# Poor Boy Airspeed Indicator

Discussion in 'Instruments / Avionics / Electrical System' started by Geek1945, Feb 23, 2014.

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1. Feb 25, 2014

### Aviator168

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3. Mar 7, 2014

### nerobro

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I'm looking at doing the same thing. I've got a few pressure sensors and some solid state gyros.

But here's the important part. Your brain doesn't handle "numbers" very well. That's where steam guages rock. The moving needle is the big deal there. ... Getting a moving needle is easy. Arduino can output pwm to a servo, and you put the servo behind a guage face. By default you get around 180deg of needle sweep. If you need mulitple turns you can use a gearbox, or a sail servo. Servos behind glass are a lot lighter than steam guages anyway.

4. Mar 7, 2014

### Aviator168

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FYI. Be careful about solid state gyros. Some of them are not gyros; they are just accelerometers. You will notice if place them at level position, their readings will change when rapidly moved to one side without rotation. There are micro gyros you can buy (something actually spins). Not expensive at all.

5. Mar 8, 2014

### bmcj

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Excellent point. As a good example, the ill-fated Air Forcd CT-43 that crashed in Croatia with Secretary of Commerce Ron Brown aboard was found to have been the victim of inertial navigation error. The flight was at night in bad weather on approach to Dubrovnich. The Airport there didn't have the required nav systems working, so the pilots switched to inertial. The error that Aviator168 mentions led to CFIT.

6. Mar 8, 2014

### Aviator168

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These days. $150 can buy you a laser ring gyro. If your life depends on it, won't hurt to spend a few more dollars. How do you know that? A black box was not installed on that plane. 7. Mar 8, 2014 ### Pops ### Pops #### Well-Known Member Joined: Jan 1, 2013 Messages: 7,205 Likes Received: 6,101 Location: USA. That's a great one. Looks like it cheaper that it was a short time back. Dan 8. Mar 8, 2014 ### Pops ### Pops #### Well-Known Member Joined: Jan 1, 2013 Messages: 7,205 Likes Received: 6,101 Location: USA. That's a great one. Looks like its cheaper than it was a short time back. Dan 9. Mar 10, 2014 ### nerobro ### nerobro #### Well-Known Member Joined: Nov 6, 2011 Messages: 1,109 Likes Received: 312 Location: Northern Illinois There are MEMS gyros too. And laser ring gyros. Both are "true" gyros. The MEMS gyros use flapping bits of sillicon. Laser ring gyros use the speed of light to count up and down in different axies. You'll run into "cheap" accelerometers, ($2-3) and MEMS Gyros, which are somewhat more expensive. (\$10-12) You're looking for the rotational data, instead of "down." The chip in your phone, most likely just says "down" versus checking acceleration on each rotational axis.

10. Mar 10, 2014

### Aviator168

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Current MEMS gyros are good enough; but you do have to evaluate them before using on your aircraft. Still, ring laser gyros are the most accurate. Now, if you use laser accelerometers for distance calculation, you can even say good bye to the GPS.

11. Mar 21, 2014

### jedi

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Don't need it between the engine and prop on rotating components that make a lot of signal noise. Strain gage the engine mount (or motor mounts) to get your torque. Getting good sensativity is the issue.

12. Mar 21, 2014

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