Ping))) now has a wider detection range?
LucM
Posts: 5
Greetings!
We've been using Ping))) sensors to implement a passenger-counting system in city buses. We use a pair of sensors set up next to (or near to) the main door of the bus to determine whether passengers are going in or out. We've had our problems with this system, as we have several types of buses to contend with, and "real life" can get somewhat chaotic on a day-to-day basis, but we're working to remedy these problems with adjustments to our BasicStamp programming.
However, recently we've encountered another, more serious problem. As some of the installed sensors became defective, we had to order some new ones. We discovered that the newer sensors have a much wider detection "cone" (roughly twice as wide as the sensors we initially installed) and this makes our twin-sensor passenger-counting system practically non-functional, because either sensors can now detect passing objects in a random manner. We need Ping))) sensors that have a narrow detection cone, which is what we had up until recently.
Is there any way to adjust the detection "cone" in Ping))) sensors?
Thanks,
We've been using Ping))) sensors to implement a passenger-counting system in city buses. We use a pair of sensors set up next to (or near to) the main door of the bus to determine whether passengers are going in or out. We've had our problems with this system, as we have several types of buses to contend with, and "real life" can get somewhat chaotic on a day-to-day basis, but we're working to remedy these problems with adjustments to our BasicStamp programming.
However, recently we've encountered another, more serious problem. As some of the installed sensors became defective, we had to order some new ones. We discovered that the newer sensors have a much wider detection "cone" (roughly twice as wide as the sensors we initially installed) and this makes our twin-sensor passenger-counting system practically non-functional, because either sensors can now detect passing objects in a random manner. We need Ping))) sensors that have a narrow detection cone, which is what we had up until recently.
Is there any way to adjust the detection "cone" in Ping))) sensors?
Thanks,
Comments
Luc, it's odd that the cone would change with the new units. Do the old and new units have different rev numbers? If so, contact Parallax tech support, give them the rev number info, and ask them what, if anything, has changed. It may also just be a matter of overall sensitivity, since the cone angle is a function only of the ultrasonic frequency and the active diameters of the transducers.
-Phil
Thanks for the suggestions Phil, I'll check and compare the rev numbers next week (when I go back to the client's bus garage) before I contact Parallax for info. All I can say for now is that I can really see the difference when I approach the palm of my hand near the sides of the cone. The cone really is wider on the newer sensors. Way too wide for our operational specs.
Sounds reasonable. Does the same apply for a baffle on the receiver?
-Phil
http://gadgetgangster.com/find-a-project/56.html?projectnum=138
Programmable range, sensitivity, and output power.
I don't work for them, just thought it was a great product.
Jim
-Phil
http://www.gadgetgangster.com/find-a-project/56?projectnum=361
John Abshier
- Phil Pilgrim: All the units I have here (new ones and older ones) have the same rev number (namely 'REV B'). I can't spot anything different between the newer and older units just by looking. About your sensivity-reducing foam idea, you have to keep in mind that city buses are the most hostile environments for electronic equipment, not just because of vibration and wide temperature/humidity variances, but because of "casual" abuse by everyday bus users and sometimes even disgruntled bus drivers. In each bus, we had to encase the sensor pairs (and central BS boards) into custom metal casings, and even then, the sensors extremities are still vulnerable to poking fingers (mostly by little kids who can't control their destructive impulses). Foam add-ons over the sensors probably wouldn't last a week. People just love to scratch anything that's made out of thin foam, for some mysterious freudian reason.
- Publison: The programmable sensor is interesting, but just looking at the 5-pin connector tells me that such a change in technology would be expensive to implement (R&D, new wires inside each bus, software protocol adjustments, maintenance of more than one type of sensor on the field, etc.), and my boss probably won't go for it unless I can provide proof that I can actually control the detection cone with it, in a precise manner. Company politics being what they are, I'd have trouble just getting the green light from my boss to order a single unit for testing purposes.
- John Abshier: There's no room for such a large reflector inside the buses.
Now with all this said, I'll be contacting Parallax shortly... and keeping my fingers crossed.
Just to clarify on the 5 pin connector for the programmable sensor, in Ping mode only 3 of the 5 pins are used, with the same wiring and protocol as the Ping. So you could possibly do a direct swap depending on the mechanics around the connector. With that said, I think Phil is on the easiest track with decreasing the Ping sensitivity. I have found foam works well, as Phil suggests, so maybe you can protect the foam with some wire screen? Another possibility might be a divider between the two transducers (sort of a nose to the transducer eyes) that shields the side view of each transducer in opposite directions. Also are you looking at the distance that the pings are measuring or just that they had a detection? It seems that even with side detections the distance will tell you which sensor they are closer to.
--Ed
PS: Jim and John: Thanks for the reference....
I would email them again...
Hello Ed.
I attached to this reply a picture of the front side of the metal casing we're using, just to give you a better idea of how we're using the sensors. This is an image I whipped up from scratch in less than a minute, so the distance between the sensors is not exact compared to real life. As you can see, putting some foam and wire screen over the holes is not exactly an easy thing to implement. Also, adding a "nose", as you suggest, is not a good solution here because passengers can bump or hit the nose and hurt themselves as they go in and out of the bus. Our clients will never accept that kind of modification.
To answer your other question, we look at the distance value when detecting passengers. If the reading falls under a certain threshold, we record it as "activity". This "activity" in front of the two sensors is analyzed to determine if a passenger is going in or out of the bus.
It is easy to overlook issues that are created just from mounting sensors like this and other devices. I rarely see it mentioned if mounting points are isolated or tied to the ground on the device. Also notes/warning about clearances and keeping certain portions of a device electrically isolated. Without considering that one can often create connections that they didn't intend and perhaps even create a ground loop.
Robert
What about a rectangular piece in the middle of your front side that blocks the sensors from seeing the middle? Or angling the sensors outward so they have less overlap?
--Ed