RE: BT_Sentry : Zero Emission Detection

aspork42 — Sat, 12 May 2018 20:27:01 GMT

Another thought - How would the system do at detecting motorcycles and bicycles?

RE: BT_Sentry : Zero Emission Detection

DAB — Wed, 09 May 2018 20:15:55 GMT

Nice update Mark.

Have you considered either a laser rangefinder or ultrasonic detector shooting across the driveway?

You could trigger off a change in distance.

DAB

RE: BT_Sentry : Zero Emission Detection

BigG — Wed, 09 May 2018 09:53:00 GMT

I have looked at a similar problem before.

I know Bluetooth tags would work quite well here as these could be left in cars of friends and family should these cars not have Bluetooth. They also happen to be cheap and operate off batteries for +years.

Detectors

For general vehicle detection, it may be worth trying a 3d magnetic sensor e.g. an old reliable would have been the freescale mag3110 but there are now newer and better out there. I found these to work quite well for vehicle detection and much cheaper than a detection loop. These only cost a few dollars and there are plenty of options out there. To ensure vehicle detection, I found that they also need to be placed on the road surface and ideally be underneath the car to ensure reliable detection of the vehicle body mass. The problem I experienced, when testing for vehicle parking, is that the vehicle also blocks the Bluetooth signal somewhat.

I quite like your Time Of Flight sensor option, but as I see you say in your comments another fall back option is PIR. This is actually not a bad option in my opinion as you can get a number of different alarm scenarios - 1. if PIR is triggered but not the magnetic sensor then it is probably a human walking up the driveway, and 2. if PIR and magnetic but no Bluetooth then an unknown vehicle etc. etc.

If you do decide on PIRs I found that for outdoors a more reliable PIR configuration to have is a dual PIR setup using a lens with wide horizontal field of view but more limited narrow vertical field of view. This can help reduce false alarms.

Here is an illustration I had made up sometime back:

[View:/resized-image/__size/620x372/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-253b55a6-c2f9-4648-abce-f3e4392c2502/7651.contentimage_5F00_187261.png:620:372]

Another, somewhat more expensive, option to consider instead of PIR / time-of-flight would be the AMG8833 Grid-EYE sensor from Panasonic. Adafruit have a breakout board for this.

Anyway, good luck and I look forward to seeing this great idea getting developed.

Colin.

RE: BT_Sentry : Zero Emission Detection

fmilburn — Wed, 09 May 2018 00:36:26 GMT

I wonder how long it would take to get one of my RCWL-0516 units to you so you can get started. Let me know by PM if you want me to try. Hopefully your order will arrive soon.

RE: BT_Sentry : Zero Emission Detection

genebren — Tue, 08 May 2018 22:25:48 GMT

Nice update on your project. There are a lot of trade offs to be made as you learn more about your hardware/performances. Good luck sorting out the variables.

Gene