The Basic NE-555 NEON LAMP DRIVER Circuit :


 A simple circuit to power a NEON lamp.   Primarily it was used to test 90 Volt neons where "tester safety" is a high requirement.
   
 Often in industry, we need to make choices as to what an employee can and cannot use in full safety in the workplace, this is one such 
 battery powered device. 

 The R1 - R2 - C1 circuit determines the output oscillation frequency of the NE-555, thus producing a voltage at Pin 3 just high enough 
 to power into the small 8 ohm transformer's primary windings, the secondary windings are 1K ohms. Thus testing any 90 Volts neon.

 This results in a ratio of about 125 times gain, however we all know based on the maths, that's not going to fly. What about the Losses ?

 The "theoretical voltage" of around 500 Volts AC passing through R3 10K dropping to around 180V AC is thus just enough to strike the gas 
 within the neon and therefore lighting it enough to detect whether the neon is a goer or just a bit of glass. It is not designed for continuous
 usage but as a "go or no-go tester", easily fitted into a small plastic box and power it by a 9 V battery and very portable. User friendly.









           The Basic NE - 555 Infra-Red Transmitter Circuit and NE - 567 Receiver :



   A simple NE - 555 circuit is employed to primarily power an infra-red LED. Virtually any brand of NE-555 may be used here. 

   The VR1 - R1 - C1 circuit determines the NE - 555 oscillator producing a square wave rise and fall voltage at Pin 3 driving the 
   Infra - Red LED 1, being fed   + Vcc  via "R2" with a set value of 10 ohms. The NE-567 is a phased-locked loop chip

   Check the data sheets for your infra-red LED as the current requirements will vary from manufacturer to manufacturer. You may need
   to increase the "R2" value to 22 ohms or more based on the operation current of the I.R. LED. (see PARTS 9 lines below)
   
   This simple NE - 555 circuit runs on a single + 9 Volt DC power source, we suggest using a power supply for long term deployment.
   The circuit is designed for security use where an inconspicuous infra-red LED beam is needed. It is open to you for experimentation.

   SETTING UP:
   Setting up is relatively easy, with power applied to the receiver portion, gently turn VR1 on the Transmitter board until the relay
   clicks ( chatters ) and operates fully and becomes as a fully latched-on mode. Be patient, this latching may take up to 2 seconds. 

   We suggest using a small plastic "tube" perhaps with a small lens on the Photo-Transistor part to direct the incoming infra-red beam 
   directly into the tube to achieve the best results.  Line both the tubes up for best results, this task will require two persons.

   Please experiment with the same "tube" concept on the transmitter end as this will make the devices respond to directional infra-red 
   input rather than a "splatter" of I.R. waves. Note: operating at lower frequencies affects latching times, making them slower. 
   PARTS: Infra-red transistor - Wagner Electronics, Part No:IRR53C (clear lens) Infra-Red Diode - CQY-89  
   (remote control IR diode)




      The Basic NE-555 Simple Flasher Circuit :



A simple and novel NE-555 dual globe flasher circuit to primarily power a relay that switches power to each globe in turn.
 
The R1 - R2 - C1 along with VR1 4K7 combo determines the NE-555  to oscillate slowly producing a voltage at Pin 3 
driving the base of Q1 2N2222 an NPN transistor, which in turn drives the relay that switches the two globes on and off. 

Diodes D2 and D3 provide the feedback logic 1 pulse to Pin 4 reset of the 555. C2/R4 forms a slight "buffering" function.

This simple NE-555 circuit runs on + 12V DC, the circuit is protected against back E.M.F. (Electro-Motive Force) or the 
collapsing coil voltage by diode 1N4004 D1 which is rated at 400 Volts at 1 amp.

The back E.M.F. from some coils measured by us has be witnessed on the C.R.O. to generate upwards and beyond a 
350 volts spike ! 

Applications: This circuit was designed for Security use or Vehicle breakdown dual lamp use where needed. Cop cars ?










      The Basic NE-555 Improved Oscillator Circuit :



A simple NE-555 circuit with a vastly improved oscillation. So simple, why did we not use it before ? It uses only one
resistor and one capacitor. For the purpose of the simplicity in display, we have "left off" the 0.01uF ceramic capacitor 
which we would usually connect from   pin 5   to ground.  The circuit draws very little current from the supply, however 
the frequency of operation will in fact be lower than a dual resistor circuit as describe in many other circuits.

