Alternative to 100 Ohm Resistors to Avoid ???

[Jim Doolittle]

I have a TEMP08. I only had a DS18S20 temperature sensor connected but then replaced that with a MD3020E containing a DS18S20 temperature and a DS2438 humidity sensor. I am now getting ??? readings for the humidity sensor only and understand I need a 100K Ohm resistor. Since this is the first extraneous sensor connected to the TEMP08 is there alternative wiring to avoid the one wire reflections?

[Midon]

Hi Jim,

The 100 ohm (not 100K ohm) resistors are normally only needed if wiring the 1-Wire bus in a star configuration. Adding just the MD3020E to a TEMP08 should not require the resistor.

Having said that, the ??? readings are a good indicator that you are probably running in parasitic powering mode for the humidity sensor. Make sure you are locally powering the sensor and that the P/L jumper is in L mode.

Mitch

[Jim Doolittle]

The "100K" was a typo. That's a big resistor. I must have been thinking about all the 1K, 2.2K, etc. resistors that all I had lying around but no 100 .

The issue is that I was trying to use parasitic power.

Thanks,

[Pete]

When to use or not use parasitic power

Mitch,

Do you have a rule of thumb regarding the use of parasitic power in a star configuration with various flavors of devices? I currently am using a Temp08 and a Temp05 with most current firmware (software). I get "???"'s and the inability to see devices on the on board temperature sensors on both of these. I also get occasional "???"'s and on the weather station and combo humidity / temperature sensors. I have installed 100 ohm resistors on the most problematic devices and I still see occasional errors.

IE: (haven't restarted HS in a couple of weeks but here is the error count on the humidity sensor which one of many of my sensors). This sensor is connected via category 5 with only the sensor on that run of about 40 feet or so and I am using a resistor for this run.

<TABLE cellSpacing=1 cellPadding=0 width="100%" border=0><TBODY><TR><TD class=tablecellcustom>Total Temp05 Errors=2878 : Last Error with device T42</TD><TD class=tableroweven>Temperature-MCS-T8</TD><TD class=tableroweven>TEMP05 Error Count</TD><TD class=tableroweven>t62</TD><TD class=tableroweven noWrap>Monitor</TD><TD class=tableroweven noWrap>Today at 2:18:40 PM</TD></TR></TBODY></TABLE>


<TABLE cellSpacing=1 cellPadding=0 width="100%" border=0><TBODY><TR><TD class=tablecellcustom><TABLE><TBODY><TR><TD vAlign=center align=left>39%</TD></TR></TBODY></TABLE></TD><TD class=tableroweven>Temperature-MCS-T8</TD><TD class=tableroweven>Humidity - B326H - Kitchen</TD><TD class=tableroweven>t42</TD><TD class=tableroweven noWrap>Humidity</TD><TD class=tableroweven noWrap>Today at 2:20:40 PM</TD></TR></TBODY></TABLE>

I noticed on your WEB site you mention parasitic power for the AAG weather station. As all of my runs are separate CAT5 connections should I consider parasitic power on the combo Humidity/Temperature sensors as well?

[Midon]

Mitch,

Do you have a rule of thumb regarding the use of parasitic power in a star configuration with various flavors of devices?

My (easy) rule of thumb is to put a 100 ohm resistor on every branch of a star. Place the resistors physically at the entry point to TEMP08, not at the sensor.

I currently am using a Temp08 and a Temp05 with most current firmware (software). I get "???"'s and the inability to see devices on the on board temperature sensors on both of these. I also get occasional "???"'s and on the weather station and combo humidity / temperature sensors. I have installed 100 ohm resistors on the most problematic devices and I still see occasional errors.

IE: (haven't restarted HS in a couple of weeks but here is the error count on the humidity sensor which one of many of my sensors). This sensor is connected via category 5 with only the sensor on that run of about 40 feet or so and I am using a resistor for this run.

<TABLE cellSpacing=1 cellPadding=0 width="100%" border=0><TBODY><TR><TD class=tablecellcustom>Total Temp05 Errors=2878 : Last Error with device T42</TD><TD class=tableroweven>Temperature-MCS-T8</TD><TD class=tableroweven>TEMP05 Error Count</TD><TD class=tableroweven>t62</TD><TD class=tableroweven noWrap>Monitor</TD><TD class=tableroweven noWrap>Today at 2:18:40 PM</TD></TR></TBODY></TABLE>


<TABLE cellSpacing=1 cellPadding=0 width="100%" border=0><TBODY><TR><TD class=tablecellcustom><TABLE><TBODY><TR><TD vAlign=center align=left>39%</TD></TR></TBODY></TABLE></TD><TD class=tableroweven>Temperature-MCS-T8</TD><TD class=tableroweven>Humidity - B326H - Kitchen</TD><TD class=tableroweven>t42</TD><TD class=tableroweven noWrap>Humidity</TD><TD class=tableroweven noWrap>Today at 2:20:40 PM</TD></TR></TBODY></TABLE>

I noticed on your WEB site you mention parasitic power for the AAG weather station.

Not sure what you mean by this - the AAG weather station is only available in parasitic power mode.

With regard to

As all of my runs are separate CAT5 connections should I consider parasitic power on the combo Humidity/Temperature sensors as well?

Heck no! Local power is a must for any humidity sensor in my experience.

Mitch

[Pete]

Thanks Mitch. Yes currently my AAG weather station / rain guage just connect to CAT5 and directly into TEMP08 (with a 100 ohm resistor on the TEMP08 side). Just two wires. By parasitic power u mean an additional two wires of 5V eh? I currently do not have local power for my "first gen" combo temperature / humidity sensors. Thanks for your suggestions.