Light-controlled oscillator: LDR + LM 555 Timer

In this report, the first "Light-controlled oscillator: LDR + LM 555 Timer" The materials used in the experiment are described in detail the LM 555 timer and photo-resistor, which fotorezistörün to the amount of light shows how much resistance, obtained from the equation of truth "least squares" and multivibrator circuits will learn about the method of data-dictive value in RCC. LM 555 timer integrated circuit using a combination of tests performed with the LDR, the output frequency which varies with the amount of light "astable multivibrator" ossilasyon circuit described how it was established, "Multisim" at the end of the circuit drawing and simulation program and test a variety of gerçeklenecek observation, measurement, and comments will be made.

Finally, "Out on the other phototransistor Raising a transistor Kulla-nara" experiment, semi-sensitivity angle, a "field of view", a cold mirror, hot mirror, the IR-lens focal length weighing şılacak concepts, changing the angle of the light source, the output of the circuit, what effects will be observed that .

"Light-controlled oscillator: LDR + LM 555 Timer" Test

Materials Used

"Light-controlled oscillator: LDR + LM 555 Timer" The materials used in experiments:

1 x LM 555 Timer

1 piece of photo-resistor

1 μF capacitor value of 1-pole

Value of 1 x 10 μF capacitor pole

1 x 4.7 kΩ resistor value

First, the circuit components used in the experiment, "Photo-resistor" in the Let's examine:

Photo-resistor (LDR)

LDR'nin English equivalent of "Light Dependent Resistor" is Turkish meaning "Light-changing resistance value is"

Photons have enough energy, valence band, conduction band electrons increases, thus falling LDR'nin resistance R, LDR basic voltage divider circuit, the potential difference increases between the load resistance RL. LDR'nin a decrease in resistance R sense, depending on the amount of light increases the conductivity. In other words, in light of a current is passed through LDR'nin increases, the decrease in the dark.

LDR, resistance to the bias voltage does not matter because it is the structure (see Figure 2). Because the LDR, is not a PN junction structure, a single crystal.

LDR, the wavelength of 0.4 μ and 0.7 μ wavelength is sensitive to visible light. LDR resistance R (Ω) with the amount of light falling on the LDR L (Lux) is located between the formula below:

LDR resistance changes linearly with the amount of light is a logarithmic function. Now, in the amount of light a certain resistance to changing the values ​​in Table 1 to examine the changing LDR:
Lux-R Measurements

The amount of light, L (Lux) LDR Resistance, R (kΩ)


The values ​​given in Table-like gra-vetch logarithmic expressions with the help of the MATLAB program çizdirildiğinde graphics were obtained with the following script:

»L = [10,100,500,700,1000,5000,10000];
»R = [84.00,12.60,2.84,2.14,1.54,0.42,0.24] * 1000;
»Loglog (L, R, 'r *-.'), grid;
»Xlabel ('log lux');
»Ylabel ('log R');
»Title ('LDR Light Resistance to the amount of change');

Now, the "least squares" method, before the help line with the slope, then the y-axis crossing point (ie, dark resistance'ı) and finally with the help of this data to find the equation: "least squares" method

xi: i. the amount of light component is expressed in logarithmic
URL: LDR resistance in ohms i. component is expressed in logarithmic

is found.

while the y-axis intercept, ie "dark resistance" value can be found in the following equation:

Rd: dark resistance is obtained to be.
Finally, the correct equation, create value, we find:

LDR'lerin applications, industrial control systems, automatic night lights, digital counters (counter), medical devices that determine the blood color density-The intensity, flash cameras, movement detectors ket, bell buttons and so on. places.

LM 555 Timer

LM 555 Timer (timer) Integration of the integrations is one of the most important and most used. That the timing of all the electronic cards (most of the digital cards) can be seen easily.

With the LM 555 timer can generate a square wave with the desired frequency

To produce a square wave

As you can see the LM 555 integrated circuit operation of Timer 1 and 8 for the voltage applied to the ends Vs. Resistors R1 and R2, capacitor C1 as it identifies the duration of filling (by VS will start to fill up capacitor C1) as the recharge time idle in the output signal Vs. R2 is then emptied through a capacitor value and this value determines the length of the output signal of 0 V. As a result, characteristic of the RC circuit can draw the following:

Resistor R1 is used in tests performed in the LDR resistance.

