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Lightning Trigger build
Posted By: Riggomatic, 04-28-2019, 12:32 PM

I was cleaning up my desk (didn't get very far) and found an old Arduino nano, that I had purchased for a project. What project, I don't remember...I have a few of those around.
Anyway, the Nano is a small micro controller with several inputs, and outputs that can be programmed to do a variety of functions.

Arduino Nano (or at least a look alike)



There are thousands of example projects all over the internet.

After a little bit of searching, I came across a plan for a lightning trigger with just a few components. So, I dug through my piles of parts scattered on my desk, rummaged through bags and forgotten drawers and came up with the components I needed to start this build.
I did have to visit Amazon to pick up a cheap wired remote, and us that to house everything for now.

I received the remote Friday, and started working on preparing the switch to hold the wires and parts. I basically removed all the plastic ribs and mounts inside the handle, drilled out the button to fit the 10k potentiometer (sensitivity adjustment).

I did leave the standoffs for the screws to hold everything together later


A little solder, a few wires and the controller is ready to program.
Yes, all the wires are red. It's what I had, and a $6 build didn't eat into my K-1 fund. Besides, it is just a prototype build.



I still need a 6 volt power source though. (dig dig dig, scrounge ...) I'm thinking my wife will be donating a couple of those LED tea light candles

An extra cell taped on will do nicely[/SIZE]


Well, the tea light was spared, as I found a pack of coin batteries which I only needed the CR2025 size, and not the other two sizes in the package. I knew there
was a reason I bought the multipack



Packaging everything back inside the remote trigger handle


I did trial it on my K-5, with a lamp flashing on and off. Everything seemed to function as intended.


Now I need a thunderstorm or two to give this thing a try....

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04-28-2019, 01:19 PM   #2
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Nice, what kind of response time can you get from that? Is the light sensor and Arduino quick enough to trigger on something like lighting?
04-28-2019, 01:52 PM - 2 Likes   #3
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It will be interesting to see the results you get. The problem is sensing the flash and opening the shutter in time to capture it. Longer or repetitive flashes are practical but brief singular flashes can be problematic. Using a photoconductive cell will slow response a bit since they are sluggish compared to a photodiode or phototransistor but they should still be fast enough for longer bright flashes. The Arduino is plenty fast enough though you'll benefit by keeping the program (sketch) as short as possible so few instructions need to be executed prior to firing the shutter. If you use the lightning flash to wake the Arduino out of sleep using an interrupt, and immediately fire the shutter, that would provide the fastest response, but sensitivity will have to be accomplished in the input circuit. It might be easier just to use an analog (high speed) comparator for the function.

Some flash triggers use an AM radio like circuit to pick up the EMF field of the flash rather than the light (to trip the shutter) and can work better where the flash is distant or in a cloud so as not to produce a bright ground flash.

Good luck and share your photos with us. Be sure to observe lightning safety and don't stand out in the open waiting for a lightning stroke - read up on safety measures - we don't want to see a photo of a fried photographer!
04-28-2019, 02:08 PM   #4
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QuoteOriginally posted by amoringello Quote
Nice, what kind of response time can you get from that? Is the light sensor and Arduino quick enough to trigger on something like lighting?
Right now, there's a planned 50 millisecond delay from the input value reading to the output writing (tripping the shutter). I just used the default values that I read on one of the tutorials.

The LDR has a response time around 2-50 milliseconds.

---------- Post added 04-28-19 at 05:23 PM ----------

QuoteOriginally posted by Bob 256 Quote
It will be interesting to see the results you get. The problem is sensing the flash and opening the shutter in time to capture it. Longer or repetitive flashes are practical but brief singular flashes can be problematic. Using a photoconductive cell will slow response a bit since they are sluggish compared to a photodiode or phototransistor but they should still be fast enough for longer bright flashes. The Arduino is plenty fast enough though you'll benefit by keeping the program (sketch) as short as possible so few instructions need to be executed prior to firing the shutter. If you use the lightning flash to wake the Arduino out of sleep using an interrupt, and immediately fire the shutter, that would provide the fastest response, but sensitivity will have to be accomplished in the input circuit. It might be easier just to use an analog (high speed) comparator for the function.

Some flash triggers use an AM radio like circuit to pick up the EMF field of the flash rather than the light (to trip the shutter) and can work better where the flash is distant or in a cloud so as not to produce a bright ground flash.

Good luck and share your photos with us. Be sure to observe lightning safety and don't stand out in the open waiting for a lightning stroke - read up on safety measures - we don't want to see a photo of a fried photographer!
I'll be in the garage, with the door open. That's about as far as I venture out during lighting storms.
This was more of a learning experience with the Arduino. I'm pretty new with it and do a lot of copy/paste and edit to see what happens.

04-28-2019, 06:53 PM   #5
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Love it. This is the kind of stuff I would build.

QuoteOriginally posted by Bob 256 Quote
It might be easier just to use an analog (high speed) comparator for the function.
I agree with Bob; an arduino verges on overkill for a project like this.

Let me know if you'd like a high-speed (nano seconds!) photodiode.
04-29-2019, 12:27 AM   #6
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Very cool.
could you use a flashslave trigger instead of an arduino?
04-29-2019, 06:00 AM   #7
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QuoteOriginally posted by Riggomatic Quote
Right now, there's a planned 50 millisecond delay from the input value reading to the output writing (tripping the shutter). I just used the default values that I read on one of the tutorials.

The LDR has a response time around 2-50 milliseconds.
On a K-5, if it's too slow, you still have the option to use MLU (see K-1 shutter lag increase with MLU / Mirror Lock Up - PentaxForums.com) for some timings.
04-29-2019, 12:23 PM   #8
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QuoteOriginally posted by pentax360 Quote
Very cool.
could you use a flashslave trigger instead of an arduino?
I suppose you could. Probably easier too.

