[Rick Masters]

Dan,
I might suggest, for what it's worth, that a thermal isn't really quantifiable over time.
You might be able to take an instantaneous snapshot of a thermal in a two dimensional frame, measure each point and create an instrument to recognize that.
But the utility of that measurement will quickly decrease to the point of being lost as turbulence, temperature difference, wind and physical drift pass through changing atmospheric environments.
This is a challenge to a supercomputer and you, as engineer, are attempting to boil all this information into a few boops and beeps.
My point is, don't try to chase this too deeply.
Know when to stop.
The most important part of the Snooper is the pilot's brain.
We take that simple audio signal and apply some kind of fuzzy logic to it, creating three dimensional images of an atmosphere in motion.
You could probably present a slew of varying responses and our brains would learn, after a while, to successfully interpret each one.
If you have indeed emulated the original Snooper, you have completed the major part of the challenge.
It is now up to the pilot.
Future tweaks will be minor adjustments.
The burden of interpretation will always be left to the pilot.
The instrument demands a great deal of imagination to be used successfully in flight.
Some pilots have it. Some don't.
Don't let this confuse you.
You can be 100% successful in designing a "perfect" Snooper and some pilots will tell you it doesn't work.
Others will rave about it.
That has been my experience.

[Bill Cummings]

Bill, I got your youtube comment. Heard that it's not sensitive enough yet.

I updated the Arduino audio code a bit to get some additional processing gain. It now does a running average on the temperature differential signal between beeps/boops. That allowed turning up the sensitivity without getting a ton of noise. I haven't shot another video, in lieu of something better...

The new snooper took a ride on a model sailplane alongside several other sensors. It was literally hanging outside a hatch unshielded from the sun, but it was quite overcast outside and didn't seem affected by the orientation. Despite the overcast, there was a huge thermal that intermittently sat on the middle of the field and the plane flew through it multiple times. In the two plots, whenever the plane went below an altitude of 150, the motor came on and held it to that altitude. Any climbs above that altitude came from thermal activity and the motor was off. On one plot, the raw temperature differential signal is shown. On the other is a processed snooper signal which needs more explanation.

The snooper signal is an implementation of how I think the original Snooper's audio works. The temperature differential signal is integrated. When it crosses a threshold, the integrator is reset and a beep or boop sound is made. If the threshold is crossed in the positive direction, that's a beep and refers to the temperature is warming. If the threshold is crossed in the negative direction, that's a boop and refers to the temperature cooling. In the plot, a beep is shown as a positive line. If there are a lot of positive lines together, that's representative of a lot of beep sounds. Theoretically, that probably means it's getting warmer and probably entering a thermal.

I don't really know what the point of this post is other than to share that the sensor has flown and show the snooper is now in digital processing land. I can plot the snooper versus the vario fairly easily next. It may be interesting to plot the snooper signal versus the GPS position as well to see if it shows flying into the thermal. Who knows??

Dan

Just now I found my Snooper.
The pilot that was going to sell you his snooper for $25.00 has changed his mind about selling it at all.
When I breathe on my Snooper (Like one does on an eye glasses lens to fog it up for cleaning) ---( I hope my scientific explanation hasn't lost you.) --- It takes 2.5 seconds for the first beep to sound.

[Rick Masters]

The pilot that was going to sell you his snooper for $25.00 has changed his mind about selling it at all.

I wouldn't take $500 for mine, although I did send my unused spare to Alan Fisher when he requested it a few years ago.
Too bad. I thought Dan was getting a great deal!    

[Harry]

Continueing this discussion from the way past...

Rick, I got my version of the thermal snooper working.
Sensitive little bugger. I still need to test it in thermal conditions, but I suspect it will work just fine.

As suggested by critics of the original Thermal Snooper, I explored using 2 diodes in a bridge circuit that feeds a differential signal into an instrumentation amplifier. Dirt cheap to build and operates on a single 9V battery. The trick with mine is to have one diode in the air stream while the second diode is in restricted air flow. When both diodes are at the same temperature, there is no output. As soon as the unrestricted diode detects heat, a differential voltage is generated, then amplified. It becomes real time measurement without software.
All I have to do is breath on the sensor and it sets it off. It detects heat from my finger if within 1/4" proximity in still air.

As soon as winter blows out, I'll be able to take it out and see if it can detect thermals at my local mountain.

I think Alan Fisher would be pleased to know that I have taken his basic design to the next level.
From here on it will just take some fine tuning and some real air time to finalize the design.

[wingspan33]

Harry,

I sure hope Rick responds! I owned a thermal snooper for a while but only got a few hours flying time with it before I knocked it off my down tube and watched as it fell into the forest below. : - (

[Bob Kuczewski]

Harry,

I sure hope Rick responds! I owned a thermal snooper for a while but only got a few hours flying time with it before I knocked it off my down tube and watched as it fell into the forest below. : - (

Thanks Scott.

I called Rick on the way home from Dockweiler to let him know about Harry's post. I wasn't sure if Rick was still following the U.S. Hawks and I didn't want the connection to be dropped. Rick let me know that he's been in touch with Harry. All's well that ends well.