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Radar Altimeter Functionality for < $200

Brantel

Well Known Member
Disclaimer: This project is for fun only. No we don't really need this on our airplanes. No I don't plan to use it to shoot approaches. Use at your own risk. Yes it is a total waste of time and money. Yes I am a GEEK! :p

Saw a quick mention in this thread about LIDAR and went investigating.....

Found that Garmin sells a small and very lightweight eye safe infrared laser distant measurement sensor for $149.99.



So I just had to try one and see how it works. This is an OTS solution that could be done slightly cheaper if you wanted to assemble your own boards.

Simple hookup to an Arduino Uno ($24.95) with 4 wires and I was up and running. I used the I2C interface so I could have access to the many setup parameters inside the unit.

lidar-lite-v3-arduino-hookup.png


Added a SparkFun MP3 player board for $24.95



So far I have only tested this on the bench and have been developing the code get the distance into a variable and to provide the audio feedback. Plan to have it call out 125, 100, 75, 50, 25, 10, 5, 4, 3, 2, 1 or something like that.

Have it working great on the bench to an earbud. It actually looks promising! This thing self calibrates for various lighting, background noise etc. based on a user defined rate of so many measurements and the measurements are super fast so it can quickly adjust for differing terrain (target types) under the airplane. Pretty neat how they pull the correct signal out of the background noise.

Will follow up after a test in the real world.

Disclaimer: This project is for fun only. No we don't really need this on our airplanes. No I don't plan to use it to shoot approaches. Use at your own risk. Yes it is a total waste of time and money. Yes I am a GEEK! :p
 
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I bow before you. I am not worthy.

Haha, I bow before you with your amazing skills in fiberglass, painting, drag reduction, cooling optimization, and detailed knowledge of almost anything mechanical and physics. I am the one not worthy!
 
When I land.....

On a typical Pete landing, it will call out 125, 100, 75, 50, 25, 10, 10, 10, 25, 10, 4,4,4,2,10, OUCH!! or something like that.

Brian - great stuff as always!
 
Winter operations

Optics can be problem in the winter or when not cleen
I was thinking more like automotive adaptive radar sensor medium range
But never had time to write code and test
 
Optics can be problem in the winter or when not cleen
I was thinking more like automotive adaptive radar sensor medium range
But never had time to write code and test

We don't get very much snow here in East TN.
 
Sonar

I was working on a similar project last year. I originally mounted an optical sensor than tried a sonar sensor In my wing inspection panel. Both worked although the sonar was easier to mount. The signal was fed to an Auduino and the signal then fed to a sound board which triggered mpeg files into my headset.
I first used a visual display mounted to the glare sheild but found the sound much more effective.
I used 25' 10, 5, 3, 2 , hold. "Hold" triggering 1' off the runway. My thought was holding 1' off would help "grease" some landings.

I have to say, it worked well as a reference on how far off the runway I was and did help my landings. I'm not a code guy and hired someone to help me with this. Unfortunately doing so made things more complex than needed as the original prototype worked. That is what stalled things for me on this project. Next on the agenda is to get back to basics, orininal code, and I am also in the process of some hardware simplicity changes. That and getting my 9 flying which
Has been a time priority. Will keep you posted. In sum, it works and is a nice added cue for helping to judge just how far off the runway you are.
 
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Weight

That's what I am working on in terms of hardware.
Getting rid of the Arduino micro controller will be the weight
Savings for your appliation. We are talking grams here for what I am working on.
What is your target weight? Can some of the hardware be in your hand controller?
Sent you a PM
 
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Look into the Arduino Micro, Feather, or other variants; you can get them about the size of a quarter weighing just a few grams. I have a pair of Megas for prototyping, but anything I planned to put into service use would be stripped way down (also, it'd use solder pads, not header strips with loose plug-in leads).
 
Look into the Arduino Micro, Feather, or other variants; you can get them about the size of a quarter weighing just a few grams. I have a pair of Megas for prototyping, but anything I planned to put into service use would be stripped way down (also, it'd use solder pads, not header strips with loose plug-in leads).


Same here... You can get the Arduino part down to a very small footprint and weight.
 
This is pretty awesome! It would also be super easy to drive some sort of panel mounted display with this. Seeing cool projects like this makes me wish I had more time to tinker and contribute to these things.
 
This is pretty awesome! It would also be super easy to drive some sort of panel mounted display with this. Seeing cool projects like this makes me wish I had more time to tinker and contribute to these things.

