External Power for ELPH 300HS - page 2 - Hotwire! Hardware Mods, Accessories and Insights - CHDK Forum
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External Power for ELPH 300HS

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Offline ahull

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Re: External Power for ELPH 300HS
« Reply #10 on: 19 / January / 2014, 11:44:15 »
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Quote from: waterwingz on 19 / January / 2014, 11:25:48
Quote from: ahull on 19 / January / 2014, 10:22:58
There is a good explanation of how to use a P-FET for reverse voltage protection here.
Agreed - it's a great video.   

However, thinking about the P-FET circuit explanation,  its clear how it protects against reversed input voltage (from the battery on the left).  However,  if you have two batteries connected in parrallel via two P-FET circuits, both circuits will have their gates at a lower voltage than their source&drains so I think both will be biased "on".  Does this allow reverse current through the FET when one battery has a higher voltage than the other?

Good question, in the case of the high side (+ve rail) P-channel mosfet protection, possibly not, but if you use low side (ground rail, n-channel mosfet) protection, if memory serves, I think it will.  Dont take my word for it though... time for a trip to CircuitLab for some simulation I think  :D
« Last Edit: 19 / January / 2014, 11:47:15 by ahull »
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Offline ahull

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Re: External Power for ELPH 300HS
« Reply #11 on: 19 / January / 2014, 12:07:02 »
Before I get bogged down in all that though, the solution of incorporating a few lines in the shooting script to detect and use a particular  shutdown voltage threshold for terminating shooting might actually be the way to go, since it will ensure that the camera closes down before either of the batteries reaches levels that are going to cause problems... and doesn't involve a visit to ebay to order up some mosfets.
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Offline drillthrall

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Re: External Power for ELPH 300HS
« Reply #12 on: 19 / January / 2014, 15:08:44 »
I understood about 3.7% of that discussion.  Get it? 3.7%  :D  Anyway, I'll try the script method first and the diode method last if I do anything at all about the lens not retracting power issue.  I do appreciate the comments.
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Offline drillthrall

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Re: External Power for ELPH 300HS
« Reply #13 on: 19 / January / 2014, 17:51:48 »
Quote from: ahull on 19 / January / 2014, 05:18:27
You can get the script to measure and log the voltage, and on subsequent runs, set a cutoff level just slightly higher than the minimum voltage you currently see the camera working reliably to. When the script sees we have reached this voltage, it shuts down cleanly.

Can you tell me where in CHDK I can do what you suggest above?
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Offline waterwingz

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Re: External Power for ELPH 300HS
« Reply #14 on: 19 / January / 2014, 17:58:28 »
Quote from: drillthrall on 19 / January / 2014, 17:51:48
Can you tell me where in CHDK I can do what you suggest above?
You need to add some code to whatever script you are using as an intervalometer (timelapse).

If you would like me to do that for you,  I'll need to know what script you are currently using.
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Ported :   A1200    SD940   G10    Powershot N    G16
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Offline drillthrall

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Re: External Power for ELPH 300HS
« Reply #15 on: 19 / January / 2014, 17:58:53 »
Here is the Part II video of the completed DIY extended battery power for my ELPH 300HS camera and a few extra comments.  It's 5 minutes long.

Not a valid vimeo URL
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Offline drillthrall

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Re: External Power for ELPH 300HS
« Reply #16 on: 19 / January / 2014, 18:02:53 »
Thanks.  I'm using the MDFB script.  It's the only script I use for both birds and lightning.  If it would easier for you I can use your updated MDFB with your added script to it, if that makes sense.
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Offline waterwingz

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Re: External Power for ELPH 300HS
« Reply #17 on: 19 / January / 2014, 18:05:43 »
Quote from: drillthrall on 19 / January / 2014, 18:02:53
Thanks.  I'm using the MDFB script.  It's the only script I use for both birds and lightning.  If it would easier for you I can use your updated MDFB with your added script to it, if that makes sense.
I get some sort of really weird itchy skin rash when I try to program in BASIC (any version) so if you are okay with running the MDFB2013.lua script,  I'll add a low voltage shutdown parameter and update the link.
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Offline drillthrall

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Re: External Power for ELPH 300HS
« Reply #18 on: 19 / January / 2014, 18:08:14 »
Yes, that's the one I meant.  I'm currently using your updated lua for my S110 and it works fine there.  Let me know.
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Offline ahull

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Re: External Power for ELPH 300HS
« Reply #19 on: 19 / January / 2014, 18:15:15 »
Quote from: waterwingz on 19 / January / 2014, 18:05:43
"I get some sort of really weird itchy skin rash when I try to program in BASIC (any version)"
I think you can get a cream for that.  :P Failing that, a bit of therapy from here might help.
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