What response time do those PIR motion sensor elements have? - Page 1
Forum section: electronics / projects

author: Deactivated-1
author_rank: Frequent Contributor
timestamp: June 10, 2022, 02:28:41 pm
content: the ones with the metal can, the window for creeping, and 3 legs.couldn't find the specification anywhere but I don't know what the sensor itself is called so no wonder.I'm planing to use it to trigger a camera to capture lighting, why am I using a motion sensor to capture change in brightness? well I thought it would give me a far better change to have it work reliably than a light sensitive resistor... but just a thought.btw an example of a sensor of which I'm walking about is RE200B, not my particular sensor tho, idk what I have and I hope there's a pretty average response time for most of the cheap ones

author: Bud
author_rank: Super Contributor
timestamp: June 10, 2022, 03:15:54 pm
content: There is plenty of specs can be found, go to Digikey, filter for PIR sensors and use links to the datasheets.I recall raw sensors with no lens are 60-70 degree, with a lens 120-180 degree aperture.However they are designed to sense the differential change as the object moves sidewise. They are not good for detecting vertical movements, slow movements or heads on movements. As to triggering on lightning events i doubt about their speed or if they even react on it. Check the datasheets for delays. The other delay will come from the camera.

author: HwAoRrDk
author_rank: Super Contributor
timestamp: June 10, 2022, 03:52:15 pm
content: Am I wrong, or will a PIR sensor not work for OP's application? I believe they only sense motion from warm bodies - i.e. humans and animals.

author: Bud
author_rank: Super Contributor
timestamp: June 10, 2022, 04:01:00 pm
content: Not sure if he means lighting as in an electric bulb, or lightning as in lightning bolt. PIR may react to direct sun light, but they are not light sensors. They are infrared devices but designed to trigger on heat emitting moving object, not static heat source.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: June 10, 2022, 05:02:48 pm
content: If you have a need for speed, it's hard to beat a good old fashioned reverse biased pin photodiode. Look for the old Burr-Brown app notes on building high speed amplifiers for them.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: June 10, 2022, 05:25:32 pm
content: I'm not sure about the PIR sensors themselves, but the circuitry around them is usually a very low frequency coupled high gain AC amplifier. Something like a low pass filter with a max frequency of 2Hz.And what do you want to trigger it with?Its quite possible that LED lighting does not have enough IR radiation to trigger your sensor. Although I've seen it a few times that PIR sensor based lighting keeps blinking because it re-triggers itself when the light turns off. Silly cheap circuits, yuch!If you want a master / slave flash for photography, then start by matching the sensor to the light source.LDR's are also quite slow but there are lots of photo diodes and transistors optimized for various frequencies.In the good old days it was a fun project to saw open old TO-3 transistors and expose their die to light to get a big phototransistor.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: June 10, 2022, 05:44:31 pm
content: Lightning is a Huge DC current through a km long antenna of ionized air. All lightning detectors I've seen use some form of radio antenna to pick up the electromagnetic field.Lightning can also be obstructed by buildings trees or clouds.Another way is to simply use the internet.There are plenty of (weather) web sites that log and view all lightning bolts worldwide in nearly real time.For example, the fist that popped up in a search is:https://www.lightningmaps.org

author: Doctorandus_P
author_rank: Super Contributor
timestamp: June 10, 2022, 05:51:52 pm
content: These have mostly antenna's to pick up the electromagnetic fields:https://duckduckgo.com/?q=lightning+detector+schematic&t=h_&iax=images&ia=imagesI think that an old AM radio also is an excellent lightning detector, and it does not matter to which frequency you tune it.

author: Marco
author_rank: Super Contributor
timestamp: June 10, 2022, 07:05:55 pm
content: The problem with VHF antennas that they aren't very directional, with the large dynamic range of lightning strikes you'll be shooting a lot of duds.You could go for microwave, but why not just go straight to what you're interested in? Which is to say optical, a visible light photodiode with a lens to only capture the part of the sky the camera is looking at.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: June 10, 2022, 08:24:49 pm
content: Using the visible light is a reasonable if you're interested in making pictures. It is also probably easier to test if there is no lightning around.On the other hand, having 100 false triggers is not a problem with modern digital camera's. It's not like you're wasting expensive film and batteries are also easy to recharge.If you go for the RF antenna, then maybe adding a visual indicator is a good idea, some kind of bargraph that shows the intensity, so you can adjust it to expected intensity.

