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Making a $3 SRF04 Ultrasonic Sensor Act Like a $55 SRF08

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Max The Magnificent
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Re: Temperature, Humidity, and Pressure
Max The Magnificent   12/29/2013 2:50:20 PM
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@Sanjib.A: Btw...why did you chose urtrasound over Infrared? What is the min-max distance directed?


No particular reason -- I was planning on using infraed sensors under the robot to detect edges (like if you put it on a table) -- I've never played with ultrasonics before, so I decided to go that way -- as I recall, they are upposed to be accurate from 2cm to about 450 cm.

 

Sanjib.A
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Re: Temperature, Humidity, and Pressure
Sanjib.A   12/29/2013 4:04:27 AM
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@Max & Duane: Thank you for sharing your project ideas. I was looking for a cheap but fairly accurate ultrasound sensor for a different application (water level measurement of the overhead water tank of my house). I am going to check this out. Btw...why did you chose urtrasound over Infrared? What is the min-max distance directed?

Robotics Developer
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Re: Temperature, Humidity, and Pressure
Robotics Developer   12/28/2013 3:33:32 PM
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Max, the other thing I would remind you of is the sequencing of the ultra sonics (say left, back, front, right) to prevent echos from interfering.  This is more of an issue with multiple robots in a common environment but the side effect is to reduce the processing overhead to 1 or 2 sensors at a time.  The other programming feature that would be nice is to increase the polling on the sensors that are closing in on an object to keep from hitting it.  All that said, it would be most helpful if you had touch bumpers all around to protect your furnature.

Max The Magnificent
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Re: Temperature, Humidity, and Pressure
Max The Magnificent   12/28/2013 12:06:12 PM
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@Robitics Developer: Max, regarding the ultrasonics make sure you test out the environment that you want to run them in...

Good point -- also my robot is going to be on its own, but if I were in a robit competition it might be interesting working on "Stealth" technology re ultrasonic and IR sensors on other robots...

Robotics Developer
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Re: Temperature, Humidity, and Pressure
Robotics Developer   12/27/2013 5:19:10 PM
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Max, regarding the ultrasonics make sure you test out the environment that you want to run them in.  In robotic competitions we "saw" problems with utrasonics and diamond plate.  It seems that with diamond plate the ranging varied greaty due to weird reflections.  Be save and test out the environment..  also could be a nice article to write up for others to learn from your experiences.

 

I did very much enjoy the pun :bouncing back and forth"!! Keep up the puns..

David Ashton
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Re: SR-04 modules
David Ashton   12/20/2013 5:53:28 PM
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@Max..."I think the on-board electronics on the '04 are just for pulse-shaping/controlling the out-going "ping" and detecting/registering/noise-filtering the incoming response..."

 

From the timing diagram in the datasheet, when you give it an initiate pulse the module will send out 8 40KHz pulses from the transmitter.  Immediately on completion of that it starts the Echo pulse - which it would appear carries on until it detects the end of the echo - that's the pulse you time with your MCU.  

The pulse (by my calculations) is 6.4 CM long....yet the unit can measure down to 2 cm.  I guess working off the trailing edges of the pluses lets it do this.  Quite clever.

Max The Magnificent
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Re: What?
Max The Magnificent   12/20/2013 1:31:50 PM
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@Duane: It's early. My brain doesn't actually start functioning until about 10:00am out here.

OK, I'll call you back later (LOL)

Duane Benson
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Re: What?
Duane Benson   12/20/2013 1:27:55 PM
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Ah. That makes more sense. It's early. My brain doesn't actually start functioning until about 10:00am out here.

Max The Magnificent
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Re: What?
Max The Magnificent   12/20/2013 11:52:01 AM
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@Duane: That type of sensor really isn't senstive enough to detect someone coming into a room,

I meant using the ultrasonic sensor to detect if someone came into the room, and THEN use the ambient light sensor to decide whether or not to turn the lights on :-)

Duane Benson
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Re: What?
Duane Benson   12/20/2013 11:49:49 AM
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Max - I'm not sure what the purpose was. The original documentation just says: "The SRF08 can be used as a light sensor." That type of sensor really isn't senstive enough to detect someone coming into a room,

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