hi,
I have posted a comment on his web site asking him if has actually built and tested this circuit, as it will not work as drawn.
If I get a response I will let you know.

E

I too did that, but he didn't gave any response at all. Is there any other circuit similar to this one

 

hi,
The 40KHz transmitter section is a typical circuit for driving a ultrasonic transducer, but the LM324 receive amplifier is poo!.

The LDR and relay types are not specified, driving a LED with such a low current drive, which is supposed to drive an LDR low enough in resistance to operate a 9V relay is doubtful.

I use a PIR sensor for my house front porch, which ding/dongs when someone comes within 3 mtrs of the door.
At night it also switches on a light.

I will look for some PIR links if you are interested.

E

 

hi,
The 40KHz transmitter section is a typical circuit for driving a ultrasonic transducer, but the LM324 receive amplifier is poo!.

The LDR and relay types are not specified, driving a LED with such a low current drive, which is supposed to drive an LDR low enough in resistance to operate a 9V relay is doubtful.

I use a PIR sensor for my house front porch, which ding/dongs when someone comes within 3 mtrs of the door.
At night it also switches on a light.

I will look for some PIR links if you are interested.

E

Please send me the PIR Sensor links

 

hi,
The 1st link is a doorbell, 2nd link is an assortment of sensors.

http://www.ebay.co.uk/itm/like/3511...3=1&ff11=ICEP3.0.0-L&ff12=67&ff13=80&ff14=108

https://www.google.co.uk/search?q=p...hannel=sb&gfe_rd=cr&ei=iLAiVK-DOueB7QbW2YGoAg

BTW: I have used LTSpice to sim that Ultrasonic circuit... its a non starter IMHO.
E

 

Please send me the PIR Sensor links

Can you tell me which all are the errors in the LM324 reciever part

 

hi,
Are you planning to build it.?
E

 

hi,
Are you planning to build it.?
E

I cant change my project

 

Can u please help me with this.

 

Can u please help me with this.

hi,
I will redraw the circuit using LTSpice and correct any errors and omissions, but I cannot guarantee the performance of the project as a whole in detecting a person at a distance of 2 mtrs.
The transducers and placement of the transducers is important in this type of detector.

Do you have any information on the type of ultrasonic transducers TX and RX that you will be using.??
Also I would suggest we redesign the relay drive circuit, drop the LED and LDR, there is no need to isolate the output, its using a relay to operate the buzzer/bell.
I will retain the 555 astable design, as that is often used with these TX sensors.

Do you agree.?
E

 

hi,
I will redraw the circuit using LTSpice and correct any errors and omissions, but I cannot guarantee the performance of the project as a whole in detecting a person at a distance of 2 mtrs.
The transducers and placement of the transducers is important in this type of detector.

Do you have any information on the type of ultrasonic transducers TX and RX that you will be using.??
Also I would suggest we redesign the relay drive circuit, drop the LED and LDR, there is no need to isolate the output, its using a relay to operate the buzzer/bell.
I will retain the 555 astable design, as that is often used with these TX sensors.

Do you agree.?
E

OK.Thank you very much sir. I think the transducers are ordinary ultrasonic tranducers. I will send a photograph of it.

 

OK.Thank you very much sir. I think the transducers are ordinary ultrasonic tranducers. I will send a photograph of it.

 

hi,
I have tried some designs using the LM324, the gain bandwidth at 40KHz, is only ~30dB [ *30], max overall gain of approx 900.
The original OPA design is set for 50 and 80 , thats an overall gain of approx 4000, which is not possible with a LM324.

I would recommend a better a OPA, are you able to buy CA3240 dual OPA's.?? or an equivalent.?
E
BTW: I did have a pair of transducers of that type on the shelf , I will look for them.

 

hi,
I have tried some designs using the LM324, the gain bandwidth at 40KHz, is only ~30dB [ *30], max overall gain of approx 900.
The original OPA design is set for 50 and 80 , thats an overall gain of approx 4000, which is not possible with a LM324.

I would recommend a better a OPA, are you able to buy CA3240 dual OPA's.?? or an equivalent.?
E
BTW: I did have a pair of transducers of that type on the shelf , I will look for them.

Yes I can buy CA3240

 

hi,
Look at this option, it works OK in LTSpice simulation.
If I get time over the weekend I will build a prototype.
It uses CA3240 dual OPA. 2 off.

I would build the TX and RX on separate PCB's, it will give you more mounting/location options.
A 9v battery operated device the TX in my opinion will drain your battery too quickly, a 9Vdc 100mA mains PSU would be better.

Its uses a transistor to drive a mini-beeper module.
E

 

Is the CA3240 an 8pin or 14pin IC .What is this virtual ground pin? sorry I'm just a beginner only

 

Hello,

The CA3240 is an 8-pin DIP.
In the datasheet there is a lot of information for you.

Bertus

 

hi rijoe,
[thanks bertus for posting the d/s]

A Virtual ground is a 'ground' created by the U2b OPA [ half of a dual CA3240] , its created by splitting the single supply from the 9V battery into a +4.5V and -4.5V to provide a common connection point for biasing U1a and U1b.
By having a virtual ground on these two OPA's the outputs pins #2 and pin #7 are at ~+4.5V, so the RX signal when amplified can swing +/- about the +4.5V level.

A virtual ground is often used on single supply in order to create a +V and -V supply.

Dont connect the vg , virtual ground to the 0V ground

Do you follow OK.?
E

 

I did this with another circuit as CA3240 was not available in my location. Before object detection i have a 9v at output after detection i have 10v how to connect a buzzer to this circuit which switches on at 10V