Super easy but as someone above mentioned, the audio feedback is where it is at. These things have a limited range of ~140' so the panel mounted display may not be as useful as you might think down close to the ground.
 
Super easy but as someone above mentioned, the audio feedback is where it is at. These things have a limited range of ~140' so the panel mounted display may not be as useful as you might think down close to the ground.


AH, yeah. A range of 140' that makes more sense. A display wouldn't do much good as you'd be eyes out and looking at your approach :) The audio would be super useful in that situation. But for ~$200 and a little bit of fun project work, thats an awesome addition to situational awareness.
 
50, 40, 30, 20, 10, retard....! (airbus)
cool project!
just because you can ;-)

keep us posted on the progress!
i always thought on or near wing access panels could be the perfect mounting location for any kind of vertical/downward looking sensor (as long as it isn't too tall).
 
A really interesting adaptation. Should be a fun challenge to get it working right.
Having flown things with radio altimetry and audio callouts I would reduce the number of annunciations from your plan. I think you will find all those 1 foot increment call outs right at the very end annoying/distracting.
In the Boeing I get calls at 1000, 500, 100, 50, 40, 30, 20 and 10. The 1000, 500 and 100 are sort of "where are you on the approach" calls. For me, the important call is the 50 foot call. When the airplane says 50 feet I know it is time to start thinking about the flare. When it says 40 I had better have some pressure on the yoke. By 30 there better be motion in the nose coming up or you are going to crush the landing without having to employ other techniques. Obviously those numbers will be different for the RV just by the shear lack of mass and vastly different wing loading. With flight testing you will have to figure out what the numbers should be. My guess is maybe 20, 10, 5 if not even less than that.
Would love to see a video with audio when you get it done.
 
RPI ( runway proximity indicator)

"RPI" (my name for it) I had this installed in my RV-3 which I sold recently. Plan to put it into my 9 which I am planning to transport to the hanger today.

Both the optical and sonar sensor I was using was fairly inexpensive. The micro controller, sound board, and sensor along with some various parts where all under $100.00. The sensors where limited in distance and more accurate on close proximity, which in my case was what I wanted. They did not begin working before 25'. The important part for me was timing the flare and easing down from there. When I heard 3' In my headset, I new I had to bring it closer until I heard " hold" triggering 1' off. I would hold and let the plane land when it was ready to. The sound cue was a big help in judging distance off.

I did this project because I was tired of having inconsistent landings and wanted to try to quantify the art of " greasing" a landing. I will put this project back on the "to do" list. The code is actually pretty basic and easy. The guy I hired was making it very complex with data recording, gps, distance offsets for different
Heights for initial mountings in the wing. Those additional code niceties can be tweeked in time but not needed
For this thing to work. I had a female telling me distance. Some of you guys may not want that. Can do both male and female voice files.
 
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Would the fish finder /depth sounder pucks work in air? I'm not an expert, but I thought they were designed for the density of water?
 
Has anyone calculated the max ground speed vs altitude and altitude vs pitch rate that this could track?

If it fires a laser spot at the ground, then there is some altitude and speed at which it will out-fly the return signal. This is the main reason any sound based system doesn't work except very close to the ground because it's trivial to out-fly the return signal. This depends on how wide the input aperture is. You have the same issue if you pitch the plane and the signal is tracking over the ground quickly because a small angle change means high velocities at the end of the radius.

Not saying it won't work, just wondering up to what speeds a device like this would work.
 
Has anyone calculated the max ground speed vs altitude and altitude vs pitch rate that this could track?

If it fires a laser spot at the ground, then there is some altitude and speed at which it will out-fly the return signal. This is the main reason any sound based system doesn't work except very close to the ground because it's trivial to out-fly the return signal. This depends on how wide the input aperture is. You have the same issue if you pitch the plane and the signal is tracking over the ground quickly because a small angle change means high velocities at the end of the radius.

Not saying it won't work, just wondering up to what speeds a device like this would work.
Lasers operate at or very near the speed of light. This thing claims to update 500 times per second. Light travels about 373 miles per 1/500 second.
My RV is pretty fast, but not that fast!
 
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Has anyone calculated the max ground speed vs altitude and altitude vs pitch rate that this could track?

