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Constructing an automatic RCA video camera feed splitter

 
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nuckolls.bob(at)aeroelect
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PostPosted: Wed Oct 11, 2017 9:04 am    Post subject: Constructing an automatic RCA video camera feed splitter Reply with quote

Quote:

My Byte Thrasher in Chief (Paul Fisher) helped me craft
a universal, 4 step timer chip described here:

http://tinyurl.com/y96wc8rh

I've used this chip on several applications and
it's easily adapted to your task. The link
above contains a description of the chip which
can be supplied you to at no cost with what
ever time intervals you wish programmed in.
Further, there is a hold function on the chip
that can be used to pause switching in the
current state.

Somewhere in the pile on my bench, I have some of the
development ecbs shown on the linked page.
You could assemble one with driver transistors
and build an array of relays to handle video
switching.

Alternatively, could cut-n-paste the ECB
artwork into a new board that would eliminate
the driver transistors and drive some really
small, surface mounted relays to handle
video switching.

http://tinyurl.com/ybhnq6m6

It wouldn't take much time to lay out the
board . . . but I'm up to my eyeballs right
now in projects that need to be cleared
off the bench. If anyone wants to take the
data posted and lay out a new board, I'd
be pleased to critique the work product before
boards are ordered.


Does anybody know of a device like this that exists? Would the circuitry for something like this be too complicated? Finally, is there any detriment to swapping out the thicker RCA cabling with 24 AWG shielded wire?

That would be fine too. There are ECB
mounted RCA jacks that could be incorporated
into your video switcher board.


Bob . . .


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Airdog77



Joined: 24 Nov 2013
Posts: 80
Location: Northern Virginia

PostPosted: Wed Oct 11, 2017 11:46 pm    Post subject: Re: Constructing an automatic RCA video camera feed splitt Reply with quote

Thanks Bob.

I'll take a look at all this and try to digest! Smile

I see a number of responses to my question that I need to go through as well.... normally I get an email update on a post, but didn't this time so I have some reading to do!

Regards,
Wade


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PostPosted: Thu Oct 12, 2017 3:22 am    Post subject: Constructing an automatic RCA video camera feed splitter Reply with quote

At 03:03 AM 10/12/2017, you wrote:
Quote:
--> AeroElectric-List message posted by: "Airdog77" <Airdog77(at)gmail.com>

Sorry for my delayed response back. Again, didn't get any of the normal email notifications that responses were being made to my question... thanks all!

The camera I'm using is a cheap 1/4" 600TVL from Amazon... the two I bought are no longer being sold, but this is close: https://tinyurl.com/yckqk3dh

There's quite an array of products offered
in these devices. I read some comments that
complained of poor/no instructions. Also,
some devices advertised as 3-12v supply were
indeed 3.3 volts only . . . anything more
smoked them.


Quote:
Yes, I'm looking at video RCA jack OUT feed that will then go into box that hooks to USB. So I don't need to mess with anything USB as far as video is concerned.

I need to dig into all this info to figure out a way ahead.

Bob, how would I go about getting boards like the one you posted pics of?

Give me an address . . . I'll mail them
to you. How are your soldering/fabrication
skills? You'll have to chase down some
parts and package the stuff up in some
suitable enclosure.


Bob . . .


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Airdog77



Joined: 24 Nov 2013
Posts: 80
Location: Northern Virginia

PostPosted: Thu Oct 12, 2017 8:15 am    Post subject: Re: Constructing an automatic RCA video camera feed splitt Reply with quote

Bob,

Thanks a ton! I'll email you my address.

Soldering skills are not horrible. Have done very little on circuit boards, but I have managed small stuff with pretty good results.

I tested out the camera hooked up to my TV using a 12V battery and the picture was really good for such a small camera. That's when I decided to press forward with these mini cameras.

Regards,
Wade


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PostPosted: Sat Oct 14, 2017 1:47 am    Post subject: Constructing an automatic RCA video camera feed splitter Reply with quote

At 11:28 PM 10/13/2017, you wrote:
Quote:
--> AeroElectric-List message posted by: "Eric Page" <edpav8r(at)yahoo.com>

I know Wade's specific request for camera switching has been solved, but it sounded like the sort of thing that might come up again so I thought I'd take a stab at it.

So... here's an alternative for switching cameras to a monitor or EFIS input using a couple of voltage regulators and three ICs. All components are through-hole. Everything on a single PCB, and no relays.

