The 555 timer integrated circuit is one of the most popular and useful integrated circuits of all time.
A lengthy tutorial here on the 555 timer and how to use it would be a duplication of effort since at http://www.uoguelph.ca/~antoon/gadgets/555.htm there an excellent tutorial, which you should study to learn how this IC works.
All of the timing calculations for circuits using the 555 timer are based on the response of a series R-C circuit with a step or constant voltage input, and exponential output taken across the capacitor.
The 8-pin 555 timer must be one of the most useful chips ever made and it is used in many projects.
Low power versions of the 555 are made, such as the ICM7555, but these should only be used when specified (to increase battery life) because their maximum output current of about 20mA (with a 9V supply) is too low for many standard 555 circuits.
The circuit symbol for a 555 (and 556) is a box with the pins arranged to suit the circuit diagram: for example 555 pin 8 at the top for the +Vs supply, 555 pin 3 output on the right.
www.kpsec.freeuk.com /555timer.htm (2390 words)
555 XXXX(Site not responding. Last check: 2007-09-19)
A national number is a unique line number in the 555 XXXX assigned to an entity for use in all or most of the geographic NPAs in the NANP Area.
A non-national number is a line number in the 555 NXX assigned to an entity for use in a specific geographic area or areas (NPAs, states, or provinces).
The complete list of 555 NXX numbers assigned in the NANP area may be found at http://www.nanpa.com.
Built into the Optio 555 is a 5x, 7.8-39mm SMC Pentax lens, the equivalent of a 37.5-187.5mm lens on a 35mm camera.
Still, the 555 should fit easily into larger coat pockets and purses, and comes with a handy neck strap that can be tightened down as a wrist strap.
Technically, the less-saturated color of the 555 is more accurate than the over-bright color of most consumer cameras, but I've found that consumers generally prefer their photographic color to be a bit brighter than real life.
This is a basic 555 squarewave oscillator used to produce a 1 Khz tone from an 8 ohm speaker.
The series capacitor (100 uF) increases the output by supplying an AC current to the speaker and driving it in both directions rather than just a pulsating DC current which would be the case without the capacitor.
A 555 timer can be used to generate a squarewave to produce a negative voltage relative to the negative battery terminal.
The holiday season is a very busy season for the majority of the UFCW Local 555 membership.
I’m encouraging every 555 member who can help to donate a new unwrapped toy and/or non-perishable food items and/or school supplies to help UFCW Local 555 members that could use a little assistance during the holidays.
The collected food, toys and school supplies will be distributed to Local 555 members and their families that need assistance this holiday season.
I have heard some amazing stories about people renting buildings for around $10 a month to people because (1) everyone knows these buildings are going to be destroyed and (2) the owners don't want insurance liability involved with an abandoned building." [6
Interstate 555 will be the official designation for 44 miles of of US 63, between I-55 at Lake David and US 49 in Jonesboro, once it has been completely upgraded to interstate standards.
Until then, "Future I-555" signs will mark the highway.