Daniel Schramm




Cat5 Cable Checker 



Exposure Timer 2 

Solder Station 

Slave Flash  MP3 Player 

MP3 Player Touch 

Home Automisation 

Can Bus Schield for Banana Pi 





Trigger Circuit for Slave Flash


Compact digital cameras contain an internal flash which is mounted close to the lens.
This flash has many disadvanteges which vary from the red eye effect, unwanted shadows to overexposed portraits in front of dark background. Using external flashes can help dealing with these issues. Since most compact digital cameras do not have any possibility to connect an ordinary flash a possibility is to trigger the external flash with the light of the original flash. This is called slave flash.
There are many schematics and modules aviable which are able to trigger on the first or second flash. (anti red eye flash)

Some cameras use more than 2 flashes to eleminate the red eye effect and can not be used with those circuits. The developed circuit is intended to be able to work with every camera with small software changes.
Good flashes have adjustable light intensity. But many flashes which you can get for a small amount of money always illuminate with the same energy. The full energy is then emitted within 1/60s (hopefully nearly constant). This gives the opportunity to control the amount of energy captured by the camera by either reducing the exposure time or the trigger delay of the flash. I intended to support the second option.
The current software does only provide minimal funtionality: Trigger on the first flash with verry small delay.
The button switch is used as a power switch and intended to be also used as mode switch. When switched off the microcontroller is still connected to the battery but since it only draws a couple of microamps the battery will last a couple of years in this mode. (Be careful that dirt and solder flux might cause much more current consumption than the microcontroller)


  • Microcontroller based
  • Adjustable to every flash sequence of the master flash by software change
  • Programmable trigger dalay planned for next release of software




    last change to slave_flash.html: 2009/05/03