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All,

I have a Canon T5 with a 2.5 mm shutter release port. I would like to be able to trigger the shutter from an audio output jack on a PC. Would it be possible to trigger the shutter release using a "beep" noise sent from the computer?

Thanks!

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  • This is a little curious and innovative. Not sure if it could be done
    – Janardan S
    Feb 28, 2017 at 15:26
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    Could be possible with something like Triggertrap. Though they only have mobile apps, it doesn't support connecting to a PC. And Triggertrap are now going out of business, so might be hard to find them.
    – vclaw
    Feb 28, 2017 at 15:39
  • You're looking for something like this: amazon.com/DSLRKIT-2-5mm-3-5mm-Studio-Adapter/dp/B00FZLKK2W
    – Janardan S
    Feb 28, 2017 at 15:48
  • @Janas I'm not asking if I can connect the two, but rather if the connection could trigger a shutter release.
    – Dan Grahn
    Feb 28, 2017 at 16:28
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    Don't plug these directly into each other. Despite the similar connector, they're totally unrelated as to purpose; the shutter release is simply an open circuit that expects to be closed with a switch, and will have current flowing through it when that happens. The audio output is an output, and doesn't particularly want to have current fed into it. Use an interface as several people have mentioned.
    – junkyardsparkle
    Feb 28, 2017 at 20:49

5 Answers 5

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Since the other answers suggesting using an interface such as triggertrap don't address the specific question to your satisfaction: No, this is very, very unlikely to work. Despite the plugs being similar, they serve very different purposes. The camera release is basically an open circuit with a voltage potential (measured at 3v on mine) waiting to be closed by a switch, either mechanical (a simple button or slide switch) or electronic (as in the case of audio triggers, intervalometers, etc). An audio output is designed to present a fluctuating voltage across a load, not to close a circuit.

Given that there's a certain threshold resistance below which the camera will decide that its circuit has been "closed", and that audio outputs of the sort that you describe may very well present a resistance in that range, there's a reasonably good chance that simply plugging the two together will trigger the release.

Even if the shutter doesn't release just from plugging the two together, playing a sound is unlikely to do any triggering, since it doesn't do anything to close the circuit. Your audio output may even have a capacitor inline blocking the DC from the camera (and if it doesn't, it might not be very happy to have the voltage applied to it). Sorry! You can probably find some DIY interface projects out there, if you just can't resist the mad science. (See Chris H's answer for an example of just how simple of an interface you might be able to use.)

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    It becomes a question of whether the OP wants to build a circuit. I might have a go myself, to see if I can get it to work as an add-on to the one I linked (no spare 2.5mm jack plugs here). You could use one channel for half press and the other for full press
    – Chris H
    Feb 28, 2017 at 22:29
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    The wonders of stereophonic sound never cease! :D Next up is interfacing 5-channel surround to Atari 2600 joystick port...
    – junkyardsparkle
    Feb 28, 2017 at 23:04
  • @junkyardsparkle I'm going to make this the accepted answer, but I want to test it out for myself. If I can get something working, I'll post it as an answer.
    – Dan Grahn
    Mar 1, 2017 at 12:29
  • @screenmutt: A true empiricist. I salute your tenacity.
    – junkyardsparkle
    Mar 1, 2017 at 21:45
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    @junkyardsparkle It did trigger plugging into the port. Interestingly, even with the device off.
    – Dan Grahn
    Mar 3, 2017 at 16:22
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Yes, you can but you need an opto-isolator

I've built a few cable releases for Canons, from a simple pushbutton to a USB (via a USB-RS232 dongle) trigger, to one triggered off a burglar alarm PIR sensor (for use as a camera trap).

It won't be simple to trigger it off a sound card. If you can get enough voltage you might be able to modify my USB trigger circuit - you'd need to rectify the audio output before feeding the opto-isolator(s).

The circuit (and code to talk to it) are freely available on my github if you want to use them as a starting point.

I don't know what voltage (and current) a typical sound card can drive - but with clever design of the rectifier circuit it should be possible. With a further power source it would be easy - but I assume you want to avoid that (you could steal enough power at 5V from a USB port, or even a serial port)

I've just done it. I used the circuit on my github, but connected an audio channel directly to the LED positive pin of the opto-isolator (no series resistor), using the LED as its own recitifer. With a 3-ish V peak-to-peak signal and a low frequency (about a 20Hz sine wave) it triggered. I'm not sure whether it wasn't 100% reliable or whether I was having trouble holding everything together (I didn't have the right connectors). I have a couple of ideas for improving things (involving Schottky diodes such as the 1N5817, capacitors, and possibly both audio channels in anti-phase), but I don't have the parts to test.

