extra long exposures (split from: Hardcore modding on a A530, thanks to CHDK!

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Offline barret

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i would like to thank all the developers for this great work!

anyway, i still have some questions:

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**Made an Amp-off circuit to control the CCD voltage during the exposure. This is to avoid the CCD glow at the corners of the image.
Is it technically possible to turn off this amp thing not in hardware but in software?


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**Peltier cooling to reduce hot pixels and slightly increasing the sensitivity.
so, i assume that in winter, when temperature drops at night, my night shots should be a bit better in terms of noise levels/quality?

greets

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Offline RaduP

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Is it technically possible to turn off this amp thing not in hardware but in software?
I was wondering about the same thing..


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so, i assume that in winter, when temperature drops at night, my night shots should be a bit better in terms of noise levels/quality?
greets

In theory yes, but the sensor is inside the camera, and the camera is relatively insulated, and generates its own heat, so the results might vary.

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Offline ewavr

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Re: extra long exposures
« Reply #42 on: 14 / April / 2009, 05:15:56 »
iIs it technically possible to turn off this amp thing not in hardware but in software?

IMHO, no (see part of IXUS65 schematics). E21_LATCH turns off both  VDD and VL (our signal?) voltages at the same time.

p.s. Maybe this is wrong thread.

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Offline RaduP

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Yeah, looks like it :/
Perhaps a hardware/software mod, where the camera can signal when the amp should be on or off, via the signal from some LED or something?


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Offline RaduP

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Hmm, I found this: http://pdf1.alldatasheet.com/datasheet-pdf/view/130796/ROHM/BD3916FVM.html
I am a really n00b at electronics, so probably I am missing something, but shouldn't the VDD be still on if  E21_LATCH is off? Otherwise, what's the point of VCC2_DET2?

Indeed a very good work.

Now we got five cameras supported.

Here's Trifid Nebula, a sum of 8 images of 80 secs @ ISO800 on the A530:

http://www.astrosanjusto.net63.net/astrofotos/nebulosas/M20/Trifida%20M20%208%20cuadros%2080s%20ISO%20800.htm

Did someone make it for A620? I'd really love to try it out (got lots of cameras here :)

Regards
« Last Edit: 15 / April / 2009, 11:03:37 by Leonardo Miguel Delgado »

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Offline whoever

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By any chance, you got a dismantled A720 (or similar with the same 8MB sensor) lying around?

The reason I'm asking is this: It would be nice to control CCD voltages from the software, most of all the preamp Vdd (just to be able to turn it off, of course!) While it is clearly impossible in general (lack of hardware capabilities), there might exist limited software access for some sensors.

The firmware of my Ixus950 (and I believe all other cameras with the same sensor -- A720, S5, Ixus80 to name a few) contains an interesting piece of code VsubCont.c, called from ImageSensorTask. The name immediately raises suspicion, as it reminds the mnemonics of Substrate Voltage Control in some CCD chips. The function (located at FF9B9C3C in my case) writes to three hardware ports (CCD voltage control??), 0xC022009C, 0xC0F18010, and 0xC0220090. Calling it with allowed parameters 1,2,4,8 doesn't produce anything spectacular -- just changing the live image brightness a bit. But does it actually change CCD voltages, and if so, which ones? The best way to find out would be to hook up a voltmeter to the sensor pins while writing to these ports -- but this requires opening up the cam, which I don't like. I thought you might have already taken one apart.

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Offline RaduP

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I have a broken A530 camera I got cheap on Ebay and I am willing to experiment on it, but the problem is the lens error message makes it hard to do anything useful with it, unless using a hardware hack. It would be much better if we could turn the lens errors off from the software..


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Offline ewavr

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But does it actually change CCD voltages, and if so, which ones? The best way to find out would be to hook up a voltmeter to the sensor pins while writing to these ports -- but this requires opening up the cam, which I don't like.

How about reading ADC channels (GetAdChValue())? This voltage can be connected to ADC.

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Offline PhyrePhoX

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ewavr added a550 in #733
i (or better: PlasmaHH) added ixus950_sd850 in #734
and to round that up PlasmaHH also coded a way to set longer exposures now via "ev step" shutterspeed enum type mode (#735).

now we have the extended range on 8 different cameras.
the a570 seems to be done as well, but either fudgey or ewavr need to check it into svn.

 

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