Forums

optical lightning detector

Started by Cydrome Leader June 24, 2014
I want to concoct a trigger to fire my camera when there's lightning in 
the area of where the camera is pointed. I do not want one of the RF burst 
detectors, as I don't care about lightning that's not in front of the 
camera itself. I'm thinking about some sort of photodiode mounted in a 
housing peeping through the viewfinder for actual flash detection.

Past that, I'm not too sure of what's next.

Has anbody build something like that before? I'd like to somehow be able 
to tune the detector's sensitivity to the flash or light as well as the 
risetime of whatever it's detecting.

I've not yet tested if photographic slave modules actually pick up on 
ligtning. Has anybody ever tested this?


On Tue, 24 Jun 2014 17:51:17 +0000 (UTC), Cydrome Leader
<presence@MUNGEpanix.com> wrote:

>I want to concoct a trigger to fire my camera when there's lightning in >the area of where the camera is pointed. I do not want one of the RF burst >detectors, as I don't care about lightning that's not in front of the >camera itself. I'm thinking about some sort of photodiode mounted in a >housing peeping through the viewfinder for actual flash detection. > >Past that, I'm not too sure of what's next. > >Has anbody build something like that before? I'd like to somehow be able >to tune the detector's sensitivity to the flash or light as well as the >risetime of whatever it's detecting. > >I've not yet tested if photographic slave modules actually pick up on >ligtning. Has anybody ever tested this? >
Roll your own... might have to use a photo-tube... that was what I used in my first slave-flash when I was ~15 years old ;-) ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Jim Thompson <To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote:
> On Tue, 24 Jun 2014 17:51:17 +0000 (UTC), Cydrome Leader > <presence@MUNGEpanix.com> wrote: > >>I want to concoct a trigger to fire my camera when there's lightning in >>the area of where the camera is pointed. I do not want one of the RF burst >>detectors, as I don't care about lightning that's not in front of the >>camera itself. I'm thinking about some sort of photodiode mounted in a >>housing peeping through the viewfinder for actual flash detection. >> >>Past that, I'm not too sure of what's next. >> >>Has anbody build something like that before? I'd like to somehow be able >>to tune the detector's sensitivity to the flash or light as well as the >>risetime of whatever it's detecting. >> >>I've not yet tested if photographic slave modules actually pick up on >>ligtning. Has anybody ever tested this? >> > > Roll your own... might have to use a photo-tube... that was what I > used in my first slave-flash when I was ~15 years old ;-)
Did these tubes act like a giant light activiate SCR?
On Tue, 24 Jun 2014 18:38:38 +0000 (UTC), Cydrome Leader
<presence@MUNGEpanix.com> wrote:

>Jim Thompson <To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote: >> On Tue, 24 Jun 2014 17:51:17 +0000 (UTC), Cydrome Leader >> <presence@MUNGEpanix.com> wrote: >> >>>I want to concoct a trigger to fire my camera when there's lightning in >>>the area of where the camera is pointed. I do not want one of the RF burst >>>detectors, as I don't care about lightning that's not in front of the >>>camera itself. I'm thinking about some sort of photodiode mounted in a >>>housing peeping through the viewfinder for actual flash detection. >>> >>>Past that, I'm not too sure of what's next. >>> >>>Has anbody build something like that before? I'd like to somehow be able >>>to tune the detector's sensitivity to the flash or light as well as the >>>risetime of whatever it's detecting. >>> >>>I've not yet tested if photographic slave modules actually pick up on >>>ligtning. Has anybody ever tested this? >>> >> >> Roll your own... might have to use a photo-tube... that was what I >> used in my first slave-flash when I was ~15 years old ;-) > >Did these tubes act like a giant light activiate SCR?
I don't recall the details now... it has, after all, been 60 years, but I used it to directly fire a flashbulb. (I didn't have a strobe until a few years later.) ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Cydrome Leader wrote:

> I want to concoct a trigger to fire my camera when there's lightning in > the area of where the camera is pointed. I do not want one of the RF burst > detectors, as I don't care about lightning that's not in front of the > camera itself. I'm thinking about some sort of photodiode mounted in a > housing peeping through the viewfinder for actual flash detection.
Digital, camera? Most of them have massive delay between pushing the button and actually taking the picture. There often is a sports mode that reduces the delay. But, I suspect this will be a problem with most digital cameras, they will take a picture of black sky, a large fraction of a second AFTER the lightning. Jon
On Tuesday, June 24, 2014 10:51:17 AM UTC-7, Cydrome Leader wrote:

