www.astrocafe.hk

一般情況下，作一晚的長時間攝星曝光最少需要兩塊電池。如果氣溫較低，電池效能轉差，最少要準備三塊電池。一不小心，忘記叉電，後果可能望天長歎！一直在想，如果有產品可把常用的12V轉成Canon數碼單反的8.1V就好了！好不容易發現有這功能的產品，就是專門改裝冷凍數碼單反的韓國公司，但價錢就有點嚇人！未計運費就已經過千元 (US$130)！
http://www.centralds.net/cam/?product=ps1208

最近的起心肝，找出合用的DC-DC converter IC，用簡單的電路把12V轉成8.1V。因自己焊接手工差又無時間晒板和焊接，最後找當電腦工程師的朋友幫手。當然他貴為Senior Engineering Manager，所以不會做這些下欄工作，他找個大陸熟手技工幫我焊接。另外他改用了一枚較平的IC，代價是需要外加穩壓。還有加多個散熱(heat sink)！果然是工程師！讀物理的我只懂得基本電子學，這些工程的考慮都是工程師好！

上星期工程師朋友把prototype交給我，叫我試清楚，如果OK，他可幫我叫那位技工焊接十隻八隻！只要比番成本和人工便成！有了這個12V轉成8.1V的直流變壓器，再在淘寶買個Canon數碼單反的交流變壓器，利用它的電匣，就可解決戶外使用數碼單反耗電問題！
http://item.taobao.com/item.htm?spm=a23 ... 9850007841

由於我未買5DII交流變壓器，所以多謝xiaoer用自己的40D作白老鼠，結果無燒機！期實找單反測驗前，我已重複量度電壓和極性，確保萬無一失！今天下午把直流變壓器交給xiaoer作操作測試，等他報告。

A simpler method is to use 7.4V 10A lipolymer battery. When fully charged, the voltage is about 8V odd.

Buy from Taobao any Canon camera dummy battery (you get AC adapter to 8.1V as well). Connect the dummy battery to lipolymer battery.

You should be able to use Canon camera all night without any need to replace the original small battery.

Very useful at cold night when you do long duration timelapse/star trail. The Canon original battery dries out in about 2.5 hrs for my 5DII.

Raymond TSE 寫:A simpler method is to use 7.4V 10A lipolymer battery. When fully charged, the voltage is about 8V odd.

Buy from Taobao any Canon camera dummy battery (you get AC adapter to 8.1V as well). Connect the dummy battery to lipolymer battery.

You should be able to use Canon camera all night without any need to replace the original small battery.

Very useful at cold night when you do long duration timelapse/star trail. The Canon original battery dries out in about 2.5 hrs for my 5DII.

Did u use ur own 5DII to try it? I guess 7.4V will not burn the camera, but
1. don't know whether the behavior of noise & bias current etc will be affected.
2. An extra 7.4V battery is needed.
3. Whether one feels comfortable to use voltage which is not equal to the rated voltage.

Anyway, if u find no problem, it is ok. I need to wait for the price of this converter. But my friend told me that the price should be less than $100. Not expensive right? Perhaps the most expensive is time to design the circuit...

我用這個的，見網頁最底部：

http://www.sciencecenter.net/hutech/canon/index.htm

不單可以以市電供電給單反，亦因為電源接在IP Power後面，所以我可以透過網頁遙控西藏的5D Mark II電源開關。

社長 寫:我用這個的，見網頁最底部：

http://www.sciencecenter.net/hutech/canon/index.htm

不單可以以市電供電給單反，亦因為電源接在IP Power後面，所以我可以透過網頁遙控西藏的5D Mark II電源開關。

How much?

Willis,
預我一個！
不過我會用水电。鋰电太危險！ Overcharge 好大鑊！

另 Willis 最好做個 Long test，始終拍攝一晚短至一两小時；長至六至八小時。

Overhead 短路及电線融化有可能產生問題！

我臺 CoolDSLR 450D 就是电線融化，現正找強一點电線！

funoooo 寫:Willis,
預我一個！
不過我會用水电。鋰电太危險！ Overcharge 好大鑊！

講明先，燒機閣下自理！不過我會細心測試所有電壓和極性！如有興趣，請自行加名。我只會造十隻八隻。

1. funoooo

funoooo 寫:另 Willis 最好做個 Long test，始終拍攝一晚短至一两小時；長至六至八小時。

Overhead 短路及电線融化有可能產生問題！

我臺 CoolDSLR 450D 就是电線融化，現正找強一點电線！

xiaoer is doing a prolonged test. Pls wait for her report.

正!!!!!!
幾時有得玩，我想要.....

1. funoooo
2. Lewis

1. funoooo
2. Lewis

今日趁上堂時在課室進行了小測試。
室溫28C
相機canon 40D mod
電 鋰電(capacity = 3.7 V 20000 mAh, output voltage = 12 V)
用programmable shutter 影5分鐘一幅連拍了三十幾幅約三小時，相機冇熱, DC converter(連個IC)冇熱, 鋰電冇熱, 一直運作正常。三小時話多唔多, 話少唔少啦。
我估影長D都OK, 相機draw的current對舊鋰電來說太輕鬆了。
當然有其他方法，e.g. 市電, 7.4 V鋰電, etc. 只係12 V鋰電可以一次過滿足晒多個儀器的願望，方便D。
只係要研究下個plug用乜大小，呢個係啱我的，佢同LVI好似係同一款。

Thanks for ur report! And I will modify the plug & socket accordingly.

may i suggest to use the same plug & socket as used in the Canon ACK adaptor, then the same battery insert can be used with battery and with AC adaptor?

kong 寫:may i suggest to use the same plug & socket as used in the Canon ACK adaptor, then the same battery insert can be used with battery and with AC adaptor?

The original Canon adapter has a plug in the dummy side, while those compatibles in Tao Bao has a socket in the dummy side. My design is to have a economy solution. Anyway, for those have the original Canon dummy can always buy an adapter to solve the problem. The key point is to convert DC12V to DC8.1V.

剛收到朋友的回复，那位大陸技工說連工包料要RMB$40。為方便收錢，我每隻12V轉8.1V轉換器收HK$50。下星期三(1/8)截止。我最多連自己會做十隻。現有興趣的astrocafer有：

1. funoooo
2. Lewis

剛收到朋友的回复，那位大陸技工說連工包料要RMB$40。為方便收錢，我每隻12V轉8.1V轉換器收HK$50。下星期三(1/8)截止。我最多連自己會做十隻。現有興趣的astrocafer有：

1. funoooo
2. Lewis

Willis,

2 pieces, please!

1. funoooo x2
2. Lewis
3. 社長 x1 (550DH )