Reference the attached schematic:

An LM2931 5V linear regulator and a TC7660 charge pump provide +/-5V rails to power the circuit. A 555 timer is configured in astable mode to provide an output with adjustable period of about 3 to 10 seconds. This output is fed to the clock input of a CD4022B octal counter. The clock signal can be interrupted by a SP3T ON-ON-(ON) switch to stop rotation of the cameras or advance them manually. Outputs 1-3 of the counter are connected to the logic inputs of an AD8184 4:1 video multiplexer such that they cause the multiplexer to cycle through its four video inputs, connecting each in turn to the output. RCA connectors provide four camera inputs and one video output.

LM2931AZ 5V Linear Regulator: http://preview.tinyurl.com/yakjxubl
TC7660CPA Inverting Charge Pump: http://preview.tinyurl.com/y7n7g6um
ICM7555IPAZ CMOS Timer: http://preview.tinyurl.com/ybrvnnq2
CD4022BE Octal Counter: http://preview.tinyurl.com/ycjsa46w
AD8184ANZ 4:1 Video Multiplexer: http://preview.tinyurl.com/ybozz2nf
SP3T Toggle Switch: http://preview.tinyurl.com/ybpazcu5

Critiques? Suggestions?

How about replacing the 555 and counter with
a single uC. Paul Fisher can probably craft
the software to emulate these two components
to include the scan, step, rate and hold functions
in one, 8-pin dip device and about 1/20th the
hardware.

Do you want to terminate unused outputs with
dead shorts or 75 ohm resistors? RCA jacks
are more robust than most miniature headphone
jacks. Further, they're available to solder directly
to an ECB. If termination of an unused output is
necessary, a 75 ohm resistor can be installed
in an RCA plug.





Bob . . .


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Eric Page



Joined: 15 Feb 2017
Posts: 241

PostPosted: Sat Oct 14, 2017 5:00 am    Post subject: Re: Constructing an automatic RCA video camera feed splitt Reply with quote

Eliminating the 16-DIP-packaged counter and most of the passives sounds fine to me. It will certainly shrink the PCB. If you can give me a pin-out for the uC you propose using, I’ll amend the schematic. I’ll need to know pin numbers for Vcc, Gnd, two outputs to the mux, how we’ll read user input for run/hold and rate, and if an ICSP header is needed. I’m guessing you propose the same (PIC12F683?) used for the recent prop current limiter...

The AD8184 multiplexer has just one output, so I didn’t figure a termination resistor was necessary. The connectors shown actually are RCA jacks, despite the CAD symbol looking like a headphone...

http://preview.tinyurl.com/ycpmbhj5

They connect the AD8184 inputs to ground with an internal switch contact if no RCA is plugged in.

Eric


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Airdog77



Joined: 24 Nov 2013
Posts: 80
Location: Northern Virginia

PostPosted: Sat Oct 14, 2017 8:21 am    Post subject: Re: Constructing an automatic RCA video camera feed splitt Reply with quote

Eric,

As an end user --I'll emphasize that aspect since you & Bob are speaking on a cosmic ethereal plane that this mortal struggles to follow Wink -- having another option is never bad.

I really like the ON-ON-(ON) switch form factor for control. Simple and small, which is exactly what I need in a Long-EZ. Probably could be incorporated for most designs, but I'm glad you made note of it.

Regards,
Wade


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PostPosted: Sat Oct 14, 2017 2:27 pm    Post subject: Constructing an automatic RCA video camera feed splitter Reply with quote

At 08:00 AM 10/14/2017, you wrote:
Quote:
--> AeroElectric-List message posted by: "Eric Page" <edpav8r(at)yahoo.com>

Eliminating the 16-DIP-packaged counter and most of the passives sounds fine to me. It will certainly shrink the PCB. If you can give me a pin-out for the uC you propose using, I’ll amend the schematic.

See attached

Quote:
I’ll need to know pin numbers for Vcc, Gnd, two outputs to the mux, how we’ll read user input for run/hold and rate, and if an ICSP header is needed. I’m guessing you propose the same (PIC12F683?) used for the recent prop current limiter...

Yeah . . . only 'case they're cheap and we got lots
of them!

Probably wouldn't fuss with ICSP, just put the chip
in a socket. This lets a user drop a new chip
into a fielded assembly should any future feature be
desired/necessary.

The sequencing software could be set up to default to
either SCAN or STEP at power up. Your choice. If the default
is STEP, then Channel A input is the first up.

Momentary depression of the switch to STEP would advance
to next channel in sequence. Momentary depression to SCAN
would initiate steps through the four inputs at a rate
commanded by the potentiometer. Setting a rate of
say 3 to 10 seconds for zero to 5 volts seems a
good starting point.

I didn't suggest any DO-160 like protections for
inputs to the command pins. If the switch is
on the board it's not needed. If off the board,
extending the lines in a shielded-twisted pair
would offer plenty good prophylactics for our
environment.