> I want to concoct a trigger to fire my camera when there's lightning in > the area of where the camera is pointed. ... I'm thinking about some sort of photodiode mounted in a > housing peeping through the viewfinder for actual flash detection.
With a vidicon-type camera, that could work: the image remains readable for a few microseconds after the light is received. With solid-state, though, there's a cycle of erase/integrate/readout. If you keep the camera in erase mode, the flash is over before you can get to integrate mode. Best, might be to alternate two cameras, having one always in the integrate phase, and capture the associated readout data only when a flash was detected during the integrate phase. So, you'd be discarding a lot of frames of a video feed. It's easier with film: just open a shutter, and close it if/when enough incident light is seen. Probably a used point/shoot 35mm camera is the best way to proceed; with a tripod, using an IR remote to start the exposure. Extra points for electric film advance...
Jon Elson <jmelson@wustl.edu> wrote:
> Cydrome Leader wrote: > >> I want to concoct a trigger to fire my camera when there's lightning in >> the area of where the camera is pointed. I do not want one of the RF burst >> detectors, as I don't care about lightning that's not in front of the >> camera itself. I'm thinking about some sort of photodiode mounted in a >> housing peeping through the viewfinder for actual flash detection. > Digital, camera? Most of them have massive delay between pushing > the button and actually taking the picture. There often is a sports > mode that reduces the delay. But, I suspect this will be a problem > with most digital cameras, they will take a picture of black sky, a > large fraction of a second AFTER the lightning.
the camera is fast, so lag won't be a problem, but figuring out how to adjust everything will be, as I can't summon a lightning storm at any time.
On Tuesday, June 24, 2014 1:51:17 PM UTC-4, Cydrome Leader wrote:
> I want to concoct a trigger to fire my camera when there's lightning in > > the area of where the camera is pointed. I do not want one of the RF burst > > detectors, as I don't care about lightning that's not in front of the > > camera itself. I'm thinking about some sort of photodiode mounted in a > > housing peeping through the viewfinder for actual flash detection. > > > > Past that, I'm not too sure of what's next. > > > > Has anbody build something like that before? I'd like to somehow be able > > to tune the detector's sensitivity to the flash or light as well as the > > risetime of whatever it's detecting. > > > > I've not yet tested if photographic slave modules actually pick up on > > ligtning. Has anybody ever tested this?
One strategy is to just concoct a trigger like you envisioned, the camera is in "bulb" mode which opens the shutter for say 20 seconds each time. Since lightning often occurs in clusters of strikes, you have a chance at catching the follow-on strikes. 'Pro' phtographers do this manually. The trigger has to catch a sudden burst of light. How to do? A simple way is just trigger on any bright flash. Take a bwp34 photodiode and lens. connect to a transimpedance op-amp and then to a schmitt trigger circuit to trigger the camera open for 5-30 s. I'm assumimg you have dark condx.
On Tuesday, June 24, 2014 5:34:25 PM UTC-4, haitic...@gmail.com wrote:
> On Tuesday, June 24, 2014 1:51:17 PM UTC-4, Cydrome Leader wrote: > > > I want to concoct a trigger to fire my camera when there's lightning in > > > > > > the area of where the camera is pointed. I do not want one of the RF burst > > > > > > detectors, as I don't care about lightning that's not in front of the > > > > > > camera itself. I'm thinking about some sort of photodiode mounted in a > > > > > > housing peeping through the viewfinder for actual flash detection. > > > > > > > > > > > > Past that, I'm not too sure of what's next. > > > > > > > > > > > > Has anbody build something like that before? I'd like to somehow be able > > > > > > to tune the detector's sensitivity to the flash or light as well as the > > > > > > risetime of whatever it's detecting. > > > > > > > > > > > > I've not yet tested if photographic slave modules actually pick up on > > > > > > ligtning. Has anybody ever tested this? > > > > One strategy is to just concoct a trigger like you envisioned, the camera is in > > "bulb" mode which opens the shutter for say 20 seconds each time. Since > > lightning often occurs in clusters of strikes, you have a chance at catching > > the follow-on strikes. 'Pro' phtographers do this manually. > > > > The trigger has to catch a sudden burst of light. How to do? A simple way is > > just trigger on any bright flash. Take a bwp34 photodiode and lens. connect to > > a transimpedance op-amp and then to a schmitt trigger circuit to trigger the > > camera open for 5-30 s. I'm assumimg you have dark condx.
