Hello friends, I am working on a project where I am only allowed to use analog components. I cannot use ICs, microcontrollers, or microprocessors. I plan to use a passive transducer pair as a motion sensor. The main component I need to use in my circuit is the 555 Timer. I will use the 555 Timer as a 40kHz wave generator to drive the transducers. A part of the circuit's schematic is shown in the image below. However, I am not sure how to connect the transducer pair. Could you help me with this?
(Also, this circuit is not mine. It’s a 555 Timer circuit I found online that outputs a 40kHz signal. How should I connect the transducers to the output of this circuit?)

 

In principle, the 555 will work,but the output will not be a square wave, in the sense, it will not be 50% duty cycle.
If you need a 50% duty cycle, you will need to use a D FlipFlop driven by the 555 running at 80 KHz to get a 40 KHz square wave with 50 % duty cycle.

In its simplest form, the Transducers take the place of 1 (or both) of those LED's.
Whether this simple setup works satisfactorily will depend on the Tranducer specifications. Voltage, Current, ....
A 555 has sufficient capacity to drive most transducers.

 

I don't need a %50 duty cylce. For driving transducers i just need 40kHz frequency square wave. How should i design the circuit?

 

Specs of the transducer?
The simplest is connecting the Transducer between 3 of 555 and Ground. But, since I do not know the specs of the Transducer, I don't know if the Transducer will get overloaded and damaged.

 

We didn't have enough time to order passive pairs from the internet, so we decided to use the HC-SR04. By heating the solder, we extracted only the pair components (the circular transducers).


HC-SR04 Specifications:

• Working Voltage: DC 5V
• Working Current: 15mA
• Working Frequency: 40Hz
• Max Range: 4m
• Min Range: 2cm
• Measuring Angle: 15 degrees
• Trigger Input Signal: 10µs TTL pulse
• Echo Output Signal: TTL level signal proportional to the range
• Dimension: 452015mm

Since the use of ICs or similar components is not allowed, we are only utilizing the circular transducers from the HC-SR04 module.

 

Connect the Transducer between pin 3 (output) of the 555 and Ground.
Limit the 555 voltage to 5 Volts.

I don't think a 555 is required at all. That Transducer has all built in.

 

i have a last question, should i give 5v from vcc or 2/3 vcc (control voltage) ? and for all ur responses thanks a lot

 

Read
https://www.elprocus.com/hc-sr04-ultrasonic-sensor-working-and-its-applications/

working, para 3

 

i have a last question, should i give 5v from vcc or 2/3 vcc (control voltage) ? and for all ur responses thanks a lot

You do not require a 555.
Please read the web link above,
AFAIK, that circular Transducer outputs 40 KHz when supplied 5 volts.

 

If you are "not allowed to use ICs", that means no 555 timer IC, and so you have a bit of a problem. Or is the limitation about DIGITAL LOGIC ICs?? Is the motion sensor to be reflective type or a beam-break arrangement? Is it intended to sense human motion or object motion?? One great scheme is to use the detector as the input to an amplifier and the sound generator connected to the amplifier output, so that they form an oscillator with acoustic feedback. Then motion between will prevent the oscillation. I have seen that scheme used in security alarm systems, it has worked well.

This seems more like an end-of-term project, really.

 

I am only allowed to use analog components. I cannot use ICs, microcontrollers, or microprocessors

No ICs, doesn't that mean the 555 is not allowable? You may have to use transistors instead.

 

there is just one ic that allowed. and its 555 timer. i must use just this.

 

OK, so you have the 555 timer feeding a healthy square wave to one transducer. The other transducer is sensing that frequency and delivering a 40KHzsignal. So you need to detect a variation in the phase due to external motion?? Or a change in amplitude?? or how will you detect motion???

 

https://www.adafruit.com/product/3942
So, what are you triggering from? Missing pulses on the module?