wired world


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  1. #1

    Default wired world

    just a comment this forum is very usefull however it could be great if
    getting actual hook up diagrams values was not like pulling teeth i know some of the information is availabe in the listing but this is hard search for those of us that are into the actual connections diagrams

    example using the ds1821 there is a couple of listings and some mention of the correct pullup but no diagrams \

    believe this could go a long way for help
    just a beginners thought
    do appreicate the help

  2. #2
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    Default

    Quote Originally Posted by jcleaver View Post
    some mention of the correct pullup but no diagrams \

    believe this could go a long way for help
    Well at the risk of sounding harsh, " PULLUP " Pulls UP, up to where? To the supply voltage. PULLDOWN pulls Down to Ground. There now you have a schematic. NOW, as to the value of those pullups. It depends upon what voltage you are using, what you want it to be, and how much current you want them to draw. OHMs law involved here. imagine an LED in series with a resistor.
    one end is hooked to power + the other hooked to ground. We will call the resistor Rs. If you have a supply of 5 volts and an LED operating on 1.5 volts and the LED specs call for 20ma then: Rs = Vin - V led / I led or Rs = ( 5 - 1.5) / .02, or Rs = 175. General rules of thumb apply, many people use 10K resistors as port pullups a load of .0005 amp at 5 volts.
    If you do not believe in MAGIC, Consider how currency has value simply by printing it, and is then traded for real assets.
    .
    Gold is the money of kings, silver is the money of gentlemen, barter is the money of peasants - but debt is the money of slaves
    .
    There simply is no "Happy Spam" If you do it you will disappear from this forum.

  3. #3


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    Default help

    thanks for your responce
    don't know whas occuring
    but unable to get expected readings showing 213 c ds1821 using any of the programs above
    thought it might have something to do with pullups usinga4.7 to vdd

  4. #4


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    Default new

    i seem to be confused (not something new)
    must have posted in wrong spot trying to use a ds1821
    with a 877a and a osc of 20 did a search of this temp sensor
    and there were a couple of examples tried them and one show no ds1820
    the other gives poor reading 96 deg c or something else
    am using a 4.7k res to vss
    any help
    sorry about the misplaced posting

  5. #5
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    Default

    I do not know, you might look at this thread, it looks like he is doing the same thing, as you.
    If you do not believe in MAGIC, Consider how currency has value simply by printing it, and is then traded for real assets.
    .
    Gold is the money of kings, silver is the money of gentlemen, barter is the money of peasants - but debt is the money of slaves
    .
    There simply is no "Happy Spam" If you do it you will disappear from this forum.

  6. #6


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    Default ?

    dont see the thread your talking about

  7. #7


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    Default

    wrong place for this
    however i am having problems with a dallas ds1821 temperature sensor
    connected to a 16f877a pin rc2 with a 4.7 k pullup and running at 20 mhz
    it is working but readings are incorrect fairly sure i am communicating

    listing

    A
    'display message on the 2 X 16 character LCD using pic16f84a and DS1820
    @ DEVICE pic16f877a, HS_OSC, WDT_ON, PWRT_ON, LVP_OFF, PROTECT_OFF

    ' Define LCD registers and bits
    Define LCD_DREG PORTB ' Port for LCD Data
    Define LCD_DBIT 4 ' Use upper 4 bits of Port
    Define LCD_RSREG PORTB ' Port for RegisterSelect (RS) bit
    Define LCD_RSBIT 3 ' Port Pin for RS bit
    Define LCD_EREG PORTB ' Port for Enable (E) bit
    Define LCD_EBIT 2 ' Port Pin for E bit
    Define LCB_BITS 4 ' Using 4-bit bus
    Define LCD_LINES 2 ' Using 2 line Display
    Define LCD_COMMANDUS 2000 ' Command Delay (uS)
    Define LCD_DATAUS 50 ' Data Delay (uS)

    define loader_used 1

    DEFINE OSC 20

    symbol DQ = PORTC.2
    temp var word
    cou var byte
    cou1 var byte
    pause 100
    main:
    owout DQ, 1,[$CC, $44]
    owin DQ, 4,[cou]
    if cou = 0 then
    owout DQ, 1, [$cc, $BE]
    owin DQ, 0,[temp.lowbyte, temp.highbyte, skip 4, cou,cou1]
    endif

    temp = (((temp >> 1) * 100) - 25 ) + (((cou - cou1) * 100) / cou)
    lcdout $fe,1," Environment Tempera"
    lcdout $fe, $c0, dec (temp / 100), " . " , dec temp, " C"
    pause 1000
    lcdout $fe,1
    pause 2000

    lcdout $fe, $c0, dec (temp / 100), " . " , dec temp, " C"
    pause 1000
    goto main
    end

    can someone check this thanks

  8. #8


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    Default still trying

    update tried several programs for this chip

    however none work ?
    does the owin and owout require changes for 20 mhz
    it the only thing i seem to have different
    other than using a loader

    help?!

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