DIY Video switch for multiple FPV cameras

[arocholl]

Hi there,

I was looking for such a project already started by someone, but except I am missing something, I found nothing.

The idea is to have a simple video switch implementation controlled by a RC channel to quickly switch from camera 1 to camera 2 onboard. I find it useful, for instance, to have two onboard cameras one with large view angle and other with narrow focused viewfinder. Or to have a front and rear camera.

Looking for options,

1) simple approach, just having both cameras connected with a Y cable (probably AC coupled with capacitors) and then switch energy on to camera 1 or 2. Drawback is gain losses due to coupling, and perhaps a few milliseconds in which you have no video from any of the two cameras.
2) Use an analog switch or a video multiplexer chip. Maxim has solution for both, this would do the trick just selecting which channel you want to feed video from. Drawback here is both cameras are taking power all the time from battery.

Any more ideas?

[thomasscherrer]

soon.,.. I heard a bird sing about such a product that will be released really soon,
you might want to look in the FPV section

[questtek]

One way I have done this with great success is the following:
1. Forward video camera on a servo that pans vertically from the horizon downward.
2. At the top end of travel of this servo in the dead ahead position I put in a miniature Push-on, Push-off switch.
3. I can move this forward looking camera to adjust downward looking angle but when I move it in the direct forward position itdepresses the miniature switch and thus switches to a camera mounted on top of the rudder.
4. When I want to switch back to the downward looking camera I just move the servo again to engage the switch to the other position.

Hope this helps, Joe

[arocholl]

One way I have done this with great success is the following:
1. Forward video camera on a servo that pans vertically from the horizon downward.
2. At the top end of travel of this servo in the dead ahead position I put in a miniature Push-on, Push-off switch.
3. I can move this forward looking camera to adjust downward looking angle but when I move it in the direct forward position itdepresses the miniature switch and thus switches to a camera mounted on top of the rudder.
4. When I want to switch back to the downward looking camera I just move the servo again to engage the switch to the other position.

Hope this helps, Joe

Interesting solution Joe. And what does the push button do? switch power on/off the different camera VCC power? Are they connected with a Y video cable?

- Ariel

[arocholl]

soon.,.. I heard a bird sing about such a product that will be released really soon,
you might want to look in the FPV section

I didn't see anything about this in the FPV thread either, ...

If this comes as a commercial product, my fear is will be much more expensive than needed. This is a simple circuit... in fact I am surprised why some of the most sophisticated OSD doesn't include this already. It would be a $5 addon to a commercial OSD, but as a separate board a shop will likely ask for $30 for this...

[thomasscherrer]

so what,, I will be happy to pay 30 to save several hrs of my spare time
none if the things we purchase for your hobby represent the actual part cost,
that is the whole idea offcourse in the DIY section, you pay the cost of components
and have alot of fun soldering it all together and figuring out how to make it work,
all that fun is wasted every time we purchase anything we could have made our self.

[arocholl]

so what,, I will be happy to pay 30 to save several hrs of my spare time
none if the things we purchase for your hobby represent the actual part cost,
that is the whole idea offcourse in the DIY section, you pay the cost of components
and have alot of fun soldering it all together and figuring out how to make it work,
all that fun is wasted every time we purchase anything we could have made our self.

That is not my point. My point is this is a cheap commercial addition to a commercial OSD, but an expensive separated part. Not to mention it is yet another pcb with cables, etc.

As a separated part yes, I prefer a DIY, this is why I posted this in this section.

[Tomapowa]

A few commercial solutions...

http://www.nghobbies.com/cart/index.php?main_page=product_info&products_id=128

http://www.rc-cam.com/rcswitch.htm

http://procerusuav.com/Downloads/TechSheets/TechSheet_VMv1.1.pdf

I've used the Procerus video mux in a few UAVs... digital/logic controlled instead of being R/C (pwm) controlled... great for connecting to APs with discretes, such as the Kestrel AP.

I also built one years ago (home automation video switching project) and it used a Texas Instrument OPA4872 4:1 High Speed Multiplexer:

http://focus.ti.com/lit/ds/symlink/opa4872.pdf

The 2:1 version is the OPA875:
http://focus.ti.com/lit/ds/symlink/opa875.pdf

[arocholl]

Excellent pointers, just what I was looking for. In fact, the one from Mr RC-CAM is using one of the maxim chips I looked for as well.

Thanks

[questtek]

Interesting solution Joe. And what does the push button do? switch power on/off the different camera VCC power? Are they connected with a Y video cable?

- Ariel

The way I have it set up is that power is supplied to both of the board cameras by a separate LiPo battery, thus they are always on. The switch selects the video output of each camera module to either the rocorder or the video transmitter. You can think of it as a two way toggle switch, one position is camera A and the other camera B. However, instead of the toggle a tiny Push on-Push off switch is much easier to implement but does the same function for video select.

This approach permits pan of one camera, (or tilt), and video control of two cameras for the price of a small servo and a $1 switch!

