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slave flash trigger

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techmanx

New Member
Also built it

I have now buildt the PIC slave flash trigger described at this link:
http://www.fancon.cz/slave-flash-en.html

It works great! Have not got it put in a box yet.
Slave Flash DIY using a PIC (Programmable Interrupt Controller) Photo Gallery by Rolf at pbase.com
I have also built the unit and find it very good, I had to add a PNP stage to the photo diode (rather than source a darlington photo transistor), as the photo diode I was using was not sensitive enough at distances over 1 Metre.
Well Designed, compliments to Fancon.
 

techmanx

New Member
hi,
are you seeking to build a bigger infra red flash unit or a normal xenon type flash triggered from the infra red flash?
regards brian
 

chasingame

New Member
I am trying to extend the original flash with additional IR LEDs in the form of an slave IR array. Many of the cameras on the market are underpowered in the flash area because the manufacturer made sacrifices for battery life over flash range. Its understandable but I would like to develop a solution for this.
 

techmanx

New Member
Hi, I understand. Its a new one on me using infra red flash, but if this helps here is my suggestion.

You need to consult the IR led manufacturer (or experiment) in order to ascertain two important factors,
1. what is the best IR led to use as to its maximum power (milliwatts) against cost.
2. what is the maximum short pulse current that the led can endure and survive? in order to give a power pulse higher than the normal constant duty current .
Having found these details, you can then build an array of these leds (calculated from the forgoing details) big enough to give you your required extra illumination. I envisage the array would be fired by a low voltage capacitor discharge triggered from an infra red diode detector.As the pulse on time would only need to be very short (about 300 uS) a relatively low power led could theoretically provide many times its normal power for this short period!
In practice I see no reason (if your existing flash uses pre-flashes), why you shouldn't use the very practical circuit that we have mentioned in this thread.
You might need a little extra amplification of the diode input, but otherwise the overall circuit should be simpler than an xenon type flash unit. If your unit doesn't use pre flashes, then it would be even more simple and not require the micro controlled trigger here mentioned.
Hope this is helpful and to be understood, regards Brian.
 

chasingame

New Member
Thanks for your reply.

Unfortunately things are a bit more complicated than this. In the IR flash realm, cameras turn on the IR array and wait varying amounts of time. These varying amounts of time arrive from differing firmware programs in the different manufacturers and models.

There is no pre-flash "pulse" like you mention except in the top of the line cams where much attention is spent on firmware programming.

Many cameras I have tested (and I have tested them all) will turn on the IR array as much as a second or more prior to shuttering a picture.

From an outward appearance there is no way to know "when" the shutter clicks.

The only thing you can do is turn on the slave as fast as possible and keep it on for the duration.

Keep in mind my application will be used for night movie mode as well. Cameras may leave the ir array on for up to two minutes.
 
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chasingame

New Member
Rolf, a member here has offered to try and build a prototype for me. I am paying him for the service and parts. I am remain open for new ideas and alternatives. Pm me if you would like to attempt a circuit design.

Thanks for your interest.
 

CaveMole

New Member
multi-stage detector amp suggestions

I do some cave photography as a hobby.
We have a problem where most commercial slave triggers do not work in our environments.
Slaves rarely trigger in dark caves, especially off of secondary reflections, when the slaves are hidden from direct line-of-sight of the main flash. We almost always want to keep the slaves behind rocks, or models, out of direct line-of-sight of the camera.

Most cave slave trigger designs I see have 2 or 3 filtered amplification stages for the trigger. They seem to have tuned R-C coupling between stages designed to trigger on the fast pulses from photostrobes, but not on regular changes of lighting leves or flashlights.

Any recommendations on how to change the sensor part of the circuit to use one of these tuned, multi-stage amplifiers?
 

Rolf

Member
I do some cave photography as a hobby.
We have a problem where most commercial slave triggers do not work in our environments.
Slaves rarely trigger in dark caves, especially off of secondary reflections, when the slaves are hidden from direct line-of-sight of the main flash. We almost always want to keep the slaves behind rocks, or models, out of direct line-of-sight of the camera.


Most cave slave trigger designs I see have 2 or 3 filtered amplification stages for the trigger. They seem to have tuned R-C coupling between stages designed to trigger on the fast pulses from photostrobes, but not on regular changes of lighting leves or flashlights.

Any recommendations on how to change the sensor part of the circuit to use one of these tuned, multi-stage amplifiers?
I can understand why you would want to hide the slave flash from the direct view of the camera.
But the slave flash triggers that is smaller than a book of matches and can trigger a flash from a small point and shoot camera from a distance of over 50'; so it could not possibly be seen in the picture. With a professional camera this distance should be more like 50' to a 100'.
If this is not sufficient there are allays cheap radio controlled remote flash triggers.
The PIC controlled slave flash trigger code, I designed, adjust the sensitivity of the trigger by taking in to account the ambient light. This eliminates the necessity for any additional amplification, in most cases.

Many of the slave flash problems stem from the fact that most digital cameras have any number of pre-flashes. My design's code is designed to only trigger on the last flash, the number of flashes before, is of no consequence.
 
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adrian99fm

New Member
please help me

I used the design from Pavel Janko

write hex in microcontroler led is working described but not output

i am measure pin7 and ground with the analog device no digital or osciloscope
is possible to working??? actualy i not have Slave Flash for prove this
schematic

please help me sorry for my english
 

Rolf

Member
please help me

I used the design from Pavel Janko

write hex in microcontroler led is working described but not output

i am measure pin7 and ground with the analog device no digital or osciloscope
is possible to working??? actualy i not have Slave Flash for prove this
schematic

please help me sorry for my english
I can't remember exactly how Povel's design worked so the my comments are based on my code.
If the LED blinks it is a good chance everything is working up to the gate of the SCR.
To prove this, take a close-up flash picture of the SFT and verify that the LED is in sync with the camera flash.
If the LED is illuminated in the picture that proves that the signal on pin#7 is in sync. You can't measure this with an analog meter.
 
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