Sometime buttons need to be debounced in software. This article has good information on how to do it. The simplest method of debouncing is by sampling the switch every 50 milliseconds.
Software button debounce
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Monthly Archives: April 2009
Hitec Servo
These are some of Hitec servos that I looked at:
| Size | Speed
(Time/60° (s)) |
Torque (Kg.cm) | Price
(US$) |
Bang per buck (Torque/Time/Price) | |
|---|---|---|---|---|---|
| Analog | |||||
| HS-475HB | Standard | 0.23 | 4.4 | 15 | 1.3 |
| HS-645MG | Standard | 0.24 | 7.7 | 34 | 0.9 |
| HS-985MG | Standard | 0.16 | 9.6 | 58 | 1.0 |
| HS-755HB | 1/4 | 0.28 | 11.0 | 25 | 1.6 |
| HS-805BB | Mega 1/4 | 0.19 | 19.8 | 34 | 3.1 |
| Digital | |||||
|
HS-5085MG |
Micro | 0.17 | 3.6 | 41 | 0.5 |
|
HS-5645MG |
Standard | 0.23 | 10.3 | 48 | 0.9 |
For standard size analog servo, the HS-985MG performs best. It is based on a coreless motor. It provides the highest torque as well as the fastest speed.
The HS-475HB is the best value servo. It has the advantage of using Karbonite (just like kryptonite 🙂 ) gears. Karbonite is supposed to be stronger than nylon but has less wear and tear compared to metal.
The HS-645MG has good torque compromise without being overly expensive. It uses mostly metal gear.
For a mega 1/4 scale servo. The HS-805BB looks awesome.
Hobby Servo
RC or hobby servos provide a convenient actuator to be used in a small-scale robotics project.
Inside a servo there are a DC motor, a gear reduction system, a potentiometer as a position sensor, and some electronics that control the motor based on the desired position.
A hobby servo is great, as it provides all the above in a convenient small package. Due to its popularity, hobby servo is quite cheap.
However there are shortcomings in using a hobby servo in a robotics project:
- No position feedback. Once commanded to move to a target position, we don’t know when or whether the servo has reached the target position
- No torque sense. We cannot tell if the servo mechanism is unexpectedly obstructed.
- Sub-optimal control system. The servo manufacturer cannot know what load the servo will be connected to, so as a result the control system will not be optimal. The problem shows up as: overshoot, slow response, and steady state error.
My plan is to use all the mechanical components of a servo, but replace the electronics with one that I design myself to solve the above issues.