Having a moisture sensor problem - tips where I should look?

[ksdehoff]

Hello All:

I've got a moisture sensor in line with a solar/humidity/temp sensor (both of them are powered) running off the 6 channel hub. I've got an odd problem with the moisture sensor - readings are stuck at 110 for moisture and 32 deg f temp. I'm not honestly sure where to look - the s/h/t sensor readings appear to be fine.

One more point of info - the voltage between the +12v and gnd at the sensor is only 2.5 volts and I've confirmed my power supply is putting out 16 at the hub - could this low voltage be responsible and would it affect both the temperature and moisture readings?

Ken

 

[geoff]

Hello All:

I've got a moisture sensor in line with a solar/humidity/temp sensor (both of them are powered) running off the 6 channel hub. I've got an odd problem with the moisture sensor - readings are stuck at 110 for moisture and 32 deg f temp. I'm not honestly sure where to look - the s/h/t sensor readings appear to be fine.

One more point of info - the voltage between the +12v and gnd at the sensor is only 2.5 volts and I've confirmed my power supply is putting out 16 at the hub - could this low voltage be responsible and would it affect both the temperature and moisture readings?

Ken

It sounds like a wiring problem to me. If you have 16v at the hub you should have 16v at both of the sensors. The mositure needs at least 7v to work. Time to check the cabling I suggest.

 

[ksdehoff]

I had this particular cable run working correctly for about 6 months so I don't think it is a cabling problem. As a follow up question - can I assume that the 5v regulated power from the hub does not matter for the moisture sensor since it doesn't have an input for it? The fact that the 12v only shows 2v I think is my biggest issue - can the hub interfere with that power signal at all or would it be exactly what's coming from the power supply?

My assumption is that when the sensor got wet (very wet, not damp) that it blew something upstream, either the hub and/or the power supply.

Ken

 

[geoff]

You need 3 wires at the moisture sensor board. GND, DQ, and +12V. The 12V can be more or less, but needs to be at least 7v I think. The regulated 5v wire is not needed. I still suspect a wiring problem. Disconnect the cable run at the hub, plug in a short un-terminated cable instead and check that you really do have 16v downstream from the hub. Measure it on pin7. If you do then replug the cable run and check again at the sensor. If its down to 2v there then disconnect the sensor and just measure at the wire. If it goes back up to 16 when you disconnect the sensor then it looks like the sensor board is drawing a large current (which it shouldn't). More likely the 16v line is broken somewhere and the 2v that you are measuring is actually originating from either the mositure sensor or the solar/temp sensor.

 

[ksdehoff]

This is a new failure for me but at least I finally figured the problem out. My cabling is cat5 with rj-45 jacks. I have the cable running from an RJ-45 port on the outside of the house to my sensors, the ones that got wet. When I couldn't troubleshoot at the sensors I worked backwards and at the rj-45 jack I found the problem.

Explain this - pin 7 is the +12v pin which I'm assuming is getting simply passed through from my power supply. The pin was gone. After the last water failure I put a beefier power supply on the hub and I'm guessing that there must have been some power-assisted process that ate that pin away but its odd that it was just that pin and no others and nothing wrong on the plug.

Anyways I've got a new board and cable in place and am hoping I've waterproofed it all better this time. Trying out the tool handle dip.

Thanks Again
Ken