Input For PIC uC - Electronic Circuits Projects Diagrams Free

mesamune80 · 30th April 2008, 08:51 AM

Hi all,

i am using a comparator ic and LM393 ,configured it as windows detector circuit with the output go to LED and pic uC pin.
But i could not read any high logic from the ic output pin when the pin is goes high. i am using a 1k pull up resistor for the power (12v) to LED which is parallel to uC pin as well which i want the uC to detect it is logic high.
Any problem with my configuration?

Gayan Soyza · 30th April 2008, 08:56 AM

Remove the comparator part from the uC & check the comparator whether it is working correctly?

Can you see the LED goes on when input logic = 1 (in between your range)?

What input did you feed the input?Inverting pin or for the non inverting pin?

Note that its output open collector type.

mesamune80 · 30th April 2008, 09:10 AM

ya,my LED lit but i could not get any signal to my uC pin.
my circuit is look like this with the VrefA and VrefB to my pic uC pin (input pin)
Is there anything i need to add so that my uC can detect logic 1 and 0 respectively?

**Nigel Goodwin** · 30th April 2008, 09:13 AM

Remove the LED's, they are stopping the outputs going high!.

mesamune80 · 30th April 2008, 09:18 AM

i see ,thanks nigel ,but i need some indication for that? (high and low limit indication)
can i do it in a different way? or any alternative for that?

**Nigel Goodwin** · 30th April 2008, 09:25 AM

Use a transistor to feed the LED.

Or, more crudely, put a resistor in series with the LED - but this will still restrict the output of the comparator from going fully high, and reduce the LED's brightness.

ericgibbs · 30th April 2008, 09:27 AM

Quote:

Originally Posted by Nigel Goodwin

Use a transistor to feed the LED.

Or, more crudely, put a resistor in series with the LED - but this will still restrict the output of the comparator from going fully high, and reduce the LED's brightness.

Hi Nigel,
Just noticed he is using a +12V supply to the LM393...

mesamune80 · 30th April 2008, 09:29 AM

It seem like i got not much choices,either a transistor or a dim LED =_="
what transistor is suitable for this i can use 2N222?

mesamune80 · 30th April 2008, 09:31 AM

anything wrong with 12V? @_@"

**Nigel Goodwin** · 30th April 2008, 09:40 AM

Quote:

Originally Posted by mesamune80

anything wrong with 12V? @_@"

Not as long as you have a current limiting resistor feeding the PIC.

mesamune80 · 30th April 2008, 09:45 AM

okay i'll try it out ,thanks guys.

eblc1388 · 30th April 2008, 12:28 PM

Or you can use 3.3V 250mW zener diode in series with each LED.

ericgibbs · 30th April 2008, 12:49 PM

Quote:

Originally Posted by mesamune80

okay i'll try it out ,thanks guys.

hi,
You could do it this way.

I have modified the top LED, I'm assuming a Red LED about Vfwd=2V

The LM393 is open collector output, also the PIC analog is a high impedance.

mesamune80 · 5th May 2008, 01:25 AM

Thanks for all the replies,really thanks for all of you.
i think i might choose either zener or voltage divider method to power up both my LED and also signal to my uC. =)

mesamune80 · 5th May 2008, 02:54 AM

Can i put it this way? so that i can adjust untill the voltage to my uC is about 5V at the same time i also can light on my LED.
Or any better idea i can use? at the moment i have 10k adj resistor and 1k resisitor.

30th April 2008, 08:51 AM	#1 (permalink)
mesamune80 Experienced Member Join Date: Oct 2004 Location: Malaysia Posts: 93	Input For PIC uC Hi all, i am using a comparator ic and LM393 ,configured it as windows detector circuit with the output go to LED and pic uC pin. But i could not read any high logic from the ic output pin when the pin is goes high. i am using a 1k pull up resistor for the power (12v) to LED which is parallel to uC pin as well which i want the uC to detect it is logic high. Any problem with my configuration?

30th April 2008, 08:56 AM	#2 (permalink)
Gayan Soyza Experienced Member Join Date: Oct 2006 Location: Colombo Posts: 946	Remove the comparator part from the uC & check the comparator whether it is working correctly? Can you see the LED goes on when input logic = 1 (in between your range)? What input did you feed the input?Inverting pin or for the non inverting pin? Note that its output open collector type. __________________ Gayan Forum Supporter Last edited by Gayan Soyza; 30th April 2008 at 09:07 AM.

30th April 2008, 09:13 AM	#4 (permalink)
Nigel Goodwin Super Moderator Join Date: Nov 2003 Location: Derbyshire, UK Posts: 22,790	Remove the LED's, they are stopping the outputs going high!. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

30th April 2008, 09:25 AM	#6 (permalink)
Nigel Goodwin Super Moderator Join Date: Nov 2003 Location: Derbyshire, UK Posts: 22,790	Use a transistor to feed the LED. Or, more crudely, put a resistor in series with the LED - but this will still restrict the output of the comparator from going fully high, and reduce the LED's brightness. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

30th April 2008, 12:28 PM	#12 (permalink)
eblc1388 Experienced Member Join Date: Jan 2005 Location: UK Posts: 1,966	Or you can use 3.3V 250mW zener diode in series with each LED. __________________ L.Chung

30th April 2008, 09:18 AM	#5 (permalink)
mesamune80 Experienced Member Join Date: Oct 2004 Location: Malaysia Posts: 93	i see ,thanks nigel ,but i need some indication for that? (high and low limit indication) can i do it in a different way? or any alternative for that?

30th April 2008, 09:29 AM	#8 (permalink)
mesamune80 Experienced Member Join Date: Oct 2004 Location: Malaysia Posts: 93	It seem like i got not much choices,either a transistor or a dim LED =_=" what transistor is suitable for this i can use 2N222?

30th April 2008, 09:31 AM	#9 (permalink)
mesamune80 Experienced Member Join Date: Oct 2004 Location: Malaysia Posts: 93	anything wrong with 12V? @_@"

30th April 2008, 09:45 AM	#11 (permalink)
mesamune80 Experienced Member Join Date: Oct 2004 Location: Malaysia Posts: 93	okay i'll try it out ,thanks guys.

5th May 2008, 01:25 AM	#14 (permalink)
mesamune80 Experienced Member Join Date: Oct 2004 Location: Malaysia Posts: 93	Thanks for all the replies,really thanks for all of you. i think i might choose either zener or voltage divider method to power up both my LED and also signal to my uC. =)

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