purpose of opamp in a REED SWITCH module

[DiptenduPramanik]

Hi,
I want to know why LM393 is placed in a reed switch module?

Thanks in advance

 

[KlausST]

Hi,
LM393 is a comparator.

There are many different reasons why a LM393 is used. Terefore we need more information.

I'm sure you ask because you have seen this elsewhere. Tell us or show us where you found this.
Picture, schematic....

 

[DiptenduPramanik]

Hi,
LM393 is a comparator.

There are many different reasons why a LM393 is used. Terefore we need more information.

I'm sure you ask because you have seen this elsewhere. Tell us or show us where you found this.
Picture, schematic....

@KlausST thanks for replying. yeah you are right.Here are the two types of reed switch module. I understand the simple one , Connect one terminal of reed switch to GND and other with microcontroller. Simple interfacing like push buttons. I don't understand the one with pot and L393. What are the benefits and application? specifically where it is used and why does simple module can not be used for that application?

 

[Gorgon]

Without knowing anything about the module in the picture, a shot in the dark may be that it is an interface in a security application. The input is balanced and the reed switch may be part of a tamper protection.
2 comparators will typically form a window comparator. If the input impedance is inside a 'window' all is good, if it is too high, or too low, there is an alarm/ fault condition. Triggering the reed switch result in an alarm condition, like trying to open a connection box. This will remove the magnet from the switch and sound the alarm.

 

[betwixt]

Alternatively, it may be that some other component could be connected instead of the reed switch. The PCB with polarity markings on it may be designed to take a different component, maybe an optical sensor or even a capacitor across the switch with the potentiometer used to set the output switching threshold.

Brian.

 

[KlausST]

Hi,

Another possibility:
Maybe it sends out a frequency when switch is closed and another frequency when open. So it is more difficult to hack the signal lines.

A crystal ball is a nice toy....

Klaus

 

[DiptenduPramanik]

Hi ,
First of all I am extremely sorry for late reply. I would like to thank everyone.
After looking closely to both side of the PCB, I found one reason. The PCB used for this module was made for Hall Effect sensors/ IR receiver like that. Here in this particular case of reed switch the OPAMP is not used. What do you think ?
Again I am really really Sorry. I mean it.

 

[betwixt]

Looks like I was right. Those kinds of devices can produce analog signals so the comparator would be used to 'digitize' them.

Brian.

 

[DiptenduPramanik]

Hi betwixt ,
Thanks for your reply. Yes sir, you were right.