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16F628 has no ADC. How to use LM35 ?

 
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kiuFelix



Joined: 25 Apr 2012
Posts: 2
Location: Nairobi,Kenya

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16F628 has no ADC. How to use LM35 ?
PostPosted: Wed Apr 25, 2012 4:45 am     Reply with quote
Hi everyone. I am new in CCS and I think I am running the same problem in PIC16F628.
I need help please. Thanks.
Check out my issue posted in www.edaboard.com http://www.edaboard.com/thread249842.html#post1068773
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Mike Walne



Joined: 19 Feb 2004
Posts: 1785
Location: Boston Spa UK

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PostPosted: Wed Apr 25, 2012 3:00 pm     Reply with quote
What else is available to you?

R,C,L,OPA etc ?

Mike
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Wed Apr 25, 2012 3:13 pm     Reply with quote
Change the PIC to a 16F88, 16F818, or 16F819. They all have an A/D
converter, and they are all in the same 18-pin package as the 16F628.

Or, use a different temperature chip. Use a chip with an i2c interface
such as ds1621. CCS has a driver file for that chip (ds1621.c) so it's
easy to use.
kiuFelix



Joined: 25 Apr 2012
Posts: 2
Location: Nairobi,Kenya

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Thanks
PostPosted: Fri Apr 27, 2012 10:59 pm     Reply with quote
Thank you all for quick reply. Great information. I got 16F88 and it works great. I appreciate your efforts. Thanks again.
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Mike Walne



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PostPosted: Mon Apr 30, 2012 10:46 am     Reply with quote
If you want to measure negative temperature connect LM35 as:-

Code:

                      ----------- Analogue Input
           -------   |
          |       |  |
      ----| LM35  |----WWWW--
     |    |       |          |
     |     -------           |
     |        |              |
     |        |              |
5V ----WWWW-----------WWWW------- GND
        R1             R2

Don't forget to decouple LM35.

Choose R1, R2 to give an R1/R2 junction voltage of 500 - 1000mV.

You will need to correct LM35 output voltage to compensate for GND offset.

Do this either by calculating from R1, R2 values or by measuring with another A2D channel.

Mike
Gabriel



Joined: 03 Aug 2009
Posts: 1067
Location: Panama

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PostPosted: Mon Jun 04, 2012 7:54 am     Reply with quote
Hi!

I'm using a 16F88 and an LM35 as well in my project.
My LM35 circuit is exactly as Figure 7 on page 7/13 of the datasheet
https://www.national.com/ds/LM/LM35.pdf

I'm reading Out+ on AN0 and Out- on AN1.

LM35 is fed/powered via a charge pump (running on pin RA7)outputting 9.20V stable, no ripple (i have an O-scope).
When i read the output with my DMM i get a nice 30C temp reading (as it should be (Panama is hot).

My ADC reads 0 on both inputs...
Can you post your adc code?

Thanks
G.
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