555 timer ic
TRANSCRIPT
555 timer ICFrom Wikipedia, the free encyclopediaJump to: navigation, search
NE555 from Signetics in dual-in-line package
Internal block diagram
The 555 timer IC is an integrated circuit (chip) used in a variety of timer, pulse generation and oscillator applications. The part is still in widespread use, thanks to its ease of use, low price and good stability. As of 2003, it is estimated that 1 billion units are manufactured every year.[1]
Contents [hide] 1 Design 2 Usage
o 2.1 Pins o 2.2 Modes o 2.3 Monostable o 2.4 Bistable o 2.5 Astable
3 Specifications 4 Derivatives
o 4.1 Dual timer 556 o 4.2 Quad timer 558
5 Example applications o 5.1 Joystick interface circuit using quad timer 558 o 5.2 Atari Punk Console o 5.3 Pulse-width modulation
6 References 7 Further reading
8 External links
[edit] DesignThe IC design was proposed in 1970 by Hans R. Camenzind and Jim Ball. After prototyping, the design was ported to the Monochip analogue array, incorporating detailed design by Wayne Foletta and others from Qualidyne Semiconductors. Signetics (later acquired by Philips) took over the design and production, and released the first 555s in 1971.
Depending on the manufacturer, the standard 555 package includes over 20 transistors, 2 diodes and 15 resistors on a silicon chip installed in an 8-pin mini dual-in-line package (DIP-8).[2] Variants available include the 556 (a 14-pin DIP combining two 555s on one chip), and the 558 (a 16-pin DIP combining four slightly modified 555s with DIS & THR connected internally, and TR is falling edge sensitive instead of level sensitive).
The NE555 parts were commercial temperature range, 0 °C to +70 °C, and the SE555 part number designated the military temperature range, −55 °C to +125 °C. These were available in both high-reliability metal can (T package) and inexpensive epoxy plastic (V package) packages. Thus the full part numbers were NE555V, NE555T, SE555V, and SE555T. It has been hypothesized that the 555 got its name from the three 5 kΩ resistors used within,[3] but Hans Camenzind has stated that the number was arbitrary.[1]
Low-power versions of the 555 are also available, such as the 7555 and CMOS TLC555.[4] The 7555 is designed to cause less supply glitching than the classic 555 and the manufacturer claims that it usually does not require a "control" capacitor and in many cases does not require a decoupling capacitor on the power supply. Such a practice should nevertheless be avoided, because noise produced by the timer or variation in power supply voltage might interfere with other parts of a circuit or influence its threshold voltages.
[edit] Usage
[edit] Pins
Pinout diagram
The connection of the pins for a DIP package is as follows:
Pin Name Purpose1 GND Ground, low level (0 V)2 TRIG OUT rises, and interval starts, when this input falls below 1/3 VCC.3 OUT This output is driven to + V CC or GND.4 RESET A timing interval may be interrupted by driving this input to GND.5 CTRL "Control" access to the internal voltage divider (by default, 2/3 VCC).6 THR The interval ends when the voltage at THR is greater than at CTRL.7 DIS Open collector output; may discharge a capacitor between intervals.8 V+, VCC Positive supply voltage is usually between 3 and 15 V.
[edit] Modes
The 555 has three operating modes:
Monostable mode: in this mode, the 555 functions as a "one-shot" pulse generator. Applications include timers, missing pulse detection, bouncefree switches, touch switches, frequency divider, capacitance measurement, pulse-width modulation (PWM) and so on.
Astable – free running mode: the 555 can operate as an oscillator. Uses include LED and lamp flashers, pulse generation, logic clocks, tone generation, security alarms, pulse position modulation and so on. Selecting a thermistor as timing resistor allows the use of the 555 in a temperature sensor: the period of the output pulse is determined by the temperature. The use of a microprocessor based circuit can then convert the pulse period to temperature, linearize it and even provide calibration means.
Bistable mode or Schmitt trigger: the 555 can operate as a flip-flop, if the DIS pin is not connected and no capacitor is used. Uses include bounce free latched switches.