If it fires a laser spot at the ground, then there is some altitude and speed at which it will out-fly the return signal. This is the main reason any sound based system doesn't work except very close to the ground because it's trivial to out-fly the return signal. This depends on how wide the input aperture is. You have the same issue if you pitch the plane and the signal is tracking over the ground quickly because a small angle change means high velocities at the end of the radius.

Not saying it won't work, just wondering up to what speeds a device like this would work.

Well the laser works at ~ the speed of light and the sensor has up to a 500hz update rate but it needs multiple good reads to pull the correct signal out of the background noise. The distance variable is still updated at a very fast rate. It's max range is 140' and I suspect that is best case. Most likely it is only going to be usable for about 100-125'.

If the round trip is 280' max then that will take ~0.00028 milliseconds. The receiver aperture is about 0.5" so to be conservative we can half that to 0.25" as the available distance the plane could move before it would outrun the reflected signal. So we have 0.25" we can move in ~0.00028 milliseconds or somewhere around 50,730 MPH @ 140' if I did the math correctly.

As for pitch rate, @ 140' the plane should not be changing pitch very fast so it may be a moot point. The distance also increases with a change in pitch which will make the calculation more complex. During the flare where the pitch rate is high, the distance would also be very short resulting in a much higher available rate. I am no math expert so I will defer on this one. Since the linear speed limit at 140' is so high, I suspect the pitch rate is also going to be well above what would be seen in an RV landing pattern.

It appears that the drone community are using these and similar sensors with much success.
 
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My feeble attempt

I tried an automobile back up (3) sensor kit which had women's voice audible reports of "8 feet, 5 feet, 3 feet, 2 feet and then crash". It reported quite well but the prop wash under the plane triggered the sensors on take off and cruise so it was necessary to switch it off in flight except for final. This inconvenience caused me to ditch the project.:D
 
Has anyone calculated the max ground speed vs altitude and altitude vs pitch rate that this could track?

If it fires a laser spot at the ground, then there is some altitude and speed at which it will out-fly the return signal. This is the main reason any sound based system doesn't work except very close to the ground because it's trivial to out-fly the return signal. This depends on how wide the input aperture is. You have the same issue if you pitch the plane and the signal is tracking over the ground quickly because a small angle change means high velocities at the end of the radius.

Not saying it won't work, just wondering up to what speeds a device like this would work.

I first tested the system driving my car down the highway at various speeds.
I used a visual display and held my arm out the window at various heights to make sure I was getting results. It worked on the highway, I thought it worth a shot in my Plane. The system worked great from 20' to close to the runway. The inexpensive sensors are limited on distance. My ten ft signal did not always fire off which would be explained by your input. The 5' 2' "hold" (1') was more consistent.

My question to all you tech guys out there is what should be a better sensor in theory, optical IR or sound? They both worked. I ended up with the sonar sensor simply that it was easier to mount if people ever wanted to put them in their planes. The more expensive optical sensor from Garmin may be overkill depending on the application but also maybe a bit more robust than a $25 sensor.
 
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Well the laser works at ~ the speed of light and the sensor has up to a 500hz update rate but it needs multiple good reads to pull the correct signal out of the background noise. The distance variable is still updated at a very fast rate. It's max range is 140' and I suspect that is best case. Most likely it is only going to be usable for about 100-125'.

If the round trip is 280' max then that will take ~0.00028 milliseconds. The receiver aperture is about 0.5" so to be conservative we can half that to 0.25" as the available distance the plane could move before it would outrun the reflected signal. So we have 0.25" we can move in ~0.00028 milliseconds or somewhere around 50,730 MPH @ 140' if I did the math correctly.

Your math is fine, but moot. The outgoing beam is spatially coherent, but the return (reflected) beam is not; if it were, you wouldn't be able to see the spot on the wall from off-axis! Because the return isn't coherent, your 1/2" sensor can detect a section of ground a lot larger than 1/2" (what, exactly, it can see will depend upon the lens--the longer the focal length, the narrower the field of view, just like a camera with a telephoto lens).

I first tested the system driving my car down the highway at various speeds.
I used a visual display and held my arm out the window at various heights to make sure I was getting results. It worked on the highway, I thought it worth a shot in my Plane. The system worked great from 20' to close to the runway. The inexpensive sensors are limited on distance. My ten ft signal did not always fire off which would be explained by your input. The 5' 2' "hold" (1') was more consistent.

My question to all you tech guys out there is what should be a better sensor in theory, optical IR or sound? They both worked. I ended up with the sonar sensor simply that it was easier to mount if people ever wanted to put them in their planes. The more expensive optical sensor from Garmin may be overkill depending on the application but also maybe a bit more robust than a $25 sensor.

