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Thread: Shutter Ideas

  1. #11

    Shutter Ideas

    I bought a new shutter about 40 years ago in Japan intended to mount on the front of a barrel lens. It works like the Speed Graphic shutter Murray described, except it has only one slot. Varying the shutter tension varies the exposure from about 1/30 to 1/90 second. Of course it also has provisions for time exposure. Such a shutter could perhaps be improvised from an old Speed Graphic or other focal plane shutter press camera, or made from scratch. Adapting or fabricating these shutters is far easier than the more common two-curtain focal plane shutters.

  2. #12

    Shutter Ideas

    I'll take your word on whether that'll work -- I can't see the magic smoke in that drawing, so I'm lost.

    I don't know if you'll be able to get the Packard mechanism to go faster than the 1/15 "instant" speed, however; the shutter consists of a pair of biggish, relatively heavy leaves that pivot at one edge, so they open like a wedge and then reclose, and I think 1/15 is about as fast as the shutter's internal mechanism can open and close those leaves. Nice, accurate slower speeds, however, would be a very welcome thing with a Packard. You can, BTW, buy new Packard shutters that are built with a solenoid to be fired by a number of different voltages; I don't know if they're any faster than the pneumatic variety, but they can use a smaller hole in the standard or lens board (wires instead of a tube) and are more convenient to control with electronics (like what you're working on here).

  3. #13

    Shutter Ideas

    I started to answer you earlier today but ran out of time, and I see you've changed your circuit from the earlier post.

    It took me some head-scratching to figure out what you are up to here. The connection from the relay back to the timing network was puzzling, but now I see that the rotary switch disconnects the timing network from +9 (disabling the timer) and connects +9V to the relay, giving you the "bulb" function you wanted. I think that will work (pretty creative, really). There is one problem, though. It looks to me like the diode on pin 3 is backwards. The way it is, when the 555 output is high the diode is reverse-biased and no current will flow. Worse, when you select the "bulb" function, current from the 9V supply flows through the diode (now forward-biased) into pin 3 which in that condition is a saturated transistor straight to ground. The result would be fatal to the diode and the 555. Incidentally, as you may have figured out, the way the "bulb" button was connected in the earlier circuit would have fried the 555 output in very much the same way.

    If you turn the diode around, it is now forward-biased when the 555 output is high so current can flow through the relay. When you select the "bulb" function, the diode is now reverse-biased to block current from toasting the 555 output transistor. The smoke will remain inside where it belongs .

    A couple of other points. There should be a diode like a 1N4001 across the relay coil (cathode connected to positive so it's reverse-biased) to absorb the reverse voltage "kick" from the coil when the relay turns off. I think your earlier circuit had one. Also, the earlier version had one more pullup resistor and a protection diode on the trigger. You can probably live without the diode but I think the trigger will be more reliable with the second pullup on the button side of the capacitor.

    I am curious as to the nature of the relay. Is the relay you have shown actually the solenoid on the shutter, or is it just being used as a switch to control that solenoid? I'm also curious as to what sort of battery supply you are planning to use.

  4. #14

    Shutter Ideas

    The output looks OK now.

    The resistor you added to the trigger should be a pull-up, so connect the capacitor directly to the switch contact as you had it. The resistor then goes from that connection to +9V. The idea is that it provides a solid source to keep that side of the capacitor high when the trigger button isn't pressed. Without it, the trigger might work but it might also be flaky.

    If you need more current for the solenoid (watch out for power dissipation limits of the 555), instead of using a relay as a switch use a driver transistor. With a relay you have another coil sucking power from your battery, whereas with a driver transistor it is just a switch. I did a quick search and found a page that has some info that might be helpful.

    http://www1.jaycar.com.au/images_uploaded/relaydrv.pdf

    The lower figure on the linked page that shows the 555 is not using it as a timer so I'd ignore that. The upper figure showing the driver transistors is what I'm referring to. The transistor numbers they mention are European, so if you're a yank you need to get something similar.

  5. #15

    Shutter Ideas

    Moot,
    Thanks again, I have since revised the design to reflect the change. I'll check out the link you supplied. Right now Im just going to try to get the circuit to flash an LED - at least that way I know I did something right

    Thanks again,

  6. #16

    Shutter Ideas

    Ok....
    So I couldn't get my hands on a bread board, but I did find a gridded PCB. I revised the plans (yet again !), and instead of using a resistor pack, I installed a bank of potentimeters. This way, I can dial in the speeds better.
    I assembled everything, but I goofed some where. When I hit the button, I get voltage from the output, but it never turns off. Perhaps I need an actual load (and not just the multimeter ?). I either need to ground the out put (which will imediately turn the circuit off), or disconnect the battery.
    Attached files

  7. #17

    Shutter Ideas

    I wasn't sure why D1 was needed or if a 555 has enough current capability to drive very many relays...you'd need a 'sensitive' one, and I don't mean artistic. the missing D2 was what I first thought about too.

    I stopped shopping at RS - it got way too annoying -

    I had to learn the part numbers, the package colors and the store layout before I went there because the employess invariably would tell me they didn't have what I was looking for. Armed with that research I could either show them where it was or get in and out before they accosted me with the standard "Duh, whatcha buildin'?"

    A few years ago, you could get away with saying "...Grrr, a b_ _ b", but that isn't funny these days.

    The insult, indignity and inequity in pricing sent me to mail order.

    In a few days I'll scrounge up some links to shutter patents. Hopefully it hasn't been dumped from the server, but I posted instructions here once on searching the USPTO website. Earl was the only one who commented. It's useful but not friendly.

  8. #18

    Shutter Ideas

    Murray,
    Thanks ! Ya, S**Tshack just about sums it up. The pieces should be here tomorrow or friday, so we'll see what happens.

  9. #19

    Shutter Ideas

    A success of sorts.
    I came hom e for lunch today to find my package from mouser (!!). I didn't pay for next day shipping, but it arrived here anyway.
    I tossed a quick circuit together, using a 100k pot in the place of the switched packs. I used this basic idea here:
    http://www.kpsec.freeuk.com/breadb.htm
    Just to get the blood flowing a bit

    Soooo...Tonight will be the big trial.

    Keeping my fingers crossed.....

    -Steve

  10. #20

    Shutter Ideas

    A complete success.
    The circuit works like a charm. I have it on a plug-in breadboard at the moment, so its not the cleanest looking thing in the world, but it works ! Im going to transfer it over to a PCB tomorrow or Friday.
    As it sits now, I do not have the selector switch and resistor banks installed on the breadboard...Just a 10k pot. I've been able to get some rough times of 1/4-3s; but that is with a 100uf cap (which, isn't the most stable thing). I have a 1uf cap that will replace that on the PCB, and I'll just start off the resistor bank with an extra resistor.
    Anyway, some quick photos. Attached files

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