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Old Mar 11, 2011, 11:03 AM
Specializing in RC since 1972
Temple, GA, USA
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How FPV stuff works

Quote:
Originally Posted by RcNewbAddict View Post
Thanks, I like soldering, and I like wiring, I just want to know the basic concept of the wiring like, just wire the camera to the receiver (receiver of the camera) and then power it up, and that's it and then connect the other receiver or watever is it called to the old laptop or a dvd player and I can now see what the plane sees?

Aircraft components that require power (maybe different voltages) in a simple FPV setup:
- camera
- video transmitter

In the aircraft, video output of the camera goes to the video transmitter. The video signal travels through the air. The video receiver on the ground receives the signal and converts it back into a normal video signal which is connected to the display device. Often there is a microphone too and the video transmitter sends both video and audio back to the ground.

Quote:
Originally Posted by RcNewbAddict View Post
also, please tell me more about the system that if the radio goes out, the plane comes back home by itself, how is that possible?
In the airplane you would usually add:
- OSD (On Screen Display) with GPS (Global Positioning System) and RTL (Return To Launch) capability
- Flight stabilization system attached to ailerons to keep the wings level

OSD is connected between the RC receiver and the rudder servo so it can pass the rudder signal through or change it if it wants to. A wire comes from the RC receiver RSSI (signal strength) signal and goes to the OSD, so the OSD can tell when the RC receiver can no longer hear the RC transmitter. A flight stabilization system is set up to keep the wings level by using the ailerons. If the wind hits it stays level. If the rudder is used it stays level. If the RC transmitter tells the ailerons to move, the aircraft will bank somewhat, and only stay banked as long as you hold the aileron. As soon as you let off the aileron control, the aircraft will level the wings again. The aileron stick on the transmitter thus has been effectively changed from a roll rate control to a bank angle control (think about that). That is quite different from a normal control.

OSD gets and remembers the GPS location when it is turned on (or starts to move for some models).

If you turn off the RC transmitter, the OSD sees the RSSI drop and turns the rudder to steer a GPS course back to the launch point. The flight stabilization system keeps the wings level even though the rudder is held over for a turn. The result is a slow flat turn. When the aircraft is pointed back to the launch point the OSD puts the rudder back to neutral. If it starts drifting left or right the rudder corrects for a straight flight back. With a very stable airplane (high wing with a LOT of dihedral) and a careful setup (configure RTL to use just a LITTLE rudder for turns, and test it), RTL can be used without a flight stabilization system.

There are several ways for a flight stabilization system to work, including watching the heat signature of the sky vs the ground with infrared detectors, and fancy inertial navigation systems that figure out which way down is by mixing 3D compass readings, accelerometers and gyros with fancy math.

On a system this fancy, you will usually have a connection on the OSD so that it can be connected between the battery and motor speed controller. This is used to monitor both the battery voltage and the battery current. The current is integrated (added up... small amounts at low throttle and large amounts at high throttle) and displayed as a total amount of the battery that has been used, like a fuel gauge so that if you have used 3000mah of a 4000mah battery you had better start thinking about landing.

On a system this fancy, I wouldn't be surprised to find camera pan (a left and right camera servo) and possibly camera tilt (up and down camera servo). These servos can be attached to knobs / sticks on the RC transmitter or connected to a head motion tracking device (compass / gyro / potentiometer based) which has wires connected to the RC transmitter's extra channels. Of course, if you are using a head tracker, you are using video goggles for the display device. The camera moves where you point your head and you see the result in the goggles.

Some OSD's that have RTL also have waypoint navigation. You set up several sets of waypoints (GPS coordinates) in a list and a function similar to RTL steers the aircraft from one place to the next.

Some very fancy systems have a "ground station" which is a laptop with a map on it and you can click points on the map to set up way points.

Some very fancy systems have a way for the aircraft to report it's position back to the ground station and can display the aircraft position on the map and do other fancy things.