[Andy W]

Powering up as needed saves battery, and simplifies the overall solution. The only issue is the momentary glitch in the signal, if recording this can be edited out, so it should not be an issue..
..a

[arocholl]

Wondering why I didn´t see the RC-Cam solution before on his web page, I found it is not listed in the project list entry (or I am getting really old and can't see it myself). Anyway, looking closer to his solution, Thomas works with 5v power supply for cameras, whereas I work on 12v. Certainly can be easily adapted, but in addition I prefer my pic to switch with a single shot, so I move camera 1 <> 2 with the push of a button (e.g. the same channel used to pan or tilt can swtich camera 1-2 when it goes fast enough to 2ms and back to prev position, as opposed to regular camera movement). In this way the same channel can do many things, not only 2.

I would take Thomas solution as an input but likely build a new one. Just some pointers below for reference on the topic:

http://pdfserv.maxim-ic.com/en/an/AN3823.pdf
http://www.glolab.com/freeinfo/images/videosw.pdf

[arocholl]

Wow, I did a quick prototype and test today with this analog switch http://focus.ti.com/docs/prod/folders/print/ts3a4751.html and works perfectly. Single supply, no noise introduced, no need for complex external circuitry, up to 4 cameras in and it cost less than 1€... will plug it in a PIC and test onboard soon I hope.

[rclinks2002]

Hello,
I understand that this may be a bad question but I have had problems finding the answer. Is it possible to transmit 2 video signals through a single transmitter, then split it back on the ground? The Application that I am looking for is to have one person flying the plane with a camera on the tail, then another person looking through a different camera at the ground.

Any thoughts?

Thanks
Ben

[FAKHREALAM]

Wow, I did a quick prototype and test today with this analog switch http://focus.ti.com/docs/prod/folders/print/ts3a4751.html and works perfectly. Single supply, no noise introduced, no need for complex external circuitry, up to 4 cameras in and it cost less than 1€... will plug it in a PIC and test onboard soon I hope.

That's the way to go, good job. Here is simple solution.

1) use two analog sw or video sw (get it from ti or maxim)
2) feed two camera output to sw, turn one on, one off by servo or by
detecting the spare rc channel pulse on time.
3) combine both analog sw output and use as video output.

The other solution is just use one 4v or 5v SPDT relay, put two video camera to relay input and get the video output from SPDT. Turn relay on by servo or by pic or microcontroller. When relay is off u are getting on camera output when relay is on you are getting the other camera out put, it will cost you may my $5.00 or less US$.

Fakhre Alam

[arocholl]

Hello,
Is it possible to transmit 2 video signals through a single transmitter, then split it back on the ground?

No, you can't multiplex 2 video signals together and distribute them on one single channel. Think on bandwith as the physical limitation.

[arocholl]

The other solution is just use one 4v or 5v SPDT relay, put two video camera to relay input and get the video output from SPDT. Turn relay on by servo or by pic or microcontroller. When relay is off u are getting on camera output when relay is on you are getting the other camera out put, it will cost you may my $5.00 or less US$.


I may be way too cautios, but don't really like mechanical relays on a plane. Even though they may work well initially, hard landing and on-fly vibration may end up with a surprise at some point. Not to mention EMI noise every time the relay switches. Based on price and reliability, I think analog switch is a better solution.

[FAKHREALAM]

I may be way too cautios, but don't really like mechanical relays on a plane. Even though they may work well initially, hard landing and on-fly vibration may end up with a surprise at some point. Not to mention EMI noise every time the relay switches. Based on price and reliability, I think analog switch is a better solution.

U are right relay option is not good due to EMI. I was just mentioning couple solutions that will work for u, its up to u.

Thanks.
Fakhre Alam

[Tomapowa]

No, you can't multiplex 2 video signals together and distribute them on one single channel. Think on bandwith as the physical limitation.

Isn't that what this does?
http://www.colorado-video.com/interframe_video_multiplexer.html

[arocholl]

Isn't that what this does?
http://www.colorado-video.com/interframe_video_multiplexer.html

Of course, at the cost of reducing quality (halfing the refresh rate or the resolution), as you can see on the description. By reducing 50% the bandwith required you can put 2 half quality channel in 1 single channel.

I assume the question was by doing a straightforward conversion. You need to process and post-process the signal to be able to multiplex it in the same channel. That is by no mean easy thing to do DIY.

[Tomapowa]

Of course, at the cost of reducing quality (halfing the refresh rate or the resolution), as you can see on the description. By reducing 50% the bandwith required you can put 2 half quality channel in 1 single channel.

I assume the question was by doing a straightforward conversion. You need to process and post-process the signal to be able to multiplex it in the same channel. That is by no mean easy thing to do DIY.

My point was that it can in fact be done... (granted not easily in a DIY project)... just be careful when you generally say something can't be done... with a little research, you'll probably find otherwise. :)