Here's the circuit I used this evening. You really should have a series resistor between the LED though I didn't while testing:

Circuit diagram link as imgur still isn't working

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  • No promises but I'll try to look into how to drive my design off sound card outputs in a bit more detail.
    – Chris H
    Feb 28, 2017 at 20:17
  • Real line outputs are typically 3v peak-to-peak nominal, but the kind designed for driving headphones probably won't deliver that, they're more concerned with being able to supply current to a potentially very low impedance load.
    – junkyardsparkle
    Feb 28, 2017 at 20:43
  • @junkyardsparkle I switched mine with an opto-isolator drawing about 20mA, and Vf 1.2V (in the past I've used a relay) so the sound card should be able to drive that even with a series resistor. I'm sure that's how triggertrap would have done it (unless they did something cheaper/simpler/less robust).
    – Chris H
    Feb 28, 2017 at 22:21
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    Just using a transistor was actually my first crazy thought, but I like the opto-isolator idea much better, if the output will drive it (I was skeptical that it would, tbh). I would probably stick to higher frequencies for transistor experiments - 20Hz seems like it could produce some retriggering, or just a very confused camera. ;)
    – junkyardsparkle
    Mar 3, 2017 at 21:40
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    Deleted my comment about the slow optos probably doing some smoothing - those PC817s are fast! But still worth noting that one with this "feature" could be used if desired.
    – junkyardsparkle
    Mar 3, 2017 at 22:46
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The shutter release ports on Canon cameras as well as pretty much any other DSLR (there is at least one notable exception: Panasonic/Lumix) are very simple. The only difference is the shape of the connector selected. All you need is continuity to trigger them.

If the camera is in Bulb mode the length the continuity is maintained will determine the length of the exposure. If the Tv is set by the camera the circuit need only to be closed for a duration long enough for the camera to recognize it.

The defunct TriggerTrap app used the headphone jacks of phones to trigger cameras via a dongle that translated the tone from the phone to the continuity needed by the remote circuit connected to the camera. The dongle was acting as a relay. When it detected an audio signal from the phone it closed the circuit connected to the camera.

Here's a link that shows the pinouts for most recent DSLRs.

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    The 2.5 mm socket on a Canon doesn't expect a voltage. It expects a switch (as you say). Supplying a voltage won't work. I've made a cable release from a pushbutton and a 35mm film can, and I've made a USB trigger. And a tone is by definition ac - sound cards can usually only output ac, so without a further circuit it's much more likely to break something than to work.
    – Chris H
    Feb 28, 2017 at 20:08
  • Indeed, even if you create a digital DC "audio" source (which is easy enough) the DC will never make it to the output on a consumer device, which will probably have capacitors inline precisely to prevent this.
    – junkyardsparkle
    Feb 28, 2017 at 20:56
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    I don't know what I was thinking, that somehow the voltage supplied from one side of the switch could be emulated by an external source. Answer edited to remove that craziness.
    – Michael C
    Feb 28, 2017 at 21:01
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    I admire the mad scientist spirit, though. ;) In that same spirit, i put a pot across the release on my Oly PL7 just to see at what resistance it would trigger... turns out to be ~75k, so my hypothesis is that just plugging into a typical line output would be enough to trigger at least some cameras.
    – junkyardsparkle
    Feb 28, 2017 at 21:11
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    I suspect internally there's something like a 100k pull up (big) to the positive rail, and it needs to be pulled down to trigger,with the threshold just below 50% of the rail-to-rail voltage
    – Chris H
    Feb 28, 2017 at 22:25
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Hell NO!

They both use jack as the plug and socket and this is the only thing they have in common at all.

  • Sound card sends voltage signal to channels with respect to the ground wire. (so the speker's coil move the core and make a sound)
  • Camera waits for connection between a channel and the ground.

See Caleb's link to my, sligthly different, question

In the remote control there are two simple switches, one closes the circuit of AF and the second one the circuit for shutter release.

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There was a cellphone app called TriggerTrap (its since gone under) that used the headphone jack of a phone to control a camera of your choice so I think there is a solution for it if using a relay.

If you are using a computer instead of a device like a phone. You can use the EOS Software to control your camera via USB cord and you can get really long USB cords. If the EOS software doesn't do exactly what you are looking to do and you have some development skills, look into the Canon SDK. Some information can be found at Canon.

I use a USB micro to USB micro with another app that I have purchased with my phone that is designed for Canon cameras. It allow you to control your Canon Camera with many different functionalities. More details about the app can be found at How to programme EOS utility to take n number of shots?

I use a Canon 7Dii and T4i. It also worked on a T2i before I sold off the T2i. I did not design the app but only came across it when I was looking to try out time-lapse.

DSLR Controller (BETA) - it costs about $7.99 (CAD or USD, I forget)

Remote Release - A Test app before purchasing the DSLR Controller

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  • Thank you for your response, but this is not at all what I am asking.
    – Dan Grahn
    Feb 28, 2017 at 17:09
  • I was using TriggerTrap as an example of using a headphone jack to control your camera but added a 2nd solution for the idea.
    – thebtm
    Feb 28, 2017 at 17:14

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