[edit] Monostable
Schematic of a 555 in monostable mode
The relationships of the trigger signal, the voltage on C and the pulse width in monostable mode
In the monostable mode, the 555 timer acts as a “one-shot” pulse generator. The pulse begins when the 555 timer receives a signal at the trigger input that falls below a third of the voltage supply. The width of the output pulse is determined by the time constant of an RC network, which consists of a capacitor (C) and a resistor (R). The output pulse ends when the voltage on the capacitor equals 2/3 of the supply voltage. The output pulse width can be lengthened or shortened to the need of the specific application by adjusting the values of R and C.[5]
The output pulse width of time t, which is the time it takes to charge C to 2/3 of the supply voltage, is given by
where t is in seconds, R is in ohms and C is in farads. See RC circuit for an explanation of this effect.
While using the timer ic as a monostable the main disadvantage is that the time span between the two triggering pulses must be greater than the RC time constant.
[edit] Bistable
In bistable mode, the 555 timer acts as a basic flip-flop. The trigger and reset inputs (pins 2 and 4 respectively on a 555) are held high via Pull-up resistors while the threshold input (pin 6) is simply grounded. Thus configured, pulling the trigger momentarily to ground acts as a 'set' and transitions the output pin (pin 3) to Vcc (high state). Pulling the reset input to ground acts as a 'reset' and transitions the output pin to ground (low state). No capacitors are required in a bistable configuration. Pin 5 (control) is connected to ground via a small-value capacitor (usually 0.01 to 0.1 uF); pin 7 (discharge) is left floating.
[edit] Astable
Standard 555 Astable Circuit
In astable mode, the 555 timer puts out a continuous stream of rectangular pulses having a specified frequency. Resistor R1 is connected between VCC and the discharge pin (pin 7) and another resistor (R2) is connected between the discharge pin (pin 7), and the trigger (pin 2) and threshold (pin 6) pins that share a common node. Hence the capacitor is charged through R1 and R2, and discharged only through R2, since pin 7 has low impedance to ground during output low intervals of the cycle, therefore discharging the capacitor.
In the astable mode, the frequency of the pulse stream depends on the values of R1, R2 and C:
[6]
The high time from each pulse is given by
and the low time from each pulse is given by
where R1 and R2 are the values of the resistors in ohms and C is the value of the capacitor in farads.
Note 1: The power capability of R1 must be greater than .
Note 2: particularly with bipolar 555s, it is essential to avoid low values of R1 as the discharge current capability of the IC is limited. If the limit is reached, the discharging output DIS will not be saturated (ie not essentially at GND as assumed for the timing calculations), so the capacitor voltage will not discharge from 0.67*Vcc towards 0, and the output low time will be greater than as given in the above equation.
To achieve a duty cycle of less than 50% a diode can be added in parallel with R2 towards the capacitor. This bypasses R2 during the high part of the cycle so that the high interval depends only on R1 and C.
[edit] SpecificationsThese specifications apply to the NE555. Other 555 timers can have different specifications depending on the grade (military, medical, etc).
Supply voltage (VCC) 4.5 to 15 VSupply current (VCC = +5 V) 3 to 6 mASupply current (VCC = +15 V) 10 to 15 mAOutput current (maximum) 200 mAMaximum Power dissipation 600 mWPower Consumption (minimum operating) 30 mW@5V, 225 mW@15VOperating temperature 0 to 70 °C
[edit] DerivativesMany pin-compatible variants, including CMOS versions, have been built by various companies. Bigger packages also exist with two or four timers on the same chip. The 555 is also known under the following type numbers:
Manufacturer Model RemarkAvago Technologies Av-555MCustom Silicon Solutions CSS555/CSS555C CMOS from 1.2 V,
IDD < 5 µACEMI ULY7855
ECG Philips ECG955MExar XR-555Fairchild Semiconductor NE555/KA555
Harris HA555IK Semicon ILC555 CMOS from 2 VIntersil SE555/NE555Intersil ICM7555 CMOSLithic Systems LC555Maxim ICM7555 CMOS from 2 VMotorola MC1455/MC1555National Semiconductor LM1455/LM555/LM555C
National Semiconductor LMC555 CMOS from 1.5 V
NTE Sylvania NTE955MRaytheon RM555/RC555RCA CA555/CA555CSTMicroelectronics NE555N/ K3T647Texas Instruments SN52555/SN72555Texas Instruments TLC555 CMOS from 2 VUSSR K1006ВИ1Zetex ZSCT1555 down to 0.9 VNXP Semiconductors ICM7555 CMOSHFO / East Germany B555
[edit] Dual timer 556
The dual version is called 556. It features two complete 555s in a 14 pin DIL package.