Start with a simple FPV system, but buy the stuff with future purchases in mind. Don't get a video transmitter that interferes with GPS. Get an OSD with RTL if that is important to you. Plan on the range that you want. I have heard it said that you should not get a video link with longer range than the RC link. I say get a long range video link now, and if you want longer range later, all you need is a longer range RC link. As long as the video reception is good and you are holding the RC transmitter down normally, if you run out of RC range, just raise the RC transmitter over your head for better range and keep it there while you fly back. Note that this does not work with 2.4g RC if you have flown behind a building or hill. With a 35mhz to 72mhz (depending on country) RC link, you will still have control behind hills and buildings, but your higher frequency video link will fail and you won't be able to see the video. The higher the frequency, the more LOS (line of sight) it is for all radio signals. In short, never fly behind anything big and solid, like a hill or building. At very least the video link will go out and you will be blind. You will loose your aircraft unless you get lucky in your quick blind attempt to turn around and fly back out.

Cliff
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Old Mar 14, 2011, 06:19 AM
what goes up, must come down..
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Quote:
Originally Posted by theothercliff View Post
Aircraft components that require power (maybe different voltages) in a simple FPV setup:
- camera
- video transmitter

In the aircraft, video output of the camera goes to the video transmitter. The video signal travels through the air. The video receiver on the ground receives the signal and converts it back into a normal video signal which is connected to the display device. Often there is a microphone too and the video transmitter sends both video and audio back to the ground.



In the airplane you would usually add:
- OSD (On Screen Display) with GPS (Global Positioning System) and RTL (Return To Launch) capability
- Flight stabilization system attached to ailerons to keep the wings level

OSD is connected between the RC receiver and the rudder servo so it can pass the rudder signal through or change it if it wants to. A wire comes from the RC receiver RSSI (signal strength) signal and goes to the OSD, so the OSD can tell when the RC receiver can no longer hear the RC transmitter. A flight stabilization system is set up to keep the wings level by using the ailerons. If the wind hits it stays level. If the rudder is used it stays level. If the RC transmitter tells the ailerons to move, the aircraft will bank somewhat, and only stay banked as long as you hold the aileron. As soon as you let off the aileron control, the aircraft will level the wings again. The aileron stick on the transmitter thus has been effectively changed from a roll rate control to a bank angle control (think about that). That is quite different from a normal control.

OSD gets and remembers the GPS location when it is turned on (or starts to move for some models).

If you turn off the RC transmitter, the OSD sees the RSSI drop and turns the rudder to steer a GPS course back to the launch point. The flight stabilization system keeps the wings level even though the rudder is held over for a turn. The result is a slow flat turn. When the aircraft is pointed back to the launch point the OSD puts the rudder back to neutral. If it starts drifting left or right the rudder corrects for a straight flight back. With a very stable airplane (high wing with a LOT of dihedral) and a careful setup (configure RTL to use just a LITTLE rudder for turns, and test it), RTL can be used without a flight stabilization system.

There are several ways for a flight stabilization system to work, including watching the heat signature of the sky vs the ground with infrared detectors, and fancy inertial navigation systems that figure out which way down is by mixing 3D compass readings, accelerometers and gyros with fancy math.

On a system this fancy, you will usually have a connection on the OSD so that it can be connected between the battery and motor speed controller. This is used to monitor both the battery voltage and the battery current. The current is integrated (added up... small amounts at low throttle and large amounts at high throttle) and displayed as a total amount of the battery that has been used, like a fuel gauge so that if you have used 3000mah of a 4000mah battery you had better start thinking about landing.

On a system this fancy, I wouldn't be surprised to find camera pan (a left and right camera servo) and possibly camera tilt (up and down camera servo). These servos can be attached to knobs / sticks on the RC transmitter or connected to a head motion tracking device (compass / gyro / potentiometer based) which has wires connected to the RC transmitter's extra channels. Of course, if you are using a head tracker, you are using video goggles for the display device. The camera moves where you point your head and you see the result in the goggles.

Some OSD's that have RTL also have waypoint navigation. You set up several sets of waypoints (GPS coordinates) in a list and a function similar to RTL steers the aircraft from one place to the next.

Some very fancy systems have a "ground station" which is a laptop with a map on it and you can click points on the map to set up way points.

Some very fancy systems have a way for the aircraft to report it's position back to the ground station and can display the aircraft position on the map and do other fancy things.

