Some thoughts.3.2V-3.6V @ 600-750mA is 1.92-2.7watt (3 Chinese watts?).2.5watt needs cooling, so a star base?Yes, all the leds are mounted on star bases and would be stuck to the acrylic dome with silicon adhesive, maximum illuminated period for any one LED would be < 5 seconds and then off for 2 -3 minutes so I though additional cooling wouldn't be necessary.12volt supply to ~3.3volt LED is a big drop.Linear regulation at 750mA would produce a lot of heat.You might have to use pre-regulation in the form of a 12>5volt buck converter.That 5volt could also power the Arduino.I was thinking 12v purely because I have a range of 12v batteries I already use for photography, no issue with adding in a dc-dc regulator to drop the supply voltage to the LED driver and probably a 12v - 9v regulator for the arduinoPWM is turning the LED 100% on and off, with varying duty cycle.You might see that as a dimmer light, but a fast camera sees this as a flash with 100% intensity.Might be better to use linear dimming.Ok, I can understand that, the shutter speed is likely to be 2-3 seconds when the target is illuminated by a single 3 watt LED, adjusting the LED supply current is probably a better option than PWM but the dimming would need to be constant for all the LEDs which is why I was thinking of using a single LED driver. An alternative would be to use 1/2 second on 1/2 off 1/2 second on for x number of times to limit the total light output (a very crude PWM but probably adequate and easily coded)I am thinking: high-side linear constant current source, with the current controlled by the Arduino, connected to the anodes of all the LEDs, and each LED individually switched to ground.What arduino controlled TTL device would switch the current on the anode side?That's the sort of think I'm visualising, using multiple LED drivers doesn't make too much sense as only one LED will be lit up at any one timeI don't know of any chip that can switch 750mA, so I think you have to use 50-60 logic level mosfets.Shift registers or I2C port expanders and a Nano could be better/easier than a Mega.Can you suggest a suitable Mosfet? Could I drop the number of wires by using an 8 x 8 array with Mosfet switches on the anode and cathode sides of the array and all the anode side switches connected to the same constant current source? I've only select a Mega because I have handfuls of them for various camera projects Leo..
no issue with adding in a dc-dc regulator to drop the supply voltage to the LED driver and probably a 12v - 9v regulator for the arduino