Lets kick this thing off!

Initial requirements discussion

Moderator: seaton

Postby mattsteg » Fri Sep 21, 2007 3:18 pm

Elv000 wrote:Canon doesn't have manual flash control for or from the on board camera flash. To trigger slaves you need a transmitter in the hotshoe (ST-E2) or use a flash on camer as the master 550/580EX.

Thats why it would be good to just convert the preflash light pulses (of any master) to radio and back at the flash. That way your not decoding any proprietory systems just passing the signal on! (just as Radiopopper.com claims to have done). So it works with any brand. Seems silly to do it any other way if it makes it more complicated?!

So many peolpe have previously come in and stated they know how to do this hopefully someone that does will still find this board?!

Does anyone actualy know if there actualy is two way communication???. Can anyone put a scope on an ITTL/ETTL slave and see if there is any irregular pre flahshes (sending info back to the master).
Someone posted something similar off a Pentax or other brand on the Strobist thread (on camera)
The problem with preflash systems is that they induce a delay, plus they're cumbersome. If a flash does TTL of any sort, you can control its power via hot shoe connections. If that wasn't the case, TTL wouldn't work.
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Interference and Timing

Postby Thonord » Fri Sep 21, 2007 3:31 pm

All eBay trigger owners know about interference.
And
The trigger signal needs to be synchronized to the shutter. We will be operating in RealTime. Fortunately we have pretty good time (in msec)

Perhaps we should look into adding some robustness to the "Over the air signal" or wireless protocol data unit (wPDU) for lack of a better word.
And while I'm BrainStorming and no lilitations have been set. Why not make it duplex so we can cope with misfiring as well?
This will also enable data transmission between the flash and canera. Who was asking about e-TTL?

I have some thoughts and will jump into the wireless area.

Note to Programmers, set aside some memory space. It may be needed.

Tom
Somebody - stop me!
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Postby tim-j » Fri Sep 21, 2007 4:07 pm

Does anyone actualy know if there actualy is two way communication???. Can anyone put a scope on an ITTL/ETTL slave and see if there is any irregular pre flahshes (sending info back to the master).
Someone posted something similar off a Pentax or other brand on the Strobist thread (on camera)

As far as I recall (I'm open to correction on this), at least with the Nikon system, the camera tells the slaves to fire an evaluation burst, then the camera measures the light received off the subject (by the camera), calculates what each slave should put out, tells them this with preflashes, and then says "go".

Simplified if the slaves are just doing "remote manual" instead of TTL.

So the slaves don't send optical signals back to the camera -- I think.

When I say camera, the "camera" is actually the camera/hot-shoe flash combo, under some circumstances.
Tim J.
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Postby mattsteg » Fri Sep 21, 2007 4:33 pm

tim-j wrote:When I say camera, the "camera" is actually the camera/hot-shoe flash combo, under some circumstances.
Or just an sb-800 or su-800 for that matter.
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Postby pinhead » Fri Sep 21, 2007 5:52 pm

can i suggest that the goal for the first version is to be on par with pocket wizard plus 2 fuctionality?

a selection of channels
tranciever / auto mode switch capable
relay mode
range of "enough to be reliable for most shots"

if we do that but slash the cost in half, we will be doing great

the only req to add are to make it expandable and flexible.

*reprogram port
*open bus on the board with enough contacts to run TTL in the future
*un populated spot for DA converter, can be used to hack in remote manual control of dumb flahses later
*provisions on board for user to input manual power adjustments to multiple channles

and can we get decent performance with the antenna inside the plastic enclosure instead of stickin out? or use an RF connector and attach a ham radio antenna as needed?
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Postby mattsteg » Fri Sep 21, 2007 6:31 pm

pinhead wrote:*reprogram port
*open bus on the board with enough contacts to run TTL in the future
*un populated spot for DA converter, can be used to hack in remote manual control of dumb flahses later
*provisions on board for user to input manual power adjustments to multiple channles
What does this DA converter do? I can't really think of a useful way to use one for controlling a flash offhand. Remote manual control of dumb flashes is actually much easier to implement than remote control of computer flashes, plus the hardware and software needed to do so will work with new flashes as well.
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Another thought...

