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Topic: How do I prevent video interference caused by electric motors (Read 7666 times) previous topic - next topic

zoomkat

Quote
so what specifically needs to change in my original 'wiring diagram' so that it becomes a star ground wiring system?


This will be interesting to see what changes, as all the grounds seem connected. If you can change your wiring which you said you couldn't) then there may be other solutions.
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David82

it's only when the power door lock motor is on it's own battery power supply that the problem goes away.

zoomkat

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it's only when the power door lock motor is on it's own battery power supply that the problem goes away.


Bummer
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David82

yea, that doesn't help. How do you simulate two separate power supplies using one?

oric_dan

Quote
so what specifically needs to change in my original 'wiring diagram' so that it becomes a star ground wiring system?

Look in the link I've pointed you at twice now.

David82

#35
Jan 06, 2013, 05:36 am Last Edit: Jan 06, 2013, 05:43 am by David82 Reason: 1

Quote
so what specifically needs to change in my original 'wiring diagram' so that it becomes a star ground wiring system?

Look in the link I've pointed you at twice now.

ok. I read it. It talked about using a main capacitor to absorb voltage spikes and drops. I tried using a 1000uF, 35v cap. It didn't have any effect. So, back to where we left off at. It flickers even when a charged cap is applied, it doesn't flicker when a the power door lock is being powered by batteries that share the same ground as the original power supply. Given these clues, what specific tests can be performed to find out what needs to be added to calm the voltage or current? What about an inductor? Maybe the capacitor isn't large enough?

zoomkat

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Look in the link I've pointed you at twice now.


I looked at the single link i see posted that led to other links, and in a quick scan of the resultant pages didn't see anything helpful to the current issue (well maybe if a capacitor the size of a microwave oven is used). If the OP can't change the power supply or make any modifications to his current setup, his project is toast. It is what it is, and no amount of wishful thinking will change that fact. The laws of physics generally ignore fantasy thinking.
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dc42

#37
Jan 06, 2013, 12:28 pm Last Edit: Jan 06, 2013, 01:29 pm by dc42 Reason: 1
If you want to run both the motor and the battery from the same 12V supply, then at the very least the motor should have its own power and ground cables between the it and the power supply. Do not share any part of the motor power or ground lines with the power feed to the video camera. But this probably won't be sufficient, because switch mode power supplies don't react instantaneously to large changes in load current.

1000uF is probably nothing like large enough to supply the current peak when the motor starts up. 20000uF would be more like it.

Consider adding slow-start to the motor. This will reduce the current surge when it switches on and give the power supply time to react. One way is to replace the switch with a mosfet, and feed the mosfet with a slowly-increasing PWM signal. Don't forget to put a diode across the motor if you do this. Similarly, use slow-stop.
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David82

#38
Jan 06, 2013, 01:20 pm Last Edit: Jan 06, 2013, 01:26 pm by David82 Reason: 1
What you're saying makes a lot more sense and matches the results I get through experimentation. Wouldn't an inductor of the right size smooth out current spikes and solve it?

dc42


Wouldn't an inductor of the right size smooth out current spikes and solve it?


An LC filter between the power supply and the motor, and/or between the power supply and the video camera, would fix it. But the inductor needed would be very large, so I don't think this is a practical solution.
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

David82

wow. I've been messing with this for days now and tried so many things. Is there someone I can pay to solve it with the constraints I mentioned?

Here is the challenge:

while everything is powered on and working, connect an uncharged capacitor, motor, or any other device that draw significant current to terminal A, with any additional components, such that the video feed does not flicker. You cannot change the wiring. Everything shares a ground as illustrated including the ground portion of the video feed.

HazardsMind

Can you make a list of how much current and voltage your components use, like what they are rated for VS what your able to supply? Also a visual picture and/or video would be helpful too.

And if you want to pay someone to do this for you, you need to make a post in "Gigs and Collaborations".
My GitHub:
https://github.com/AndrewMascolo?tab=repositories

David82

ok, I'll post in there too. It seems like this problem will occur throughout a WIDE range of possible component specs (amp draw, voltage etc.) making that question not only very hard to answer, but largely irrelevant. I'll humor the idea anyway though. the power supply is a 90W computer power supply. All sorts of stuff can be hooked up to terminal A to make the video flicker so specs on that don't exist. The specs on the camera and LCD screen are unknown and don't seem to be relevant anyway..

This problem should be immediately recognizable to someone with the proper experience.

zoomkat

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This problem should be immediately recognizable to someone with the proper experience.


Sure, you most likely have an inadequate power supply.
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David82

The same effect is seen even when using 8AA batteries instead of the pc power supply :/

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