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Asked — Edited

About Making Sonars Have A Narrow Detection

I mostly know about every sensor made and run many many tests on them
some for work but mostly for robot designs i ,might have well over 30 different types

ON sonars narrow detection is needed to mostly detect the corner of the 2 walls that meet for good navigation ,but also thin table legs or chair legs ,also doorways .

When a sonar transmitt a utrasonic pulse it sends like a cone shape.wider the cone shape wider the detection.

So there is 2 ways to do it,so far maxsonars sells smaller cone angles $30 each

Other way is easy with like SRF-04 types like EZB sells on the transmitt side you need to reduce the SIDE SLOPES or cone angle.
its fairly easy only need a tube that fits on the outside of the ultrasonic tranducer and in the inside place a foam tube smaller the ID smaller the cone
and length is about 1 1/2 inch long on the tube,can use cardboard type
on foam tube inside length is about 1 inch
try to match it to get a tight fit inside the cardboard tube

also best place to place them on robots is on each corner at 45 deg
and then have 2 facing forward like headlights with no cardboard tube or foard to pick up wide angle objects


latter on will give you info on IR sensors too

#1  
And where do you find a "foam tube" like the squishy stuff?
#2  
mcmaster has plenty of them all sizes

foam tubes
closed cell tubes all work and they have many more,kind the use for hot water pipe cooling
i think the size i got was 5/8 OD 1/4 ID OR 1/2 OD will work too
need to measure the OD of the transducer,i dont have one in my bedroom where i am now
#3  
Forgive me for sounding argumentative but have you tried narrowing the field of view with a plastic tube that slides over each sender /reciever? It seems like (and im no expert) that just a sleeve over the sensors that are longer by say 1/2" narrows the sensors view. The foam part doesn't seem absolutely needed though im sure it absorbs some "noise"
#4  
plastic doesnt work,i tried many types of materials only foam blocks the sonar
thats why it wont detect foam stuff ,carpet or bedding or sofa's
just like in speakers foam blocks sound,
utrasonic receiver dont really need it ,it only picks up the return pulse
#6  
Here is the Hero-1 way, it also incorporates foam.
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#7  
You mention the best place for the sensors on a robot is on the corners at 45 degrees but that's not ideal on smaller robots such as the Omnibot or my Hearoid (same body) and probably the Omni 2000.

What position would you suggest for these robots? Also, is height a big factor and if so, what is better, higher or lower?

Also, I think I got the general idea of how to reduce the cone for the sonars EZ-Robots sell but is there any chance of a photo or sketch to reinforce this? Do I basically just put a small tube made from foam around the ping?

I'll make one and put up a photo shortly to hopefully help explain how I have read your instructions.
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#8  
Nevermind, found your link which had a photo. I'll try this later on if I get chance as I am looking to find the best object avoidance method for my build.

I assume if narrowing the cone helps object avoidance and distance measuring then having the sonar on a servo for sweeping is not a good idea?
#9  
Rich that is an interesting idea. The Heath/Zenith 2000 has a sonar mounted on a rotating motor that does a 360 degree sweep making a virtual map.
See the attached image of the Polaroid sonar in the top housing


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#10  
@Robotmaker, is this what you were explaining to do to the Sonar EZ-Robots sell?

A small piece of foam (I used a camping mat which is made of EVA Foam)
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Roll up in to a tube and push over the tx of the Sonar (excuse the crude method of self amalgamating tape and poor photos)

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I appreciate these are probably too long, I still need to cut to size but if this is right I intend to glue the seam rather than use tape to make it a tube.

Also, does it have any effect if I do this to the Rx too? The reason I ask if purely cosmetic as if this is right I plan to make a front piece to fit in the chest of the Omnibot body so it has 2 holes rather than 2 tubes sticking out.
#11  
THATS kinda whats done,mostly need to check different size length
been about 2 years since i did this test i need to find info and my data ,i think it was near 1/2 inch Above the sonar,i think its needed for both,since i use MAXSONARS that uses only one utrasonic sensor.

Second on placing on the robot ideal spot is sonar detects above sofa's or what most do it add a IR INLINE WITH IT

Good item about adding a IR sensor to it is that one sensor is good for detecting certain types of material ,and other will pick up the ones the other misses,do need to set sensors at the right distance

to detect corners of walls on a small robot design use a panning design to pan to 45 deg left and right
radar wont really work,it need to pan left stop and take a reading and then right

as soon as i get my optic bench in or make one ,will do a full testing on all types of materials for both sonar and IR

My favorate of all sonars are MAXSONARS ,very low current (3ma), 3 outputs ,small size and only one hole to make,plus with much more accuracy