User avatar
morcup
Posts: 4
Joined: Sun Apr 28, 2019 5:50 pm

Lightning Sensor and external camera shutter release

Sun Apr 28, 2019 6:04 pm

Hello all, first post here, hopefully I'm in the right place. :?:

I am hoping to make a lightning sensor and shutter release for my digital camera. Does anyone have any experience in this?
I found a https://scribblesandsnaps.com/2015/02/2 ... y-cameras/ that has good information on the shutter release portion, but may need help along the way, especially with the programming/tuning aspects of it.

I am completely new to Raspberry Pi (have not yet purchased one), mostly inept at programming, and capable of doing the hardware aspects of this project. I have a friend who tells me he is good with Pi, so feel free to explain things in a technical manner, as I can pass it along to him.

My camera is a Sony A7ii, and I will likely be using the Pi 3 B+

User avatar
Joel_Mckay
Posts: 289
Joined: Mon Nov 12, 2012 10:22 pm
Contact: Website

Re: Lightning Sensor and external camera shutter release

Mon Apr 29, 2019 7:24 am

This camera likely supports tethering:
http://gphoto.org/proj/libgphoto2/support.php

People use several tricks to trigger the shutter in a lightning storm, and as they must be fast it usually limits the complexity of the circuit.

In general, with a high-end capture rig ( https://www.krontech.ca/ ) you simply externally trigger the camera to store a recent high-speed moment you wanted to recover.

For consumer equipment used by some, it is usually a Radio-receiver circuit hooked up to a remote burst-capture shutter trigger. Unlike audio, the radio EMI noise created by a strike will tend to occur at around the same time as a strike event. ( https://en.wikipedia.org/wiki/Comparator )

Probably not a great idea to stand next to an aluminum tripod in a lightning storm ;-)

User avatar
HawaiianPi
Posts: 4463
Joined: Mon Apr 08, 2013 4:53 am
Location: Aloha, Oregon USA

Re: Lightning Sensor and external camera shutter release

Mon Apr 29, 2019 9:42 am

The way you photograph lightning is to use a small aperture so little light gets in and lock the shutter open, then close the shutter after the strike (or several, depending on how many you want in the frame). Timing is easy that way.
Lightning1.jpg
Lightning1.jpg (39.56 KiB) Viewed 492 times
My mind is like a browser. 27 tabs are open, 9 aren't responding,
lots of pop-ups...and where is that annoying music coming from?

User avatar
morcup
Posts: 4
Joined: Sun Apr 28, 2019 5:50 pm

Re: Lightning Sensor and external camera shutter release

Mon Apr 29, 2019 12:05 pm

HawaiianPi, thanks for sharing, nice photo. I will remember to do that next time I try to catch a storm.

Joel_Mckay, thank you for the information and links. Do you think that there would be too much latency to use a raspberry pi to trigger the camera for lightning? I read that the average lightning strike has a duration of .2 seconds, while each stroke is 60-70 microseconds.

If the pi could work, do you know what frequency range I should be looking at for the radio receiver circuit?

As for being next to the tripod during the storm, it is probably a good idea to keep some distance to be on the safe side. That said, the info on this website ( http://stormhighway.com/small_metal_obj ... g_myth.php ) makes me feel a bit safer about being out there.

Andyroo
Posts: 3832
Joined: Sat Jun 16, 2018 12:49 am
Location: Lincs U.K.

Re: Lightning Sensor and external camera shutter release

Mon Apr 29, 2019 3:38 pm

This video popped into my feed a few days ago https://www.youtube.com/watch?v=zdRKhaDI7Ms

$25 with a very long range (40Km they quote) and built for the Arduino boards BUT it has SPI and I2C on it so you can connect it if you are up for a bit of coding :lol: :roll: :lol:
Need Pi spray - these things are breeding in my house...

User avatar
morcup
Posts: 4
Joined: Sun Apr 28, 2019 5:50 pm

Re: Lightning Sensor and external camera shutter release

Mon Apr 29, 2019 3:49 pm

Thanks Andyroo. That will be very helpful.

User avatar
morcup
Posts: 4
Joined: Sun Apr 28, 2019 5:50 pm

Re: Lightning Sensor and external camera shutter release

Sun May 05, 2019 2:32 am

Update on the project.

tl;dr
Got a Pi 3B+
Followed the guide for the shutter release (using octocouplers instead of transistors, as I found in an update to the original guide).
Have a basic prototype for using LDRs , but might need a way to convert the analog signal to digital.
Have more questions, and a desire to reduce latency in the circuit design.
Hope to contact the author with some questions.
Ordered the lightning detector circuit, put it on the backburner for now (still interested though).


So, that tl;dr got a little bit long, but it sums it all up pretty well. I'll go into a bit more detail here and ask a few questions as well.

First, the link to the update to the original guide: https://scribblesandsnaps.com/2015/02/2 ... ocouplers/

I managed to not see the link to the update near the end of the first guide until a few days ago. I think the transistors cost about $2, and will be useful in other projects, so no loss there.

Resistance
The prototype octocoupler I made according to the guide seems to be functioning, in the sense that it is reducing resistance across the correct wires (focus to camera ground, and shutter to ground) when the led is on, but I don't know how much resistance is tolerable/recommended for the wires leading to the camera. There are varibles- like led brightness, LDR design resistance, and what percent of the light is actually hitting the LDR (my prototype now is using green electrical tape, but I have heat shrink for the real deal).

Latency
I've found and glanced at a few component sheets to look at response times, but not done any serious calculations yet. I've already got all the parts for the project (minus a possible need for an analog to digital converter), so the experience gained makes this worthwhile to me even if the project does not succeed.

I'm using a fairly cheap multimeter right now, but not getting any idea of response time in the circuit. Is there a good way to measure this, perhaps through a little circuitry or having the Pi read out signals at pins (with timestamps or similar).
Another latency source that I have no idea about is how long the lightning detected signal will take to be handled by the Pi and sent to the focus/shutter wires. The scripts I have used are in python, is this a good way, or should I look into another method?
Focus/shutter delays- the program in the guide has a half second delay between focus and shutter. That's fine for general use, but I do not know if that is just a generic value, or a minimum. If it is identical to the way the camera button works (half press to focus, full press for shutter), it should be fine to have no delay between the two signals. I will have to look more into that, as well as pre-locking the camera focus.

Lightning Detector
Well, that thing is just really cool, so I got it. I am in pretty deep already with the LDR method of detection right now, so I will look into making more use of the lightning detector when I have finished the LDR method.

Programming
The programming aspect of things has been a challenge for me, but the scripts have been short enough and usually commented well enough for me to be able to figure out what is going on, and make basic customizations to them. I'm sure this is the area I will need most help in, but I don't have specific questions just yet.

Analog/Digital Conversion
The LDR will have a drop in resistance when light hits it. This will produce a voltage drop? How would I convert that to a usable signal for the Pi? I need to do more research, but it seems like an ADC would be useful here?


If you made it here, thanks for reading. Please don't feel obligated to answer all of the questions, many of them are partially here in part to help me conceptualize what has been done and what needs doing.
If anyone is interested, I have a few pictures / short movies at various stages of the project.

Return to “Automation, sensing and robotics”