Main page
List of articles

Voltage Reduction on Flash Trigger Contacts

If you want to connect a budget flash unit to your electronic camera, it will be a good idea to use a special adapter to reduce high voltage on trigger contacts. That voltage may be up to 350 VDC, which is quite dangerous for a camera.

I suggest the following device be used in such cases (see the picture below).

VS1 KU103V
R1 36 K
R2 1 K
R3 0...1 K
C1 1200 pF
C2 0.47 µF
GB1 1.5 VDC

This device is almost the same as that described in the article about a flash trigger unit. I decided to publish the solution twice, since its function is different in this case. Those of you who prefer universal solutions may combine two functions (voltage reduction and remote flash triggering) within a single device.

A tablet-like watch battery (1.5 VDC) can be used as GB1.

Generally speaking, the device can operate without the R3 resistor. However, if R3=0, the peak current through camera contacts can reach dozens of milliamps. Since in many cases we know nothing about camera contact specifications (I hope you can guess why), it would be a good idea to reduce that current too. Alexey Smolentsev (aka Al) suggested that R3 could help us to cope with the problem. Its value should be chosen by trial and error. The larger R3, the smaller the peak current. However, if R3 is large enough, the device may stop operating, when the battery voltage drops a little. Alexey claims, the peak current can be reduced below one milliamp. Please take into account that it will also depend on the particular thyristor you used in the device.

Although the contact rating of 1.5 VDC / 10 milliamps can be considered as absolutely safe for modern cameras, I decline any responsibility for any damage caused by such devices. If you are uncertain, please use the devices the manufacturer of your camera recommends.

Attention! Some flash units have dangerously high voltage (up to 350 VDC) on their trigger contacts! To avoid electrical shock, be very cautious during your experiments with this device.


Main page
List of articles - Russian Photo Links

Igor Yefremov, 2002, all rights reserved

You must obtain a written permission from me to use any materials of this site for any commercial or non-commercial purposes, unless there is an explicit statement to the contrary.

Hosted by uCoz