Components: drive Module

In order to assemble the drive module of its own OpenFC system, it is necessary to have the components listed below. It is possible to replace them with equivalents to adapt the system to its convenience – for example by using a smaller and lighter motor – but the other components and workpieces plans must be modified accordingly.

Prices and suppliers are indicative. A limited number of suppliers was preferred to a lower price for some components to optimize the total cost of components AND shipping. Other combinations are probably possible and cheaper : do not hesitate to report it, the list will be updated.

Components for the drive module (total cost excluding shipping: €115)

Components Spec. REF. Qty. Price (€) Provider / Link
Stepper motor (1) NEMA11 SM28HT45 – 0674A 1 19.95 PAOParts →
Worm gear (2) Module 0.5, 1 thread W0.5 – 1 1 28.60 HPC →
Wheel for worm gear (2) Module 0.5, 30 teeth M0.5 – 30/1 1 28.30 HPC →
Ball bearings flanged 6x10x3mm 6x10x3 MF 106 2RS 2 6.95 (2 pcs) Univers du roulement →
Angled socket RJ45 female (3) Modular base RJ45 8P8C Right Angle PCB Socket 1 1.60 RS-Online →
Nut M5 1 0.10
Gear (4) 36 teeth, Module 0.8 GEABM0.8 – 36-5-B-6 1 14.10 Misumi (5) →
Knurled knob (6) M5x35mm NKOSJ5-35 1 7.40 Misumi (5) →
Steel rod (7) 6mm diameter 44mm long SFJ6-44 1 1.65 Misumi (5) →
Set collar 6x12x8mm SCCN6-8 1 0.54 Misumi (5) →
Screws (8) M2.6 SFBJ2.6 – 10 6 5.22 (6pcs) Misumi (5) →
Hex socket set screws M3 MSSK3-3 1 0.96 Misumi (5) →
POM/PEHD 10mm plate 10x80x150 1 –(9) Blockenstock →
POM/HDPE 5mm plate 5x50x170 1 –(9) Blockenstock →
POM/HDPE 3mm plate 3x50x50 1 –(9) Blockenstock →

(1) the choice of the step motor is crucial for several aspects of the OpenFC system. The diameter of its axis determines the worm's one, which determines the wheel, shaft, collar set and bearings size. Its size and weight determine the power of the system. The chosen engine is the most powerful among those of the NEMA11 size, which allows to turn the hardiest focus rings.
(2) the choice of the worm gear – determined by the diameter of the shaft of the motor – should be done WITH the wheel, as the two elements must be compatible. The number of teeth of the wheel gives the coefficient of reduction of the system (a wheel with 30 teeth gives a reduction of x30).
(3) RJ45 connector type was preferred to others for its security system that prevents the cable from being easily disconnected or ripped off.
(4) It is possible to replace the plastic gear with a stainless steel or brass one, provided that they have 36 teeth or more and are module 0.8. Heavier, they can be threaded more strongly on the axis and do not slide on it, even if the focus ring is very resistant.
(5) Attention: this provider does not sell unless you can provide a SIRET number, and it takes a couple of days to open an account. It is possible to command components with a "1901" association.
(6) the knurled knob is not indispensable and can be easily replaced by an M5x35 bolt and a M5 nut.
(7) it is possible to make oneself an axis from an aluminum or steel tube of the same diameter, but this is not advisable: the diameter and approximate linearity make the Assembly less accurate and more difficult – and the price of a machined steel axis is very low.
(8) Screws listed here are pretty expensive: it is possible to find "free" screws which fit very well by taking to pieces some computer hardware – HDD or DVD player for example.
(9) the price and the reference of the POM/HDPE plates are not indicated because this provider constantly offers different sizes – this is the counterpart of low price. Nevertheless, and even taking larger than necessary plates, all three thicknesses should not cost more than € 10.

In addition to these components, you also need a gear for camera lenses allowing the drive module to rotate the focus or zoom ring: one can find a flexible (belt gear) or rigid (ring gear) on eBay, Amazon or Edelkrone, from € 5.

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