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--- gh2-usage:gh2-power [2013/03/25 20:07]
vitaliy_kiselev created
+++ gh2-usage:gh2-power [2013/03/25 20:13] (current)
vitaliy_kiselev
@@ Line 5: / Line 5: @@
 My post is divided in two parts: Part 1 is about the concept. Part 2 is about the implementation.
-Part 1: Concept
+**Part 1: Concept**
 I will try to give you a straight forward description of my doing but it actually was a very iterative process with countless loops.
@@ Line 49: / Line 49: @@
 {{http://www.personal-view.com/talks/uploads/FileUpload/6c/5073d067b9e4a5c8ad73a2d3d0544d.png}}
+**Part 2 Implementation**
+First find the bill of material with links to the manufacturers. Second the bill of material as a picture, see picture "bill of material.jpg"
+Housing: Panasonic DMW-DDC8 (http://panasonic.net/avc/lumix/systemcamera/gms/gh2/optional_accessories.html#acc06)
+DC-Converter: Step-Down-Converter based on LM2596 (unknown chinese manufacturer)
+Cable: Kabeltronik LifYY 2x0.25 mm2 (http://www.kabeltronik.de/electronics-industry/control-cables-unshielded/control-cable-extremely-flexible-lifyy)
+Plug: Lumberg 1634 02 (http://lumberg.de/main/common/produkt_fs.asp?lang=eng&produktname=1634_02)
+Bracket: self-made (see drawings)
+{{http://www.personal-view.com/talks/uploads/FileUpload/ac/24bf3400f1fb4e452ecacb52097460.jpg}}
+Next the steps to bring everything together:
+You can open the DC coupler by just pressing carefully but with a good amount of pressure the cutter between both parts of the housing. Both parts are glued together. It sounds like something breaks but except the glued areas (which actually really breaks) the housing stays undamaged. See picture "cutter.jpg"
+{{http://www.personal-view.com/talks/uploads/FileUpload/d5/305b18c185671fb00e41b3aba1f979.jpg}}
+You have to remove all stringer inside to make room for the step-down converter. Don't remove the little nibs which hold the circuit board. I processed the housing with my Dremel. A lot of handwork and it does not look very professional, but it's inside the housing. See picture "housing.jpg"
+{{http://www.personal-view.com/talks/uploads/FileUpload/ce/fffb1982427ae916999efd500073e7.jpg}}
+You have to use abrasive paper to trim the size of the step-down converter. Just move the circuit board back and forth on the paper and make sure to evenly remove the material of the board. You have to remove almost 0.5mm on every side until it fits into the housing (the idea with sheet metal and the cable junction also requires some space for the sheet metal inside the adapter housing). Be careful because almost all the components are soldered on top of the board. Additionally I removed the sockets as already mentioned in part one. And I have sanded very carefully some millimeters off of the pins beneath the board with my Dremel. See picture "resize step-down converter.jpg"
+{{http://www.personal-view.com/talks/uploads/FileUpload/a0/cf4767b7ac3056af4b3ebdd7b59c1f.jpg}}
+The circuit board of the step-down converter, the original little circuit board out of the adapter and the sheet metal now fits into the housing and i can close the housing without exertion. See picture "assembly.jpg"
+{{http://www.personal-view.com/talks/uploads/FileUpload/ab/799051ee0250bf53b1755da18fb4bc.jpg}}
+In the picture above you can already see the sheet metal with the cable junction. In the picture below you can see it fully assembled. I have glued all together with a two component epoxy resin adhesive. The cable junction is made out of PVC. Don't use other plastic like POM which can be machined very good but you will have problems while glueing. The sheet metal is made out of stainless steel. Both can be glued together very well with a two component epoxy resin adhesive. I stripped the outer cable coating and kept 3 mm of this outer cable coating to put it back on the wires from the other side, see second picture below. I have attached some more pictures to give you a better idea of what I have done, see pictures "cable1.jpg", "cable2.jpg" and "cable3.jpg"
+{{http://www.personal-view.com/talks/uploads/FileUpload/8a/403954adf870f11503997e6bf5ab7d.jpg}}
+{{http://www.personal-view.com/talks/uploads/FileUpload/bc/f8e630059779a4c21fd276bfa9f005.jpg}}
+{{http://www.personal-view.com/talks/uploads/FileUpload/89/f46a8e1ec354b2aa68f15b5e0a5b51.jpg}}
+And here find the drawings of at least the cable junction, see pictures "drawing1.png" and "drawing2.png I have no drawings of the sheet metal because it is made by hand freestyle. The material is as mentioned PVC-U. I've defined no production tolerances. Just make it as accurate as possible and make sure the two parts fit together. But one hint: Don't go under 1.3 mm of hight of the lower ring. For me it was absolute the minimum!
+{{http://www.personal-view.com/talks/uploads/FileUpload/2f/fe59218bf4df3da4e45143061bd4b8.png}}
+{{http://www.personal-view.com/talks/uploads/FileUpload/63/6d4b3ce709dd4ec7ab3530be00c4b8.png}}
+The last thing to do is to solder everything together. The cables go across each other because the input of the step-down converter is located to the opposite of the housing opening. That's because otherwise the cable from the little circuit board with the two resistors out of the original adapter would be located directly behind the potentiometer (the blue box with the screw on top). That is not working. And to be honest. It's much easy to solder a cable that is about 3 cm long than a cable that is just 0.5 cm long. Don't wonder that the plug is not yet screwed together. I want to wait until I put everything on my support rig. Maybe I can further shorten the cable. see picture "final assembly.jpg"
+{{http://www.personal-view.com/talks/uploads/FileUpload/59/0ffc795e30d78f6f4c65312c2b47e3.jpg}}
+The most important thing (and I have expected nothing more than that due to the fabulous spadework of a lot of other people): It works and my GH2 is still alive, see picture "GH2 attached to LIPO.JPG"
+{{http://www.personal-view.com/talks/uploads/FileUpload/34/2c4acc637293edbb69ff7c3969aff6.jpg}}
+Hopefully it is interesting and helpfull for you guys!
