Electronics > Projects, Designs, and Technical Stuff
Old camera speedlight low voltage trigger conversion
OldEE:
I bought one a Wein adapter a number of years ago for a similar application. Looks like they are not being made anymore and BHPhoto in New York is clearing them out for about half price $25. B&H does ship internationally.
https://www.bhphotovideo.com/c/product/245292-REG/Wein_W990560_Safe_Sync_Hot_Shoe_to.html
Larry
cprobertson1:
--- Quote from: StillTrying on June 19, 2019, 04:30:28 pm ---Have you blown anything up yet. :)
--- End quote ---
Not as part of this project! :-DD
--- Quote from: StillTrying on June 19, 2019, 04:30:28 pm ---235mA/10mA = 23 hours = approx. 82,000 1sec triggers.
--- End quote ---
Ah, good, my method was fine (though I deliberately chopped a third of the capacity off for "undisclosed reasons").
--- Quote from: StillTrying on June 19, 2019, 04:30:28 pm ---The flash's 380V only has to be shorted for about 4us so you could reduce the camera's trigger to just a 30us pulse through an opto or ~3ms for a small relay and even smaller batteries would last forever.
You can usually see the trigger transformer ringing by bringing the flash near to a scope probe, no physical connection is needed, it only rings for a few us, then there's another 5-8us delay before the tube lights, I've watched it many times!
--- End quote ---
So I modified the Sunpak. It's a Sunpak 134 - which, according to this site should have a trigger voltage of "only" 50-ish volts... so I don't know why my unit sits at 380V (were there different revisions of the same flash? ::shrugs:: )
There was barely enough space for my modifications - I decided to go for the optocoupler since I had it to hand, and it was smaller. Optocoupler powered by a CR2032 stuffed down a tiny gap between the PCB edge and the case, triggers the TRIAC on hard via an NPN transistor. Ended up using SMD parts on some stripboard and then cutting the remainder off with side cutters and filing the edges down to keep the size as low as I could manage.
The only problem I see is the creepage distance - I cut the board with a hacksaw and soldered the optocoupler across it (about a 5mm gap) - but because it's wedged in a small space, there may be creepage across the side of the case (I put a sil-pad in there, but I don't know how that performs when it comes to surface creepage.)
I think I'll keep it away from my camera for now just in case: I'll relegate that one to wireless triggering once I can afford that!
As for the Hanimex TZ7000... turns out it runs with a trigger voltage of 4.4-4.5V - I'd call that a win!
--- Quote from: Peabody on June 19, 2019, 05:06:20 pm ---I believe your Pentax uses a standard hotshoe, but my memory is the Hanimex is for a Minolta hotshoe. If that's true, the Hanimex will not fit on your Pentax. I mean it physically will not fit. You didn't say what model your Sunpak is.
I would just encourage you again to use these old flashes off-camera. You will find that the results you get with off-camera lighting make it look like you know what you're doing, even if you don't, and of course your camera would not be at risk from high voltage. You would need a light stand, an umbrella adapter and an umbrella, plus some way to deal with the high voltage. And you can get a basic wireless trigger set for $20. This would be manual triggering of course - both camera and flash(es) in manual mode. None of this ETTL rubbish. :-)
--- End quote ---
Aye, I didn't realise the wireless units were that cheap - I may partake once I get enough money together for a new flash.
The Sunpak is a "134" - though other people are only measuring around 50V on their trigger pins, so I don't know what mine is doing (different board rev maybe? ::shrugs:: ).
The Hanimex is indeed supposed to fit a Minolta (Maxxum 7000?) camera, but it seems to fit my pentax and fujifilm no bother. There is an extra pin for the AF illuminator and the functions of the other two pins are flipped round - BUT the foot of the flash is actually longer than the modern ISO hot shoe, so they don't make contact anyway. The trigger pin makes contact though, so it ends up working fine anyway: I'd call that a win!
I might add in a similar optocoupler + battery anyway, just to be on the safe side. It's thyristor triggered (I think?) and there is some control circuitry in the bottom module. Oh, there's an interesting point about the construction - the Hanimex flash is two modules that clip together - the bottom module contains what I assume is some control circuitry, and connects to the rest of the flash via a board-edge connector. It's entirely enclosed and can be disconnected with no tools from the rest of the flash - I assume they reused the control circuitry across several different flash units - just a matter of slotting it in: interesting!
Zero999:
I you use a relay, there is absolutely no point in having an opto-coupler as well.
