For many years, authors of popular science materials describing future technologies have been regaling us with stories about micro- and nanorobots, which will be able to perform precise missions, completely impossible for larger devices. But in amateur robotics, even building a platform of a few centimetres was, until recently, completely beyond the reach of a robotics enthusiast. However, technological progress has entered this field as well. For here we present DC sub-micro motors with gearing - so small that it is difficult to imagine even smaller drives.
Silniki z przekładnią planetarną DC sub-micro
Sub-micro DC Motor 26:1 2500 RPM 0,1 kg*cm - Pololu 2357
Small, cylindrical, coreless motor with a 26:1 planetary gearbox powered from 3 to 6 V. Speed is 2500 rpm, torque 0.1 kg*cm. Outer diameter is 6 mm, length 16 mm and total...Sub-micro DC Motor 700:1 90 RPM 0,9 kg*cm - Pololu 2359
Small, cylindrical, coreless motor with planetary gear 700:1 powered from 3 V to 6 V. Speed is 90 rpm, torque 0.9 kg*cm. External diameter is 6 mm, length 21 mm and total...Sub-micro DC Motor 5.1:1 13000 RPM 0,02kg*cm - Pololu 2331
Small cylindrical coreless motor with 5.1:1 planetary gearbox powered by 3 V to 6 V. Speed is 13000 rpm, torque is 0.02 kg*cm. The outer diameter is 6mm, the length is 17.5mm,...Sub-micro DC Motor 136:1 500 RPM 0,6 kg*cm - Pololu 2358
Small, cylindrical, uncored motor with planetary gear 136:1 supplied with 3 - 6 V. Speed is 500 rpm, torque 0.6 kg*cm. External diameter is 6 mm, length 16 mm and total weight...See also
Your pass to the world of microrobotics
Experienced electronics engineers are able to successfully solder SMD components of a fraction of a millimetre in size. The availability of small PCBs equipped with microcontrollers - be it AVR or modern ARM - also gives a huge field of possibilities. The situation is similar with lithium rechargeable batteries of a dozen or so millimetres in size. So the only thing left is the mechanics. Building a gearbox with gears of a single millimetre diameter is not feasible at home, but fortunately it is not necessary - you can buy ready-made DC sub-micro motors with planetary gears, which will allow you to build a really small mobile robot. You'll find three versions of these drives in our range to suit different applications.
It doesn't get any more compact than this
Our range of DC sub-micro motors with gears offers speeds from 90 rpm (1.5 rpm/s), through 500 rpm (8.3 rpm/s), up to 2500 rpm (just under 42 rpm/s). As the speed of the output shaft of the gearbox increases with the gear ratio, hence the torque also becomes lower. Therefore, the fastest of the listed DC sub-micro motor models has a torque of 0.1 kg*cm (which is still excellent for these dimensions), the medium model offers a torque of 0.6 kg*cm, and the slowest model is as high as 0.9 kg*cm. Such a wide selection allows you to choose the right motor model for your miniature robot. For racing applications, the fastest motor will work best, while for micro sumo applications you may want to consider the medium or slowest model (but with the highest torque).
Application of DC sub-micro motors
When building a robot powered by geared DC sub-micro motors, it is worth remembering that, as with any other motor, a suitable controller must be selected to meet the power requirements of the drive. Despite their small size, DC sub-micro motors can require a current of up to 400 mA - although the average current consumption with a 6 V supply is only 45 mA, this value can change dynamically at times of higher mechanical load on the gearbox shaft. Therefore, it is worth anticipating the use of a battery with an appropriate discharge current and a sufficiently powerful H-bridge - preferably with a maximum current of 600 mA or even 1A (per channel).