[edit] Quad timer 558
The quad version is called 558 and has 16 pins. To fit four 555s into a 16 pin package the control, voltage, and reset lines are shared by all four modules. Also for each module the discharge and threshold are internally wired together and called timing.
[edit] Example applications
[edit] Joystick interface circuit using quad timer 558
The Apple II microcomputer used a quad timer 558 in monostable (or "one-shot") mode to interface up to four "game paddles" or two joysticks to the host computer.
A similar circuit was used in the IBM personal computer.[7] In the joystick interface circuit of the IBM PC, the capacitor (C) of the RC network (see Monostable Mode above) was generally a 10 nF capacitor. The resistor (R) of the RC network consisted of the potentiometer inside the joystick along with an external resistor of 2.2 kilohms.[8] The joystick potentiometer acted as a variable resistor. By moving the joystick, the resistance of the joystick increased from a small value up to about 100 kilohms. The joystick operated at 5 V.[9]
Software running in the host computer started the process of determining the joystick position by writing to a special address (ISA bus I/O address 201h).[10][11] This would result in a trigger signal to the quad timer, which would cause the capacitor (C) of the RC network to begin charging and cause the quad timer to output a pulse. The width of the pulse was determined by how long it took the C to charge up to 2/3 of 5 V (or about 3.33 V), which was in turn determined by the joystick position.[10][12]
Software running in the host computer measured the pulse width to determine the joystick position. A wide pulse represented the full-right joystick position, for example, while a narrow pulse represented the full-left joystick position.[10]
[edit] Atari Punk Console
One of Forrest M. Mims III's many books was dedicated to the 555 timer. In it, he first published the "Stepped Tone Generator" circuit which has been adopted as a popular circuit, known as the Atari Punk Console, by circuit benders for its distinctive low-fi sound similar to classic Atari games[citation needed].
[edit] Pulse-width modulation
The 555 can be used to generate a variable PWM signal using a few external components. The chip alone can drive small external loads or an amplifying transistor for larger loads.
[edit] References1. ^ a b Ward, Jack (2004). The 555 Timer IC – An Interview with Hans
Camenzind. The Semiconductor Museum. Retrieved 2010-04-05. 2. ̂ van Roon, Fig 3 & related text.
3. ̂ Scherz, Paul (2000) "Practical Electronics for Inventors," p. 589. McGraw-Hill/TAB Electronics. ISBN 978-0-07-058078-7. Retrieved 2010-04-05.
4. ̂ Jung, Walter G. (1983) "IC Timer Cookbook, Second Edition," pp. 40–41. Sams Technical Publishing; 2nd ed. ISBN 978-0-672-21932-0. Retrieved 2010-04-05.
5. ̂ van Roon, Chapter "Monostable Mode." (Using the 555 timer as a logic clock)
6. ̂ van Roon Chapter: "Astable operation." 7. ̂ Engdahl, pg 1. 8. ̂ Engdahl, "Circuit diagram of PC joystick interface" 9. ̂ Engdahl, "Joystick construction". 10. ^ a b c Engdahl, "PC analogue joystick interface". 11. ̂ Eggebrecht, p. 197. 12. ̂ Eggebrecht, pp. 197-99
[edit] Further reading IC Timer Cookbook; 2nd Ed; Walter G Jung; Sams Publishing; 384
pages; 1983; ISBN 978-0-672-21932-0. IC 555 Projects; E.A. Parr; Bernard Babani Publishing; 144 pages;
1978; ISBN 978-0-85934-047-2. 555 Timer Applications Sourcebook with Experiments; Howard M
Berlin; Sams Publishing; 158 pages; 1979; ISBN 978-0-672-21538-4. Timer, Op Amp, and Optoelectronic Circuits and Projects; Forrest M
Mims III; Master Publishing; 128 pages; 2004; ISBN 978-0-945053-29-3.
