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Help needed with dummy battery NB-9L for ELPH520-HS

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Offline lyzby

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Help needed with dummy battery NB-9L for ELPH520-HS
« on: 20 / March / 2014, 17:24:42 »
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Not deterred by the fact that the NB-9L battery has 3 contacts, as does the camera, I made a wooden blank for the battery and wired it up with some small screws as contacts for + and -.  The fit seems good.

I hooked it up to an adjustable power supply set at 3.7 volts, and turned the camera on.  It came on and then immediately turned off.  I inched the voltage up to 4V, and it still did the same.  (The actual battery says 3.5V, the camera says 4.3V.)

I think the supply is gutsy enough to handle the inrush current (but it might not be), so I suspect that the third (middle) contact does some handshaking with intelligence within the battery.  Does anyone know anything about this?  If the protocol is known and not too complex, I can program a microprocessor to do the battery's side of the handshaking.

Does anyone have information about this?

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Offline waterwingz

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Re: Help needed with dummy battery NB-9L for ELPH520-HS
« Reply #1 on: 20 / March / 2014, 17:48:50 »
The third terminal is for a thermistor - used to monitor battery temperature during charging.  Typically the A/C external power supplies that use dummy batteries do not have anything hooked up to that terminal so it's not likely that's your issue.

More information on the subject is available here : http://chdk.setepontos.com/index.php?topic=10385.msg102899#msg102899

You might want to measure the open circuit voltage of a charged battery and compare it to what you have set your power supply to.  Also,  you might find you need as much as 1.5 A for brief periods while moving the lens or charging the flash.  How much juice can your P/S put out?
« Last Edit: 20 / March / 2014, 17:58:19 by waterwingz »
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Offline Microfunguy

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Re: Help needed with dummy battery NB-9L for ELPH520-HS
« Reply #2 on: 20 / March / 2014, 18:24:09 »
Quote from: lyzby on 20 / March / 2014, 17:24:42
I think the supply is gutsy enough to handle the inrush current

I do not think so.
That has been my experience in a similar situation.
Less current is required if you boot into Playback mode and then press shutter button to enter Record mode.
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Offline lyzby

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Re: Help needed with dummy battery NB-9L for ELPH520-HS
« Reply #3 on: 20 / March / 2014, 20:56:44 »
Ok, thank you for the reassurance on the middle pin and for the suggestions.

Lack of guts it is, then.  It will start up in play mode, and I can manually load chdk from the micro sd card.  But it dies when I press the shutter, even after I added 1000uF to the input and 1500uF to the output of my DC-DC converter.  I'll check out the referenced thread.
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Offline lyzby

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Re: Help needed with dummy battery NB-9L for ELPH520-HS
« Reply #4 on: 20 / March / 2014, 21:17:24 »
This is the module I'm using:  http://www.ebay.ca/itm/3-5-28V-to-1-25-26V-DC-DC-Converter-Boost-Buck-Step-Up-Step-Down-Voltage-Module-/131137670623?pt=LH_DefaultDomain_0&hash=item1e886a0ddf

It says "maximum output 3A", but also says "rated output 1A".  I have a 12V 1A supply.  I have a second one of these.  Tomorrow I'll rig it up in parallel, put power diodes on the outputs before joining them, set the voltage at 4.3 volts (which is the number on the camera), and see what I get.  The diodes should drop the voltage down to about 3.7V.  I'll measure first to see what the no-load voltage is.

Any links to what others have used to provide this voltage and current?

Still, it's encouraging that I was able to get to play mode.
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Offline waterwingz

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Re: Help needed with dummy battery NB-9L for ELPH520-HS
« Reply #5 on: 20 / March / 2014, 21:25:32 »
« Last Edit: 20 / March / 2014, 21:28:07 by waterwingz »
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Offline Microfunguy

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Re: Help needed with dummy battery NB-9L for ELPH520-HS
« Reply #6 on: 20 / March / 2014, 22:04:53 »
Quote from: lyzby on 20 / March / 2014, 21:17:24
This is the module I'm using:  http://www.ebay.ca/itm/3-5-28V-to-1-25-26V-DC-DC-Converter-Boost-Buck-Step-Up-Step-Down-Voltage-Module-/131137670623?pt=LH_DefaultDomain_0&hash=item1e886a0ddf

I have a couple of them.
I use them when my small Pololu converters are not 'robust' enough or I need to set the output voltage precisely.

They should be able to handle any of the cameras.
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Offline lyzby

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Re: Help needed with dummy battery NB-9L for ELPH520-HS
« Reply #7 on: 20 / March / 2014, 22:40:43 »
I used the Pololu-type buck converters successfully for dummy batteries (AA-type) for an A590 and an sx120is, but with the elph 520 it just started up and shut down.  Same for the beefier buck/boost converter.  I'll see what ganging two together do, after testing the voltage with a dummy load. 

Too late tonight for me to try anything where a crossed wire might fry the camera.

I hope this works since I have a sweet little pan and tilt rig to try it out in.

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Offline waterwingz

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Re: Help needed with dummy battery NB-9L for ELPH520-HS
« Reply #8 on: 20 / March / 2014, 23:09:56 »
I guess there is always the possibility that your 12V 1A supply dips enough to throw off the DC-DC converter long enough to trip the camera ?
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Offline ahull

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Re: Help needed with dummy battery NB-9L for ELPH520-HS
« Reply #9 on: 21 / March / 2014, 00:05:12 »
Quote from: waterwingz on 20 / March / 2014, 23:09:56
I guess there is always the possibility that your 12V 1A supply dips enough to throw off the DC-DC converter long enough to trip the camera ?

... I suspect waterwingz is right, fluctuations in the input voltage to the regulator may well cause it to brown out and crash the camera.
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