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Convert micro stepper to geared dc motor?


Jan 16, 2022
Jan 16, 2022
Hi. I’ve modified an internet security camera unit to make a ~1:1 scale robot head rotate to track a moving person (see below for model info). I used this unit as it did what I wanted, without requiring complex electronics assembly and programming.
The camera/electronics security module is now mounted on the robot forehead, and drives the small 5-wire, geared stepper motor now set in the robot neck. It’s perfect...but the motor is just a little bit too weak for the mass of the head. I’m worried about substituting a much larger 5-wire stepper motor eg NEMA17 (I have one) or larger, as it may draw too much current and fry the electronics, especially an ungeared stepper with greater torque output.
The current stepper gears ‘hold’ the head rotation position when no movement is required, which is nice, and why I like the geared dc motor option.

My question: is there a way to convert the electronics ‘stepper output’, to drive a geared dc motor? Worm drive versions seem quite powerful for their size, current and voltage. I don’t think the output shaft speed is particularly critical, since the existing stepper is geared. A higher geared equivalent would be perfect. Pref. any solution would not require changing the existing electronics, they work just fine now for tracking movement. Perhaps adding an intermediary module to convert the signals eg Arduino plus code?

Model information:
The security unit is a “1080P IP Security Camera WIFI Smart Wireless Indoor Night Vision Pet Cat Dog Cam” I bought on eBay.
It’s stepper motor is a 24BYJ48 (5v, 5-wire). From googling it, it’s either a 5.625/32 or 5.625/64 step degrees/reduction, unipolar 4 phase; I can’t distinguish which. I’ve tried to source a 5v say ~80-100 reduction geared unit, but I can’t find one.

The 2 main chips on the back of the security module electronics board are a “ULN2803A” and a “Gk7102S” which seem to be related to the steppers and the camera respectively (via google).

I have no programming skills, but can do VERY basic electronics (solder components, wire up modules etc). So if possible, could any answers need be in relatively plain English please (I’m a real beginner)?
I’m retired so cost is also factor for what is just a hobby.

Can you help?

Photo: back of security unit, showing stepper motor output socket (labelled neck stpr), plus an identical stepper motor (was the tilt function in the security unit, but I’m not using it).


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