Quote:
The AD8184 multiplexer has just one output, so I didn’t figure a termination resistor was necessary. The connectors shown actually are RCA jacks, despite the CAD symbol looking like a headphone...

Aha! Been there . . . fiddled with several
canned libraries for about an hour each
before I dumped them all and crafted my
own.


Quote:
http://preview.tinyurl.com/ycpmbhj5

They connect the AD8184 inputs to ground with an internal switch contact if no RCA is plugged in.

Understand.

I propose we make this another open source program like
the wig-wag was . . . I'll be pleased to set up a folder
to host all the work product.


Bob . . .


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Eric Page



Joined: 15 Feb 2017
Posts: 241

PostPosted: Sat Oct 14, 2017 4:32 pm    Post subject: Re: Constructing an automatic RCA video camera feed splitt Reply with quote

nuckolls.bob(at)aeroelect wrote:
I propose we make this another open source program like the wig-wag was . . . I'll be pleased to set up a folder to host all the work product.


Great. I kinda figured we were doing an open-source effort. With that in mind, I had a good think about this while slogging for six hours against 145-knot headwinds this morning...

I think there are a few issues that argue against changing to a PIC microcontroller in this project. Wade alluded to the first one in his post this morning when he joked about the details being over his head:

- It would make the project considerably less accessible to many builders. Anyone without a hardware programmer and the Microchip IDE software will either have to get them, then find the code to download and learn how to program the PIC, or buy a PIC with the code already loaded. On the other hand, anyone pretty much anywhere with a soldering iron and minimal skill can put my design together for as long as its jellybean components are available.

- Software updates will require removing the unit from service, removing the PIC to send for reprogramming, or buying a new PIC to replace it.

- A PIC won't simplify the user interface. We still need a switch for the run/hold/step function and a knob to adjust scan rate. Perhaps a system using buttons or a rotary encoder could be devised, but it would probably be less intuitive than the switch and knob.

- If a PIC could replace the $7 video multiplexer chip, you could make a good case for lowering cost, but we're talking about replacing a couple of 50 to 80-cent jellybeans and a few passives that are tens of cents each -- about $3 total. Can anyone deliver a programmed PIC for $3 and make it worth their trouble?

- The size of the PCB is going to be driven largely by the five RCA jacks, so deleting a 16-DIP and a few passives probably won't shrink the board appreciably.

I think this is a case where a microcontroller may be overkill, given that suitable cheap ICs are readily available. Given the simplicity of the problem, wouldn't it make more sense to keep the solution simple?

Thoughts?

Eric


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Last edited by Eric Page on Sat Oct 14, 2017 4:41 pm; edited 1 time in total
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Eric Page



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PostPosted: Sat Oct 14, 2017 4:38 pm    Post subject: Re: Constructing an automatic RCA video camera feed splitt Reply with quote

Wade,

Question: do you want to be able to adjust the scan rate as a matter of routine operation (i.e. with a panel-mounted knob), or do you envision setting the rate where you like it at installation, and leaving it alone?

The answer will dictate whether we put a small trimmer potentiometer on the circuit board or design for a larger panel-mounted potentiometer and knob.

Eric


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PostPosted: Sat Oct 14, 2017 8:06 pm    Post subject: Constructing an automatic RCA video camera feed splitter Reply with quote

At 07:38 PM 10/14/2017, you wrote:
Quote:
--> AeroElectric-List message posted by: "Eric Page" <edpav8r(at)yahoo.com>

Wade,

Question: do you want to be able to adjust the scan rate as a matter of routine operation (i.e. with a panel-mounted knob), or do you envision setting the rate where you like it at installation, and leaving it alone?

I was thinking a 10-turn pot on the board . . . probably
left in place after some in-service experience . . .


Quote:
The answer will dictate whether we put a small trimmer potentiometer on the circuit board or design for a larger panel-mounted potentiometer and knob.

How about pads for extending the pot leads out
on a shielded pair, or simply installing a couple
of resistors to set the rate to some pre-determined
value. We could publish a table of resistors versus
rates to minimize the fiddling.


Bob . . .


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PostPosted: Sat Oct 14, 2017 8:14 pm    Post subject: Constructing an automatic RCA video camera feed splitter Reply with quote

At 07:32 PM 10/14/2017, you wrote:
Quote:
--> AeroElectric-List message posted by: "Eric Page" <edpav8r(at)yahoo.com>


nuckolls.bob(at)aeroelect wrote:
> I propose we make this another open source program like the wig-wag was . . . I'll be pleased to set up a folder to host all the work product.


Great. I kinda figured we were doing an open-source effort. With that in mind, I had a good think about this while slogging for six hours against 145-knot headwinds this morning...