Engineer's Mini-Notebook – 555 Timer IC Circuits; Forrest M Mims III; Radio Shack; 32 pages; 1989; ASIN B000MN54A6.
[edit] External links
Wikimedia Commons has media related to: 555 timer IC
Datasheets Single Bipolar Timer, Texas Instruments, 30 pages, 2010. Single CMOS Timer, National Semiconductor, 12 pages, 2010. Single CMOS Timer, Diodes Inc, 11 pages, 2006. Single / Dual CMOS Timer, Intersil, 12 pages, 2006. Dual Bipolar Timer, Texas Instruments, 16 pages, 2006. Quad Bipolar Timer, NXP / Philips, 9 pages, 2003. NE555 datasheet collection.
Articles Surtell, Tim (2001). 555 Timer Circuits – the Astable, Monostable
and Bistable Electronics in Meccano. Hewes, John (2010) 555 and 556 Timer Circuits The Electronics
Club.
Falstad, John (2010)Java simulation of 555 oscillator circuit. Falstad.com
Roca, Juan Carlos Galarza (2007) Using NE 555 as a Temperature DSP "The Parallel port as an Input/output Interface" (unpublished book)
NE555 Frequency and duty cycle calculator for astable multivibrators. Daycounter.com. 2004. Notes 20% inaccuracy.
"Eagleapex" (2007) Time-lapse intervalometer for SLRs using a 555. Instructables.com.
Van Roon, Tony (1995). "555 Timer Tutorial" Tony van Roon (VA3AVR) Website. Retrieved 2010-04-05.
Engdahl, Tomi (1994). "PC analogue joystick interface". EPanorama.net. Retrieved 2009-06-06.
Eggebrecht, Lewis C. (1983). "Interfacing to the IBM Personal Computer". Sams Publishing. ISBN 978-0-672-22027-2. Retrieved 2010-04-05.
Common Mistakes When Using a 555 Timer
Popular Culture The 2011 555 Design Contest
Retrieved from "http://en.wikipedia.org/w/index.php?title=555_timer_IC&oldid=456711233"
View page ratingsRate this pageWhat's this?Trustworthy
Objective
Complete
Well-written
I am highly knowledgeable about this topic (optional)
Submit ratings
Saved successfully
Your ratings have not been submitted yet
Trustworthy
Objective
Complete
Well-written
Categories:
Oscillators Linear integrated circuits
Hidden categories: Articles containing potentially dated statements from 2003 All articles containing potentially dated statements All articles with unsourced statements Articles with unsourced statements from January 2011
Personal tools
Log in / create account
Namespaces
Article Discussion
Variants
Views
Read Edit View history
Actions
Search
Navigation
Main page Contents Featured content Current events Random article Donate to Wikipedia
Interaction
Help About Wikipedia Community portal Recent changes Contact Wikipedia
Toolbox
What links here Related changes Upload file Special pages Permanent link Cite this page Rate this page Rate this page
Print/export
Create a book Download as PDF Printable version
Languages
العربية বাংলা Česky Dansk Deutsch Español Euskara فارسی Français हि�न्दी Bahasa Indonesia Italiano Lietuvių Bahasa Melayu Nederlands Norsk (bokmål) Polski Português Slovenčina Svenska ไทย 中文
This page was last modified on 21 October 2011 at 18:06. Text is available under the Creative Commons Attribution-
ShareAlike License; additional terms may apply. See Terms of use for details.Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization.
Contact us
Privacy policy About Wikipedia Disclaimers Mobile view