Descriptions
the 555 was the first tour or time base timer (Timer) to about 1971 of the company with the Signetics SE555 / NE555. It was necessary for DIYers or professionals in a stable and friendly applications and mono stable astable. Since the first device a myriad of new channels summers have developed and presented in several publications professional or amateur. ten years some manufacturers stopped making these timers because of the competition in this market or for other reasons.
Other companies, like Philips still makes this circuit is nearly 30 years still very popular and used in many patterns. It's very unique and amazing in the history of electronic components or modes and technology change very fast. Although nowadays the CMOS version of this circuit, like the Motorola MC1455, is mostly used, the standard type is still available, however there have been many improvements and variations in the circuit. But all types are compatible with each other.
In this course I will show you what that is exactly the 555 and how to use it itself or in combination with other devices without the requirement to achieve a degree of engineering.
This timer uses a maze of transistors, diodes and resistors and for this reason I will use a chart with blocks to simplify the explanations and internal organizations of 555.
Examples of references according to the manufacturers:
The main features of the components are:
Max pulses less than 2 ms
Time base can be a few microseconds to hours
2 MHz max frequency
It works in single stable or astable
It operates from 4.5 V to 16 V, TTL compatible (5V)
Temperature stability of 0.005% per ° C
Output current 200 mA
The interior of the 555 is the equivalent of 20 transistors, 15 resistors and 2 diodes, depending on the manufacturer.
The equivalent circuit in the diagram below, provides control functions for threshold triggering, comparators, switches, and output stage.
Here is the internal principle of 555:
The value of the oscillation frequency output depends on the components C1, R1 externally.
The 555 includes two comparators connected to a voltage divider for determining a high threshold and a low threshold, a flip-flop set / reset, an output stage (3-Output), and a transistor for discharging the external capacitor C1 ( 7-Discharge).
The voltage control voltage (5-Threshold) is 2 / 3 of Vcc and the threshold voltage less than 1 / 3 Vcc.
The trigger (2-Trigger) is used to trigger the comparator low, stable single mode that activates the switch (set) and the timer output goes to 1, then if the reset control signal (4-Reset) passes 0 the output is also 0.
The diagram above shows the wiring in single stable (one-shot), the output is 1 when applying a negative pulse on the trigger of short duration. The duration of the pulse output is determined by R1 and C1, the output voltage is approximately 2 / 3 Vcc.
the time constant is:
Astable multivibrator mode:
Moreover, from the previous state, C1 begins to discharge through R2 during a period of time t2 until the voltage of C1 reaches 1 / 3 of food. In this interval, the output will be low.
Then the cycle begins again.
The total period of the cycle will be:
The 555 in the figure. One housing the oldest (20 years ago) metal round
Pin 1 (Ground): Ground is connected to the negative potential of food.
Pin 2 (Trigger): the trigger or trigger mono stable mode is used to trigger the start of the output signal; Astable mode have connected with pin 6.
Pin 3 (Output): Output (about 2 / 3 of the supply voltage)
Pin 4 (Reset): Reset, mono stable mode is used to force the signal low.
Pin 5 (Control Voltage): Control of the voltage divider bridge or internal modulation, not very useful and often not connected or related to a capacity to ground.
Pin 6 (Threshold): The trigger or comparator, in mono stable have connected with the discharge.
Pin 7 (Discharge): The landfill is used to short circuit the external capacitor of the timer.
Pin 8 (Vcc): Food + circuit 4.5 V to 16 V, the supply voltage n 'is a very influence on the period of the timer (0.1% per volt) but it influences the output voltage and current.
Application mono stable S1 triggers the output signal to light the LED for a time determined by R1 and C1.
Bicycle Rear Warning: Have just used the 555 in astable multivibrator fed by three or four 1.5 V batteries and LEDs in series and parallel flash.
Alarm Auto simple: S0 open starts the alarm, the door contacts S1 to S4 are normally closed, out of the car you have a few seconds determined by R1, C1, and then when one opens a door he 3 seconds R2, C2 S0 to operate before the relay triggers an alarm when tripped over the fact that closed the doors n 'not stop the alarm, only in the closed position S0 cut the alarm. (Contact S0 may be a shunt on DIN socket)
the 555 was the first tour or time base timer (Timer) to about 1971 of the company with the Signetics SE555 / NE555. It was necessary for DIYers or professionals in a stable and friendly applications and mono stable astable. Since the first device a myriad of new channels summers have developed and presented in several publications professional or amateur. ten years some manufacturers stopped making these timers because of the competition in this market or for other reasons.
Other companies, like Philips still makes this circuit is nearly 30 years still very popular and used in many patterns. It's very unique and amazing in the history of electronic components or modes and technology change very fast. Although nowadays the CMOS version of this circuit, like the Motorola MC1455, is mostly used, the standard type is still available, however there have been many improvements and variations in the circuit. But all types are compatible with each other.
In this course I will show you what that is exactly the 555 and how to use it itself or in combination with other devices without the requirement to achieve a degree of engineering.
This timer uses a maze of transistors, diodes and resistors and for this reason I will use a chart with blocks to simplify the explanations and internal organizations of 555.