Start with a simple FPV system, but buy the stuff with future purchases in mind. Don't get a video transmitter that interferes with GPS. Get an OSD with RTL if that is important to you. Plan on the range that you want. I have heard it said that you should not get a video link with longer range than the RC link. I say get a long range video link now, and if you want longer range later, all you need is a longer range RC link. As long as the video reception is good and you are holding the RC transmitter down normally, if you run out of RC range, just raise the RC transmitter over your head for better range and keep it there while you fly back. Note that this does not work with 2.4g RC if you have flown behind a building or hill. With a 35mhz to 72mhz (depending on country) RC link, you will still have control behind hills and buildings, but your higher frequency video link will fail and you won't be able to see the video. The higher the frequency, the more LOS (line of sight) it is for all radio signals. In short, never fly behind anything big and solid, like a hill or building. At very least the video link will go out and you will be blind. You will loose your aircraft unless you get lucky in your quick blind attempt to turn around and fly back out.

Cliff
that's a great explaination in lay-man's terms! credit to you for taking the time to type that out

cheers
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Old Mar 14, 2011, 08:23 PM
RIP Ric
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Marietta, GA
Joined Jun 1999
43,312 Posts
I got a Cam/Tx/Rx combo from HK. I also got a commercial patch antenna and the recommended V Tx antenna from a vendor mentioned here.

The Rx connector is a different size than the one on the lead from the patch. Can I get an adapter at Fry's without impacting the signal, or do I need to change out one of the connectors to match?

Thx!
..a
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Old Mar 16, 2011, 04:29 PM
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Hillsboro OH
Joined Sep 2005
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Quote:
Originally Posted by Andy W View Post
I got a Cam/Tx/Rx combo from HK. I also got a commercial patch antenna and the recommended V Tx antenna from a vendor mentioned here.

The Rx connector is a different size than the one on the lead from the patch. Can I get an adapter at Fry's without impacting the signal, or do I need to change out one of the connectors to match?

Thx!
..a
I would like to know the answer to this one to, just put in an order from hobbyking
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Old Mar 16, 2011, 05:39 PM
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Joined Jun 2006
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You need a male F to Female SMA adapter. You will lose about 0.2db using this.

-Alex
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Old Mar 16, 2011, 05:55 PM
RIP Ric
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Marietta, GA
Joined Jun 1999
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What I want to know is if that affects signal quality..
..a
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Old Mar 16, 2011, 08:12 PM
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North vancouver, B.C. Canada
Joined Apr 2008
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If there is an electronics store near you, they can shorten the coax to your preferred length an professionally crimp on most likely abetter crip than stock.

Its nice to have the video rx close to the rx antenna with the right connector.

Quote:
Originally Posted by Andy W View Post
What I want to know is if that affects signal quality..
..a
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Old Mar 16, 2011, 08:36 PM
Winter Sucks!!
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United States, WI, New Berlin
Joined Aug 2002
751 Posts
This is all very good stuff. Thanks to all that are contributing the information

Question about the RTL feature
Is the RTL something that comes with an OSD or an integral part of it,
or is it bought separately. I could not find it on any of the vendor sites.
============================================

What do you need to buy to have the RTL feature?

============================================

With the flight stabilization, I am assuming that you must have ailerons.
I found this flight stabilization system on DPC:
http://www.dpcav.com/xcart/product.p...cat=277&page=1


Thanks,
Randy


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Old Mar 17, 2011, 03:48 AM
Specializing in RC since 1972
Temple, GA, USA
Joined Jun 2009
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Quote:
Originally Posted by romans1015 View Post
This is all very good stuff. Thanks to all that are contributing the information

Question about the RTL feature
Is the RTL something that comes with an OSD or an integral part of it,
or is it bought separately. I could not find it on any of the vendor sites.
============================================

What do you need to buy to have the RTL feature?

============================================

With the flight stabilization, I am assuming that you must have ailerons.
I found this flight stabilization system on DPC:
http://www.dpcav.com/xcart/product.p...cat=277&page=1


Thanks,
Randy
Full disclosure: I do not have an OSD or RTL or a flight stabilization system. This is what I have learned though.

RTL is a function of the OSD. Buy an OSD that has RTL. The OSD must have GPS capability or they cannot make it do RTL.