LM 555 timer integrated circuit, digital circuits are more application areas. Because the 555 timer, an integrated digital sense, 0 and 1's generating very important. For example, the digital clock output signal is performed second (second part of the time), making available. The output signal is done in a minute, minute portion of the digital clock can be managed. As another example, an open staircase light exposure time can be adjusted as desired.


Digital circuits used in electronic circuits too. These signal generator (square, triangle, rectangle, etc.), timer (timer), and the memory element (Memory Unit) is used for such purposes. Multivibrators, such as transistor circuits realized, special purpose logic gates or integrate it can be carried out.

Multivibrators generally divided into three categories:

Monostable (One-Stable) multivibrator

Bistable (two stable) multivibrator

Astable (Unstable) multivibrator

Monostable (One-Stable) multivibrator

You're changing the timing signal is applied to the trigger input of staff and time remaining in this position for the time determined at the end of the first rotating position circuits. So, Monostable multivibrator, a transistor and other lean-tımda transmission is a circuit which has a single fixed location. The location of the circuit is to modify the areas of the transistor transmission circuit to pass a trigger pulse must be applied.

Bistable (two stable) multivibrator

Bistable multivibrators forever unless an external trigger signal applied to the outside and to protect the status of all circuits that trigger signal changed state. Bistable multivibrators, flip-flops in a sense the foundation of the memory element. Has two stable state. Start-up until the trigger pulse applied to the circuit maintains a fixed position. After applying the trigger pulse enters the circuit in steady-state and the other to return to the previous steady-state re-trigger trigger pulses are needed.

Basic bistable multivibrator circuit shown in Figure 9. Transmission, while the other is a transistor isolation. For example, suppose you have insulation transistor Q1 Q2 transmission. Start-export-rida bulunulmadığı any impact as long as the co-numunu protect the transistors. With the insulation applied to the outside of a trigger Q2 transmission, transmission of the insulation will be the Q1. In other words, a trigger pulse to be applied from out of position change with the circuit.

Astable (Unstable) multivibrator

Astable multivibrators, time-from start operating voltage is given, Monostable and bistable multivibrators unlike any trigger signal from out-za-manlama elements in the circuit without the need for well-being that changes continuously with time intervals determined circuits.
LM 555 timer, astable multivibrator circuit used in the LED lamp blinks and fighting, pulse generation, logic clock, security alarms, there are application areas, such as pulse position modulation.
After the detailed information provided about the materials used in the experiment as necessary to pick up, thanks to this experiment, the LM 555 timer IC used in combination with LDR, with a varying amount of light output frequency astable multivibrator circuit ossilasyon establishment and the various observations and measurements will be done.

Try Preparation

• the installation of the circuit before performing the first, the pole placement of capacitors on the board and you must submit the drop of the LM 555 timer was the definition of connectors.
• LDR formed together with the LM 555 timer integrated circuit ossilasyon circuit board was founded on the output signal back to the amounts of light by moving parts and a variety of frequency / period is observed. LDR'yi Multisim circuit drawing program that represents the resistance values ​​and the simulated correlation, Table 1, varying according to the amount of light is determined as the LDR resistance.
• In this case, darkness or twilight, close to the light environment of the 10 Lux'te LDR'nin deti severe resistance, the nature of the LDR is very high-value corresponds to the 84 kΩ'a. Under this light intensity LDR'yi ossilasyon circuit board that represents the resistance and the output signal is observed in Figure 10 and Figure 11 are, respectively, were obtained as.
• The amount of light a little bit by increasing the media environment in a setting that represents the light intensity-ni 100 Lux'te LDR'nin resistance, a pre-capture the light of the nature of the LDR has further reduced depending on the severity and 12.6 correspond kΩ'a suggests. Under this light intensity LDR'yi ossilasyon circuit board that represents the resistance and the observed output signal, respectively, were obtained as in Figure 12 and Figure 13'teki (the difference between the output signals on the oscilloscope to-MEK 100 ms / div and 2 V / div is set to .).

