What is the differ ?

[nafezfares]

Hi every body,

Iam using pascal compiler for PIC4 .
My questiones : -

1-What are the main differences between LM35 and DS1820 ( temperature sensors ) ?

2- For LM35 ....every 10mv = 1c
but howmuch for DS1820?

3- Why they said, it is a digital sensor (DS1820) while they connect it A0 ( analog to digital channel ) ? like LM35 is connected to A/D Channel .

Iam looking forward to hear from any body.

W B R
Nafez

[janni]

DS1820 is a digital sensor communicating over so-called one-wire interface. mP has OW (one-wire) library and there are code examples to be found on the forum.

A0 is not purely analog - it may be cofigured as digital I/O, as well.

[nafezfares]

Hi janni,

Thanks alot for your reply ,

This means that sensor ( DS1820 ) has converter inside , which in turn converted the analoge signal to digital , Is this true?

regards
Nafez

[joseLB]

...This means that sensor ( DS1820 ) has converter inside , which in turn converted the analoge signal to digital , Is this true?....

Exactly that. But that not mean that using DS1820 is simpler than use of lm35...
see this: http://www.mikroe.com/forum/viewtopic.p ... light=lm35

[nafezfares]

Great Job joseLB>>>>>>>>>>>>>>>
THANKSSSSSSSSSSSS

[nafezfares]

Hi every body,

I get the temperature reading on LCD by using LM35.
But it is not stable ( changed every second from 23 to 24 to 25 , 23, 24, 25 and so on ).

I tried to put an electolyte capcitance ( 10 micro farad ) on the output of the lm = (enterance of the PIC ).
It becomes stable but not practical values.

Please who can advise ? as much as can .

wIth Best Regards
Nafez

[joseLB]

[quote="nafezfares]...But it is not stable ( changed every second from 23 to 24 to 25 , 23, 24, 25 and so on[/quote]Hi, I could suggest

• xxx
  xxx
  xxx

[joseLB]

...But it is not stable ( changed every second from 23 to 24 to 25 , 23, 24, 25 and so on

Hi, I could suggest

• 1- try to put a 100kpf cap at the +- of LM at the board
  2- try to put a 100Kpf cap betwen the +- of PIC (at the +- pins preferably)and the same at the LDC.
  3- remember that 23-> 25v = 0.02 change! If you are using as ADC vref the 5v PIC, your are converting very near the low end of the range. Better would ber to have an smaller verf.
  4- i'm not recomending to use a LED as vref - 1.62 -> 1.67 v, (as it's lower than minimum 2.5v recomended at manual), BUT I use it a lot and never had a problem. I use leds as they are very voltage stable unde current changes (much better than zenners at low currents).
  5- if you are using an external vref, put the 100kpf caps on them.

good luck
Jose

[joseLB]

===> important: try to use a shielded cable from board to LM, first connecting the shield to LM and later to board.

[nafezfares]

DEAR joseLB,
Thanks for your reply.

[/quote]Hi, I could suggest

• 1- try to put a 100kpf cap at the +- of LM at the board
  >>> 100Kpf = 0.1pf
  
  3- remember that 23-> 25v = 0.02 change! If you are using as ADC vref the 5v PIC, your are converting very near the low end of the range. Better would ber to have an smaller verf.
  >>>Yes I use 5V as V ref, I will try to use 3.3 V
  
  4- i'm not recomending to use a LED as vref - 1.62 -> 1.67 v, (as it's lower than minimum 2.5v recomended at manual), BUT I use it a lot and never had a problem. I use leds as they are very voltage stable unde current changes (much better than zenners at low currents).
  >>>Iam new in this field , and can't understand this idea, so please post to me the circuit diagram to build it , may be it easy for me.
  
  5- if you are using an external vref, put the 100kpf caps on them.

>>> I already using the same 5V to all the circuit.

W. B.R
Nafez

[nafezfares]

Dear Jose,
thankssssssssssssss

===> important: try to use a shielded cable from board to LM, first connecting the shield to LM and later to board.

[color=blue]>>>I am already using a shielded cable from LM to the PIC board,
copper wire covered by plastic , is it ok ?[/color]

W.B.R
Nafez

[Dany]

Hi, I could suggest

• 1- try to put a 100kpf cap at the +- of LM at the board
  >>> 100Kpf = 0.1pf

Normally the value 100nF is used, and not the double prefix unit 100KpF.
100 KpF = 100000 pF = 100 nF.

[joseLB]

Thanks dany, 100nF
Hi Nef: start putting the 100nF at the +- pic's pins. Decoupling sometimes does miracles....
and connect the shield first at board and later at LM. By the way, as smaller the wire, the better.
Take a look at this manual, what it suggests for noise reduction (page 6 of pdf). http://www.national.com/ds/LM/LM35.pdf
LED as vref

Code: Select all

+5 <------+
          |
         [ ] 1KR
          |
          +------> PIC Vref
          |
          _
          V   led
          | 
          _
         ///

good luck
Jose

[nafezfares]

100 KpF = 100000 pF = 100 nF.[/quote]
>>> thanksssssssssss alot

WBR
Nafez

[nafezfares]

[quote="joseLB"]Thanks dany, 100nF
Hi Nef: start putting the 100nF at the +- pic's pins. Decoupling sometimes does miracles....
[b]
>>>Thanks alot Jose for declearation with Dany, yes sometimes happened
.[/b]

and connect the shield first at board and later at LM. By the way, as smaller the wire, the better.
Take a look at this manual, what it suggests for noise reduction (page 6 of pdf). http://www.national.com/ds/LM/LM35.pdf
[b]
>>>This need alot of work .
Can you please send apicture (THE WAY OF SHIELDED ) for me even from the internet, to start apply like it. [/b]

LED as vref

>>>> Also Iam v. happy with 3.3 Vref .

W.B.R
Nafez