This Timer is a highly stable controller capable of producing accurate timing pulses. With a monostable operation, the delay is controlled by one external resistor and one capacitor.
With astable operation, the frequency and duty cycle are accurately controlled by two external resistors and one capacitor.
555 Datasheet Fairchild
• High-Current Drive Capability: 200 mA
• Adjustable Duty Cycle
• Temperature Stability of 0.005%/°C
• Timing From μs to Hours
• Turn off Time Less Than 2 μs
LM555 Ordering Information
Application Information ( 555 datasheet fairchild )
When the low signal input is applied to the reset terminal, the timer output remains low regardless of the threshold voltage or the trigger voltage. Only when the high signal is applied to the reset terminal, the timer’s output changes according to threshold voltage and trigger voltage.
When the threshold voltage exceeds 2/3 of the supply voltage while the timer output is high, the timer’s internal discharge transistor turns on, lowering the threshold voltage to below 1/3 of the supply voltage. During this time, the timer output is maintained low. Later, if a low signal is applied to the trigger voltage so that it becomes 1/3 of the supply voltage, the timer’s internal discharge transistor turns off, increasing the threshold voltage and driving the timer output again at high.
555 pdf datasheet
Related Partnumber : 555, LM555CM, LM555CMX, LM555CN
RS-485, also known as TIA-485, EIA-485, is a standard defining the electrical characteristics of drivers and receivers for use in serial communications systems.
Part Number : RS485
Description : RS-422 AND RS-485 APPLICATION NOTE
Manufactures : B&B Electronics ( http://www.bb-elec.com )
These port-powered RS-232 to 422/485 converters change TD and RD RS-232 lines to 422/485 signals. All of our serial port converters feature Automatic Send Data Control. SDC automatically enables the RS-485 driver when data is present on the RS-232 side. Control of the driver is automatic at rates up to 115.2 kbps.
( http://www.bb-elec.com/Products/Serial-Connectivity/Serial-Converters/Port-Powered-RS-232-to-RS-422-485-Converters.aspx )
The purpose of this application note is to describe the main elements of an RS-422 and RS-485 system. This application note attempts to cover enough technical details so that the system designer will have considered all the important aspects in his data system design. Since both RS-422 and RS-485 are data transmission systems that use balanced differential signals, it is appropriate to discuss both systems in the same application note. Throughout this application note the generic terms of RS-422 and RS-485 will be used to represent the EIA/TIA-422 and EIA/TIA-485 Standards.
What is an RS-485 network? RS-485 allows multiple devices (up to 32) to communicate at half-duplex on a single pair of wires, plus a ground wire (more on that later), at distances up to 1200 meters (4000 feet). Both the length of the network and the number of nodes can easily be extended using a variety of repeater products on the market.
RS-485 Application Note