Success PC Port output on HVL-F7S (Sony NEX) without PREFLASH!!!

Started May 21, 2012 | Discussions thread
RussellInCincinnati Veteran Member • Posts: 3,201
it's not *necessary* to kill the flash's output, 1 of 2

Fabianbono: it's amazing how a brainstorm like this can provide these results.

Of course this is the Holy Grail of a free public forum. Every once in a while something of value gets created from the forums, that realistically would not have happened without them. Put another way, the main idea of a forum is not call each other idiots, etc.

Fabianbono: First...My C3 is my family camera, so it is used by ...iAuto mode (that I must set before turn it off!!) and ...some case, use the flash.

Well then it would make sense for you to leave the flash tube in your modified flash, and also to not disable the hinge switch. Hmm, even better, have the hinge switch work in parallel with the Yongnuo RF603 switch, so that either raising the flash or hitting the Yongnuo switch would turn everything on.

Fabianbono: Also sometimes I don't want to travel with a full bag of stuff, just the camera on his small bag hung from my shoulder.

You are starting to make me think that the way to do this is glue "velcro" on top of the flash, and the bottom of the RF603, with a tiny "plug" between the flash and the RF603 that can be disconnected also. This plug would be a little ribbon cable, there would be more than a couple of wires between the devices with my scheme.

A nice thing about my proposal is that the velcro would be strong enough to hold the 38 gram RF603 on it, because that's the only thing the velcro would be holding onto. In the case of the RF603 being a radio trigger with nothing further attached to it.

Fabianbono: Then, I need to have available the original flash too, just in case I use the C3 as Point and Shot.

Am forcing myself to keep in mind, that there is no law against owning 2 little Sony flash units. One modified, one standard. Remembering that for anyone with a serious interest in proper viewfinder behavior and radio flash, "wasting" 40 dollars on a Sony flash to be turned into a radio trigger (with the addition of a $17 dollar part plus a few resistors, transistor etc) is not a terrible expense at all.

Fabianbono: And last, also I like to use the C3 mounted on a bracket, with the Yongnuo 560II flash at side, just connected by PC cable, without using Wireless triggers.

You don't have the wireless trigger fever yet. Please consider carefully the many advantages of wireless $17 dollar triggers, with the triggers on the flashes powered by good old rechargeable AAA batteries. Will personally never go back to wired triggers again, even for a flash on a camera bracket. The RF603s are just too easy, and their range is super.

fabianbono: Basically, I don't want to loose any feature on the camera or in the flash.

Keep the flash swiveling and don't take out the tube then. Or consider dedicating a spare flash to becoming a trigger.

RussellInCincinnati: RF-603 can probably run fine off of a tiny bit of 5 volt POWER.

fabianbono: I think just use 3V inside from two AAA, is enough for current CMOS technology. But agree that can be powered on that way.

Getting the weight down to 38 grams for the RF603 is quite significant, since we are talking about attaching it to the little Sony flash. Similar considerations motivate me wanting to pull the big capacitor out of a modified flash as well.

RussellInCincinnati: Discard flash tube, the light output device. This "flash" is going to be just a radio transmitter now, it will never emit any light again.

Fabianbono: Here I suggest to add some resistor to simulate the bulb, and discharge the capacitor to complete the circuit functioning.

That would be elegant. Works well with my idea of using a much smaller capacitor, because the resistor would have so much less dummy power to dissipate. Have a feeling you are describing that we put a quite high voltage little transistor (not fun and scary to isolate from low voltage circuits) in series with the dummy resistor, so that when the flash signal comes, we drain the flash capacitor.

Am agreeing that a resistor in place of the flash tube (with series transistor?) would ever-more-perfectly emulate a flash tube. However my guess is that it isn't important to do so. Can't imagine that the Nex will care that, after the flash signal is issued, the flash capacitor hasn't after all been drained any. On the contrary, my guess is that the flash will, immediately after giving the fire-flash signal, just judge that hey, we're all ready to go again, immediately.

fabianbono: We don't know the chip inside flash what kind of controls make on the circuit.

True, but consider that the Sony flash circuitry must, like with any flash, deal with an extremely wide variation in capacitor charging times. The variation coming from depending on the state of charge and internal resistance of the flash's battery power supply. My guess is that a circuit that can handle both short and very long recharge times gracefully, will also react with graceful flexibility to ultra short recharge times. A recharge time of zero seconds being "ultra short".

RussellInCincinnati: A final power lead goes from the output side of the RF603 on-off switch, to just beyond the now-disconnected hinge switch in the flash, to become the main "flash" power as well.

fabianbono: We need to investigate, but need to care on how much current use the RF603, in order to save the camera battery, that will serve all the stuff!!

My guess is that the entire RF603 basically takes very little energy. Would appeal to your sense of logic, that whatever the RF603 takes, it is tons less energy than a flashtube requires. Also have never heard of a power supply that runs off a (once again highly variable) 3.2 volts or so of battery input power, that is so marginally specified that the RF603 would be blown away by the 5 volts coming from the Nex camera. My guess is that none of us would ever notice the current draw of the RF603 trigger in the great scheme of things.

Continued in next message 2 of 2...

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