• the media is further increased by the amount of light representing the light intensity 500 Lux'te LDR'nin resistance cloudy day, the LDR of the nature of the conductivity increased by more than the previous light intensity decreases and corresponds to 2.84 kΩ'a. Under this light intensity LDR'yi ossilasyon circuit board that represents the resistance

• the media is increasing the amount of light 700 Lux beklenil-digi LDR'nin resistance further down to 2.14 corresponds to kΩ'a. Under this light intensity LDR'yi ossilasyon circuit board that represents the resistance and the observed output signal, respectively, were obtained as in Figure 16 and Figure 17'deki.

• Increasing the conductivity of the media light of 1000 Lux LDR'nin artmasıy-la resistance, a decrease of 1.54 corresponds to kΩ'a. Under this light intensity LDR'yi ossilasyon circuit board that represents the resistance and the observed output signal, respectively, were obtained as in Figure 18 and Figure 19'daki.

• Relative amount of light, sunny day in a close environment, the increase in the conductivity value of 5000 Lux LDR'nin resistance is increased, decreased, this time corresponds to 420 Ω'a. This light golden-intensity resistance representing the LDR'yi ossilasyon circuit board and the observed output signal, respectively, obtained as in Figure 20 and Figure 21'deki e-acquisition card.

Figure 20: LM555 + LDR Ossilasyon Circuit (5000 Lux 420 Ω)

Figure 21: 5000 Lux Light Output Signal Obtained by Amount

• Finally, the amount of ambient light environment, representing a sunny day and removed from the LDR'nin resistance up to 10,000 Lux, 240 drops to Ω'a. Under this light intensity LDR'yi ossilasyon circuit board that represents the resistance and the observed output signal, respectively, were obtained as in Figure 22 and Figure 23'teki.

Figure 22: LM555 + LDR Ossilasyon Circuit (10000 Lux  240 Ω)

Figure 23: 10000 Lux Light Output Signal Obtained by Amount

• measured values ​​of the received output signals, frequency, and Thigh-Tlow fairy-yotları observed. Observations made as a result of the ambient light is low Thigh bone-tar does not increase the duration, and thus obtained does not change the duration of the pulse Tlow increase in the total period of observation-filled glass pipette (see Figure 24). In addition, the frequency is inversely proportional to the pulse frequency decreases the period was also examined (see Figure 25). Decrease in the amount of ambient light is increased, the duration of the Thigh, Tlow value does not change the total period of the coup, and therefore reduced from the observed (see Figure 24). Pulse frequency was increased only by implication, the difference (see Table 2 and Figure 25).

Table: Amount of Light, Output Signal
Total Period, and Frequency Effect

Amount of Light (Lux) LDR Resistance (kΩ) Thigh (ms) Tlow (ms) T (ms) Frequency (Hz)
10 84 615.0 32.9 648.0 1.54
100 12.6 120.2 32.9 153.2 6.53
500 2.84 52.6 32.9 85.5 11.69
700 2.14 47.7 32.9 80.7 12.40
1000 1.54 43.6 32.9 76.5 13.07
5000 0.42 35.8 32.9 68.7 14.55
10000 0.24 34.6 32.9 67.5 14.82

Figure 24: Changing the Amount of Light, Output Signal
Total Period Effect

Figure 25: Changing the Amount of Light, The Effect of Frequency Output Signal


The experiment showed that the resistors R1 and R2 (the resistance of resistor R2 to represent LDR), capacitor C2 determines the time for filling (Vs by the capacitor C2 will begin to fill up) from the time it expires as the output signal vs. the duration of the Thigh. R1 and then emptied through a capacitor value and the value of the output signal of 0 V to determine the ability of the Tlow time.
As a result, increase the amount of ambient light, increased resistance reduces LDR'nin conductor-ischemic scales provided, so that is independent of the LDR resistance-daemon Tlow time unchanged, but were decreased Thigh time. Because the capacitor C2 quickly filled with a low time constant were also founded. With a decrease in the amount of ambient light, the conductivity of LDR'nin decreased, this led to an increase in the resistance. For this reason, the LDR resistance that is independent of time Tlow not changed, but the increased duration of Thigh. Because this time with a high time constant of capacitor C2 were not allowed to discharge more quickly.

NOTE: The value of capacitor C2, the AC metric oscilloscope rise-fall time affects the duration of time. Therefore, the value of capacitor C2 if the AC measurement of how much low-value will be more healthy. Still, just in case the experiment measurements, the oscilloscope is set to DC and AC location were easily reduced, the observations being seen up was conducted.

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