author: rstofer
author_rank: Super Contributor
timestamp: June 11, 2022, 06:08:58 pm
content: https://www.sparkfun.com/products/15441

author: Doctorandus_P
author_rank: Super Contributor
timestamp: June 12, 2022, 12:31:51 am
content: I like the Element 14 video much better.It starts with SDR to sniff the surroundings and using a spark generator to trigger the sensor, and after that it goes in depth about using the AS3935.I did not see the whole video though. One thing to look out for you is the reaction time. I don't know if this sensor has a quick enough output to trigger your camera.

author: floobydust
author_rank: Super Contributor
timestamp: June 12, 2022, 03:11:43 am
content: AMS AS3935 Franklin IC is a piece of garbage. The problem is using a tank circuit around 500kHz still picks up AM radio, the bandwidth is too wide. It would false-trigger based on AM radio crosstalk, especially bad with male talk show voices lol. Spurious counts and I abandoned it. You have to use E-field or superheterodyne.I found the loopstick antennas only work well in one axis. So a horizontally-oriented antenna will pick up cloud-cloud lightning in one direction, not 90 degrees so as well as it misses ground strikes which are vertically polarized.For photography I've seen a phototransistor used, or very long exposure times to capture the strikes. If professional use, a UV sensor could be very good but not sure if a bit of sunlight would scuttle that.This year I'm going VHF and seeing how that does at detection, for storm warnings researchers say it's the best.

author: Kleinstein
author_rank: Super Contributor
timestamp: June 12, 2022, 08:18:36 am
content: Quote from: ELS122 on June 10, 2022, 05:35:43 pmNo need to cut an optocoupler: phototransistors are easily available as seprate parts. If desparate to find one from scrap: old mechanical nice usially had some in there incremental decoders.The optical spectrum light is probably a good bet for a fast reaction and not too many false triggers, as one can limit the sensitive angle relatively easy.A photodiode would be slightly faster and this could help to trigger only on the fast rising signal - many other lights (e.g. passing car) turn on relativey slow.The question is if the cameary is fast enough to react.

author: Marco
author_rank: Super Contributor
timestamp: June 12, 2022, 08:39:39 am
content: Alternatively, brute force it. Get an Arducam with say a Raspberry Pi and continuously shoot images in a circular buffer with minimum shutter speed for the framerate and check those for brightness. You can keep a couple of the images before detection in case lower intensity flashes were in there.Then you can combine them into whatever exposure time you want during post processing.

author: Peabody
author_rank: Super Contributor
timestamp: June 12, 2022, 02:08:18 pm
content: The CHDK project for Canon PowerShot point-and-shoot cameras loads a Lua script into the camera for lightning detection. So it uses the camera's sensor as the detector. And it works for any motion detection. I used CHDK for kite aerial photography, and for timelapse, but never tried motion detection. But my understanding is that the scripts work quite well.The idea of loading additional temporary firmware into the camera's ram was migrated to Canon DSLRs as the Magic Lantern project, and I believe it comes with a Motion Detection function in its menu. So if you're shooting with a Canon, you may not need any circuit at all.

author: mycroft
author_rank: Regular Contributor
timestamp: June 12, 2022, 02:53:46 pm
content: This is more from a historical perspective:https://books.google.com.br/books?id=ng-G4fxbMskC&pg=RA17-PA19&lpg=RA17-PA19&dq=Lightning+detector+is+photocell-and-amplifier+circuit+detecting+flashes+of+light+against+steady+or+slowly+varying+bright+background.+Measures+luminous&source=bl&ots=i71c3X8aiP&sig=ACfU3U39x6DV9C-DkDzDYNzfbv_TgQdrYQ&hl=en&sa=X&ved=2ahUKEwiF8JqNlKj4AhVIArkGHblQAhAQ6AF6BAggEAM#v=onepage&q&f=false

author: ledtester
author_rank: Super Contributor
timestamp: June 12, 2022, 03:34:07 pm
content: There are some commercial products, e.g.:https://www.bhphotovideo.com/explora/photography/hands-review/lightning-activated-shutter-triggers-ubertronixThat page says in part:QuoteFrom the pictures it looks like the sensor is a single T-1 3/4 device.Also found the "Lightning Trigger" LT-3 and LT-IV:https://lightningtrigger.com/specifications.aspxSome marketing claims:Quote

author: tepalia02
author_rank: Regular Contributor
timestamp: June 15, 2022, 12:33:38 pm
content: sorry. Can't understand which PIR sensor you're referring to? Are you talking about the HCSR501 that we commonly use?https://www.elektor.com/hc-sr501-pir-motion-sensor-module

author: Marco
author_rank: Super Contributor
timestamp: June 30, 2022, 08:49:41 pm
content: With minimum speed I meant maximum slownessI should have said longest exposure time for the framerate.