Examples of references according to the manufacturers:
The main features of the components are:
Max pulses less than 2 ms
Time base can be a few microseconds to hours
2 MHz max frequency
It works in single stable or astable
It operates from 4.5 V to 16 V, TTL compatible (5V)
Temperature stability of 0.005% per ° C
Output current 200 mA
Composition: Diagram component NE555
The interior of the 555 is the equivalent of 20 transistors, 15 resistors and 2 diodes, depending on the manufacturer.
The equivalent circuit in the diagram below, provides control functions for threshold triggering, comparators, switches, and output stage.
Units; Formulas
The value of the oscillation frequency output depends on the components C1, R1 externally.
The 555 includes two comparators connected to a voltage divider for determining a high threshold and a low threshold, a flip-flop set / reset, an output stage (3-Output), and a transistor for discharging the external capacitor C1 ( 7-Discharge).
The voltage control voltage (5-Threshold) is 2 / 3 of Vcc and the threshold voltage less than 1 / 3 Vcc.
The trigger (2-Trigger) is used to trigger the comparator low, stable single mode that activates the switch (set) and the timer output goes to 1, then if the reset control signal (4-Reset) passes 0 the output is also 0.
the time constant is:
t = 1.1 x R1 x C1
If the resistance value is 1 and the ability megaohms 1uF (micro-Farad). The time constant in this case: t = 1.1 x 1,000,000 x 001 = 0.000 1.1 seconds
but we must take into account the tolerance of components. Astable multivibrator mode:
Astable multivibrator mode (free-running) produces continuous slots. The frequency of slots is determined by R1, R2 and C1. Initially the capacitor C1 is discharged. As a signal is applied on the trigger, the capacitor begins charging through resistors R1 and R2, for a time t1, during which the output is high, and this, until the voltage in C1 reaches 2 / 3 of food.
Then the cycle begins again.
t1 = 0.693 x (R1 + R2) x C1
t2 = 0.693 x R2 x C1
T = t1 + t2 = 0.693 x (R1 + 2XR2) x C1
The oscillation frequency is the inverse of the period: F = 1 / T = 1.44 / (R1 + 2XR2) x C1
In the circuit below has two diodes up to control the charging and discharging of the capacitor C1.Ont obtained by setting P1 and P2 a symmetrical output signal t1 = t2. Values
and figure. 2 housing the most familiar 8-pin
rare 14-pin fig 3.
DIP 8-pin SOP package version CMS.
The definition of Pins:
Pin 1 (Ground): Ground is connected to the negative potential of food.
Pin 2 (Trigger): the trigger or trigger mono stable mode is used to trigger the start of the output signal; Astable mode have connected with pin 6.
Pin 3 (Output): Output (about 2 / 3 of the supply voltage)
Pin 4 (Reset): Reset, mono stable mode is used to force the signal low.
Pin 5 (Control Voltage): Control of the voltage divider bridge or internal modulation, not very useful and often not connected or related to a capacity to ground.
Pin 6 (Threshold): The trigger or comparator, in mono stable have connected with the discharge.
Pin 7 (Discharge): The landfill is used to short circuit the external capacitor of the timer.
Pin 8 (Vcc): Food + circuit 4.5 V to 16 V, the supply voltage n 'is a very influence on the period of the timer (0.1% per volt) but it influences the output voltage and current.
Variants
The 556 is a dual 555 in a housing 14 - pin The 558 also has four 555 in boitier14 - pin.
Uses:
Application mono stable S1 triggers the output signal to light the LED for a time determined by R1 and C1.
Application mono stable with reset:
Same but with S2 have can stop the signal.
Astable Application: LED flashes continuously.
Example output:
Examples of uses:
Touch-sensitive: with a resistance of 10 M on the trigger (2-Trigger) triggering the timer becomes very sensitive, simple and touching with a finger triggers the lighting of the LED for a time determined by R1 and C1.
Alarm Auto simple: S0 open starts the alarm, the door contacts S1 to S4 are normally closed, out of the car you have a few seconds determined by R1, C1, and then when one opens a door he 3 seconds R2, C2 S0 to operate before the relay triggers an alarm when tripped over the fact that closed the doors n 'not stop the alarm, only in the closed position S0 cut the alarm. (Contact S0 may be a shunt on DIN socket)
voltage doubler circuit 24V to 12V TO BASE NE555: The Description of 12v/24v assembly. The diagram of a voltage doubler using simple NE555 timer is shown here. Here IC NE555 is wired as an astable multivibrator operating at about 9kHz. The basis of the two transistors (Q1 and Q2) is bypassed and the output of astable multivibrator (pin 3) is connected. When the output of astable multivibrator is low, Q1 and Q2 will be turned OFF. The negative terminal of the capacitor C3 will be shorted to ground through Q2 and will be charged to the voltage power input. When the output of the astable multi vibrator is high, the transistor Q1 is ON and the transistor Q2 will OFF.Le capacitor C4 will be charged to the voltage across the capacitor C3, the higher the supply voltage input (which is double the input voltage).
The voltage doubler circuit can provide up to 50 mA output current and just above the current limit of the output voltage will be significantly reduced. The actual output voltage will be around for a 19V input and 12V DC output voltage will be a little unstable. Nevertheless, for low current applications this circuit is quite good.
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