I purchased several Chinese clones of Hitec HS-55 micro servos on eBay for $2.50 each, including postage. They are called "Micro 9g servo". I tested them using a simple sketch (see below) that uses a potentiometer to set the servo position. I posted a video on YouTube of its operation. My conclusion - pretty good for the money!
#include <Servo.h>
/*
Demonstration of a Micro 9g RC servo
Edward Comer
This code serves no useful purpose other then to demo a servo.
*/
// Global variables
char buffer [50];
Servo myservo; // create servo object to control a servo
int potValue; //variables to hold A2 input
int iOldPos, iNewPos = 0; // servo position
int potPin = 2; //potentiometer connected to A2
void setup()
{
// Establish Arduino pin usages
pinMode(13,OUTPUT); // Use the built-in LED
//Initialize serial port
Serial.begin(9600);
Serial.println("Servo Demo");
// Initialize servo
myservo.attach(9); // attaches the servo on pin 9 to the servo object
}
void loop()
{
potValue = analogRead(potPin); // read the value of the potentiometer
iNewPos = potValue/5; // convert to quasi-degrees (alter per your potentiometer)
if(iOldPos != iNewPos) { // Issue command only if desired position changes
digitalWrite(13, HIGH); // set the LED on
iOldPos = iNewPos;
Serial.print("Pot = "); // Human readable verification on serial port
Serial.print(potValue); // View full range from 0 - 1024 in Serial Monitor
Serial.print(", ~degrees = ");
Serial.println(iNewPos);
// Set shaft angle in degrees from approximately 0 to 180 (limited by integer math)
myservo.write(iNewPos); // tell servo to go to position in variable 'pos'
delay(15); // waits 15ms for the servo to reach the position
//delay(1000); // slow to human speeds
digitalWrite(13, LOW); // set the LED off
}
}
That's a good find. I just paid twice that recently for one, and I thought that was a good price. It's amazing to me that these things can be shipped from China at that price.
I just ordered a couple of ultrasonic sensors from eBay for less than $4 USD each. Search for HC-SR04. Only a few years ago I paid $25 + shipping for one.
I mount the ultrasonic sensors on those micro servos.
I purchased one of those HC-SR04 units a few weeks ago and liked it so much that I purchased two more ($3.89 e/w postage), which just arrive in today's mail. On December 22nd I posted a YouTube video of my Arduino using the HC-SR04 as input to drive a full-size RC servo while displaying the distance on a KTM-S1201 LCD display (eBay $2.98 delivered). The video is at: Arduino demo of HC-SR04 and RC Servo - YouTube
The Chinese are selling this stuff cheaply but what gets me is the super cheap postage - often included. Obviously they do not pay the postage prices that the USPS charges. A package from China arrived last week that contained less than $5 of goods yet its tracking required a signature. The postman stopped his vehicle, came to the door and I had to sign for it. Just the labor costs for that effort far exceeded any contribution shared by China Post with the USPS, if, indeed, they share any. Nonetheless, I have been buying numerous Arduino stuff from China. I don't mind the wait for delivery and I certainly enjoy the prices.
I too don't quite understand what is going on with the free shipping charges on small electronic items from Asian sellers on E-bay. Last month I bought a electronic item for 99 cents that included free shipment from China. How can that be a money making thing for anyone? I suspect there is some kind of subsidies from their government for shipping costs.
Not complaining as I've taken advantage of lots of cheap Asian components and modules, never had a problem with quality or function of the items, and as a budget limited hobbyist I am overjoyed. But that doesn't mean I understand it is possible to sell an item with free shipment for such low costs.
I recently ordered a pack of 100 resistors from Thailand for $1.49, including shipping. When the package arrived the postage stamp was for 37 Bahts which is equivalent to $1.18. This means that the seller netted 31 cents. Given their labor, eBay fees, etc., they could not have made money on this sale and may have even lost money. I can only assume that they hope for large quantity orders where shipping may work out better for them, yet they honor the small orders. Bewildering but, as you say, I'm not complaining.
As long as the package is small/light weight, the air mail charge is low (probably large numbers of air flights to the US). Get anything large and the freight charge can go out of sight (below). At least the Chinese have paypal. India is a poster child for export unfriendly. Seems only air expre$$ to the nearest large airport for large packages and bank wire transfers for payment.
Maybe their products are Trojan Horses with in-built bugging devices that send back info on all the projects you are working on.
Or, by selling cheap (beads to the natives ?) you eventually become dependant on them as your only source of supply because your national suppliers have all gone into liquidation.
Somewhat similar to what some multi-national grain supplying companies do - by selling "modified" seed corn to farmers who find out when the seed crops that, although good enough for food, is sterile so cannot itself be used for future seed and the customer becomes dependant on the original supplier.
Not to be too political but "you eventually become dependant on them as your only source of supply" has already happened - in all things, not just Arduino items.
