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BMMCC 14.8V Battery Module by RADIOPROEKTOR

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  • #46
    Some current work in progress updates. Shiny LP-E6 plate CNC master model and CNC machined rear support plates instead liquid urethane casting ones.

    All my custom made accessories for BMMCC/BMMSC now available here


    • #47
      Looking good, so the final unit will have CNC machined rear support plates?


      • #48
        Just a question shijan: why don't you do a crowdfunding?


        • #49
          Originally posted by Denny Smith View Post
          Looking good, so the final unit will have CNC machined rear support plates?
          Yes, i simplify the design and now this part is made of flat 2mm plastic. Simpler and less expensive to manufacture.

          Originally posted by bmpcc_bel View Post
          Just a question shijan: why don't you do a crowdfunding?
          Crowdfunding is complicated in the place i am located. Also i have no idea how to setup manufacture in larger than hand made batches. For small batches i have my own funds to invest.

          BTW if someone don't hear yet, last week i burn HDMI port on my BMMCC camera. I still not sure if it is due electrostatic damage or due ground loop (or both), or due some build-in HDMI chip defect. I was looking to add some kind of isolated ground module to battery outputs but i am still not sure if it possible yet. I described problem in details here

          The concept of the same battery for monitor and camera looks not too bright now. Here is quote from BMD support email:

          Potential causes of SDI failure and how to minimize them.

          Isolated Grounds
          Isolated grounds may be implemented on a battery plate for safety reasons to allow for isolation between individual devices powered by the plate.
          If two devices are connected to individual power connectors AND also have an additional cable between them, there could be the chance of voltage offset.
          For example, with an EVF setup, where the camera is on one battery plate power connector, the EVF is on a second plate power connector, and an SDI cable is connected between the devices. Assuming that the SDI connector is internally connected directly to the power negative on each device (chassis ground), then the circuit design will be utilizing the SDI cable shield to provide the common ground connection between the two power supplies. If either the camera or the EVF DO NOT have their SDI shield conductor connected directly to chassis ground, if the SDI cable length is sufficiently long or of poor quality, then the shield in the SDI cable will act as a low-value resistor, and a current will flow through the cable shield between the two devices. You could expect a potential difference measured from one supply's ground to the other.
          If the camera and monitor are using either two independent power sources or two power sources on the battery plate where the D-Tap connector may be connected directly to the battery terminals it may have a different negative potential to that of the rest of the power connectors. Ground connection contact bounce may occur and there could be a chance of damaging SDI ports. Contact bounce may also cause all manner of transient voltage spikes to go through the equipment and could cause unforeseen issues.

          If you have a battery plate with isolated ground supplies, it is recommended to only use it if both the camera and the EVF were powered from the exact same power connector. This can be achieved by plugging a D-Tap multi-tap into the plate D-Tap connector, then connect individual D-Tap cables from the multi-tap to the camera and EVF. That way they are using a common negative connection, with no chance for floating voltage potential variations.
          If avoidable SDI interfaces should not be hot-plugged. When setting up or dismantling camera setups make sure that all devices are completely turned off before making any connections to any of the device's inputs or outputs, and any batteries that can be, should removed or disconnected since some battery outlets are always powered.

          Electrostatic Discharge (ESD)
          This can occur randomly at anytime and can be caused by clothing, packaging, plastics and atmospheric conditions. If you are carrying even a small static charge, you could possible damage sensitive electronic components.
          Whilst BNC connectors are designed to minimise contact with the center conductor, if you inadvertently touch near the center contact you could cause a static discharge.

          The same static prevention measures used when handling sensitive electronic components should be employed when handling video production equipment
          As a matter of course discharge yourself when handling a device by touching any large metal object next to you such as a metal table or metal stand or water pipe etc.
          SSD drives and the SATA interfaces also do not have high ESD protection.
          Always keep any antistatic bags that the SSD drive came in, and always use them for transport and storage of the drive. Use care and try to never touch the drive contacts. SDI ports may also quite sensitive to ESD so static safety precautions should also be implemented when connecting or removing cables.
          All my custom made accessories for BMMCC/BMMSC now available here


          • #50
            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?


            • #51
              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.

              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, 12:16 PM.
              All my custom made accessories for BMMCC/BMMSC now available here


              • #52
                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


                • #53
                  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; 05-24-2019, 06:41 AM.
                  All my custom made accessories for BMMCC/BMMSC now available here


                  • #54
                    Good job! When can we hope to buy it?


                    • #55
                      Yes, looking forward to getting a couple of theses battery rigs also. Good luck getting this finished.


                      • #56
                        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, 06:24 PM.
                        All my custom made accessories for BMMCC/BMMSC now available here


                        • #57
                          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, 03:41 AM.
                          All my custom made accessories for BMMCC/BMMSC now available here


                          • #58
                            And photo etched connection parts are here! Manufactured at TMN ELECTRONICS factory. Made of C194 Copper-Iron (CuFe2P) alloy, corrosion resistant and high electrical conductivity.
                            Also during this time i made special useful tool to bend parts with proper fixed radius.

                            Last edited by shijan; 01-29-2019, 10:40 AM.
                            All my custom made accessories for BMMCC/BMMSC now available here


                            • #59
                              So i finally adjust the workflow and was able to fully assemble first 5 boxes. All goes fast and easy now!

                              But there are also bad news.
                              1. I still don't setup manufacture of LP-E6 plates.
                              2. Unfortunately casted rear caps appears not too reliable as i expected. They are hardened and also seems shrinked over time. Some of them still works well, but some accidentally cracked at the corner when i put them on and off the body for a test. My guess it may caused by random micro air bubble inside the wall that begins cracking process. This also combined with not too elastic enough material. So my next workaround is to find a more flexible casting material. Also because material is not too flexible and shrinked, the caps are not too easy to take off until you have some learning experience how to do it. Not too user friendly as for me.
                              Another option is to redesign those caps for aluminum CNC manufacture which probably makes them look less pretty but more reliable.

                              Last edited by shijan; 03-01-2019, 07:09 PM.
                              All my custom made accessories for BMMCC/BMMSC now available here


                              • #60
                                Nice update, keep,on trucking...