Intuitively, I'm inclined to say optical. Sound sensors are going to be subject to being drowned out by engine noise and slipstream, and the return signal is going to be vanishingly weak at any kind of distance (inverse-square law, and remember, the distance it has to travel is twice your altitude). A laser will be coherent on the way down, so you don't have the power dimunition for the first half of the trip, and optical sensors are both A) more sensitive than sound, and B) not going to be subject to noise from engine and slipstream. The downside is that they can be obscured by cloud, but if you're not out of the clouds by the ~140' AGL at which the sensor starts operating, you probably need to be going around anyway.
 
Using back up sonic sensors for two years

The backup sensors are available for less than $15, and work great. Mounted about 3 ft forward of the tail on RV-8, and the alarm is wired to a vibrater on the throttle.

At about 10 ft, I get about 1 "pulse" in about 5 seconds, transitioning to about 1 pulse per second at wheel landing attitude, and continuous vibration at the moment of 3-point altitude and attitude. It's been a great training tool for me where continuous bifocals and age somewhat degrade depth perception.

I would consider it indispensable for an amphibian! Above about 90 mph there is some false triggering due to turbulence, but rock solid at landing speeds. I switch it on as I enter the pattern and off at landing. I'll be using an Arduino to control it to only turn on at landing speeds as time permits. Arduino now controls my autopilot through servo in aileron.

Word of caution: You will take a lot of KRAP from the 3-point greasers (and the Van's crew at Oshkosh) if you tell them about it.

I'll post wiring diagram, and pictures if anyone is interested. Scroll down for pictures.

Roger Bloomfield
RV-8 N51BL
RV-9A 711ED
KAEJ (8,000 msl)
 
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My two cents...

I listen to the fallouts when I fly for work. It calls out 1000, 200, 50, 40, 30, 20, 10. I will tell you that after awhile, you think you don't really hear it. Problem is that you actually do hear it and your flare and landing become based on the call outs. Not an issue until it doesn't call it out. You will realize that it didn't make the call as you impact the ground and bounce back up into the air...a "friend" relayed that story to me😜

Lesson to be learned, don't get lazy, always fly the airplane!
 
Here are the pictures with wiring diagram

30hvn20.jpg


The unit is wired to protected 12 Volts through a switch as shown.

The output on pin 4 pulses 12 volts which I have connected to a small motor with an offset weight to provide vibration to my throttle control as shown on the following picture. Slow pulses at about 10 feet going to continuous vibration at 3-point altitude and attitude. The sensor can be connected to any of the 4 inputs.

28p0rq.jpg


Here is the motor/vibrator mounted in the throttle quadrant, along with flap switches. (most any small motor with an offset weight pressed onto the shaft.

I originally had a 555 tone generator tied to the intercom, but it was too distracting since my MGL calls out speeds (CO-Pilot mode)

sxhx5v.jpg


Sensor is mounted in an approximately 7/8 inch hole 49 inches forward of the rudder (Just forward of the bulkhead). I get no false triggering at landing speeds, and turn it on below 90 MPH, and off when on ground.

The display and Sonalert furnished with the unit is not used, and I believe that an in cockpit display would be a huge distraction. I view it as a training aid, and certainly no substitute for visual references.

Roger Bloomfield
RV-8 N51BL at KAEJ (8000 MSL)
 
Reviving this old thread - LIDAR

Has anyone made progress on a simple package? Looks kind of fun . . .
 
Time Marches On

And if you are ready for your own plug and play LIDAR rather than roll your own you can have it now at Microkit Solutions, LLC.

Well, it's a little more than the <$200 proposed in the original post, but still at $875 it isn't a lot in airplane money if you really want this sort of thing.
 
Recommended

And if you are ready for your own plug and play LIDAR rather than roll your own you can have it now at Microkit Solutions, LLC.

Well, it's a little more than the <$200 proposed in the original post, but still at $875 it isn't a lot in airplane money if you really want this sort of thing.

I have an earlier version of their solution in my 7A, and it's a great addition. Do you need it? No. Is it good to have? Yes, especially on an unfamiliar runway (different width) or at night.
 
Any Updates on how to build one?

I have the LIDAR unit. I am looking for help on how to get the signal to have voice callouts and then into my 245 panel.

Any assistance would be appreciated.
 
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