Hot-shoe signal to external GPS

BobORama wrote:

Hi,

You can implement an edge triggered debouncing circuit. It will activate on the rising edge and the output will stay logic high until a certain time elapses. I am quickly cribbing from the Internet, and this diagram has more than you actually need:

See http://www.talkingelectronics.com/projects/100%20IC%20Circuits/1-100_IC-Ccts.html

The left most pair of NAND gates acts as a debouncing circuit / latch which will set pin 3 logic high for a predetermined amount of time when the leading edge of the input to pin 1 is detected.

The right hand pair of NAND gates forms an square wave generator for driving the speaker. Unless you need an audible alarm when the shutter goes off - you can skip that and the transistors

So no matter how short the duration of the input pulse, the output from Pin 3 will stay high for as long as indicated by the R-C circuit in between the two left most gates. So for, say, a 100ms pulse you would want 1 microfarad and a 10K resistor? Or a small potentiometer so you can adjust it later.

Thanks a lot Bob; I've doing some checks/tests and I think there might be a problem with the GPS configuration/set-up: I've posted on the Ublox forum hoping someone can shed some lights on this matter.

Thanks again for your suggestion.

Regards

Giovanni

I don't know what you mean by "hot-shoe signal".

If this connects to the hot-shoe center pin then it is usually a switch that closes temporarily. This will usually only tolerate 6 volts which implies it is solid state. (If using an pre digital era flash check to make sure it is not putting out higher V and ignore the lists on the internet - the V will vary with the same flash type and could be 200 V.)

The most common problem that I have seen is the ground or common on the side of the hot-shoe making poor contact. Rarely they are painted with the wrong paint and scraping down to bare metal works. Just see if the paint is conductive with a meter or an LED  and battery.

You could connect an LED and a battery to the center terminal and side to get an idea of the duration. If too short a duration it would be hard to see.

An analog meter that uses a AA battery set to lowest ohms might also give an idea in the same way. (The old meters use 22 volts for high ohms.) I just tried this on a Canon XTi and the hidden switch on the right side had to be closed to get it to work. The meter needle bounced. There was also a polarity. With it hooked up one way it was open and went low, the other way there was low ohms which went lower with the shutter. The hidden switch detects a dumb external flash so the internal flash does not pop up. If your camera has a hidden switch in the slot make sure your device pushes on it.

(just trying to figure out what you are looking for)

Just to be sure:

What do you want to accomplish exactly? Do you want GPS EXIF Metadata with each image you shot with your D3300?

If so, why don't you use a GPS device like one from http://di-gps.com? Or other solutions that connect directly to your DSLR?

I've used several devices over the years (with my D200, D700 and D800E) which all did a great job of writing GPS EXIF metadata to each image I've shot while the GPS gadget was active.

Or do you mean something else?

I have a similar issue: when a hot shoe adapter is used on a Sony a6000 camera, to mark an event on a GNSS reciver (EMLID REACH); It is able to mark events on all shutter velocity (1/60; 1/1000; 1/2500, etc...).

This fact is known according to some forum research.... I do not have a Sony camera.

I use a Samsung NX300 camera, and the events are only marked up to 1/250 shutter velocity (1/60...1/250).

I wonder if it is possible to 'break' this limitation with some eletronic or software implementation.

Thank's

Hi there,

I've done this many times with Sony and Ricoh cameras, and you generally have to simply use a "Pull-up resistor".  To implement, on the GPS Event input, simply connect a 10k resistor from the Event input to the 3.3 volt power bus.  Connect the input to the hot shoe center contact, and a ground wire from the GPS ground to the hot shoe ground.  When you actuate the shutter, the camera will usually generate a "low active" signal while the shutter is open.  The GPS should easily accommodate any pulse width down to at least 1 micro second which is much shorter than any shutter setting you can generate.  Be sure to configure the GPS even input for "high to low" transition detection.  You should not need any debouncing circuit.

