Thread: BMMCC 14.8V Battery Module by RADIOPROEKTOR

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  1. #51  
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    thats kind of interesting

    so what they are saying is if you are using same power source for both monitor and camera where they are connected via SDI (applies to HDMI also?) you DON'T want isolated grounds for the two connections, and they should actually share a ground?
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  2. #52  
    Senior Member shijan's Avatar
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    Stelvis, all grounds are connected but if you connect monitor to camera, turn them on and measure voltage between monitor DC ground and HDMI cable ground, you will see some very small voltage there (average 0.06V). I have no idea why.
    I found that this voltage leak depends of HDMI cable quality. Branded cables with better isolation leaks 0.01-0.02V. Highly used cheaper OEM China cables leaks 0.06-0.15V. This ground voltage leak exists even if you power camera and monitor from separate batteries.
    If you turn off any device there is no voltage leak between HDMI and DC grounds.

    Not sure if i understand the thing but i have a theory that it may be due both electrostatic damage and due ground loop same time. Without ground loop when you touch the camera, electrostatic voltage splash from your body goes away somewhere to camera body and next somewhere to outer ground. But when there is a ground loop with HDMI/SDI, electrostatic voltage splash may go to electronic circuit and damage HDMI chip. This is explains why those damages are so random. I used single battery setup about the month without any problem and once upon a time i turned camera on and no HDMI signal.
    beside electrostatic voltage splash this also could be a moment when you insert cable into the battery and produce small electric spark and due ground loop it somehow may damage HDMI circuit.

    I don't believe that average measured 0.06V potential between different grounds may somehow actually damage HDMI chip. Ground loop cause hum, noise, interference, but how so low voltage can damage electronic chips?

    Maybe we need to look for some kind of electrostatic protection instead of isolated grounds? But i am not so advanced in electronics so this is just a guesses.

    UPDATE:
    I found that same small voltage leak is present even if you measure between grounds on both HDMI cable ends. (Cable must be connected to the camera and monitor and both devices must be turned on)
    Last edited by shijan; 10-09-2018 at 03:16 PM.
    All my custom made accessories for BMMCC/BMMSC now available here https://lavky.com/radioproektor/
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  3. #53  
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    I think a small DC Offfset is very unlikely to be the problem - but transient voltage spikes on connection or disconnection is the likely culprit
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  4. #54  
    Senior Member shijan's Avatar
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    Today i tested new low profile UGREEN HDMI cable. It is well made and no any voltage leak between cable ends. But i got new very strange thing during measurement. When i touch to the camera body with only one of the multimeter's connector, the image on the monitor became solid grey fill. I repeat this 2 or 3 times and image on the monitor keeps change to grey fill. Few moments later it is not respond to the voltage meter's connector touch. Monitor and camera where powered from two separate LP-E6 batteries. I really have no idea what in going on inside all those electric circuits. Maybe it also was electrostatic, but voltage meter's connector was insulated from my hand so electricity can not spread from my body through it. Maybe it was just a HDMI connection lost due not to well connected lug, i don't know as well...

    And some update here. First LP-E6 plate mount final mold samples are ready! The good thing - it fits to BMMCC socket really smooth. The bad thing - due strict tolerance it is fits but not locks into SmallHD monitor battery socket. It is odd but seems i miss some extra 0.5 mm during measurement. But i think it is not a huge problem because it s very easy to grind those 0.5 mm with knife if someone somewhere really need to mount it into SmallHD monitor LP-E6 socket

    UPDATE: After some research i found that it won't clamps to SmallHD 501 monitor because it was blocked by SmallRig tilt monitor adapter. So there is no any problems with LP-E6 plate itself



    Last edited by shijan; 12-23-2018 at 10:09 PM.
    All my custom made accessories for BMMCC/BMMSC now available here https://lavky.com/radioproektor/
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  5. #55  
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    Good job! When can we hope to buy it?
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  6. #56  
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    Yes, looking forward to getting a couple of theses battery rigs also. Good luck getting this finished.
    Cheers
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  7. #57  
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    To save time (as i expected) I put outsource order for plastic parts casting to the small factory in the other city, but that company appears not too reliable. They got very nice high pressure box for casting but it appears they work too slow, too unpredictable and too hard to communicate. So i cancel my collaboration with them. Currently i have only two test samples of the LP-E6 plates that you can see in earlier post. Over this time i got a lot of experience about liquid urethane casting and setup my own small home factory. There are still some things to do, and some tools to add but as a result i will be able to manufacture things in time and with my own degassing vacuum chamber and quality control.

    This is what i done today (i'll add better photos later) Those are still beta test samples, but now i can tell you that all parts of this project are now reproduced and tested in real life and ready for batch production. Rear cap feels very solid and clamps very secure and same time very easy. It holds well even without screws fixation. I am really happy how this cap design works in real life.


    Last edited by shijan; 12-20-2018 at 09:24 PM.
    All my custom made accessories for BMMCC/BMMSC now available here https://lavky.com/radioproektor/
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  8. #58  
    Senior Member shijan's Avatar
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    After third copy assemble i start to feel that some things are overcomplicated. Those short and thick custom bended wires are real pain in the ass when it goes to batch manufacture. Very hard to fit properly and too slow to solder.




    So few days later i got new idea.
    New design will use bended commonly available 2.8mm PCB terminal inserts. So it should look like this:





    If this concept also appears unusable and too hard to assemble in real life, i will probably look to order batch manufacture of custom sheet tin plated copper stamping parts. So it will look like this:



    Casting process goes really well. I experimented with few different materials and end up with Axson F38. It is easy to cast because low viscosity. It is also very rugged and shockproof material with highest possible impact resistance value. I was able to cast 4-6 parts per day in lazy mode.


    UPDATE. Factory made custom stamped parts appears too expensive manufacture method for small batches. But seems i found the solution - custom made photo etched parts.
    Photo etching, also known as chemical etching or metal etching, is a highly precise, tightly controlled corrosion process used to produce complex metal components with very fine detail.
    It appears a very popular inexpensive and fast manufacture method. Perfect for small projects!
    This is how the connection parts kit will look like:

    Last edited by shijan; 01-12-2019 at 06:41 AM.
    All my custom made accessories for BMMCC/BMMSC now available here https://lavky.com/radioproektor/
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