+===== Lithium batteries =====
+First of all I am talking about naked Lithium-Polymer-Batteries used for RC Cars & Co. and not about the Battery-Packs you can buy to power your mobile devices! Second with my explanations I have always the idea of powering the GH2 with a battery via a converter in mind!
+The basic discharge characteristic of a LIPO primary cell looks like this example, see chart „Discharge rate characteristics“ in file „data sheet primary cell.pdf“.
+[[http://personal-view.com/talks/uploads/FileUpload/fe/9e846951088088dfedb402114dff0d.pdf]]
+A primary cell can provide fully loaded 4.2 V and fully discharged around 3.0 V. With the application of powering the GH2 with a big LIPO you have rather small discharge currents. That means a flat curve over time with a steep end. Often it is suggested to cut off a cell between 3.3 V and 3.6 V and not at 3.0 V. That makes sense to me because it is better for the battery to not be fully discharged and the discharge curve is so steep at the end, that it can take only seconds to over discharge your battery.
+When you put more primary cells in series together then you get higher voltages. That means for one up to four cells you get the following voltage ranges:
+S: 3.0 V up to 4.2 V with nominal voltage of 3.7 V
+S: 6.0 V up to 8.4 V with nominal voltage of 7.4 V
+S: 9.0 V up to 12.6 V with nominal voltage of 11.1 V
+S: 12.0 V up to 16.8 V with nominal voltage of 14.8 V
+To power the GH2 you need between 8.4 V and 8.8 V. 8.8 V has been measured as output voltage of the original Panasonic power supply. Below 8.4 V we get an error message from the camera and above 8.8 V I don’t know what will happen.
+How to get a voltage between 8.4 V and 8.8 V? The first option is to always convert from higher voltage down. The second option is to always convert from lower voltage up. And the third option is a combination of both conversions. The charts below show an up and a down conversion (simplified and not to scale), see pictures “down conversion.png” and “up conversion.png”.
+{{http://personal-view.com/talks/uploads/FileUpload/27/1952d8f3db72d2c0b2e801fff47ff4.png}}
+{{http://personal-view.com/talks/uploads/FileUpload/8d/8832677be9b0a5e73a909d5045ec51.png}}
+The next chart tries to show the effect that @Mike_C has observed (simplified and not to scale), see picture “combi-conversion.png”.
+{{http://personal-view.com/talks/uploads/FileUpload/03/5819915325b506678ea3703ab79816.png}}
+You can clearly see the extra time which an additional step-up-converter stage will bring. Without it the camera would turn off before all the energy of the battery has been used. But as I mentioned before I would not prefer this approach. I don‘t know if the current of the battery has to pass always both converter stages or if the unnecessary stage is bypassed. But if the current has to pass both stages the efficiency gets worse. Let’s assume a converter stage has 0.85 efficiency. With two stages you get 0.85 x 0.85 = 0.7225 efficiency. Not good! So even if you gain some extra time a lot of your energy goes into heat due to several converter stages! Better is to make sure you have only one converter stage. But then your battery needs to be bigger which means provide a higher voltage. If you use a Battery-Pack whose nominal output voltages are different to 3.7 V, 7.4 V, 11.1 V or 14.8 V or in general multiples of 3.7 V I am quite sure that there is another converter inside the Battery-Pack to deliver voltages like 12 V, 9 V and 5 V.
+But in reality things often get more complicated. The converter needs a little bit more input voltage than it outputs, see the data sheet of the LM2596, page 4, chart „Dropout Voltage“ which you can find right here http://personal-view.com/talks/discussion/comment/116764#Comment_116764 That means you need additionally about 1 V if you use your own converter. In total your battery must provide at least 9.4 V up to 9.8 V. The last chart illustrates this fact, see picture „down conversion with voltage offset.png“.
+{{http://personal-view.com/talks/uploads/FileUpload/5a/c0c5de6a4e0b7a5b1d3b859c741b39.png}}
+I have chosen a 5S-LIPO because I also want to power an external field monitor which needs at least 12 V. A 4S-LIPO would do the job. But due to the fact that the efficiency of the LM2596 is better with higher voltages and because I wanted even more energy I decided to use a 5S-LIPO. Assumed that a primary cell has 5 Ah then I get 3.7 V/cell x 5 Ah/cell x 5 cells = 92.5 Wh instead of 3.7 V/cell x 5 Ah/cell x 4 cells = 74.0 Wh. But you have to check what your LIPO supplier can offer. You can play with the number of primary cells and with the capacity of a primary cell to determine your overall battery energy.
+All this applies only if you use a LIPO for RC Cars & Co.! I don't want to conceal the big disadvantage of this solution: It's about the Battery-Management-System. With this solution you also have to take care not to over charge and over discharge your battery. This problem is not existent with Battery-Packs for mobile devices because all the electronic controls are already inside the Battery-Pack. Just load it. Just use it. With a LIPO for RC Cars & Co. you need a charger with a so called balancing feature and at least a so called LIPO saver which indicates your battery is empty. The advantage of this solution is of course the high efficiency which can be translated in longer run-times and the opportunity to design your battery-system according to your needs.

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