Let's Make Robots!

ultrasonic 1 transducer vs. 2

MaxSonar-EZ1.jpg

 

why dont we see robots made with these? http://www.sparkfun.com/commerce/product_info.php?products_id=8502

is there something bad about it having 1 transducer only? sparkfun does not carry the SRF05, so will this be a viable replacement?

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very cool documentation about this product here (lots o pictures)

http://www.maxbotix.com/MaxSonar-EZ1__FAQ.html

 

and here it claims to outdo the SRF sensors

http://www.maxbotix.com/Performance_Data.html#Pendulum_Test

My robotics team tested these sensors. We made our 150 pound "kill you instantly" robot follow walls with it. It went full speed down the hallways, oblitterating anything in the way. Destroyed a couple of chairs and a table.
Mmmm... that sounds like the kind of robot video I'd like to see in here :-D

 

I've been a solid user in these since I've tried them. Their capability has been pretty close to their performance info at :

http://www.maxbotix.com/Performance_Data.html 

And I much prefer having a micro directly read an analog voltage or a pulse width, rather than use I2C, though others may prefer the query-response method. One thing that was a little strange on the Maxbotix sonars, was the serial connection. I think it needed to be inverted, but never used that interface method.

On using one transducer, the old Polaroid sonars (now Senscomp) used active "blanking" to quiet the transducer after a ping. These probably have something similar. 

As to cost, even though they have one less transducer, there still is a PCB, a microcontroller (Microchip PIC) and support circuitry to pay for, just like the dual types. The PCB cost is still the pretty similar at this size, even though it's a smaller board (don't know if it's more than 2 layer, but probably not).  The micro cost is probably the same.The sonar transducers are probably $2 each, so not a great impact on the total price.

I have wondered the same thing! What is the functional diffrence? and on our small short distance obstacle avoidance robots, would it matter much anyway? A better question is "why isn't it half as much?" :-)

 

 

 

 

Having only one transducer usually makes the minimum range longer.  They have to wait a little while for the vibrations from transmitting to stop before they can receive.  Whether it matters depends on how close you want to sense.

This one actually has an interesting feature as it can "detect" objects from 0-6 inches with accurate "ranging" from 6-254 inches.

These series of sensors seem to have narrower beams which is nice as I've found the wide beam can cause chaotic detection with some objects.