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Old 11-23-2011, 06:51 PM
XexorZ's Avatar
XexorZ XexorZ is offline
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Join Date: Oct 2011
Location: Spokane, WA
Posts: 73
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I just received my HF PP in the mail and noticed this - yes, it has a temperature stability issue. This is likely to do with the Op-Amp used but I'm not sure until I completely reverse engineer it and make a schematic (which I will eventually do, for now I only have a parts list generated, haven't removed the PCB to make schematic yet.).

My goal is to make the buzzer volume depend on distance to the target which should be totally doable with a few extra parts.

I suggest adjusting the internal variable resistor (VR1) until it stops beeping when set to 50% on the external VR and no metal around. Do this at the median temperature you operate at.

Originally Posted by deerhunter View post
Has anyone had problems using the HF detector in the heat?? If it gets about 100deg. it will not shut up!! Anybody else have this problem?? I havent done any mods to it yet. Another thing, sometimes when it is working right, if I turn the shaft towards the ground ie. upside down it goes off also(no metal around) almost as if something is loose and moving inside...... Any help or ideas???

EDIT- Ok, I tested out my theory.
1. Put a mark on sensitivity knob at the point it wouldnt beep
2. Put the detector in the sun and got it warm
3. Try it out in same spot and it beeps like crazy until I turn sensitivity knob way down.
4. Put on A/C vent to cool it down and now I can turn the sensitivity knob alot higher than in step #1

To sum it all up heat has a very negative effect on this detector, guess I have to bring a cooler with me!
Anyone else have this problem with any other brand of PP? Or is it just the HF one? Or just mine lol

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