Results : the stepper used previously for RA is mounted on DEC
The CC motor bought for RA is not powerful enough (the gearbox is too fast) > Order 17HS13-0404S-PG27 (geared stepper motor 200 steps and approx 1:27)
Second step : using a continuous motor for RA AND DEC (to autoguide the mount)
RA :
Ratio at RA handle : 144 (144 revolutions of the handle for 1 revolution of the RA axis)
->there are 24*60=1440 minutes in a day -> the handle has to spin @0.1 rpm (approximately)
Ratio at DEC handle : 144 (144 revolutions of the handle for 1 revolution of the RA axis)
Donc
RA : motoréducteur CC + 16/40 en GT2 avec courroie GT2 pas 266 largeur 6mm * 140 ou 160mm + carte de puissance déportée
DEC : le moteur pas à pas existant avec 16*40 GT2.5 + carte de puissance existante
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Motorizing an EQ5 mount with a stepper motor from an old printer (the same motor used for the barndoor tracker project) with an Arduino board.
Electrical diagram
Before leaving for work, I launch the systeme (@7h34) : Skywatcher 200/1000+2″ eyepiece + finder + counterweight / 8*1.2 AA batteries / half steps with 200ms holding time
So, 12hours and 3 minutes laters, it seems to be on time.
First tests
Electrical diagram :
Electrical diagram
Arduino code :
Original calculation :
| 16 | teeth | 1 pulley, mounted on the stepper motor | |||||
| 40 | teeth | 2nd pulley (which replace the manual handle) | |||||
| r1 | 2.5 | ||||||
| 20 | revolutions of the handle | ||||||
| 7200 | degrees | ||||||
| 3.33 | hours of the RA axis | ||||||
| 49.95 | degrees | r2 | 144.1441 | between handle and RA | |||
| rTotal | 360.3604 | ||||||
| The stepper motor has | 200 | steps/rev | |||||
| 1 revolution (24h) has | 72072.07 | steps | |||||
| 1 revolution should last | 86164.1 | sec | (duration of the sideral day :23h56min4sec) | ||||
| which makes | 0.836451 | step/s | |||||
| or a period of | 1.195527 | sec between steps | |||||
| 1195.527 | ms | ||||||
| 1195527 | us | ||||||
| quartz ucontroller | 16 | MHz | |||||
| Prescaler | 1024 | ||||||
| Period | 64 | usec/tick | |||||
| Resolution | 16 | bits | |||||
| 65536 | ticks | ||||||
| Nb of tick between 2 steps | 18680.11 | or | 9340.054 | in half step mode | |||
| Increment | 0.001 | ||||||
| 18.68011 | ticks +/- | ||||||
Original xls file : calcul_eq5m