---------- Post added 04-29-19 at 03:33 PM ----------

QuoteOriginally posted by AstroDave Quote
Love it. This is the kind of stuff I would build.



I agree with Bob; an arduino verges on overkill for a project like this.

Let me know if you'd like a high-speed (nano seconds!) photodiode.
What wavelength would I need to use for lightning?

I saw those on Digikey. Looks like a simple circuit with an opamp and optoisolator

04-29-2019, 01:16 PM   #9
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Even if it borders on overkill, it's at the same time simple and flexible with respect to e.g. delays, implementing MLU, troubleshooting timing etc. I used an arduino and a prototype board for exactly the same kind of trigger, just using a spark instead of lighting for Playing with Fire - PentaxForums.com at macro scale, with some particular timing requirements. Using a photo-diode to detect the sparks, I needed an amplifier (simple DC opamp) though for the analog input, but the light intensity will likely be on a different order of magnitude.
04-29-2019, 03:55 PM   #10
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QuoteOriginally posted by Riggomatic Quote
What wavelength would I need to use for lightning?

I saw those on Digikey. Looks like a simple circuit with an opamp and optoisolator
The optical response of the diodes peaks in the infrared, but they are sensitive over a wide range of wavelengths (do a search on SFH 229 or SFH 309 for typical values). So, don't bother/worry about any kind of optical filtering - just expose them to the lightning. I think the trickiest part will be having some kind of a differentiator circuit - you will want to crank up the sensitivity of the diode (use a big resistor - 100k or more; hurts the time constant a bit, but still in the microseconds) to "see" the lightning, but it will be getting lots of ambient light as well. You want to be able to pick out a sudden increase in light intensity. The diodes also tend to have a narrow angle of sensitivity, so you may need a diffuser in front.

Yeah, I got mine from Digikey - bought 5 of them, 'cause the postage was more than the diodes otherwise!! I think they were 60 cents a piece for QSD2030s.
04-29-2019, 04:09 PM   #11
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QuoteOriginally posted by AstroDave Quote
The optical response of the diodes peaks in the infrared, but they are sensitive over a wide range of wavelengths (do a search on SFH 229 or SFH 309 for typical values). So, don't bother/worry about any kind of optical filtering - just expose them to the lightning. I think the trickiest part will be having some kind of a differentiator circuit - you will want to crank up the sensitivity of the diode (use a big resistor - 100k or more; hurts the time constant a bit, but still in the microseconds) to "see" the lightning, but it will be getting lots of ambient light as well. You want to be able to pick out a sudden increase in light intensity. The diodes also tend to have a narrow angle of sensitivity, so you may need a diffuser in front.

Yeah, I got mine from Digikey - bought 5 of them, 'cause the postage was more than the diodes otherwise!! I think they were 60 cents a piece for QSD2030s.
Thank you! I've been told by our EE at work that I scare him, since I play around with electrical items, scrounge around in the steel hopper (lots of industrial buttons, motor starters, boxes...).
I'm an ME, and he doesn't think I should be playing around with that stuff.

But how else are you supposed to learn.
04-29-2019, 04:29 PM - 2 Likes   #12
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QuoteOriginally posted by Riggomatic Quote
Thank you! I've been told by our EE at work that I scare him, since I play around with electrical items,
Keep the voltages below 24 V or so, and you can't get hurt!

I learned, too, by hands-on experience.

"How do you learn good judgment - from experience
How do you get experience - from bad judgment!"
05-16-2019, 06:54 PM   #13
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Didn't work as expected. Too many flashes in the clouds, and my $6 trigger just wasn't sophisticated enough.

I managed this one with the click-click-click-delete-delete-delete method. It was mostly in the cloud lightning, and only caught glimpses of bolts.

05-17-2019, 07:25 AM   #14
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Try the output of a cheap AM radio receiver (one of those pocket sized ones with an earphone output). If you tune it to a space between stations (which might be difficult depending on where you are), and use the audio output as a trigger, it would be more reliable than the photo detector though it may pick up some things other than the lightning. A lightning strike will produce a good audio spike which you can use with a comparator (or the Arduino) to trip your shutter. The advantage is that you don't have to have a certain amount of light on the sensor or have it pointed in the right direction. Also, it could be a tad bit faster than a photoconductive cell since the pulse is directly produced by the lightning strike with no delays whatsoever. A problem you'll have with the photodetector route, no matter what type of detector you use, is that you have to get the flash on it with a certain intensity. That can vary depending on clouds and distance to the strike. Again, be careful (I'm referring to the lightning and not your electronics construction) and good luck!!!
05-17-2019, 10:53 AM   #15
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QuoteOriginally posted by Bob 256 Quote
Try the output of a cheap AM radio receiver (one of those pocket sized ones with an earphone output). If you tune it to a space between stations (which might be difficult depending on where you are), and use the audio output as a trigger, it would be more reliable than the photo detector though it may pick up some things other than the lightning. A lightning strike will produce a good audio spike which you can use with a comparator (or the Arduino) to trip your shutter. The advantage is that you don't have to have a certain amount of light on the sensor or have it pointed in the right direction. Also, it could be a tad bit faster than a photoconductive cell since the pulse is directly produced by the lightning strike with no delays whatsoever. A problem you'll have with the photodetector route, no matter what type of detector you use, is that you have to get the flash on it with a certain intensity. That can vary depending on clouds and distance to the strike. Again, be careful (I'm referring to the lightning and not your electronics construction) and good luck!!!
Interesting! I'll look into that option as well.

Shots are being taken from inside my garage, over looking the neighborhood. Although it would be safer to have the trigger, and be inside the house.
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