Postby aalto » Fri Sep 21, 2007 8:11 pm

I have read the strobist thread and some of the ideas here. I have, as so many others, been irritated by IR and Ebay triggers, and would of course like to have the best of all the systems. I dont care for TTL, but i would like to have the ability to change the power remotely, and i want reliability and atleast some range, though the 500m of the PWs is not required for my use.

Right now everybody is talking about triggering their flashes remotely, and discussing different protocols for this and that brand. I have been thinking for a while that what i really would like, is a new flash. Not a way to sync my SB800s or Vivitars, but rather a new flash made with diy in mind.

This is because i really dont use them on the camera any more, and I dont think im the only one.

So, instead of paying a lot of money for the TTL, Repeat, etc functions that i never use, i would like a flash that does the things i want it to do and heres some ideas:

- Low cost aluminium tube housing. One end is the bulb, behind a glass. And the other is the On/Off button. Changing batteries and channels - screw off the rear, change, screw back on. Why? with 2 rubber o-rings, this construction could be made waterproof, and if the necessary damping for the electronics is made, it would also be shockproof.

- Next up: since we are using a round tube, lets make about the size of a regular lens, that way it goes into any camerabag without further considerations.

- And since were talking about a round tube looking like a lens, lets give it a 77mm thread in front of the bulb, that way all those old color corrections, etc filters from the good old days are suddenly usable again. And in case you want to make your old DIY light enhancer, you can just get an old UV filter, break the glass and use whats left to glue and solder your own stuff. Do i hear GRID?

- And the stupidest thing so far is the Umbrella swivel that one can buy at ebay. A thing almost as big as the flash itself to get one extra hole to put a umbrella through? come on guys, this is hardly well thought through... Lets put in a small collar with a 8mm hole and a small clip that gives it resistance.

- And now everybodys going: but you cant adjust the direction of the flash without the swivel!!! Well lets, build a neat little "fold-to-the-back" thing that does exactly what it needs to do, rotate a few degrees, nothing more.
And make that fit right to a arca mount as well, without any extra bits.

- And while we have the aluminium tubing, lets put in some 1/4" threads around it, so that you can mount some other quickplates as well. Or maybe a handle for the running around. The tube is there, what everybody screws unto it, should be their own business, not decided by "what people generally do"

Image

So now we have the flash, waterproof little compact beauty that we can stick everywhere and connect whatever we want on it.

Then we need to control the thing, and without the "walkingoverthereandpushingbuttons"-bit. We want a thing in our hot shoe that triggers it.

And read the last sentence again. the key word is triggers. I really dont like the idea of having a huge thingamajig with 5 billion buttons clinging to my camera while im trying to use it. I mean whats the point of having the controls connected to your camera? The microsync is a small thing that everybodys seen by now. Lets have one of those on our camera, and then have ANOTHER remote, which we can have in our pocket, give to the assistant, in our bag, wherever. The control enables us to set the power of the flashes and test them, the trigger is just a small thing on the hot-shoe. You could put the control to an ipod for all i care, just a nifty little FM transmitter on the bottom ,use the click wheel, etc, just as long as i dont have a antenna, two more batteries and a lump connected to my camera while im taking pictures.

Thank you for reading.[/img]
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Postby Bluphoto7 » Fri Sep 21, 2007 8:12 pm

Was just using the term E-TTL as a generic name for any of the canon/nikon/sony/minolta/olympus/pentax "Smart" flash auto-exposure communication protocols. I figure we have to call it something and "canon/nikon/sony/minolta/olympus/pentax "Smart" flash auto-exposure communication protocol" seemed a bit long winded.

Does anyone know the proper name for it, so we can start referring to the right thing?

If we can't call it E-TTL then we also can't call it E/I-TTL as that isolates all the Sony/Minolta/Pentax/Olympus users. So what is the generic principle actually called - is it simply TTL? Can we call it A-TTL (meanin "Advanced TTL") We need to use consistent terminology.

