LPR day & night Success with DIY setup

m00st

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Being an active reader on IP Cam Talk I have been working on my own 'cheap' ANPR / LPR setup for the past two and a half years or so. At the end of the day, it's not been the least expensive option, but certainly enjoyable as i've learnt a lot on cameras, infrared and capturing license plates since then :). And while I am happy with the results today, I may still end up buying something like a DH-IPC-HFW7442H-Z4 ;).

So let's start with where I am today; a somewhat inconspicuous waterproof (I hope) box housing both a 2MP camera and a 850nm IR illuminator. It provides 24/7 images to computer running an OpenALPR / Watchman agent. Here are both the darkest and lightest images from the last day:

Screenshot 2020-07-12 14.34.15 (1).jpg Screenshot 2020-07-12 14.35.23.jpg

Both images are taken at the same 1/2000 shutter speed. The camera is a simple 2MP box camera with CS mount, IMX291 sensor and Hi3516 chipset (link to AliExpress listing). I ordered with a 5 - 100mm lens and that's the one I use now. May switch to a much more compact 25mm lens or so later. The camera uses your standard chinese XMeye firmware which requires IE and a horrible plugin to be configured. No ability to switch profiles that I am aware of, but I guess I was lucky being able to use a fixed shutter time with both darkness (and sufficient IR light) and full sunlight. Hats of to the OpenALPR algorithm since it is pretty good even at washed out images. The 850nm IR illuminator used is one that can be focussed (link to AliExpress listing) and as long as the camera and the illuminator are aligned, it works pretty well. It's probably focussed wider than needs to be so might even be able to throw some more IR at the license plates. Good thing all license plates in Europe are reflective.

Both camera and illuminator are in a grey 'electronics' box that is used for installation purposes mostly. It is supposed to be IP65 waterproof, but obviously I had to make a few holes on it. One hole is for a UTP cable to go trough and using a grommet I hope it will keep the water out. For the camera and the IR illuminator to 'see through' I've used black 962 perspex or plexiglass and silicone kit to keep the water out. To the naked eye, this is 962 pespex looks like black plastic, but it passes infrared light. So while humans can't see through, my camera can see the infrared part of the spectrum. But that's okay, it means I'll also need to use the infrared mode during the day. This is what the box looks like:

IMG_0716.jpg IMG_0719.jpg


For powering the camera and the IR illuminator I've used a simple 802.3af PoE to 12v converter of AliExpress. It supposedly delivers a max of 2A at 12v (24 watts). Should suffice as the illuminator uses < 5 Watt with a 3W led and probably even less for the camera. Every time I've checked my PoE switch it reports < 6 watts so that is not bad. Less power also means less heat so hopefully the temperature inside stays below the point of damaging electronics as I really don't see much opportunity for active cooling. Today was a sunny day and the outside temp of the box was 45 degrees C in the sun. No idea what the inside temp is, maybe I should have put an esp8266 with a temperature sensor inside was well. I guess I can always still do that..

During the night (as dark as it gets), this is how the box looks, positioned a few centimeters from the ground with a slight upward looking view:

IMG_0820.jpg
The purple glow is a very vague red circle for the human eye.

(continued in post 2)
 

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m00st

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All in all I am quite happy after some failed attemps. Some learnings over the pas 2,5 years:
  1. Doing this yourself means a lot of reading forums, trying and failing a few times before it works
  2. OEM Chinese cams come with horrible and limited firmware
  3. Wireless is unreliable
  4. Creating a DIY LED board/emitter is nice but not necessary
  5. 962 perspex is great for hiding your camera and/or IR sources

Stuff I still need to look at/want to improve on:
  1. control the shutter time / profiles without using the IE plugin of XMeye
  2. Hiding the entire thing in a black flower pot (again using a black perspex window)
  3. Smaller camera with a fixed lens (either CS mount or m12)
  4. Using the OpenALPR webhook to store and/or alert on certain license plates

A fun project, still stuff to tinker with. Here are some more pictures:

Screenshot 2020-07-12 17.55.24.jpg Screenshot 2020-07-12 17.56.45.jpg Screenshot 2020-07-12 17.57.17.png

Let me know if you have tips, suggestions or questions.
 

m00st

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Cars are between 20 and 23 metes (65 - 75 feet) away. It's a bit of a trade-off between the throw of the IR light and the angle.
 
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