EZ-B v3 Servo Info

A standard servo is what you normally find in R/C Hobby Toys. They are high precision devices that can rotate a shaft up to 180 degrees. With the EZ-B and a Standard Servo, you can easily configure how many degrees to rotate the output shaft.

The EZ-B SDK and EZ-Builder takes care of the electrical communication to the servo for you. Standard servos can be used for the head or arms of your robot.

However, here is some technical information on how servos work. The servo is controlled using pulse controlling. The control pulse is a positive voltage with a length of 1 to 2 ms which determines the angle of the shaft. The control pulse is repeated every 18-25 ms.

The EZ-B has timing below 1ms and above 2ms to accommodate all servo types. Some servos do not fall within the specifications and require unusual timing. When testing with your servo, make sure you recognize the max and min values and set them in the control. If a servo attempts to move further than its maximum position, it may be damaged. Additionally, if a servo is rotated too far then it will consume a lot of current and the EZ-B may reset.

Here are the timings for the EZ-B...

Position 1 on v4, Position 1 on v3
Screengrab of timing points
Position 90 on v4, Position 50 on v3
Screengrab of timing points
Position 180 on v4, Position 100 on v3
Screengrab of timing points

The EZ-B v4 has high accuracy which results in 180 servo positions. The EZ-B v4 can control 24 servos simultaneously while it performs other various user specified tasks. If your servos draw more current then our specification sheet defines, the EZ-B may run out of power and reboot itself. This is called a Brown-Out. To prevent brown-out with many servos, provide alternate power. Check the manual on how to do that.

The EZ-Builder and EZ-SDK handles the technical work for you. Merely specify the servo position and voila!

Now that we covered the basics of how-a-servo-works, the next question is torque. Torque is how much power the servo has. Different applications will require higher or lower torque. In most cases, you can get away with using a regular average torque servo. Average torque of a plastic servo is 2-3kg/cm @ 5 volts.

Something that is often overlooked is energy consumption. Consider this: there is no free energy. Torque equals energy and vice versa. If you find a high torque servo at the hobby shop, you'll require more energy to move it. If too many high torque servos are connected to the EZ-B, it will "brown-out". Browning-out means the voltage regulator could not keep up with the current draw so the microchip rebooted itself due to low current.

The EZ-B designers were smart and used 2 seperate voltage regulators to limit the risk of brown-outs. Still, this isn't fool proof because your battery supply only has so much current also.

So what do the torque numbers mean? Let's speculate the torque value of a servo was 50 Ounces per Inch

Well if you had a servo arm that was one inch long on your servo it would be able to produce 50 ounces of pull or push force at the end of the servo arm before stalling. If you had a 1/2 inch servo arm what do you think the force would be? Yup, 100 ounces of force. How about a 2 inch arm, 25 ounces of force - easy huh?