I shot another art show for an the online version of the reality. It also serves as an archive of all the artwork that’s been shown since the beginning.
One of the pieces in the most recent show was this neon piece that’s close to 5 feet in width and height. Here is the final image I ended up with after doing three separate masking layers. It was the most challenging piece in this show.
A recent previous post detailed the first and second passes at converting Norman 200B strobe packs to low voltage so as to be compatible with modern cameras. Those were not quite up to snuff because the first pass stole too much voltage to be usable and the second allowed 20mA of current to flow through the camera or trigger it was connected to.
After doing some reading about the subject, it would appear that at least for some older cameras, the trigger circuitry used an SCR, in which case the 2nd implementation above would fail because the constant 20mA would keep the SCR latched on. It might also be way too much current for the trigger circuitry to handle. The numbers I recall were 1.5mA max trigger current that decayed to something under 750uA.
So, back to the drawing board… Here’s what I came up with:
During the presentation Kevin Kubota gave on CreativeLive.com several months back, he mentioned DIY scrims he had built that were sized to fitPhotoflex Litepanel covers. He even made a video detailing the construction.
So, how could I help myself? I had to make some, but with some enhancements of my own…
Not having any Photoflex panels, I was not constrained to a certain size so kept things simple. I maximized the material usage by cutting all the 3/4″ PVC pipe to 39″ in length. I also used electrical PVC conduit because it was slightly cheaper than the same size plumbing PVC pipe. Instead of using a hack saw like Kevin Kubota, I used a PVC pipe cutter. They are much simpler to use and so much less messy than sawing – I highly recommend getting one. It’s definitely worth the money.
Seven lengths of pipe are required for each panel. Instead of running bungie cord through them, I opted to leave them separate. I just glued the elbows and Tees to all the horizontal pipes. This lets me know which joints come apart without having to mark anything. It also prevents the loss of any of the fittings while in transit or during storage. Additionally, no bungie means the panel pieces can be configured into a light tent using four end pieces (elbows) and four plain lengths of pipe, similar to the one detailed in this blog post.
One panel breaks down into these pieces:
Recently, I came across a nifty light modifier for small battery flashes called the Saberstrip. It’s a tube with a mount for the flash at one end, and a mirror at the other end, and a long window covered with diffusion fabric. The long linear light source makes a diffuse shadow in one direction. They can be doubled up and oriented as an “L” to give a look closer to an umbrella or soft. One big advantage of the Saberstrip is that it’s not a big sail that’ll catch the wind out on location. At US$135 plus another 15 for shipping, though, it’s rather expensive for the hobbyist.
**** UPDATE *****
UPDATE: NEW DESIGN COMING SOON THAT REDUCES CURRENT IN THE CAMERA/TRIGGER SWITCH AS ~20mA MAY BE TOO HIGH FOR CAMERA INTERNALS.
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This post needs to be prefaced with a major disclaimer: Open your Norman 200B at your own risk. The 500V inside is potentially lethal. The author was careless once and accidentally discharged the cap with a meter probe which caused a big char streak in the connector and took a hunk out of the meter probe and one of the head plug pins. Proceed/attempt at your own risk. If you die, break your 200B, or both, I am not responsible.
Now that that’s out of the way, on the to the good stuff.
The Norman 200B trigger voltage is on the order of 100V. It was fine for old film cameras with mechanical sync switches. Modern digital cameras don’t care for such high voltages, so some sort of conversion or adaptation needs to be made. Optical slave triggers are one way to go, but the author smoked one accidentally by just letting the 200B sit waiting to flash. Apparently, some modern optical slave triggers do not care for such a high trigger voltage either. They are also going to end up dangling and exposed where they can become disconnected or in the extreme, get broken off.
Slave triggers and the like are not inexpensive, either. Sure, they come encased in a nice little plastic package and all, but at $8-10 or more apiece, they add up quickly, especially after having acquired four complete pack and head sets. Sometimes, it’d be useful and nice to use all that fire power at the same time and not have to carry all those little slave triggers and wires and stuff…
So, what to do? Reverse engineer the trigger circuit and make and a low voltage adapter for it using piece parts… Here’s the photo of the board alongside a mirrored and colorized photo of the traces on the bottom side that was used:
Here is the partial trigger circuit (please ignore all the extraneous numbers and notations) of the stock 200B blue circuit board:
Observant readers of Harold Edgerton’s book, Electronic Flash, Strobe, will notice that this circuit is pretty much the opposite of one within his book. The difference is that the Norman 200B is uses a positive ground, so everything is upside-down in comparison to Edgerton’s circuit. Another thing that should be noted is that when the SYNC connection is grounded, the charged 0.02uF capacitor discharges, turning on the gate of the SCR. Only a small amount of current will flow if the SYNC connection is held grounded, probably as an added safety benefit.
One would think that adding an optoisolator across the SYNC connection and the chassis would be sufficient to adapt the 200B for low voltage operation. That was tried but it did not work because the current that flows is too small to latch the triac within the optoisolator ON, so the capacitor does not discharge quickly enough, and the 200B never triggers. An early attempt to correct this consisted of shorting the diode. When the two resistors dividers are shorted together at their center points, the 200B could be fired with an optoisolator between SYNC and the case. But then additional current flows unnecessarily from the high voltage supply.
The first incarnation of the low voltage adapter was built into a plastic Tic-Tac and hung off a house hold plug that was plugged into the head. A sync cord then plugged into the Tic-Tac trigger. It was too many connections, something extra to carry and/or break. So when the opportunity to use two of the Normans for a photo shoot presented itself, it was time to move the adapter inside the pack and make the outside connections simpler…
In order to hook this into the 200B, three parts on the blue controller board need to be removed: a diode and two resistors. The colored circles indicate where the tap points are for the adapter board. The three parts need to be removed to completely isolate the SYNC connection to the head so that only optoisolated low voltage goes to the head socket. Note that two of the removed devices have a colored circle on one of their leads. The third one is unmarked in this photo but it is to the right of the orange filter capacitor and +12V connection (it can be seen in a later photo).
Here is the schematic for the low voltage adapter:
And here is the parts list with Digikey part numbers:
Digikey part number |
Description |
Note |
497-2960-5-ND |
IC REG LDO -5V .1A TO-92 |
negative 5V regulator |
160-1378-5-ND |
OPTOISO 400VDRM TRIAC OUT 6-DIP |
optoisolator, MOC3023 |
CF18JT180RCT-ND |
RES 180 OHM 1/8W 5% CF AXIAL |
I limit resistor |
399-1249-1-ND |
CAP CER 0.1UF 50V 10% X7R 1206 |
output cap |
399-1285-1-ND |
CAP CER 0.33UF 25V 10% X7R 1206 |
input cap |
The negative 5V regulator is probably not absolutely necessary, but the most often quoted number for DSLR maximum sync voltage I’ve seen is on the order of 7-9V; 12V would then be too high. A negative regulator is required because of the positive ground design of the 200B. The two capacitors are required by the regulator; surface mount chip caps were used because they take up a whole lot less room. The 180 Ohm resistor limits the current for LED inside the MOC3023 to about 20mA.
The circuit was wired onto a small perforated prototype board as can be seen below on the left. The board is positioned in this photo so the devices can be seen. The bottom of the board is normally up when assembled into the pack.
The pack assembled with the “protective” plexiglass cover can be seen in the photo below. The protective plexiglass is often broken on these old units… The cover also does not afford a whole lot of protection anyway since fingers can still get at the high voltage. I typically keep my fingers well clear when the power is applied and for a long while after the power is turned off as a precaution.
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