I plan to trigger an Atoto Android radio to turn the side mirror camera on when the right turn light comes on. Prefer to use a wire under the dash versus going to the light itself. Will use a cube relay, a 3300uf capacitor (acts like a battery supply) to keep relay closed during the off part of the flashing and 4 isolation power diodes for reverse current flow circuit isolation

Will putting the capacitor across coil of a 40 amp auto cube relay keep it closed as the the turn signal flashes on and off?

Plan is to have rear camera and side mirror camera switching inputs into an Atoto Android Radio using a relay.
Relay energized by right turn signal when right turn light comes on.

On Atoto, when power is applied to the pink trigger wire, Atoto displays a connected camera on RCIN port.
When right turn signal flashes, Atoto pink wire triggers on camera view on screen, and the cube relay swaps in the side mirror view from default rear backup camera. When cube relay is not energized, camera signal will be connected to the rear camera.

Just like on our Odyssey.

 

no... relay coil is some 80 Ohm +/- 10%. this will drain capacitor too quickly.

 

better solution is to latch relay and have supply steady. it can be turned off by missing pulse circuit or timer for example when turn signal stops. the other option is to increase capacitor value at least 3x (more like 8-10x)

 

easiest way for me is to boost up capacitor value.

Can you share a simple alternative circuit plan different from a large capacitor?

Did find 22,000-27,000-33,000uf for $13 which is not too bad.
if I went with 33,000uf, how long will relay stay closed when flasher turns off?

https://www.ebay.com/itm/2366318735...iAJnHk2en|tkp:Bk9SR7DT6f2RZw&var=537150000714

 

You have to know the following;

1. The resistance of the relay coil.
2. The minimum holding voltage of the relay.
3. The on and off times of the blinker.

Then the size of the capacitor can be calculated.

 

exactly.. there are online calculators for that or you can try simulating it yourself. there are plenty of options such as LTSpice, Falstead...

but... why not consider alternatives? why bother with 40A relay? a diode and small capacitor can do the trick if you are controlling mosfet instead of relay. you can still have a relay (controlled by that mosfet).

 

https://www.the12volt.com/relays/relaydiagram22.html
here says you need 10,000 uf
This is slightly different idea as to where that capacitor goes.
coil ohms is 80
voltage on a truck is from 11.5 to 14.5 vdc



Why bother with that draining resistor?
The coil will drain it.

 

exactly.. there are online calculators for that or you can try simulating it yourself. there are plenty of options such as LTSpice, Falstead...

but... why not consider alternatives? why bother with 40A relay? a diode and small capacitor can do the trick if you are controlling mosfet instead of relay. you can still have a relay (controlled by that mosfet).

Yes, I know some people understand how to make such a thing.
The relay swaps the video input to the Atoto android radio, so the 5 pin relay made sense to me SPDT relay
2 video inputs 2 cameras, go to one display device. Display device sees one or the other depending on turn signal switch.

Atoto has a trigger wire so that when it sees 12vdc, it shows the camera input on the screen.

 

Been discussing this with Gemini too. Gemini says 3300uf will work for me.
I have ten 3,300uf capacitors here, I can double them up and experiment with how long relay stays closed.

I asked Gemini, It shows a 10,000 uf capacitor. And why have the drain resistor, the coil will drain the capacitor



Gemini said
You are 100% correct. In a standard automotive relay setup, the relay coil (connected to Pins 85 and 86) acts as a natural resistor. Once the blinker signal stops, the coil will consume the energy stored in the capacitor until the voltage drops below the "release threshold," causing the relay to click off.
The Drain Resistor: Why is it in the diagram?
The 10kΩ resistor in that the12volt diagram is a "bleeder resistor." Its job isn't to help the relay click off—it's a failsafe.

• The Coil's Limitation: A relay coil has a "drop-out voltage." It might stay engaged until the capacitor hits 3V or 4V, then click open. However, a 10,000μF capacitor can hold that tiny bit of remaining voltage for a long time.
• The Purpose: The resistor ensures the capacitor drains to zero quickly once the relay has dropped out. This prevents the relay from "stuttering" if you turn your blinker off and then back on very rapidly.
• Do you need it? For your ATOTO setup, no. The relay coil itself (which usually has a resistance of 70Ω to 100Ω) will drain your 3300μF or even a 10,000μF cap plenty fast enough for a turn signal application. You can safely skip the resistor.

The 10,000μF vs. 3300μF Debate
The diagram suggests 10,000μF because it’s designed for universal blinker speeds (some old trucks have very slow "thermal" flashers).

• Your 3300μF Cap: This is actually a "sweet spot." It will hold the relay for about 0.5 to 1.0 seconds.
• The Benefit: If the cap is too big (like 10,000μF), your side camera might stay on the screen for 2 or 3 seconds after you finish your turn. With the 3300μF, the screen will switch back to your Rear View (or home screen) almost immediately after the blinker stalks click off.

 

resistor is there just as backup. this will allow capacitor to drain even in case when relay is removed from its socket (or fails). you may not like to find out that circuit stopped working, then you popup the hood and start messing with things around relay and then see a spark because capacitor was charged.

 

relay dropout voltage is usually some 30% of specified coil voltage. to be sure read the relay specs.
30% of 12V is 3.6V.

as the green graph in post #2 shows, voltage drops below 2V (well below 3.6V threshold). so clearly this will NOT work. and it will be even worse if OFF time is longer.

in post #3 voltage stays above 9V (well above 3.6V threshold). this CAN work.

 

I can double, triple etc... my existing 3300uf to see what does work.
I dont mind 1-4 caps in parallel, after that gets bulky
I bought 5 relays' with wire harness for $5 on Ebay

 

Going the mosfet route would significantly reduce the layout, if desired.

 

yup, and that low value capacitor is not just cheaper and smaller but can have better specs (voltage rating, leakage current, temperature range...). also much lower load on flasher circuit...

 

If you insist on using a capacitor only approach, try connecting a 3900uf, or 4300uf, capacitor across the relay coil (connected in parallel with the relay coil). After testing, connect a 10 ohm resistor is series with the chosen capacitor to limit current, in the event of a future short circuit.
Be sure to respect the polarity of the capacitor, and connect the + side of the capacitor to +12V, or the capacitor can blow up.

 

I also found this board, time delay spdt relay, then found it wont work, it resets when power goes off, I think. And a flasher I think goes to zero volts
https://www.qualitymobilevideo.com/...4l7RS38S3LouW0B3mB0a9tMcapo0IpvaCVkj0Nwr7hr2U

 

there you go, ready unit. just set it to about 1 sec and you are done.

 

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.

 

There may be a bit of a problem using an unshielded POWER relay for switching low level video.

The relay contacts will apply a 12 volt dc trigger signal to the radio to switch between cameras, not switching video.

 

The relay contacts will apply a 12 volt dc trigger signal to the radio to switch between cameras, not switching video.

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??