external flash triggering

beq

4

« 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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Microfunguy

4037

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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beq

4

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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Microfunguy

4037

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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A630Lover

115

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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Microfunguy

4037

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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A630Lover

115

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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