Etronix 21.8Kg 0.16s Standard Digital Servo Metal Gear Waterproof ET2070 & horns

ETRONIX 21.8KG/0.16S STD DIGITAL SERVO METAL GEAR WATERPROOF ET2070

Etronix standard sized waterproof digital servo. Full selection of servo horns x5 (round, straight, cross, star and double ended), mounting hardware, rubber and servo horn screws included. Perfect for car, boat or aircraft applications with its high output and metal gears.

Spec Check:

• Speed (sec/60degrees): @6.0v 0.16s
• Torque (kg-cm): @6.0v 21.8kg
• Dimensions: 40.5 x 20.2 x 38mm
• Weight: 58g
• Gears: Metal
• Case: Metal/Plastic
• Lead: 180mm
• Connection: Futaba
• Splines: 25t

Need help choosing the correct servo. Here is a handy TOOL and extra informatino below.

CHOOSING THE CORRECT SERVO - FAQ

Servos from the outside

From the outside, the servo has a few basic parts:

1. Case
2. Mounting tabs
3. Output shaft
4. Servo horn
5. Cable
6. Connector

Let us consider each of the parts in a bit more detail.

1. Case

The case holds together most of the servo and protects its internal components. The case is usually made of three plastic sections screwed together, but some really small servos might only be held together by heat shrink or stickers. In some fancy servos, the middle section of the case is made of metal for better heat dissipation to keep high-performance motors and electronics from overheating. Some servos are better sealed than others for moisture protection with extra gaskets or O-rings between the case segments and on the screws. In the picture to the right, the top of the case is removed, showing the blue O-ring between the top segment and middle segment.

2. Mounting tabs

The mounting tabs are molded into the case, but I am listing them separately because of their distinct function. In a typical installation into a sheet of material, a rectangular hole that is big enough for the case but smaller than the tabs is cut out; the tabs can then be screwed down to the sheet. Many servos are supplied with a small bag of hardware including screws and grommets for mounting the servo with some shock or vibration protection. Since the mounting tabs do not involve the workings of the servo, they can be cut off for space-constrained installations. Servos, especially small ones, are often mounted with double-sided tape or cable ties.

3. Output shaft

The output shaft is usually not visible until we take off the servo horn; here are the same servos as before with the horns removed:

The output shafts have splines, little grooves along the shaft, and screw holes for securely mounting servo horns without any slipping. Servo output shafts are generally not standardized: different servo sizes require different outputs, and even within standard-size servos, different manufacturers use different splines that are incompatible with each other. If you ever need to count the splines, a digital camera can function as a good magnifying glass or microscope: it's much easier to take a picture, zoom in on your screen, and count the splines than to try to count them directly on the servo.

4. Servo horns

Servo horns are attachments that fit over the output shaft that allow you to mechanically link the servo output to the rest of your mechanism. Servos are usually supplied with an assortment of servo horns:

Unfortunately, the exact horns included are usually not specified and can vary. And, since servo output shafts and their splines vary, horns are often incompatible between brands and models of servo. Various specialty horns, for instance extra large ones and metal ones, are available from some servo manufacturers or as aftermarket accessories. Another type of specialty horn is the "servo saver", which has an integrated spring to limit shocks transmitted from the external mechanism to the servo.

5. Cable

Servos have three-wire cables that supply power and commands to servos. The cables are typically six to twelve inches long, with 22 gauge and thinner wires (smaller servos tend to have shorter and thinner wires). Since the connectors have become more standardized, the order of the wires has also become standardized, with the power wire in the middle flanked by ground and signal wires. However, the color schemes still vary. Common ones are:

• Black for ground, red for power, white for signal
• Brown for ground, red for power, and orange for signal
• Black for ground, red for power, blue for signal

My preference is for the first scheme since that offers the most contrast; the orange and brown of the second scheme can look kind of similar with bad lighting, as can the blue and black of the third approach. You are almost guaranteed to instantly destroy a servo if you connect power backwards, so make sure you double-check your connections.

6. Connector

The three-conductor cable is terminated with a 3-pin connector, which is almost universally a female connector with 0.1" spacing. Unfortunately, much of the RC world calls this female connector a male connector. As with the cable colors, the connector colors can vary. The "Futaba" plug, on the left in the picture below, has an extra polarizing tab (on the left side in the picture) that can be cut off to match the others, which are called "JR" (center) and "Airtronics Z" (right). Some of the brand names might vary by country; the most common names I see from generic servo makers in China are "Futaba" and "JR".

Viewed from the end, the connectors have two beveled corners to help prevent plugging servos in backwards. That prevention mechanism relies on the RC receiver having a corresponding cutout, which is not present on most servo controllers and other electronics a robot builder might be using instead of the usual radio control components. Again: pay attention when plugging in your servos!