function of the components

[dummy55555]

UltraSonic Radar (UltraSonic Radar)

Can anyone briefly tell me the function of the component in the circuit.
such as why there is a capacitor at the ic 1.. and why there is diode 1,2,3,4 connected like this.. and more. can anyone just give me a simple answer for all the component in the circuit...
i really appreciate it. TQ

 

[Sceadwian]

There is no simple answer, all the components work together to form the complete circuit there is no way to explain it to you easily or quickly, and you'd really need to talk to the designer of the circuit themself ideally, people don't design circuits the same way. I would recommend checking out allaboutcircuits.com as they have pretty solid introductory course in electronics for the basics.

 

[Nigel Goodwin]

As with most circuits at that site, that specific one is not only particularly poor, it's also drawn incorrectly, so wouldn't work.

 

[karyoker]

Radars work with square waves and pulses. The cap is used for negative feedback and stability. In the case of D1-D2 On a + the signal is clamped and clipped to .6 volts by D2. With a negative the opposite occurs and you wind up with a 1.2 volt P_P square wave. C8 and resistor is a filter to clean up the rising and trailing edges.

 

[mneary]

The circuit shown is not radar. I've seen similar circuits work, but the descriptions in the article, and by karyoker, are wrong. I did find two schematic errors: TR3 emitter is missing (connected to R4 & C5) and R6 not labeled (it's across C8).

IC3 generates an ultrasonic signal, and receives what is hopefully a steady return signal amplitude. (The frequency is of no concern). It is amplified by TR3 and IC1, and then rectified by voltage doubler D1 and D2, charging C8. R6 (not labeled) discharges C8 when the signal changes. C10 and R7 form a high pass filter, to detect when the voltage on C8 (representing the return signal amplitude) changes. So a moving object in the field causes a changing voltage on IC2. P1 sets the AC gain of IC2. As the voltage on IC2 changes, these changes are rectified by voltage doubler D3 and D4. When the doubler output reaches the threshold of IC3, it latches and triggers the alarm connected to TR1.

 

[Nigel Goodwin]

The circuit shown is not radar. I've seen similar circuits work, but the descriptions in the article, and by karyoker, are wrong. I did find two schematic errors: TR3 emitter is missing (connected to R4 & C5) and R6 not labeled (it's across C8).

Check the incorrect connection of C1 as well.

 

[karyoker]

ROFL Actually it resembles a metal detector more than a radar. I just gave a general account what it might do as wired.

BTW I did work on the SPW2 missle guidance and ANSPG 49 tracking radar in the Navy for ten years. I do know how radars work. These did not have transistors or chips they were all tubes. The final was a klystron that weighed 300 pounds and was water and oil cooled.

49

 

[mneary]

Check the incorrect connection of C1 as well.

Also the 0V in that part of the circuit isn't properly marked. Fortunately the PCB appears to be correct.

 

[dummy55555]

i know the circuit had draw wrongly but the PCB i think is the correct 1.
i really need to know how is the whole circuit operate.
can anyone tell more detail..
thank you..

 

[HiTech]

Why the intense need to understand this circuit? Do you plan to modify it somehow? Did you read the beginning of the text where it explains the basic operating principle?

As mentioned by others here, the circuit has inherent problems and for us to take the time to explain the engineering design behind it is both time consuming and wasted effort... nothing bad intended towards you.​

 

[mneary]

What part of the careful explanation that I took the time to write was inadequate for your purpose of understanding? You hopefully have specific questions, or did you read it at all?

I worked very hard on that description and I feel hurt that you simply repeated your request for an explanation without acknowledging my efforts.

 

[blueroomelectronics]

Next time you should format your replies in a way they can be handed in to the teacher

 

[mneary]

I guess that was the problem

 

[audioguru]

The circuit is an extremely old ultrasonic motion detector kit.
The first opamp IC1 was probably an old one in the original design that needed the external frequency compensation capacitor C3 that doesn't do anything with the newer (but still ancient) 741 opamp that is used today.

 

[mneary]

If dummy55555 even cares, we probably won't know unless we format it ready to hand in to the teacher.

[edit] The 4.7 pF capacitor between pin 1 and pin 8 could boost the high frequency response, even on the 741, but I'm too lazy to simulate it and find out how much. [/edit].