-Wayne

lidar532 wrote:

Hi there,

I've done this many times with Sony and Ricoh cameras, and you generally have to simply use a "Pull-up resistor". To implement, on the GPS Event input, simply connect a 10k resistor from the Event input to the 3.3 volt power bus. Connect the input to the hot shoe center contact, and a ground wire from the GPS ground to the hot shoe ground. When you actuate the shutter, the camera will usually generate a "low active" signal while the shutter is open. The GPS should easily accommodate any pulse width down to at least 1 micro second which is much shorter than any shutter setting you can generate. Be sure to configure the GPS even input for "high to low" transition detection. You should not need any debouncing circuit.

-Wayne

Hi Wayne,

Some of the new cameras have an electronic shutter mode that is used for the 1st and 2nd shutter, thus no mechanical shutter, and totally silent/vibration free. I found that the hot shoe "flash" trigger is disabled when in this mode with the Nikon D850, but believe other cameras also block the hot shoe trigger during this mode. The reason may be to prevent flash/strobe bleed thru when reading out the sensor (electronic shutters are not totally opaque).

Anyway, here's a link to a circuit solution I did using a 555 timer. Other software based solutions are available in macro stacking controllers.

https://www.photomacrography.net/forum/viewtopic.php?t=36356&postdays=0&postorder=asc&highlight=555+timer&start=15

BTW why not just trigger the GPS with the same signal that triggered the camera?

Best,

I am trying to get an interrupt into a microcontroller at the shutter-open event. I am using a Canon EOSR camera. I hope to be able to use the hotshoe to provide this interrupt signal.  The Canon has 5 connections at the hotshoe plus the ground (rails).

I have tested the pins using a scope. The only setting in this camera that seems to be useful is to set the flash to "enable".

I can set up the oscilloscope to read the time-signal between the 5 pins and ground.  I click the shutter (manually) and can see the response from the pins. I show the oscilloscope connection below. I also show the oscilloscope traces for several clicks.

The only pins that seem to respond are the two "middle" pins. The left pin produces a 5V pulse of two secs duration and the right pin produces a pulse of 3.3V also for two sec. The pulse is initiated at the pre-fire (half-down) button press -- the two sec timer is initiated at the time of the fire pulse. This seems to be highly repeatable.

Can anyone assist with explaining this behavior?

ProfHankD --

Thanks for your response and the excellent articles.

I see in the paper you are using the stereo jack for the PCSynch as a shutter indicator (end of curtain travel). Is the same info provided by the XSynch on the Hotshoe?

The stereo "tip" (and I think the XSynch) is shorted to ground as an indication of the event. I assume that, to get an oscilloscope signal, you would connect a resistor (e.g., 2Kohm) to the XSynch and the other end of the resistor to a power source (e.g., 3,3V). By placing the Oscilloscope leads across the resistor, we should see the shutter event as a voltage pulse (3.3V).

So far, I am not getting the expected results. I see no voltage activity when using the circuit described above.  I'll keep trying -- maybe you have a suggestion?

I have the Canon mirrorless EOSR settings as I show below for the flash menu. Flash is "enabled" and the Slow Synchro is set to 1/200.  Per your paper, I should be able to set the center of the capture time by backing up the 1/200  by my shutter setting (e.g., 1/2000).

Fabio Lobo wrote:

I have a similar issue: when a hot shoe adapter is used on a Sony a6000 camera, to mark an event on a GNSS reciver (EMLID REACH); It is able to mark events on all shutter velocity (1/60; 1/1000; 1/2500, etc...).

This fact is known according to some forum research.... I do not have a Sony camera.

I use a Samsung NX300 camera, and the events are only marked up to 1/250 shutter velocity (1/60...1/250).

I wonder if it is possible to 'break' this limitation with some eletronic or software implementation.

Thank's

Fabio, I know this is old.  But I want to trigger an event in the Emlid M2 (or M+)  but do so with the signal from the Micro SD card.  I have ordered some extension ribbons so that I can extend the necessary wires from the ribbon to the Emlid.  Do you happen know if this is in fact possible and what the setup would need to be?

Thanks,

Tim