An Evaluation Of The LM555 For Servo Motor Control Purposes
The LM555 for servo motor control fulfills a vital role in the proper functioning of those servo motor controls in which it’s installed, namely timing. And that it does virtually without parallel. The device is marketed as a direct replacement for the SE and NE models of 555 IC Time Machines, but it’s an improvement on the stability and accuracy of previous models, and offers timing from microseconds through to hours. It’s capable of operation in both monostable and astable modes, has an adjustable duty cycle, and has a temperature stability that varies over less than 0.005 per degree Celsius.
Consequently, it’s a fantastic device if you need to create accurate time delays or other oscillatory action. In the case of the time delay operational setting, timing is precisely controlled by a single external capacitor and a resistor. In the case of the inherently astable oscillatory function, the frequency and duty cycle of the machine are externally controlled by two resistors, along with the capacitor. This allows the circuit created to be reset and triggered in accordance with falling waveforms. Thus the device becomes capable of pulse generation, while also possessing the capacity for pulse width modulation and pulse position modulation.
The 555 Timer IC was originally designed by Hans R. Camenzind in 1970, and the part name was, perhaps a touch melodramatically, the IC Time Machine. It was and has been proclaimed by some that the 555 was so named for the 5 kilo-ohm resistors commonly present on early versions of the device, but the inventor has repeatedly stated that the number was merely a name, arbitrarily chosen. At present, the part continues to enjoy wide application, a success best explained by its excellent stability, low price, and ease of installation and use.
The standard 555 Timer IC, of which the LM555 for servo motor control is an improved iteration, consists of 15 resistors, 2 diodes and 20 transistors, all on a single silicon chip installed in an 8-pin mini DIP. There are several variants currently on the market, among which are the 556, a 14-pin version that combines two 555s on a single chip, and the doubly powerful 559, which combines four 555s on a single chip, using DIS and THR for their internal connections.
The chip is also available in several super-low power versions, including the 7555 and the TLC555. These call for custom wiring that utilizes fewer external components. This is of special interest to builders of remote control robotics, whose servo motor controls might otherwise exhaust their onboard power sources within too short a period. By giving over the task of, say, interfacing their computer joystick with their robotic construction to the LM555 for servo motor control, RC builders can help conserve battery power, thus enjoying longer runs of play or testing for their new constructions.
This, of course, should not be thought to imply that there’s anything hobby-ish about the LM555 for servo motor control. While the NE555 might be more suitable for home-built robotics, grades of 555 IC are numerous, ascending all the way to the level of military application, wherein the LM555 is quite regularly found.