I suppose that a flight stabilization system could conceivably be put on a stable (high wing with dihedral) 3 channel FPV plane with the left-right channel being either rudder or aileron. You could even have RTL steer the ailerons on a 4 channel. The effect would be to change the left-right control (even on a rudder airplane) from a "roll rate" control to a "bank angle" control e.g. when you hold full left, it will fly at a 45 degree bank instead of doing continuous rolls.

You would:
1 - connect RC Receiver to OSD/RTL to Stabilization to Servo
2 - set the RTL up to give say a 15 degree bank (takes a long time to turn around)
3 - the stabilization would keep the plane in a constant bank and keep it from rolling all the way over

This would work in a similar fashion to having a setup without flight stabilization and with the RTL set up to put in just a tiny amount of left-right. Be aware when setting up without a flight stabilization system that it will fail if your plane is out of trim. Either left trim will cancel out the right given by the RTL or left will add to left and cause too steep of a turn.

I believe that RTL with a flight stabilization system on a 3 channel plane would work better than RTL without stabilization on a 3 channel plane because the bank angle is more predictable.

The better way is to have a stabilized 4 channel with stabilization on the ailerons and RTL on the rudder. This is kind of the minimum standard.

An even better way to do this is to have flight stabilization on both aileron and elevator and RTL set a fixed throttle setting plus control the rudder to steer a course, but that is a lot of hardware. The elevator stabilization helps in the turn arounds. The main problem left here (for this and any simple system where elevator is not controlled by RTL and altitude) is that the plane will probably constantly ascend or descend a little and may get too low or too high over a long RTL.

Think about it. You were a long way away. You plane flew away. Some time later your quiet plane crosses overhead 1000 feet up from some direction and you don't notice it. It flies away, turns around and comes back from some different direction and maybe higher still. The battery runs out and it continues to do this while gliding down. The plane is probably somewhere within a 1/2 mile radius of the launch point, but that generally means it is lost. Better get a loud beeper hooked up to RTL too, and hope there is enough power left in your battery after ESC cutoff to control the plane for several minutes and run the RC and beeper for an hour. Better have an ESC with a hard cutoff at a high voltage to leave juice.

The best way to do this is to have a complete auto-pilot (the yet to be released openpilot.org comes to mind) that controls everything (keeps the plane from ascending or decending by watching altitude) has stabilization too, and will auto-land after circling for 5 minutes (probably in a tree, but close to launch point at least).

Sorry, but I don't know which OSD systems have what capabilities. It would be good for someone who knows to give us a table of functionality (the basics like how many channels the RTL controls).

Cliff
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Old Mar 17, 2011, 11:17 AM
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By the way, does RTL stand for "Return To Launch" ??
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Old Mar 17, 2011, 12:08 PM
Just trying to get a nut.
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United States, VA, McLean
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Quote:
Originally Posted by romans1015 View Post
By the way, does RTL stand for "Return To Launch" ??
Yes....

as well,

RTH = "return to home"

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Old Mar 17, 2011, 04:53 PM
Fly FPV, sleep; repeat
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Sander cracks me up when he starts talking about RTG systems.

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Old Mar 18, 2011, 08:57 PM
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Has anyone used a aurora 9 radio with there 2.4 gig system for FPV flying. This is the system I have & would like to use it. I was told it has a strong signal for long range.
Thanks Marc
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Old Mar 18, 2011, 09:52 PM
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Quote:
Originally Posted by Pixturethis View Post
Has anyone used a aurora 9 radio with there 2.4 gig system for FPV flying. This is the system I have & would like to use it. I was told it has a strong signal for long range.
Thanks Marc
Distance is in the RX, not the TX. We can't help you unless we know what RX you are using. And even then, it's a guess. The best way to do it is to put it on the roof (not inside) of a car and have a friend start driving away with it down a long open road. Move the servos back and forth the whole time. Have your buddy check his odometer when the servos stop moving. That will be your max distance.

-Alex
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Old Mar 19, 2011, 08:21 AM
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Thanks for the info, I'll be using there 7 channel receiver, unless I need more. But I don't think I will as I'm flying a radian, only 3 channels. I'll try the range check.
Good idea.
Looking forward to some FPV flying, so far there is soooo much info to read. Almost gets you lost before you start flying.
Marc
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