Of course, an LCD and buttons would be a fantastic solution, but we have to remember that the whole point of this is to build a CHEAPER alternative to the PocketWizard. By the time you count the cost of the LCD, along with the buttons to operate it and the code to run it, maybe with battery draining backlights etc, then the cost will start to climb.

I'd go for robustness over bells and whistles, although I do like the idea of the device being pretty much a trigger only, with power adjustment for each "group". I reckon the simplest way to do this is via some sort of Potentiometer on the unit, and the simplest way to do that is via some sort of Knob, Slider (or thumbwheel if you're worried about knocking off the knobs). Again, the easiest way to do that would be to have one potentiometer PER SLAVE GROUP. You can have fifty of the things on there for all I'm worried about, but I would think four would be a nice number which would fit nicely on the unit.

Remember that this is four slave GROUPS, not necessarily four flashes - you could have half a dozen slave units assigned to each slave group if you want. Just switch each receiver to channel 1..2..3..or 4.

You are right in that hard drives need to be treated gently, but isn't that the whole point of having these external enclosures - to protect the delicate electronics and drive platters inside? Also fits nicely into a shirt pocket.
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Postby JonSenior » Fri Sep 21, 2007 8:14 pm

Not directly following what has been written thus far but...

Looking at the spec for the Nordic nRF2401it strikes me that the following would work:

We would have two data channels available. Use one as a simple trigger and the other for communication between transmitter and receiver. When run in Shockburst mode these units will pull a pin high to say that data has been received. This occurs when a data packet has been received, decoded, address checked, and CRC checked. This is all done on chip and provides us nicely our error correction.

That pin going high would be our cue to trigger the flash. This could be through a micro if we want some heavy duty control, or could simply be wired to trigger the flash directly. This fulfils requirement 1 and is a very low-component count solution.

The second data channel allows us to communicate with the on-board micro for whatever reasons are necessary. This allows us the future proof path of added functionality (especially if we allow the micro to take control of the trigger path) while ensuring that if needed we can get the most rapid response possible to trigger. To use the transceiver we have to have a micro on-board, so we know we'll have it there for the future.

On a design note. I would personally lean towards a design that used a small chip count and which could be assembled from available parts. As I mentioned in the Flickr page, there is no actual requirement for a hotshoe based package. A simple hotshoe adapter and cable would suffice. If someone with access to tooling wanted to build and market a proper case then so be it, but I think that leaning towards as open a design as possible is better. Perhaps include the tooling information so that a local source could be found. Try to limit the components to those available from Radioshack, RS, Maplin, Selectronic etc. That way people have a chance of being able to build the units. Similarly the micro should be one that provides a decent upgrade path. TI's funky DSPs would have a cool factor, but something based on either PIC or 8051 assembly provides a choice of components. 8051 even offers multiple manufacturers.

Just my 0€02.

Jon
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Postby mattsteg » Fri Sep 21, 2007 9:43 pm

Bluphoto7 wrote:Does anyone know the proper name for it, so we can start referring to the right thing?
"Smart" flash is probably as good as it gets.
Bluphoto7 wrote:If we can't call it E-TTL then we also can't call it E/I-TTL as that isolates all the Sony/Minolta/Pentax/Olympus users. So what is the generic principle actually called - is it simply TTL?
TTL generally refers to first-gen TTL systems that received signals from the body to start flashing and to stop flashing. This is technology that we can implement almost trivially easy.
Bluphoto7 wrote:Can we call it A-TTL (meanin "Advanced TTL") We need to use consistent terminology.
No, A-TTL is a previous-generation canon product too.
Bluphoto7 wrote:Of course, an LCD and buttons would be a fantastic solution, but we have to remember that the whole point of this is to build a CHEAPER alternative to the PocketWizard. By the time you count the cost of the LCD, along with the buttons to operate it and the code to run it, maybe with battery draining backlights etc, then the cost will start to climb.
LCDs are not nearly as expensive as you make them out to be. In quantity they become dirt cheap. ( http://www.crystalfontz.com/cgi-bin/pri ... duct=0802a for example)
Bluphoto7 wrote:I'd go for robustness over bells and whistles, although I do like the idea of the device being pretty much a trigger only, with power adjustment for each "group". I reckon the simplest way to do this is via some sort of Potentiometer on the unit, and the simplest way to do that is via some sort of Knob, Slider (or thumbwheel if you're worried about knocking off the knobs). Again, the easiest way to do that would be to have one potentiometer PER SLAVE GROUP. You can have fifty of the things on there for all I'm worried about, but I would think four would be a nice number which would fit nicely on the unit.
Potentiometers aren't really the simplest way of doing things. To adjust power remotely with a pot, you need to take the analog pot value, convert it to a digital value, and transmit that digital value. You need to have one for each group (or start worrying about an interface to control what group is controlled by the pot). Four pots with decent knobs aren't going to be that cheap, and they will be vulnerable to snagging breaking, etc.
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Postby pinhead » Fri Sep 21, 2007 10:06 pm

