I assume the two cameras are built in and chosen by a selection button, most likely on a touch screen. All he is trying to do is switch cameras automatically when the turn signal id activated.

 

I just put this together with a 3300 uf capacitor.
Tested on the right turn signal and works perfectly.
Relay clicks on and stays on when right turn signal blinking.
Turn off right turn, and it instantly turns off the relay.


Yellow wire with diode on end is input from turn light
White wire is ground
So far very happy!

 

The cameras are AHD 1080p typical reverse backup cameras. They have a yellow RCA plug for video.
I have the Atoto HDL2-0R backup camera
and for the side view off the truck is this one here.

https://www.amazon.com/dp/B0G6BWTZHV?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1
AHD 1080p or 720p selectable by snipping wire.
Mirror by snip wire
backup grid on - off by snip wire

 

THAT SCHEME makes much more sense than directly switching the actual video signal!!!
QUESTION Does the radio HAVE a second video input?? None of that was clear to me in post #1.
The multichannel security system video switchers that I have all use diode switching rather than relay switching, But the two and three-way manual switches actually use switches, not relays or diodes.
Have you already verified that both cameras have the same video signal format??? OR are you using another , similar, backup camera in the side viewing position??

Atoto radio has 2 AHD video inputs, a front and rear camera uses yellow coax plugs

I am not using the front camera video in.
I am only using the rear camera video in.
both camera feed wires will go to the relay.
Relay will default to forwarding the rear camera feed, send rear view camera feed to Atoto rear cam in
When right turn light comes on, relay will activate and send side view camera feed to Atoto rear cam in

The relay common terminal goes to the Atoto rear camera input.

The camera signals are AHD digital not analog signals.

The Atoto has a pink trigger wire, when that gets 12v+, the Atoto switches screen to show the 'rear camera input'. That way when you back up, it shows the backup camera. When I put right turn signal on, it will show the side camera as the relay energizes and cuts the signal from rear camera to side camera. When I turn off flashing turn light, the relay deenergizes and shows the rear camera on Atoto, IF, the pink wire still has 12v+

Atoto HDL2-0R backup camera has the reverse wire bult in, so in back of truck, you connect it to the reverse lights. That runs inside camera long video cable up to radio and connects to the pink wire, which when reverse lights come on, Atoto switches to shw video feed on rear camera input plug

 

There may be a bit f a problem using an unshielded POWER relay for switching low level video.AND, how well will the camera supply voltage be filtered?
You are assuming that the video from the backup camera is the same format as the video from your alternate camera. I suggest trying it before doing anything else, because if the sweep speeds are not very close it will not work. A video circuit is a whole lot more critical than a speaker hookup! Use a much smaller relay and put the whole package in a small metal box. AND, rather than the big capacitor and a 40 amp cube relay, use a small signal relay, a single NPN transistor, and a 555 timer IC that gets reset with every turn signal pulse. The camera connects on the first turn signal flash and stays connected ten seconds after the last flash. AND NO heavy power wires. And be sure to use theright shielded wire for thecamera video signal.

When I get it all connected, will let you guys know if the picture works.
I will set both cameras to be the same video resolution, although Atoto may be able to reconfigure itself, will test it by setting camera to different resolutions.

I really dont know if AHD 1080p digital video needs to be shielded. The old analog was shielded. I dont plan on cutting open the cable to see, but a youtube video, someone did, and shows unshielded wires

 

IF you are able to use the second video input to the radio and IF YOUare able to nake the readio switch inputs then you will not need the relay to switch the video.
Isthere another wire availble to make the radio display the second video input??? That would make it very simple.

 

IF you are able to use the second video input to the radio and IF YOUare able to nake the readio switch inputs then you will not need the relay to switch the video.
Isthere another wire available to make the radio display the second video input??? That would make it very simple.

Yes, I can use the second video input of Atoto, but, there is no trigger wire to auto turn it on. I have to press a button on the radio to view front cam feed input.

Only the reverse cam line in has a trigger wire, when the wire gets voltage, it auto switches the view. Idea being, right turn signal on, Atoto auto switches view. Also for the trigger going to use the coil voltage of the circuit contraption I made.

I may also add a manual button to turn on the relay, then can drive down road with side cam continually displayed, radio will still play sound, work in background. Our Odyssey has that feature, continual live view. Atoto has a built in continual live view for the rear cam.

 

OK, it was not clear what controlled access to that second camera. So that iput would not work as required. That is unfortunate.

 

video from rear cam looks really good running through the relay. I have figured out a position for the side camera and plan to connect it up this Sunday. Dont see why it would not work like the rear cam.

