This article describes how to build a simple uC based delay circuit for photographic applications like drop or high speed photography. It can be used to control the trigger lag of cameras and flash units, generate a periodic trigger pulse or even control magnetic valves. The input and the three outputs of the circuit use standard 3. 5 mm stereo jac
delay - schematic

k connectors, so the delay element can be looped easily into your existing trigger circuitry like the SmaTrig for example. Cascading multiple delay devices into more complex circuits is easily done. As simplicity was an important design goal, there is no text display or a sophisticated analog input stage. All resources to build a copy of the delay are provided below in the Download section. A short press of the on/off button switches the circuit on and off. By holding the on/off button down while switching on you can cycle through the three time ranges indicated by the LEDs. The chosen operating range is saved in the EEPROM so the uC will remember the last setting after switching off or even removing the battery. Directly after programming the AVR your delay will work as described in this section. The delay time is set by two potentiometers. The left one is used for the coarse time setting (0-100% of the chosen range), the right one allows fine tuning (0-10% of the chosen range) of the delay time. Both knobs turned to the maximum will result in 110% delay time (1. 1 s, . ). The functions of the wheels are: The coarse/fine solution proved to be very convenient in practical use (dark room). For drop photography, the absence of a display turned out to be unproblematic, because you keep your eyes on the drop and not the delay while adjusting the time. The manual trigger button allows to simulate a trigger event and is useful...

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