This lower frequency is mostly due to the fact that the voltage delivered by the output line from  Pin 3  is 1.7 Volts less 
than the supply rails.  The output is still capable of driving up to 200mA.  Don't exceed this. You may destroy your chip!

The   R1 x C1   circuit determines the   NE-555   to oscillate  producing a voltage at   Pin 3   which also is fed back via 
R1 a 1K driving the NE-555 chip into almost perfect oscillation. Observe it on the C.R.O .(Cathode Ray Oscilloscope).

This simple NE-555 circuit runs on + 5 V to + 15 V DC. Most circuits run very well at 15 V DC all day.   This circuit was 
designed to use for "reasonably" good square wave output formations. Hey !, nothing is perfect, you may need to add
in a few potentiometers just to trim things up and get a much better looking square wave,     if that is what you want.    








      The Basic NE-555 SIMPLE TOUCH SWITCH :


This simple application of the NE-555 is   " triggered "   on pin 2 via Q1 2N2222 NPN transistor 
operating the NE-555 in Astable Mode. ( see FIGURE 30A ).    

The generated voltage is about 3 Volts less than the supply rail voltage due to   Pin 3   rising to 
approximately 1.7 Volts below the supply rail voltage, add to this the 0.6V loss through the diode.

It is sensitive enough to pick up stray voltages such as static electricity and induce mains radiation 
picked up by our bodies.      

It can be "improved-on" by the addition of a second pad connected to ground which will enhance its
operation.  

This circuit can (  with a little experimentation  ) be connected to a metal gate or similar and be used 
to produce a tone using a second NE-555 circuit such as in a modified version either Fig. 1 or Fig. 2.

Experiment away,   don't let your mind be "walled in" by convention and preceding circuits,   always 
experiment and learn.  












       The Basic NE - 555 SIMPLE SWITCH DE-BOUNCER :

This mode of operation is also called MONOSTABLE MODE   The NE-555 can indeed be wired as a monostable.
A monostable has one stable state and that is the OFF state.  The "unstable" state is called the "ON" or a "HIGH"
LOGIC state.   When Pin 2 is triggered by an input pulse,   the monostable switches to its temporary or "ON" state.
      
It remains in that state for a period of time determined by an   R - C   network   and returns to its stable previous "OFF" state. 
Put simply, the monostable circuit generates a single fixed duration pulse during each time it receives its input trigger pulse.

The monostable circuit can also be called a "ONE-SHOT" due to the single-pulse created.     This type of circuit can be 
used for many switching applications, activating an external device for a specific length of time.  They can also be used
to generate timed delays.   Another desirable use for this type of circuit is to take the brief pulse of a   push - button   and 
activate a external device. We refer to this simply as a " PULSE-EXTENDER ". 

Another novel use is that it can also be used to clean-up the noisy output of a push-button due to poor contacts or a high 
moisture area, this we refer to as SWITCH DE-BOUNCING.  

The simple diagram below shows a push-button (on left) connected to a NE-555. When this push-button is  pressed, you will 
note that a relay has been added to Pin 3 (output) the relay operates for about 5 seconds. The button must be released before
the time-interval has expired otherwise the time is extended, so please note that this is a "limitation" of this simple circuit.        
 








      The Basic NE-555 ASTABLE and MONOSTABE MODES :

FIGURE 30A and also Figure 9b ( above ) both show the NE-555 connected as an astable multivibrator.
Both the trigger and threshold inputs  (  pins  2 and  6  )  to the two comparators are connected together
and to the external capacitor.  The capacitor charges toward the supply voltage through the two resistors,
R1 and R2. The discharge pin, (  Pin 7  ) connected to the internal transistor is connected to the junction 
of those two resistors.

When power is first applied to the circuit, the capacitor will be uncharged, therefore,  both the trigger and 
threshold inputs will be near zero volts   ( see Fig. 10 ).      The lower comparator sets the control flip-flop 
causing the output to switch high.    That also turns off transistor T1.  
    
That allows the capacitor to begin charging through R1 and R2. As soon as the charge on the capacitor
reaches 2/3 of the supply voltage,  the upper comparator will trigger causing the flip-flop to reset.           

