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I need a flash extender or flash adapter with the option of connecting a cable to trigger a flash at a distance from the camera. I'm considering the JJC Standard Hot Shoe Adapter. However, when looking at the pictures, I see that it has only one electrical connection to the central pin of the camera's hot shoe mount as is shown in the picture below:

Enter image description here

However, if I understand the workings of the hot shoe, the trigger signal consists of creating an electrical connection between the central pin and ground, which corresponds to the metallic structure that makes the mount as described in this figure (taken from this post).

Enter image description here

Therefore, with only one connection, this adapter shouldn't be able to pass the triggering signal to the flash connected on the top of it or to others connected through the cables. If it does pass the triggering signal (as this video seems to suggest), how does that work? Is there an electrical connection hidden somewhere under that plastic plate surrounding the central contact on the first figure? Or am I missing something?

Side note: I'm really after capturing the triggering signal from an automated camera controller I have designed with an Arduino. This would serve as feedback to confirm that the camera indeed shoot the picture. And I need the adapter or extender to properly gain access to the hot shoe contacts.

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    \$\begingroup\$ To me the connector has space for at least two contacts - the flange and the middle pin. \$\endgroup\$
    – DetlevCM
    Commented Jun 3, 2022 at 7:34

2 Answers 2

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Although you can't tell from the image, I suspect that there is a springy bit of metal that supplies the ground, between the flange and the knurled knob.

If you have a voltmeter, set it to ohms or continuity, and slide one probe in the groove between the flange lip and the knurled knob, then touch the other probe to the outside of the PC socket. I'll bet you'll see the ohmmeter react, and/or hear the continuity tester beep!

Because, as you surmise, there's no way it would ever work, otherwise.

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  • \$\begingroup\$ A single wire can transmit AC signals, but that's a bit too esoteric for entry-level electrical engineering. e.g. youtube.com/shorts/KPNhNEqohVY \$\endgroup\$
    – Nayuki
    Commented Jun 3, 2022 at 19:22
  • \$\begingroup\$ Yeabut, we're talking about a pulse of DC here, not really AC. And the "single wire" bit isn't really accurate, either — you need a counterpoise to provide a ground reference, just like you do for DC, although in many cases, that might be the case of an electronics device, or even your body. \$\endgroup\$
    – Jan Steinman
    Commented Jun 3, 2022 at 20:38
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Jan Steinman was right. His answer encouraged me to get the product and there was indeed a contact to the camera ground hidden under the flange. Here is a picture of it: enter image description here

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