Motorizing a EQ5 mount

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)



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







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.



eq5Electrical diagramElectrical diagram

eq5_2Before 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

eq5_3 So, 12hours and 3 minutes laters, it seems to be on time.

First tests

First tests

Electrical diagram :

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