Infrared alarm barrier circuit
This infrared alarm barrier can be used to detect persons passing through doorways, corridors and small gates. The transmitter emits a beam of infrared light which is invisible to the human eye. The buzzer at the output of the receiver is activated when the light beam is interrupted by a person passing through it.
Infrared Light Alarm Transmitter Circuit Schematic
Infrared Alarm Barrier Receiver Circuit Schematic
How to make an infrared barrier alarm
The transmitter and receiver circuits of the infrared alarm system shown here have been designed for a range of several meters, almost independent of ambient light conditions. Only in the rare case of the receiver sensor being exposed to bright, direct sunlight, some screening measures have to be added.
The transmitter does not emit a continuous infrared signal, Rather, it is modulated, that is, the 36-kHz carrier used to pulse the IRED (infrared emitting diode) on and off is itself switched on an off at a rate of about 300 Hz. The reason for doing so is that most infrared sensors, including the ones suggested in the diagram do not respond very well to continuous incidence of infrared light. Switching the IR source off, even for a small period, allows IR detectors to ‘recuperate’, and so optimise their ability to minimize the response to ambient light.
The transmitter consists of two oscillators built around the ubiquitous 555 IC. Here, the current-saving CMOS version TLC555 (or 7555) is used. Alternatively, the two 555’s may be replaced by a single TLC556 (or 7556). IC1 is the 300-Hz generator, IC2, the 36-kHz source. The IRED type LD274 is pulsed at a relatively high peak current via driver transistor T1. If in your application the distance covered by the IR beam is relatively short, the value of resistor R5 may be increased to save on current consumption. Preset P1 is adjusted for a carrier frequency of 36 kHz exactly (failing test equipment, adjust it for optimum range).
The receiver is equally simple and also based on a CMOS 555. As long as the sensor picks up infrared light from the transmitter, the reset input of the 555 IC is held low and the buzzer is silent. Components D1 and C2 act as a low-frequency rectifier to cancel the effect of the 300-Hz modulation on the transmitter signal. When the infrared light beam is interrupted, the oscillator built around the 555 is enabled and starts to produce a warning tone.
Finally, the test values indicated in the infrared barrier alarm circuit diagram are average dc levels measured with a DVM, under light/no light conditions. In fact, most test points carry rectangular or sawtooth waveforms.
23 Responses to “Infrared alarm barrier circuit”
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Hi, can i know why the IC1 is produce 300hz?
f =1.4/[(R1 + 2R2) × C1]
from the formula
substitude the value
R1= 4.7k
R2=100k
C1=10n
Frequency should be 683.92hz
Hi,
Do you know what is the maximun distance between the transmitter and the receiver?
Thank you
I am building these circuits but the Infrared Light Barrier Receiver isn’t working as is shoudt be.Can i have a reponse if anyone now wy it doesn’t work.
Or has anyone a reponse wat to do.
Thank you
Important checkpoint:
You should not use just LM555 series. It does not work under 4.5 volt.
So, you can use TLC555(2-15volt) or TS555(2-16volt) series only.
Hi,
The theoretical frequency will differ from actual. because you have to consider the tolerence of capacitor and resistsnce used.
If the circuit is not working, most probably one would have connected the BD140 transistor or the IR sensor pins in wrong way.
can anyone tell me what is this preset p1 in this ckt and what is its function
Preset P1 is the small variable resistor. Its value shown is 25K.It adjusts the frequency of the Astable 555 to give desired output frequency to drive the LED.By changing the wiper of preset, it is easy to set the correct frequency of IR beam
i want to build this circuit, can we use NE 555 instead of TLc 555 ? how can we adjust the friquency without CRO. tell me this plz
thanks
TLC 555 is a CMOS version of 555 timer & use of NE555 as an alternative is not recommended.Adjusting frequency without a CRO/Frequency counter is not possible.Anyway,you can adjust it using trial&error method ie switch on receiver and then tune transmitter so that they are perfectlylocked!
I want to know more about how to build a security alarm
i like to build this circuit…’got to gather all the components…
what do the vaules like 2V5, 2V6 (transmitor circuit) means??
and same is the quiry for receiver circuit i.e values stating 4V92…
Can anyone tell me the equivalent of the LD274 and the transistor BD 140?
what is need of bd140. what is the maximum distance between transmitter and receiver
Please contact us for more detail ,also we have different types of passive infrared radiation detector like active beam infrared detector/passive motion detector/combustible gas detector/smoke detector/Glass break detector/heat detector.
And wireless home alarm system with their accessories.
CCTV camera including waterproof camera and high speed dome camera.
We can also Supply spare parts and accessoires for alarm system like alarm siren,door magnetic contact,sound&flash light ,emergency button and their bracket.
what is the alternative for BAT85?
can enyone send me the pcb design for these two circuits.,.
my mail id is
mvysakh6@gmail.com
plz snd repley if anyone would built it.
i want it too
vysakh,still need the pcb drawing? home made but it works,if you need …
any one have this circuit by proteus program
for tan :1N5819
how long does the alarm sounds when i just interrupted the signal for 1 sec?\
pls repz ASAp
tnx
hi,do you know the distance between the receiver and the transmitter cant operated normally.thanks