the time-lapse 555 circuit here:
What I need to know is when the circuit fires the shutter, are the two camera pins effectively shorted?
(going to use it for something else if so)
There needs to be some voltage (power) at the collector of TR1... provided by the camera in this cased I assume. You could apply your own power and have the transistor close a relay or something if that's what you need.
George H.
I see a + and gnd on the left - isn't that enough?
The PS on the left powers the 555. You still have to provide voltage to the collector of TR1. Where is that coming from?
George H.
What limits the base current of "TR1" ?
How does the LED get enough current to produce light ? ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
I'm not sure what you are talking about. Clearly the camera has electronics and is looking for a switch closure. The circuit referenced will provide that path to emulate a switch closure. No, it won't be identical to a switch and has a minimum voltage drop of some 200 mV, but good enough I am sure.
-- Rick
Can't work. The base of TR1 shorts out the 555.
The camera's control polarity will matter too. Use a solid-state relay instead of TR1.
And transistors should be called Q, not TR. They don't work reliably if they are called TR.
You might have power supply isolation issues too. The SSR fixes that.
Jim is right. The OP probably left out a 1K resistor in series with the base of TR1. 1K resistors seem to be a favorite.
-- Rick
All the old SLR film cameras that I'm familiar with only required a contact closure to trigger the shutter. Power is provided by the camera's battery. I assume that this also applies to digital cameras, but everyone knows what assumption can do. The circuit referred by the OP should work with any camera capable of being triggered by a switch closure, but I see a flaw. The output of the timer goes directly into the switch transistor's base, with no current limiting. Depending on which version of the 555 timer that is used, that could result in failure of the transistor or the 555, or both.
Dave M
George Herold wrote:
photography-495153.html
Magic.
-- Tim Wescott Wescott Design Services http://www.wescottdesign.com
Kinda. It would be more accurate to say that the collector pin of the transistor is shorted to ground, and even more accurate yet to say that the collector pin of the transistor is pulled down to between 0 and
0.2V. There's also going to be a limit on how much current you can sink, depending on what transistor you actually use and how you fix the circuit so it'll actually work.If that's all you need, you'd be golden except for the fact that as drawn the circuit won't work -- see Jim Thompson's comment about the lack of a base resistor on the drive transistor.
-- Tim Wescott Wescott Design Services http://www.wescottdesign.com
Black light ?>:-} ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Grin, the output impedance of the 555?
Well if we zener the Vbe junction and......
Yeah some base resistance is needed.
George H.
The OP asked if the circuit shorts the two pins... and wants to use it for something else if so.
Do you think the two pins are shorted? (It apparently worked with the camera electronics.)
George H.
Yes, I see what you mean. No, the two pins are not "shorted". The OP needs to provide more info on the intended app.
-- Rick
Use a mosfet or an SSR. And check the camera polarity.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
They are in a sense however..
You must remember the transistor can only handle up to a specific amount of voltage between the collector and emitter.
Also, it's not an AC device, meaning you can't be switching AC currents with it.
If the need is to switch an AC device, you can get solid state relays that can be turned on using this same circuit. The relays are optically isolated and will not back feed into the circuit.
but getting back to the original circuit, you can switch DC loads up to what ever the transistor is rated for. And that means, Watts, voltage and current.
Jamie
You mean how does the LED get enough *voltage*; most needfrom2V to 4V to pass enough current to emit light.
First, thanks to all for the replies.
This IS for a camera intervalometer, but not in the usual sense.
I have a toy quadcopter that has an attached camera that will either do video or single-shot photos. You press a button on the remote and the remote tells the camera to fire. The button is a short-to-ground switch.
I want to have a toggle switch on the remote that will fire the camera every seconds.
All the circuits (like that one) I see say they are for "digital cameras"; but none say if they short to ground or if they send a voltage pulse. I don't want to build something that will not work and may fry the toy controller.
The end goal is to get enough photos to make panoramas with. I tried by extracting frames from the video but the photo quality is better, and the processing is easier.
I could use another camera that does do multiple frames, but it weighs twice as much, plus you have to set it taking photos before flight and it does so continuously until you get it back in your hand.
You should be able to measure a voltage on the camera pushbutton switch, to see what the logic level is. You could also measure the current drawn when you short the switch to ground. The 555 has an open collector "discharge" transistor which should provide the logic low of the switch closure. Probably 500 mV or less would be low enough.
If you have a circuit that provides a logic level output (such as the 555 output pin), you could make it equivalent to an open collector by adding a Schottky diode to avoid possibly overdriving the camera input, but the voltage may not be a reliable logic low.
In order to reduce battery current, you may want to use the low power CMOS version of the 555 timer. But even better would be something like a Microchip PIC12LF1822 or even a PIC10LF322 which comes in a tiny SOT-23 package or a DIP-8 which may be easier to handle. You can get a development board for $13:
A microcontroller will give you a lot more options and a circuit with lower parts count, that can be reprogrammed to provide different characteristics as desired. And it can be fun to program. Good luck.
Paul
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