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## 47:1 Metal Gearmotor 25Dx67L mm LP 12V with 48 CPR Encoder

MODEL: 4885

SGD \$ 52.00
Pre-Order
In Bulk
(per piece)

This gearmotor consists of a low-power, 12 V brushed DC motor combined with a 46.85:1 metal spur gearbox, and it has an integrated 48 CPR quadrature encoder on the motor shaft, which provides 2248.86 counts per revolution of the gearbox’s output shaft. The gearmotor is cylindrical, with a diameter just under 25 mm, and the D-shaped output shaft is 4 mm in diameter and extends 12.5 mm from the face plate of the gearbox.

Key specifications:

12 V 120 RPM, 60 mA 4.8 kg⋅cm (67 oz⋅in), 0.9 A

## Details for item #4885

Exact gear ratio: $\frac{22×22×22×22×24}{}$$\frac{÷}{}$$\frac{}{12×10×10×10×10}\approx 46.85:1$

## Dimensions

The diagram below shows the dimensions of the 25D mm line of gearmotors (units are mm over [inches]). This diagram is also available as a downloadable PDF (171k pdf).

Warning: Do not screw too far into the mounting holes as the screws can hit the gears. We recommend screwing no further than 6 mm (0.24″) into the screw hole.

## Using the encoder

A two-channel Hall effect encoder is used to sense the rotation of a magnetic disk on a rear protrusion of the motor shaft. The quadrature encoder provides a resolution of 48 counts per revolution of the motor shaft when counting both edges of both channels. To compute the counts per revolution of the gearbox output, multiply the gear ratio by 48. The motor/encoder has six color-coded, 8″ (20 cm) leads terminated by a 1×6 female header with a 0.1″ pitch, as shown in the main product picture. This header works with standard 0.1″ male headers and our male jumper and precrimped wires. If this header is not convenient for your application, you can pull the crimped wires out of the header or cut the header off. The following table describes the wire functions:

Color Function
Red motor power (connects to one motor terminal)
Black motor power (connects to the other motor terminal)
Green encoder GND
Blue encoder Vcc (3.5 V to 20 V)
Yellow encoder A output
White encoder B output

The Hall sensor requires an input voltage, Vcc, between 3.5 and 20 V and draws a maximum of 10 mA. The A and B outputs are square waves from 0 V to Vcc approximately 90° out of phase. The frequency of the transitions tells you the speed of the motor, and the order of the transitions tells you the direction. The following oscilloscope capture shows the A and B (yellow and white) encoder outputs using a motor voltage of 6 V and a Hall sensor Vcc of 5 V:

By counting both the rising and falling edges of both the A and B outputs, it is possible to get 48 counts per revolution of the motor shaft. Using just a single edge of one channel results in 12 counts per revolution of the motor shaft, so the frequency of the A output in the above oscilloscope capture is 12 times the motor rotation frequency.

## Dimensions

Size: 25D x 67L mm1 101 g 4 mm2

## General specifications

Gear ratio: 46.85:1 120 rpm3 0.060 A4 0.90 A5 4.8 kg·cm5 1.4 W 60 rpm6 0.45 A6 2.4 kg·cm6 12V, 0.9A stall (LP 12V)

## Performance at maximum efficiency

Max efficiency @ 12V: 38 % 99 rpm 0.73 kg·cm 0.16 A 0.74 W