Setup for CHDK matrix bullet-time rig with Powershot A450 and A460 cameras - page 8 - Hotwire! Hardware Mods, Accessories and Insights - CHDK Forum
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Setup for CHDK matrix bullet-time rig with Powershot A450 and A460 cameras

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Offline Microfunguy

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Re: DC Socket size on Canon Powershot models 1.1mm 1.3mm ??
« Reply #70 on: 27 / September / 2009, 11:31:17 »
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A search for 'single rectifier diode' will find the higher-current types such as at the bottom of this first page:-

http://uk.farnell.com/jsp/search/results.jsp?N=1004178&isGoback=false
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Offline zcream

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Re: DC Socket size on Canon Powershot models 1.1mm 1.3mm ??
« Reply #71 on: 27 / September / 2009, 11:40:56 »
I havent access to farnell - only jaycar. They have a more limited range. Would a 400V 35A rated bridge rectifier work ?
The rectifier would ensure that the polarity of the parallel voltage supplies stays the same and would provide large resistance for reverse current..
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Offline zcream

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Re: DC Socket size on Canon Powershot models 1.1mm 1.3mm ??
« Reply #72 on: 27 / September / 2009, 11:46:00 »
Also, the cameras are all in parallel so I dont think a short or open in any camera brings down the others. Would not need a fuse for all of them.
I reckon your idea of an isolation diode with 2x PSUs is the best bet ATM. Cannot find 3V3 with 10A rating either..
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Offline Microfunguy

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Re: DC Socket size on Canon Powershot models 1.1mm 1.3mm ??
« Reply #73 on: 27 / September / 2009, 12:24:24 »
Quote from: zcream on 27 / September / 2009, 11:46:00
I dont think a short or open in any camera brings down the others.

If the camera short-circuited it could blow the fuses in both power supplies.
HOWEVER, now that you mention it, the individual cameras are fused.
I know this because I blew an A620 but noticed that it still worked via the AC adapter.
When I checked the circuitry there was a surface-mount fuse.
Bypassing it with a very thin strand of wire got the camera working again.
So, no you do not need the fuses.

Quote
Cannot find 3V3 with 10A rating either..

Hmmm ... there is a voltage drop in the power diode, if you can find one that drops about 1.5V then you could use 5V supplies that are readily available.

That may be the most practical solution.

Check Ebay item # 130300905412 for a typical switching supply.
Whether you use a switching supply (that needs a certain minimum load connected) or a linear supply, you will have to make sure that with no cameras turned-on a dummy load draws sufficient current to drop the voltage to about 3.5V.
As you turn on more cameras you will reach the stage where you can switch-out the dummy load.

Apparently, Farnell only export to the US, they do not have a branch there.

Check Ebay for power rectifiers.

These diodes drop 1V so put two in series :-

Ebay item # 150366466554


« Last Edit: 27 / September / 2009, 13:36:29 by Microfunguy »
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Offline zcream

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Re: DC Socket size on Canon Powershot models 1.1mm 1.3mm ??
« Reply #74 on: 27 / September / 2009, 23:17:29 »
I'll try the PSUs first as I have it in front of me. I'll try a 30A or 35A diode as they are rated for so much current.  Will update this thread..
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Offline zcream

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Re: DC Socket size on Canon Powershot models 1.1mm 1.3mm ??
« Reply #75 on: 28 / September / 2009, 08:04:56 »
DUH.. I know now why the converted PSUs are not giving me anything more than 1A.
Most ATX power supplies require a small load to stay in the ON mode. I added a 10 ohm, 10 watt resistor between +5V and ground to provide this small load.
The 3.3V and 5v are derived from the same source.
So now we have a 10 ohm load and the 16K Ohm of the cameras in parallel..I think that the 10 ohm load is drawing the excess current or at least reducing the load resistance to a lower level than it is meant for..
I will try to remove the load resistor and try again..
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Offline Microfunguy

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Re: DC Socket size on Canon Powershot models 1.1mm 1.3mm ??
« Reply #76 on: 28 / September / 2009, 10:59:19 »
slowly getting there ....

Make the fixed load as large a resistance as possible.

I cannot remember, do two 3.3V supplies provide sufficient current ?

If they do then I guess you do not need to do anything else.

Even with all cameras turned off or on the voltage should be within the safe range.

With all camera on I guess you could switch-out the dummy load if you wish.

« Last Edit: 28 / September / 2009, 12:56:58 by Microfunguy »
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Offline zcream

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Re: DC Socket size on Canon Powershot models 1.1mm 1.3mm ??
« Reply #77 on: 28 / September / 2009, 22:14:58 »
AARGH!

http://web2.murraystate.edu/andy.batts/ps/TheFIX_java_table.htm

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The usage of a PC powersupply as a substitute for a field charger power source falls far outside the intent of the original design specifications. Once the PS is running and stable, the overload circuitry is tuned to detect high current sinks and shut the PS down -- under normal usage, these sinks would be indicative of an internal short in the PC. When a microcomputer is running, powersupply demands change, but these are minimal and are usually associated with optical, hard or floppy drive usage or USB devices being attached.
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Offline Microfunguy

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Re: DC Socket size on Canon Powershot models 1.1mm 1.3mm ??
« Reply #78 on: 29 / September / 2009, 05:14:47 »
It also says :-

"Should none of modifications prove workable, your only remaining solution may be to purchase a standard benchtop powersupply from a retail vendor or one of the on-line auction sites"

do not forget the diodes !

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Offline Microfunguy

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Re: DC Socket size on Canon Powershot models 1.1mm 1.3mm ??
« Reply #79 on: 11 / October / 2009, 06:00:57 »
A new switch and extender unit has been introduced that will enable 'professional' operation of your proposed 52-camera rig.

The webpage is now live http://www.gentles.ltd.uk/gentstereo/index.htm

Click the icons on the left.

The 10-way USB extender should be of interest, maybe for 52-camera synchronised time-lapse or HDR imaging ?



David
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