external flash triggering - Hotwire! Hardware Mods, Accessories and Insights - CHDK Forum
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external flash triggering

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Offline beq

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external flash triggering
« on: 29 / October / 2009, 11:47:01 »
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hello,

I have an idea. My canon a540 doesn't have hot shoe for flash, but on other forum, I have read about blue led and photoresistor for sending "1" to usb. What parts I need for build external flash trigger mastered by blue led? will the led blink while the shutter is opened ? what about sync speeds? What you think about my idea for triggering external flash in a540 and other powershots ?

cheers
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Offline Microfunguy

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Re: external flash triggering
« Reply #1 on: 29 / October / 2009, 14:01:50 »
Quote from: beq on 29 / October / 2009, 11:47:01
What you think about my idea for triggering external flash in a540 and other powershots ?


I use the simple circuit below .
It relies on the fact that after you release the USB switch there is a very repeatable delay (typically 11 to 30 msec) before the camera triggers.

Depending on the coil resistance of the relay, you choose a capacitor to give the same delay/

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Offline beq

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Re: external flash triggering
« Reply #2 on: 29 / October / 2009, 17:53:26 »
can you post a test photo, with offshoe shoting at 1/300 , 1/30 shutter? ? Does it works with old flashes (~600v) and newest with lower voltage? thanks for reply
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Offline Microfunguy

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Re: external flash triggering
« Reply #3 on: 30 / October / 2009, 10:50:22 »
Quote from: beq on 29 / October / 2009, 17:53:26
can you post a test photo, with offshoe shoting at 1/300 , 1/30 shutter?

I could, but what is the point, I know it worked at 1/250 sec when I first tested it ?

Quote
Does it works with old flashes (~600v) and newest with lower voltage? thanks for reply

This is just 'clean' contacts of a small 5V DIL relay.

A typical DIL relay contacts are rated between 100V and 300V  DC :





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Offline A630Lover

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Re: external flash triggering
« Reply #4 on: 31 / October / 2009, 17:44:42 »
Or you could simply use a optical flash trigger, that can be found for about 5$ on ebay.
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Offline Microfunguy

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Re: external flash triggering
« Reply #5 on: 01 / November / 2009, 04:40:26 »
Quote from: A630Lover on 31 / October / 2009, 17:44:42
Or you could simply use a optical flash trigger, that can be found for about 5$ on ebay.

No, that would trigger on the preflash, not on the main flash.

You can buy flash triggers that ignore the preflash ...  but not for $5.


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Offline A630Lover

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Re: external flash triggering
« Reply #6 on: 01 / November / 2009, 13:56:29 »
Well, I used to use this system on my A630, but in manual mode, without TTl preflash. If the a540 doesn't have a manual flash output level, it might be a problem.
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