difference between PING and INFRA-RED sensor

sushiandmorihiko

hello,

i am wandering on whats the difference between these 2,
i tried infra-red that comes with the boe-bot kit but (page 271 where there are 5 zones of distance) the value keeps flactuacting and not stable--is it normal--i mean if it is in zone 2,it will move to zone 1 and 3 quite often although i didnt shift my hand.

i wonder if PING is much more accurate(not sure wat is this supersonic device).

thank you

Chris Savage

Hello,

IR and Sonar work on different bands of the EM spectrum. Each has its pros and cons. IR can be affected by the ambient lighting conditions. It can also be affected by the reflectivity of the surface the light bounces from. Both can explain the readings you’re seeing. Skin isn’t really a good reflective surface anyway, especially when it comes to consistency.

Sonar doesn’t bounce well off software objects such as animals or people. It also requires a nearly perpendicular or curved surface to help ensure some waves are reflected back for detection. Depending on the angle of the surface the waves could be reflected away from the sensor. In most cases it works just fine in the manner used, but you should be aware of the potential in other uses. I hope this helps. Take care.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Chris Savage
Parallax Tech Support

allanlane5

To add a bit to that:

IR uses infrared light (which you cannot see). So, that light has to 'bounce' off an object and be 'seen' by the IR-Sensor. The "distance zones" in this case is a clever hack, that uses the amount of light reflected as some indicating of 'range'. But this is really inaccurate -- it's much better as a collision avoidance method than actually measuring distance.

The Ping sensor uses high-frequency sound (which you cannot hear). Now, sound travels MUCH more slowly than light. So measuring the time-delay between when the sound is started, and when the reciever hears the echo of the sound, is much more easily done, and is appropriate for repeatable accurate distance measures (up to a few feet).

"Super-sonic" usually refers to something like an airplane moving faster than the speed of sound. "Ultra-sonic" refers to a sound-wave tone at a frequency higher than you can hear. The Ping sensor uses Ultrasonic sound.

sushiandmorihiko

thanks for the advice guys

ukkhs, sorry mistaken to refer ping as a supersonic device..really embarassing..haha. actually i want either one of these sensors to be mounted on my pan and tilt with 2 servos(2 degrees of freedom).
i want this pan and tilt to move up and down ,left and right according the movement of my hand.i was cosidering these two sensors to detect my hand or body the best.

what do you think is the most suitable guys?

thank you in advance

Mike Green

As Chris described, they both have advantages. Since the IR emitters and detectors are small and cheap, why not use both and experiment to see which works better for your application? You'd have a total of 3 I/O pins involved plus +5V and ground. If you change your application description, you could switch sensors if that makes sense or use one for one function and the other for some alternative function.

sushiandmorihiko

thanks mike green,
probably i will start with infra-red cos thats what i have right now---if the performance is acceptable then i will stick to that one.

D Faust

Infra red has its flaws so what I plan to do on my bot is have a primary IR system (various IR sensors around the bot) and have a PING that can serve as an error checker for·the·IR. (because the ping has to scan, you need to stop and take measurements)· Something to consider.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔

LOOKDOWN ThisThread, [noparse][[/noparse]Your_?, My_?, Cool_Thing], looknum
LOOKUP looknum, [noparse][[/noparse]1, 2, 3], subnum
ON subnum GOTO Hope_this_helps, Thanks!, WOW!!
END 

Chris Savage

Mike brings up something I forgot...there is a term commonly used now (of course, I forgot it!) for using multiple types of sensors for an application, such as IR and Sonar for distance. Calculations are done to essentially use the data from both sensors to make the best determination from the readings. I think Servo or Robot has an article on this.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Chris Savage
Parallax Tech Support

Chris Savage

Sensor Fusion is the catch-phrase I was trying to remember...

http://en.wikipedia.org/wiki/Sensor_fusion

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Chris Savage
Parallax Tech Support