EZIO8SA and 1-wire confusion 2009-04-30T18:55:32+00:00

HOME Forums Input/Output EZIOxx EZIO8SA and 1-wire confusion

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  • Anonymous
    Post count: 13
    #40156 |

    I am having a problem concerning getting my DS18B20+ to work (so far it doesn’t). Should it work like the DS18B20 or does the “+” make a difference? Also the instructions are confusing. The unit’s label shows a RJ-11 four connection schematic that is not the same as the RJ-12 schematic in the unit’s documentation. According to the documentation the very first pin is 5 volts +, but the units label indicates that an RJ-11’s first pin, which is really the RJ-12’s second pin is 5V+. Can you get this thing to work with an RJ-11 plug? Without a RJ-12 I can’t see how get the 5V+ for the chip.

    I would appreciate any help.

    Anonymous
    Post count: 1001

    According to the specification sheet the + indicates a lead free package, the overall specs look the same.

    The EZIO8SA 1-wire J3 connector is an RJ12 connector. An RJ12 will accept a 4 wire RJ11 or a 6 wire RJ12 plug. The label on the EZIO8SA shows the J3 pin layout for the first 4 pins; 1 5V, 2 Gnd, 3 Signal, 4 Gnd. The EZIO8SA Quick Start Guide J3 diagram shows all 6 pins; 1 5V, 2 Gnd, 3 Signal, 4 Gnd, 5 no connection, 6 GND.

    If using a 4 wire RJ11 plug you do not have access to Pin 1 or Pin 6.

    It has been several months since I connected the temp sensor but from memory if using an RJ11 you must connect the sensor in parasite mode as you would not have access to pin 1 5V. If you want to connect the sensor to 5V you will need an RJ12 where you have a connection to pin 1.

    If your findings are otherwise post back and I will get the sensor back on the test bench. It is not in a location where I can test the various pin voltages.

    Anonymous
    Post count: 13

    The label only indicates four connections, not the six it has, and since even the documents state that an RJ-11 or RJ-12 could be used, I assumed that the label was for the central RJ-11 pins,not the first four RJ-12 pins.

    I tried connecting the chip ground to pin 2 ground and the the other two pins both to pin 3 signal (isn’t that what passive mode is?) And it still doesn’t seem to work.

    Am I getting passive mode wrong????

    The only non-zero response I get is a constant value of 85, I even swapped out the chip for a brand new one and still only get the same 85, there is no fluctuation what-so-ever. I doubt that the room 85 degrees, and I know the temperature isn’y constant…

    Anonymous
    Post count: 1001

    The Vdd and Gnd pins are connected to ground when operating in parasite mode, according to the DS18B20 specs on the maxim-ic site. The DQ pin goes to pin 3 (1-W Data).

    See link for DS18B20 specs

    http://datasheets.maxim-ic.com/en/ds/DS18B20.pdf

    Anonymous
    Post count: 13

    Thanks for info. Now instead of getting an erroneous 85, I get an erroneous 127 (I tried two DS18B20+ and both report a value of 127, so at least they are consistent if inaccurate????) I even tried a DS18S20 which I previously purchased by mistake, it reports a value of 25???????

    Anonymous
    Post count: 1001

    What EZIO8SA Configuration Register options are you running with?

    Anonymous
    Post count: 13

    The following are selected/enabled:

    Enabled Analog Inputs
    Continuous A/D Conv.
    Debounce the Inputs
    Enable 1-W Sensor

    Anonymous
    Post count: 1001

    Try putting the sensor in a glass of ice water. Query the value every few seconds to see if it is going down. If it reaches zero or there about, then remove from the ice water and query every few seconds to see if it goes back up.

    Anonymous
    Post count: 13

    Well, I couldn’t really immerse it in ice water since I have it breadboarded and it isn’t waterproof. I did the next best thing and surrounded the probe/IC with a baggy filled with ice water. It went down to a value of seven and stayed there. I removed the bag and the probe reported a slow increase 7-8-10-12-14-15-17, but then jumped back to 127 a minute or two after reading 17????????

    Anonymous
    Post count: 1001

    I’ll pull my sensor arrangement from its current location and get it back where I can control its temperature. My implementation only cares when the temperature is near freezing so heaters can be turned on. This may take a day or two .

    Anonymous
    Post count: 13

    Thanks, I appreciate the help. Do you have your unit wired up for passive power, or are you using a RJ-12 connection that has access to 5V+?

    Anonymous
    Post count: 1001

    To tell you the truth I don’t remember. I tested both when on the bench and both gave me the near freeze condition I needed to detect. That is where the idea of using ice water came about. The EZIO8SA is connected to the network patch panel with RJ12 so I could have done either. I’ll try and get to it tonight but it may be tomorrow.

    Anonymous
    Post count: 1001

    You need a 4.7K pullup resister from +5v to the 1-wire signal when running in parasite mode. See the maxim-ic spec sheet figure 1 page 3 which shows the 4.7 K pullup resister. I am running in parasite mode. I started with a bowl of ice water which contained the DS18B20 sensor and an inexpensive digital thermometer that I would not count on being linear. Removed the ice cubes and logged the two temperatures as the bowl of water warmed to room temperature.

    The following are the Fahrenheit values from the digital thermometer and the Centigrade values from the EZIO8SA.


    33 – 3 51 - 15
    36 – 5 54 - 15
    37 – 6 60 - 17
    41 – 7 61 - 18
    41 – 8 63 - 19
    42 – 9 64 - 20
    42 – 10 69 - 22
    43 – 11 70 - 23
    47 – 13 73 - 24
    48 – 14
    50 – 14

    Anonymous
    Post count: 13

    Well all I have are RJ-11 plugs, so I don’t have access to the 5V+ pin. I’m a bit confused, if you need to run a 4.7K resistor from the 5V+, wouldn’t it be simpler to just connect the VDD directly to the 5V+ and not need the 4.7k pull up resistor, or would I still need to connect a 4.7k resistor between the 5V+ and the DQ pin even though it is being actively powered???

    It looks like I’m going to have to invest in some RJ-12 plugs, although I swear I recall the EZIO8SA docs say that RJ-11 plugs can be used to connect 1-wire devices.

    I wish these guys would write more detailed instructions for their products….

    Anonymous
    Post count: 1001

    I disconnected my 4.7K pullup resister and the DS18B20 reading changed from 25 to 127. Restoring the connection to the resister restored the reading to 25. The sensor board is wired for parasite power so I cannot easily test if the pullup is needed if powered directly from +5V.

    I picked up an RJ12 cable from Radio Shack this afternoon so I could bring the sensor to the bench. It came with the plugs preattached. The lower temperature readings work fine without the pullup resister so I guess it depends on how you plan on using the sensor. For my case where I want to detect temperatures that approach freezing I do not need the pullup resister. To get readings much over 50 I had to add the pullup that the Maxim spec showed in its diagram.

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