That causes the output to switch low.   Transistor T1 also conducts.   The effect of T1 conducting causes R2
resistor to be connected across the external capacitor.       Resistor R2 is effectively connected to ground    
through the internal transistor T1. The result of that is that the capacitor now begins to discharge through R2.







Check the listing in Table 2. It shows some variations in the NE-555 manufacturing process primarily by two different 
manufacturers, National Semiconductor and Signetics Corporation.        Check Manufacturers Table 2 - click here    
 
Since there are many other NE-555 chip manufacturers we suggest when you build your prototype "test" circuit first of all,
using one of these two well known brands and stick with that particular brand of NE-555 model if the results are great. 
By all means, test many others, there may be several other brands which give you comparable results on the C.R.O.       

You may wish to specify a certain brand in your own NE-555 "circuit" project and its schematics and for a very good reason, 
the circuit functions " better " with one brand than another.     Always test a batch of brands to see which one gives results.
 
Unless you "really" know what you're doing in a critical timing circuit and of course, some do and some don't, stick with one brand.







     BIG NOTICE - READ NOW - TEMPERATURE RATINGS

            The absolute " maximum" ratings (in free air) for NE/SA/SE types are:
             
                              + Vcc, supply voltage: 18V Input voltage (CONT, RESET, THRES, TRIG): Vcc

                                                    Output current: 225mA (approx)

           Operating free-air temp. range: NE555 :...........   0°C -  70°C
                                                        SA555 :........... -40°C -  85°C
                                                        SE555 :........... -55°C - 125°C
                                                       SE555C :..........  -55°C - 125°C

                                                Storage temperature range: -65°C - 150°C

                                   Case temperature for 60sec. (FK package): 260°C
 
Please folks, remember that the NE-555 chip does create a certain "noise" on the Vcc supply lines, most applications can 
live with this undesirable characteristic.       When designing a  circuit using the NE-555, observe the suuply line on a CRO.

It is however, always wise to use "filtering" capacitors, preferably a 10uF Tantalum added to this a low ESR 100uF electrolytic and 
as well a 0.1uF disc ceramic capacitor to assist in "cleaning up" spurious noise generated by the NE - 555 on the supply +ve line.
 
Connecting an Electrolytic Capacitor the value of between 100uF and 470uF between +Vcc supply line and ground 
-Vdd as well as a 10uF Tantalum ( 16V~25V ) and also utilising a 0.1uF disc ceramic just to on the side of caution.

It has been observed that the introduction of a 10uH choke in the "supply in line" does not appear to improve any further
after the addition of those three capacitors.       The three capacitors it would seem suffice in cleaning up the spurious
previously observed "noise" on the +Vcc supply in line.            These three caps will greatly improve the line "condition" 
with the NE-555 oscillating at higher frequencies,    these "noises" can be seen quite clearly on a good CRO ( Cathode
Ray Oscilloscope ).       The next generation of Oscilloscopes have Liquid Crystal Screens, so what do we call them ?    
 
Interesting name CRO, since there is no Cathode Ray Tube used, what do we call a LCD screen CRO?.. a LCDO ? Liq-crys-dis-osc?




       NE - 555 Timer - Frequency and Duty Cycle Calculator 


Enter values for Resistor R1, Resistor R2, and Capacitor C1 and press the calculate button to solve for positive time interval (T1)
and negative time interval (T2). For example, a 12,000 ohm (12K) resistor (R1) and 150,000 ohm (150K) (R2) and 0.22 uF capacitor 
will produce output time intervals of roughly 24.698 mS (millis Seconds) positive (T1) and approximately 22.869 mS negative (T2). 
The frequency will be approximately 20.979 Hz.      Please Note:  R1 should always be greater than 1K Ohms and C1 should be 
greater than 0.0005 uF. Scroll up this page for basic NE-555 information ( pin-outs &  many interesting NE-555 circuits devised for
your interest).QU: Why do we refer to figures as "about", "approximately" and "roughly" ? ANS: On paper it all looks fine, reality is different.

The Maths of any circuit looks fine on theoretic paper, however the final results once built are not always what you desired and will
need "tweaking" to get your circuit to operate exactly as you designed, largely due to component tolerances and behaviour in a circuit.




REMEMBER:   Do not run an older 1971 - 1979 NE - 555 in excess of 200KHz, it will eventually smoke-up.

Notes:   This only applies to the older NE - 555's smoking-up. The newer 1979 onwards do not have this problem.