 

ok here is a more final version of the 2 relays. One with capacitor pulls relay in. I have it switching a 12v+ acc wire to send power tp Atoto trigger and the other coax switching relay.
3300uf holds relay closed, and relay open in .25 seconds when flashing stops.

red wire carries 12v+ acc in across relay to other relay 85 pin coil then to ground.

I learned that you have to put those three shielded coax right on the terminals, when spliced to long pigtails bad signal issues on one camera. I soldered short wires to the coax grounds and joined them together with a wire nut.

Both relays have protection diodes.

The long red cylinder cut from a Bic pen contains a relay for the flasher wire

 

Atoto rear cam view, comes on with reverse gear


Atoto side cam view. Comes on with right turn signal


mounted some grounds, drilled holes. sanded rust off, slathered dielectric grease

 

I plan to put a on/off/on dash rocker. Allows viewing rear or side cam all the time driving forward
Acc+ to common terminal, then run wire down to the trigger for reverse cam, and trigger for side cam.
I put three diodes to prevent acc+ backfeed on the trigger.



I also found out you can run an RCA Y splitter. Join both cams, and other end into the Atoto input.
Must only power on one cam at a time.
I almost went that way with this till I figured out the relay coax issue.

 

I looked into using an RCA splitter cable, and turning cam power off and on, when one is on, other must be off, both must not be on at same time and like the idea, it would require couple relays or one relay. Anyone care to share circuit schematic for that? It seems could get complex.

I tried Chatgpt and Copilot and they enthusiastically shared ideas and I asked for a schematic, which is impossible to function

 

Gemini AI came up with this, someday will graph it out to see if it works. Those diodes are for stopping back feeding acc+.
So far Gemini AI has been the most useful AI, Second is Copilot, 3rd ChatGT, from what I have noticed.

Your Two-Relay "Power Selector" Logic
Since you are using the coaxial Y-splitter, here is the most efficient way to wire those two relays so they play nice with your On-Off-On rocker switch and the reverse trigger:

Relay 1 (Rear Camera)

• Pin 85: Ground (to your sanded dash frame).
• Pin 86 (Trigger): Combined feed from your Reverse Light and Switch Position 1 (use diodes here).
• Pin 87: 12V ACC+.
• Pin 30: Output to Rear Camera + and Atoto Trigger (via diode).

Relay 2 (Side Camera)

• Pin 85: Ground.
• Pin 86 (Trigger): Combined feed from your Turn Signal and Switch Position 2 (use diodes here).
• Pin 87: 12V ACC+.
• Pin 30: Output to Side Camera + and Atoto Trigger (via diode).

Why this beats the "One Relay" method:

• The "Dark" Center: With the rocker switch in the middle and the truck in Drive, both Pin 30s stay dead. Your Atoto stays on your radio/maps, and the cameras stay cool.
• Isolation: The relays act as a physical wall between your new switch and the truck's factory wiring.
• Clean Signal: Since you soldered the coax shields together and grounded them to the frame, having the power wires separated by relays prevents any "cross-talk" between the two camera feeds.

 

So I ask this then, while the above handles most cases. what happens when reverse is engaged and right turn flasher is on?

Gemini said
If you wire it with two standard relays as separate triggers, you would actually have both cameras fighting for the Atoto’s attention at the same time. Since both power leads would hit the coaxial Y-splitter simultaneously, the video signals would collide, likely resulting in a garbled, rolling, or "double-exposed" image on your screen.
To solve the "Reverse + Blinker" conflict and give your Rear Camera priority, you can wire the relays in a "daisy chain" configuration:
The "Priority Logic" Wiring
Instead of giving both relays their own 12V ACC feed, you make the Side Camera relay dependent on the Rear Camera relay being off.

1. Relay 1 (Rear Camera - The Boss):
   • Pin 86 (Trigger): Your Reverse Light wire.
   • Pin 87: 12V ACC.
   • Pin 30: Output to Rear Camera + and the Atoto Trigger.
2. Relay 2 (Side Camera - The Subordinate):
   • Pin 86 (Trigger): Your Right Turn Signal wire.
   • Pin 87: Connect this to Pin 87a of Relay 1.
   • Pin 30: Output to Side Camera + and the Atoto Trigger.

Why This Fixes the Conflict

• Normal Driving: Relay 1 is sitting on Pin 87a (the "Normally Closed" pin). When you use your blinker, power flows through Relay 1's 87a, into Relay 2, and turns on your side camera.
• In Reverse with Blinker On: The moment you hit Reverse, Relay 1 clicks over to Pin 87. This physically cuts the power feed to Relay 2's supply pin.
• The Result: Even if your right flasher is going, the side camera loses its power source, and the Rear Camera takes over the screen completely.

This keeps your coaxial Y-splitter happy because only one signal is ever "live" at once.