1 wire data

jyoung · Nov 26, 2004

I have a system that uses the ds1822 temperature sensor. To communicate to this sensor you use a single wire. You pull down the sata line for a certain time period and then read the data on the same line. My problem is that I want to use the aromat fp0-c16t plc to control this but it has 8 inputs and 8 outs, and none of them can be both, so i cant send the code and read the data on the same line. any ideas would be great

drewcrew6 · Nov 26, 2004

you need to do a little more resaerch on the sensor your using there must be a "convertor" of some type to communicate with it .
the convertors are just that they convert the string sent back on the one wire bus to data usualy sending it out a rs-232 port.

You cannot tie this to an input or output on the plc and expect to get data.

Drewcrew6

chavak · Nov 26, 2004

Never heard of this temp. sensor.

Anyway if it is the way you explained, switch the wire through a relay contact to separate input and output of the PLC. [Connect the sensor wire to the moving contact, connect the PLC output to the N/C contact and PLC input to the N/O contact. Switch the relay using a different output of the PLC whenever you want to read the data]

Good Luck

Sergei Troizky · Nov 26, 2004

Actually, input and output may be connected in parallel.
For sinking output the input must be configured for NPN sensors.
When the output is off, it will not affect another signal connected to this input.

rsdoran · Nov 26, 2004

The DS1822 is digital thermometer that uses 1 wire serial bus with 2's complement with 9 to 12 bits of resolution.
http://www.maxim-ic.com/quick_view2.cfm?qv_pk=2795

Here is an overview of 1 wire technolgy:
http://www.maxim-ic.com/appnotes.cfm/appnote_number/1796/ln/en

drewcrew6 · Nov 26, 2004

thank you rsdoran I didn't have time to pull up the links.
About the only way to interface with a plc is with 232 communication.
For my setup I use a "convertor " from midon design. Then convert the info into strings through the use of a basic card and some logic.
This type of setup is NOT industrially hardened. IE it will not last in rough enviroment, but for home automation its work well.

Drewcrew6

jyoung · Nov 27, 2004

So if I connect a "converter" like the ds9097u http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2983
to the 1-wire bus could I use my plc's f144 serial transmit and receive command to communicate with the device? or maybe this would be better. http://embeddeddatasystems.com/page/EDS/PROD/HA/HA7S

drewcrew6 · Nov 27, 2004

The maxim chip should work, but if i remember it is a litltle clunky to use. The other product could work also but I would do more research on it before buying. What kind of commands it needs to work, etc.
My setup ran continuos for about 2 years before I moved and I haven't got to set it up again.

For my use the Midon (temp05) was nice in that once configured I didn't have to command it at all. It automatically feed the info off the bus every minute. Saved in a lot of code by having more of a stand -alone product

Drewcrew6

jyoung · Nov 27, 2004

did you use the midon temp05 with a plc or pc?

drewcrew6 · Nov 27, 2004

I used an Allen-Bradley 5/03 but did not use the serial port on that, it was used for a panelview. The dh-485 port was for the pc and 2 dtams. I added a 1746-bas card to handle the 232 port needed for the Temp05. Unfortunatly I never got the basic card program working as far as the initial setup or to control outputs of the Temp05. But it worked great to retrieve the data FROM the Temp05.

Drewcrew6

PS: they no longer sell the Temp05, But they have a newer version called the Temp08.

shooter · Nov 28, 2004

yes this is possible
i used it in a small network using rs232 on several computers and it did work fine.
wire an input and output together and on the output a relais to have it not pulling with a second output (a type of enable)
however i would use the ic that is made for it as it has to do with currents. it has separate in and outputs.

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