DIY LED strobe

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rv7charlie

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Joined
Nov 17, 2014
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1,364
Location
Jackson
Couldn't you calibrate the installation by varying the angle of the sensor probe rather than adjusting the circuit?
Sure, if you're using separate probes for both the top and bottom sensors, and at least one is adjustable. But common practice is to either use pitot pressure for top (which you wouldn't want to change that angle), or a tiny hole drilled in the upper surface of the wing like AFS uses (which is pretty hard to move). The bottom sense is often either a hole in the lower wing surface, or the extra port on a pitot/AOA probe like the Dynon probe (again, angle shouldn't be changed). All the commercial products I've seen have a calibration routine in software. The obvious thing to do with that circuit is to supply an adjustment method (a 'bias adjust') for the LM3914 ladder driver.

Aaannddd, taking a closer look at the drawing's tiny lettering with my aging eyes, it's in there. Look at pins 6, 7, & 8, and the 1K180 resistor, which is actually a potentiometer. Pin 8 is labeled 'Ref Adj'. So... In the immortal words of Rosanne Rosannadana, never mind...

However, if you build the circuit, I *am* pretty sure that the IC is labeled incorrectly. It looks like it's labeled 'LM3419'; it probably should be 'LM3914'.

We now return you to your regularly scheduled programming.
 

Bill-Higdon

Well-Known Member
Joined
Feb 6, 2011
Messages
1,076
Location
Salem, Oregon, USA
Sure, if you're using separate probes for both the top and bottom sensors, and at least one is adjustable. But common practice is to either use pitot pressure for top (which you wouldn't want to change that angle), or a tiny hole drilled in the upper surface of the wing like AFS uses (which is pretty hard to move). The bottom sense is often either a hole in the lower wing surface, or the extra port on a pitot/AOA probe like the Dynon probe (again, angle shouldn't be changed). All the commercial products I've seen have a calibration routine in software. The obvious thing to do with that circuit is to supply an adjustment method (a 'bias adjust') for the LM3914 ladder driver.

Aaannddd, taking a closer look at the drawing's tiny lettering with my aging eyes, it's in there. Look at pins 6, 7, & 8, and the 1K180 resistor, which is actually a potentiometer. Pin 8 is labeled 'Ref Adj'. So... In the immortal words of Rosanne Rosannadana, never mind...

However, if you build the circuit, I *am* pretty sure that the IC is labeled incorrectly. It looks like it's labeled 'LM3419'; it probably should be 'LM3914'.

We now return you to your regularly scheduled programming.
I agree a pot there would be nice but the way I read it he has a 2 resistors in series to form a a voltage divider. He probably came up with the values from a pot then replaced it with fixed resistors
 
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