watch is fully wound overnight. The speed depends on the required number of turns to achieve full-wind, which depends on the watch movement, and whether the movement winds in one or other, or both, rotational directions.

The watch is placed in a plastic box attached to the servo motor and the motor is simple clamped in a panavise, with the axis of the servo at about 45°

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microPython code for Pyboard to control continuous rotation servo.

# main.py -- put your code here!
 
 
import pyb
 
servo1 = pyb.Servo(1)
 
# LED colours
# red flash = motor stopped
# green on = manual stop for 120 seconds
# yellow on/flash = motor running
# blue flash = 5 seconds before a change of state
 
ledr = pyb.LED(1) 
ledg = pyb.LED(2)
ledy = pyb.LED(3)
ledb = pyb.LED(4) 
 
# servo speeds to achieve approx 6 rpm in either direction.
ccw = 14
cw = -7
stop = 0
 
 
# 12 minute cycle :
# observed turns complete per stage:
# 2 min CW = ~11 turns
# 4 min stop
# 2 min CCW = ~ 12 turns
# 4 min stop
# 23 turns / 12 min = 115 turns / hour
# ETA 2836-2 requires 650 turns / day for full winding 
# this would take 5.6 hours on winder per day to guarantee full wind.
 
period = 120 # seconds
 
# turn LEDs off (unneccesary?)
ledr.off()
ledg.off() 
ledy.off()
ledb.off()
 
# interrupt function to allow changing/removing watch
def stop_servo():
 
	# red LED on at start of interruption
	ledr.on()
	ledy.off()
 
	# turn off any flashing LEDs during interruption
	tim4.callback(None)
 
	# flash blue LED to signal stop imminent
	flash_blue()
 
	# stop servo
	servo1.speed(0)
 
	# red LED off and green LED on to indicate "safe to proceed"
	ledr.off()
	ledg.on()
 
	# pause for 2 minute
	pyb.delay(120 * 1000)
 
	# flash blue LED to signal re-start imminent
	flash_blue()
 
	# green LED off to indicate end of interruption.
	ledg.off()
 
	pyb.hard_reset()
 
	# after resumption from interrupt the next stage will usually be a 
	# "stop" period, assuming the interrupt occurred during a "run" period
	# perhaps need to look at the best way of resuming? or even quit()
	# at the end of the stop_servo() interrupt and then manually reset via the 
	# RST button?
 
	# main programme resumes where it left off....
	return
 
def cycle_led():
 
	ledb.on()
	pyb.delay(500)
	ledy.on()
	pyb.delay(500)
	ledg.on()
	pyb.delay(500)
	ledr.on()
	pyb.delay(500)
	ledb.off()
	ledy.off()
	ledg.off()
	ledr.off()
 
	return
 
def flash_blue():
 
	t = 0
	while t < 10:
 
		ledb.toggle()
		pyb.delay(500)
		t += 1
	return
 
def rotate_cw(p):
 
	# solid yellow LED when going CW
	ledy.on()
	servo1.speed(cw, 1000)
	pyb.delay(p * 1000)
	flash_blue()
	ledy.off()
 
	return
 
 
def rotate_ccw(p):
 
	# flash yellow LED when going CCW
	tim4.callback(lambda t: ledy.toggle())
	servo1.speed(ccw, 1000)
	pyb.delay(p * 1000)
	flash_blue()
	tim4.callback(None)
	ledy.off()
 
 
	return
 
 
def pause(p):
 
	# flash red LED during motor pause period
	tim4.callback(lambda t: ledr.toggle())
	servo1.speed(stop, 1000)
	pyb.delay(p * 1000)
	flash_blue()
	tim4.callback(None)
	ledr.off()
 
	return
 
 
# USR on-board switch used to pause running to allow
# watch to be removed / changed
sw = pyb.Switch()
 
# callback to run the function that pauses the operation
sw.callback(stop_servo)
 
#timer to flash LEDs
tim4 = pyb.Timer(4, freq=2)
 
cycle_led()
 
# the main loop
while True:
 
		rotate_cw(period)
 
		pause(2 * period)
 
		rotate_ccw(period)
 
		pause(2 * period)

Page created Sun May 22 00:52:45 2022 by John Pumford-Green

Page last updated: 02/07/22 13:43 BST