Industrial Motion Sensor Circuit

The post illustrates an industrial motion sensor circuit using a couple of LDRs, an IC and a few other passive components. The circuit senses the movement of a cylinder illuminating the appropriate LEDs for the required detection. The idea was requested by Mr.Hasnain.


The Request


hi, sir how are you, i have sent you request on Google account, i am not sure that you got my messages or not, so i am sending you my problem here again, please help me out... plzzzzzz plzzzz, i shall be very thankful to you, i hope you will understand my problem and solve it...

sir it is related to motion sensing,  and i have no knowledge about sensors, that which type i should use..

problem :    there are two levels, ( level means height), level A, and level B.        height A > height B.

i want to use sensors at these levels, so from now i will say sensor A and sensor B..

i have two indication lights RED and GREEN.

there is a cylinder that moves from up to down and then down to up and so on...

@!!!!!!!!@  first it will move from up to down and will come in front of sensor A. ( at this time RED light should turn ON and GREEN turn OFF).

and moving downward cylinder will come in front of sensor B. ( this should make no difference, i,e RED should remain ON, and GREEN should remain OFF ).

then cylinder will start moving upward, first it will move away from sensor B. ( at this time RED should turn OFF and GREEN turn ON), then moving upward cylinder will move away from sensor A, ( this should make no difference. i,e  RED should remain OFF and GREEN should remain ON)..

then again repeat from @!!!!!!!!@

The Design

The proposed idea of the industrial motion sensor circuit is quite straightforward and can be understood with the following points:

When power is switched ON, the IC is reset through the 0.1uF capacitor ensuring the green LED illuminates first.

At this position both the sensors sensorA (LDR1) and sensorB (LDR2) are able to receive the lights from the relevant laser beams focused at them.

LDR1 switches ON BC547 transistor while LDR2 does the same for BC557 and keeps it triggered.

Due the above actions the transistor BC557 passes the supply voltage to pin#14 of the IC. However since LDR1 ad BC547 are also conducting this potential gets grounded, and the net potential at pin#14 remains at logic low or zero.

Now as the cylinder lowers and comes in front of LDR1, it blocks the beam making LDR1 resistance high, shutting OFF BC547. This allows the voltage from the BC557 to hit pin#14 producing a forward sequence at the output of IC which results in illuminating the red LED and shutting off green LED.

The cylinder continues its downward motion and comes in front of LDR2 blocking its beam and lowering its resistance, this stops the transistor from conducting such that the potential at pin#14 of the IC is again switched back to zero, however this action does not effect the IC since it's specified to respond only to positive pulses.

Next, the cylinders reverts and starts moving upwards and in the course unblocks the LDR2 beam allowing the BC557 to conduct, and yet again the positive pulse from the transistor is allowed to hit the IC pin#14 resulting in the restoration of the previous situation i.e. now green LED illuminates and the RED shuts off.

As the cylinder moves past LDR1, BC547 also switches ON, but produces no effect due to the same reasons as explained above.

The above motion detection cycle keeps repeating in response to the specified cylinder movement.

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