And, in case the lightning flash is weak, I wonder about the following comparator circuit. Assuming the photodiode is put in a transimpedance configuration, a standard way of wiring PD's to minimize capacitance effects. Now suppose you take a sensitive comparator and put the output signal of the PD amp on BOTH input pins of the comparator. ONE pin of the comparator has a cap to ground to provide a bit of time delay. When a fast changing signal comes through, one pin will lag and the comparator will fire. Slower signals will not fire it, and its schmitt one shot. I wonder if anyone has more insight into this type of simple circuit - a delay comparator in time. Be interested in hearing about. The two signals must obviously be isolated from each other -
On Tuesday, June 24, 2014 6:23:33 PM UTC-4, haitic...@gmail.com wrote:
> On Tuesday, June 24, 2014 5:34:25 PM UTC-4, haitic...@gmail.com wrote: > > > On Tuesday, June 24, 2014 1:51:17 PM UTC-4, Cydrome Leader wrote: > > > > > > > I want to concoct a trigger to fire my camera when there's lightning in > > > > > > > > > > > > > > the area of where the camera is pointed. I do not want one of the RF burst > > > > > > > > > > > > > > detectors, as I don't care about lightning that's not in front of the > > > > > > > > > > > > > > camera itself. I'm thinking about some sort of photodiode mounted in a > > > > > > > > > > > > > > housing peeping through the viewfinder for actual flash detection. > > > > > > > > > > > > > > > > > > > > > > > > > > > > Past that, I'm not too sure of what's next. > > > > > > > > > > > > > > > > > > > > > > > > > > > > Has anbody build something like that before? I'd like to somehow be able > > > > > > > > > > > > > > to tune the detector's sensitivity to the flash or light as well as the > > > > > > > > > > > > > > risetime of whatever it's detecting. > > > > > > > > > > > > > > > > > > > > > > > > > > > > I've not yet tested if photographic slave modules actually pick up on > > > > > > > > > > > > > > ligtning. Has anybody ever tested this? > > > > > > > > > > > > One strategy is to just concoct a trigger like you envisioned, the camera is in > > > > > > "bulb" mode which opens the shutter for say 20 seconds each time. Since > > > > > > lightning often occurs in clusters of strikes, you have a chance at catching > > > > > > the follow-on strikes. 'Pro' phtographers do this manually. > > > > > > > > > > > > The trigger has to catch a sudden burst of light. How to do? A simple way is > > > > > > just trigger on any bright flash. Take a bwp34 photodiode and lens. connect to > > > > > > a transimpedance op-amp and then to a schmitt trigger circuit to trigger the > > > > > > camera open for 5-30 s. I'm assumimg you have dark condx. > > > > And, in case the lightning flash is weak, I wonder about the following > > comparator circuit. Assuming the photodiode is put in a transimpedance > > configuration, a standard way of wiring PD's to minimize capacitance effects. > > > > Now suppose you take a sensitive comparator and put the output signal of the PD > > amp on BOTH input pins of the comparator. ONE pin of the comparator has a cap to > > ground to provide a bit of time delay. When a fast changing signal comes > > through, one pin will lag and the comparator will fire. Slower signals will not > > fire it, and its schmitt one shot. > > > > I wonder if anyone has more insight into this type of simple circuit - a delay > > comparator in time. Be interested in hearing about. > > > > The two signals must obviously be isolated from each other -
OH, and bear in mind that if you get 1/500 hits with a digital camera, its OK, since you just erase the 499 and keep the one. This greatly relaxes the precision requirement of your detector in time and space. Of course the more you miss, the longer you have to wait for a good pic. A detector that shoots and misses often may be better. I thought about this area a bit because I wanted to catch grasshoppers springing from grass into flight. A trick is to use a bright flash even in daylight to catch them. But they are very fast, so I had trouble with manual shooting, as they can hear you coming and spring fast.