I forgot it said 380V, so the relay I previously linked to won't do. This is better. It has two contacts rated to 220VDC, which can be connected in series. It doesn't have a built-in diode, so that will need to be added separately.
https://www.digikey.com/product-detail/en/te-connectivity-potter-brumfield-relays/2-1462039-9/PB1165CT-ND/1828459
The battery life can probably be boosted by connecting a capacitor across the battery. As the battery discharges, its internal resistance will rise. Adding a capacitor will enable it to provide a large current pulse to fire the relay, even if the battery's resistance is too high for it to happen otherwise. Try a 100µF capacitor.
If you go with a TRIAC opto-coupler, then it only needs a very short pulse to fire, so set the pulse so it's quite short. If the shutter switch produces a much longer pulse, than necessary, power could be saved by using a high value resistor to charge a capacitor and the camera shutter switch to discharge it into the opto-coupler, via a lower value resistor.
Note that the TRIAC/BJT side of the opto-coupler will need to be rate to the full flashgun voltage. If you use a BJT, then it will be polarity sensitive, unless a bridge rectifier is connected between the opto-coupler and TRIAC.
StillTrying:
--- Quote from: cprobertson1 on June 20, 2019, 08:24:08 am ---
--- Quote from: StillTrying on June 19, 2019, 04:30:28 pm ---Have you blown anything up yet. :)
--- End quote ---
Not as part of this project! :-DD
--- End quote ---
If you're not going to blow the camera or the flashes up, make a sound triggered flash and blow some other things up. :)
cprobertson1:
--- Quote from: Zero999 on June 20, 2019, 10:11:17 am ---I you use a relay, there is absolutely no point in having an opto-coupler as well.
I forgot it said 380V, so the relay I previously linked to won't do. This is better. It has two contacts rated to 220VDC, which can be connected in series. It doesn't have a built-in diode, so that will need to be added separately.
https://www.digikey.com/product-detail/en/te-connectivity-potter-brumfield-relays/2-1462039-9/PB1165CT-ND/1828459
The battery life can probably be boosted by connecting a capacitor across the battery. As the battery discharges, its internal resistance will rise. Adding a capacitor will enable it to provide a large current pulse to fire the relay, even if the battery's resistance is too high for it to happen otherwise. Try a 100µF capacitor.
If you go with a TRIAC opto-coupler, then it only needs a very short pulse to fire, so set the pulse so it's quite short. If the shutter switch produces a much longer pulse, than necessary, power could be saved by using a high value resistor to charge a capacitor and the camera shutter switch to discharge it into the opto-coupler, via a lower value resistor.
Note that the TRIAC/BJT side of the opto-coupler will need to be rate to the full flashgun voltage. If you use a BJT, then it will be polarity sensitive, unless a bridge rectifier is connected between the opto-coupler and TRIAC.
--- End quote ---
Ooop! It was just the the optocoupler that I added, I don't have any relays small enough so I decided to just stick with the opto. Come to think of it, I'm not actually sure I'd have been able to fit the ones you linked me to in the space available (in fact, I could barely fit the SMD parts I ended up using. Plenty of length, but very little height: I actually need to go back and make double-check the leakage paths on it - I thought of another path across the edge of the existing PCB that might cause even bigger problems. Sil-pads to the rescue? I that allowed?)
Good shout on the bridge rectifier for the optocoupler's BJT on the flash side, btw! There's only one diode in there just now (and I debated adding a second to act as a snubber, but being unable to probe it with the scope, I decided to wing it and go without...) - I'll modify a proper bridge in tonight.
The transistors (And optocoupler) are rated for 400V. I'd rather have a 600V or higher rating just to be safe, but the 400V ones are what I have to hand - and for 380V they should be fine for a while - they're not exactly putting much current through them, so they're within their power spec.
--- Quote from: StillTrying on June 20, 2019, 12:58:16 pm ---
--- Quote from: cprobertson1 on June 20, 2019, 08:24:08 am ---
--- Quote from: StillTrying on June 19, 2019, 04:30:28 pm ---Have you blown anything up yet. :)
--- End quote ---
Not as part of this project! :-DD
--- End quote ---
If you're not going to blow the camera or the flashes up, make a sound triggered flash and blow some other things up. :)
--- End quote ---
I reckon if I string a number of these flashes out I could visually record and work out the speed of sound from visual cues!
"flash-flash-flash-flash-BANG!" - okay, I don't have that many flashes, but still!
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