Multi DS1820 OWD's in temperature alarm

[stewart_bakeruk]

Hi,
A simple fan failure caused a near disaster to an old computer system I am working on.

As the system has no way of detecting overheating I thought that it would be good idea to put one in.

My thoughts are to use up to 8 DS1820 1 wire devices into a PIC which has pre-set temperature limits above which an alarm sounds. The device zone and it's temperature are shown on an LCD.

Having looked at the Oshon help I can see how one device can be read from, but how to do it with 7 others ?

I know that each DS1820 is manufactured with a unique code, but how to read that and tie it in with the sensor position I do not know.

Help would be very much appreciated.

Stewart

 

[Ian Rogers]

If you run the one wire devices though a 8:1 decoder (4051b) the address can be 0 - 7 on another port... That way you only read the one port but the location is set by you.

 

[stewart_bakeruk]

Inspired !

Why do I always think that programming a PIC is the answer ?

Many thanks

Stewart

 

[languer]

The following recent thread had some good info as well: **broken link removed**

 

[Mellbreak]

Stewart,

The following code will allow you to find the address of each DS1820 you want to use. You can then use a single i/o pin and run them all in parallel. Hope this is of some help.



'Set all proc pins to I/O

AllDigital

'Setup port B for LCD use
Define LCD_BITS = 4
Define LCD_DREG = PORTB
Define LCD_DBIT = 4
Define LCD_RSREG = PORTB
Define LCD_RSBIT = 0
Define LCD_RWREG = PORTB
Define LCD_RWBIT = 1
Define LCD_EREG = PORTB
Define LCD_EBIT = 2


'Setup port A pin 2 for temp sensor

Define 1WIRE_REG = PORTA
Define 1WIRE_BIT = 0

'Declare variables to be used
Dim numb As Byte
Dim hexh As Byte
Dim hexl As Byte
Dim loop1 As Byte
Dim romcode(8) As Byte


Lcdinit

start:

1wireInit
'Command to read ROM contents
1wireSendByte 0x33
For loop1 = 0 To 7
1wireGetByte romcode(loop1)
Next loop1

'Now display device family code
Lcdout "FC= "
numb = romcode(0)
Call convert_to_hex(numb)
Lcdout "h CRC= "
numb = romcode(7)
Call convert_to_hex(numb)
Lcdout "h"
'Now display serial number on LCD line 2
Lcdcmdout LcdLine2Home
Lcdout "#="
For loop1 = 6 To 1 Step -1
numb = romcode(loop1)
Call convert_to_hex(numb)
Next loop1
Lcdout "h"
WaitMs 500
Lcdcmdout LcdClear
Goto start
End
'Convert HEX byte to 2 nibbles

Proc convert_to_hex(num1 As Byte)
hexh = num1 And 0xf0
hexh = ShiftRight(hexh, 4)
Call display_hex(hexh)
hexl = num1 And 0x0f
Call display_hex(hexl)
End Proc
'Convert HEX nibble to ASCII and display

Proc display_hex(numb As Byte)
If numb <= 9 Then
numb = numb + 30h
Else
numb = numb + 37h
Endif
Lcdout numb
End Proc

 

[stewart_bakeruk]

Thanks Mellbreak.

I will have a look at your code, as although I have finished the project using the MUX technique I am interested for the future.

Best wishes
Stewart