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[wxsig] compatibility with ultrasonic sensor

John Bennett jabennett at insightbb.com
Sun Jul 13 14:55:58 UTC 2008

Jay moyer wrote:
> Would the T238 be adaptable to an ultrasonic sensor such as the ones sold on this page ?http://www.maxbotix.com/
> A local kayak/canoe club is interested in placing an APRS station on a local creek to measure water levels and temp.  The station 
> will be mounted on a bridge and the ultrasonic sensor suspended underneath to measure the distance to the water.  I suppose that a 
> program will have to be created to mathmatically figure the water level from the distance from the bridge to the suface.  Also can 
> the 238+ be programmed for sleep modes?  Such as wake up, power up the sensor and transmitter for 30 seconds each hour during 
> daylight and every other hour at night and then power down?  It would help conserve power thus enabling smaller battery packs as the 
> proposed location is in deep valleys that makes solar power unrealiable.  Thanks 
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I found your link very interesting. I have played with the idea of a 
snow-depth sensor for some time. However, it doesn't snow very much here 
in southern Indiana - at least that I could get repeatable data for 
testing. Most authorities believe that ultrasonic or uwave sensors are 
the answer. CSU has done extensive studies on this and the last paper I 
read suggested that ultra-sonic was the best approach. Your application 
would not be that much different, so what would be worked out for one 
should work for the other.

My weather server code (see http://n4xi.home.insightbb.com ) supports 
additional 1-wire sensors, some of which are supported by the T-238 and 
some are not (TAPR markets the X1W-1 and X1W-2 that work directly with 
the T-238). However, my code supports sensors beyond what the T-238 was 
designed for. The interface is expandable and should be able to handle 
any number of additional devices. The only requirement is that code must 
be added for each.

The sensors you referenced have three interfaces to the data, two of 
which should be fairly easy to interface to the 1-wire bus. The A/D chip 
currently used for barometric pressure and humidity could be used to 
measure the analog voltage out. Another interface, the serial, could 
easily be used with the 1-wire serial converter that I currently use in 
the X1W-1 for interfacing to a serial port on the PC for calibrating the 

No promises about when, but I will definitely look into this and let you 
  know. The price is certainly right - less than $25 for a single 
sensor. The only issue for you might be the fact that the system 
requires a PC running Linux. However, I know someone who recently found 
some diskless PCs for under $200 that ran off 12VDC, so it might be 
doable. He's currently using them to run weather data. Your power 
requirements might be an issue, though.



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