mattsteg wrote:
pinhead wrote:*reprogram port
*open bus on the board with enough contacts to run TTL in the future
*un populated spot for DA converter, can be used to hack in remote manual control of dumb flahses later
*provisions on board for user to input manual power adjustments to multiple channles
What does this DA converter do? I can't really think of a useful way to use one for controlling a flash offhand. Remote manual control of dumb flashes is actually much easier to implement than remote control of computer flashes, plus the hardware and software needed to do so will work with new flashes as well.



people hack manual power control into 285's by connecting a pot to the thyresitor circuit. it is an anolog control.
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Postby Bluphoto7 » Sat Sep 22, 2007 9:33 am

Don't many of these processors/ PICs come with a built in ADC? I know the ones we use at work do.

Also, are we designing a set of plans for anyone across the world to build - I think that was Stephens original concept - has this changed? or are we designing a product to be manufactured, sold and distributed? If so then we need to set up some sort of distribution office, and be able to provide warranty repairs etc, assume all the tax implications and actually go into business with these - if someone is prepared to do that then fine, but thats a lot of grief for someone to go through assuming we're cutting back on profits to keep this "open source".

If it's a set of plans, then how is anyone going to be able to get "volume discount" on LCDs, for example.

Or are we selling just a bag of components? If so, isn't there even more of a window for warranty, anyone could come back saying that their processor arrived non-functional, although it could have been blown up by their soldering!

I just figured that it'd be a lot quicker for the photographer to alter flash settings with a series of potentiometers, rather than by going through menus on an LCD.

Unless, of course, the photographer could program the master unit with the guide numbers of all the flashes or slave groups involved, together with their distances from the subject. Then they could simply select 23%...14%...100%...0% for the groups, on the back of the controller, and "know" what the result would be - the percentages wouldn't actually be the respective flash powers, but THE RESPECTIVE AMOUNT OF ILLUMINATION OF THE SUBJECT. The controller would automatically "compensate" for flash guide number and distance from subject. That I would love. Of course, flash zoom and modifiers would complicate this, but it's just an idea.

But if the LCD is simply a way of displaying the flash power for each group with easy to use buttons for navigation and changing values, I think it could be done more simply. Would you suggest a custom printed rubberised membrane keypad with custom cutouts on the bezel below the weather sealed LCD. We can't just be thinking about the electrical simplicity of the unit. We should also think about how to make it easy and cheap to manufacture - ie labour-wise, not just cost of components.

I don't know if LCD and keypad or just a set of pots is the best way to go, but we have to decide if the extra potential for adding menus and functionality is worth it. Maybe,if we're producing a kit, we could include the SW for the LCD/Keypad and have a port on the board to drive them, but also have ports on the PCB for pots, if the users want to implement them that way - especially if the PIC already has built in ADC.

I'd go for simplicity of use over simplicity of design any day - although I'm not saying that one way is simpler than another - I'll let the community decide on that one.

all the best,
Guy
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Postby JonSenior » Sun Sep 23, 2007 12:11 am

I'd go for simplicity of use over simplicity of design any day


Given an LCD and four buttons, one could interface pretty much anything. If you want the cool factor you could add a single rotary switch which is used as an analogue input (Think iPod... try not to shudder) for adjusting levels rapidly.

Up / Down / Select / Cancel will get you a long way though.
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