I think there are a few issues that argue against changing to a PIC microcontroller in this project. Wade alluded to the first one in his post this morning (which, along with one other from Clayton, has disappeared from the server) when he joked about the details being over his head:

- It would make the project considerably less accessible to many builders. Anyone without a hardware programmer and the Microchip IDE software will either have to get them, then find the code to download and learn how to program the PIC, or buy a PIC with the code already loaded. On the other hand, anyone pretty much anywhere with a soldering iron and minimal skill can put my design together for as long as its jellybean components are available.

True . . . your choice. On the flip side,
I'll offer programmed chips at cost plus
postage . . . probably less than $2 each.
The same constraints exist for the ECB itself.
My usual source for boards is ExpressPCB. I
can see this project fitting two ship-sets
per 'miniboard' x 3 for the standard minimum
order. This means that an individual builder
would have to purchase 6 ecbs and hope to sell/
trade off the excess.

It might be more practical to offer AEC 'kits'
of a programmed chip and an ECB which gets around
both the ECB batch costs AND chip programming.


Quote:
- Software updates will require removing the unit from service, removing the PIC to send for reprogramming, or buying a new PIC to replace it.

Naw, never return a chip . . . just pitch it
and replace it.


Quote:
- A PIC won't simplify the user interface. We still need a switch for the run/hold/step function and a knob to adjust scan rate. Perhaps a system using buttons or a rotary encoder could be devised, but it would probably be less intuitive than the switch and knob.

agreed


Quote:
- If a PIC could replace the $7 video multiplexer chip, you could make a good case for lowering cost, but we're talking about replacing a couple of 50 to 80-cent jellybeans and a few passives that are tens of cents each -- about $3 total. Can anyone deliver a programmed PIC for $3 and make it worth their trouble?

don't know about worth the trouble . . . but yeah,
I can beat the $3 by some good percentage.


Quote:
- The size of the PCB is going to be driven largely by the five RCA jacks, so deleting a 16-DIP and a few passives probably won't shrink the board appreciably.

I think this is a case where a microcontroller may be overkill, given that suitable cheap ICs are readily available. Given the simplicity of the problem, wouldn't it make more sense to keep the solution simple?Thoughts?

Eric


Either way works my friend . . . your choice.


Bob . . .


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Airdog77



Joined: 24 Nov 2013
Posts: 80
Location: Northern Virginia

PostPosted: Mon Oct 16, 2017 12:23 am    Post subject: Re: Constructing an automatic RCA video camera feed splitt Reply with quote

Eric,

You asked: Question: do you want to be able to adjust the scan rate as a matter of routine operation (i.e. with a panel-mounted knob), or do you envision setting the rate where you like it at installation, and leaving it alone?

For me setting it off-panel is fine. If I can get to a POT and adjust the scan rate, that'd be great... but I don't envision having to tweak the rate more than 1-2 times before getting it dialed in.

Still not getting but an occasional update email on this forum...guess I need to check in a lot more, eh?! Smile

Thanks!
Wade


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PostPosted: Wed Oct 18, 2017 11:09 am    Post subject: Constructing an automatic RCA video camera feed splitter Reply with quote

At 09:28 PM 10/17/2017, you wrote:
Quote:
--> AeroElectric-List message posted by: "Eric Page" <edpav8r(at)yahoo.com>


nuckolls.bob(at)aeroelect wrote:
> If one wishes to program SOIC chips before installation, adapters are avaiable to facilitate this task . . .
>
> http://tinyurl.com/yazkcare


Yikes! They're available a LOT cheaper than that:

8-Pin: http://preview.tinyurl.com/yasq5txd

14-Pin: http://preview.tinyurl.com/y8ngbp3p

16-Pin: http://preview.tinyurl.com/y7ebhgb3

28-Pin: http://preview.tinyurl.com/y7wmacyr

Eric

To be sure . . . I just clicked on some of the
most accessible options. The point of the posting
was to suggest that acquiring a programmed
chip need not be the longest pole in the
tent.

I have observed that DIY projects are seldom
justified in terms of the economics. I've
sold bare boards for years . . . they've
never been more than a tiny percentage of
product flow off my shelves.

I KNOW that any builder's $time$ expended
in completion of the project will probably
exceed the cost of a factory fabricated
equivalent. I think the prevailing reasons
for DIY projects are (1) no practical
off the shelf alternative has been identified
or perhaps non-existent. (2) the builder
enjoys the journey from bag-o-parts to
functional system.

I got three for four PIC programming tools
laying around. I deduce that it would be no
big deal to offer programming services because
I think the size of that task is going to be
small -and- offering that service cuts a
significant chunk of $time$ from an individual
construction task.



Bob . . .


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