Ultrasonic distance sensor + OLED panel


#1

Ultrasonic_distance_sensor

Link to YouTube video about SRF05, etc...

Organic Light Emitting Diode panel

I've just finished writing an instruction sheet for my IoT students on creating an ultrasonic distance sensor using the SRF05 device.

Please note the SRF05 works off of +5v and ground, and needs a level shifter to convert WeMos signal levels to/from the device.

DO NOT connect the 'Echo Output' signal directly to the WeMos - you must use a level shifter.

Note: There are details about level-shifters on the last page of the Ulltrasonic article.

Hope you enjoy reading this article as much as I enjoyed writing it.

Cheers from David


#2

Very very nice articles.

I have found a spec (= http://dl.behnamrobotic.com/shop/datasheet/module/module-srf05-ultrasonic.pdf) of SRF05 that says measurement range 2cm to about 4.5 meter with resolution of 0.3 cm.
This is actually impressive.

So when positioned on the floor would it be possible to measure the distance of a wall that is 4 meter away ?


#3

That sounds rather more impressive than the last U/S module I tried when building a robot with my son. Just note that ultrasonic sensors will miss some things like soft fabrics. LIDAR is more accurate but a lot more expensive of course. On robots, ultrasonics are sometimes coupled with "feelers" like on bugs or cats whiskers in order to deal with any u/s issues.


#4

Thanks for your kind comments.

If it's placed on the floor then the range will be severely limited.
This is because (as the 'spec' sheet says) the beam is conical (i.e. a cone shape) so the further it goes the wider it gets.
I've managed to achive a distance of just over 4000mm (with the unit positioned 1m above the floor) and reckon the resolution is approx 10mm.

In the past I've used PIC microcontrollers to drive the SRF05. The advantage is you can set-up an interrupt system running at a fairly high-speed which improves the resolution. With the WeMos (i.e. ESP8266) you're stuck with the internal clocking frequency (unless you're prepared to edit the plugin).


#5

Thanks for the reply.

Wow, 1 mm resolution over a distance of 4 meter (at 1 m hight) is better than I can do with tape measure. So that is impressive.

I understand that the beam is conical but would in case of placing this close or on the floor impact the measurement of a distant object (like a wall) ? It would be interesting if you could report the samething you did at 1 m above the ground also very close to the ground.


#6

Where did you get the 1mm from???
In my text it says 10mm


#7

sorry, my mistake. Read to quickly.


#8

If the unit is placed on the floor, then I suspect the beam will bouce back or be reflected back to the sensor before it reaches the far wall. The on-board PIC microcontroller on the SRF05 will take the 'echo' line low as soon as it receives an echo.

I'll be at the school next week (as this week is half-term) and will get a couple of the students to perform some experiments. I'll report back.

Cheers from David.


#9

Dave, in case you have never seen it, there is a nice video on youtube about these sensore from 'The guy with the Swiss accent" - https://www.youtube.com/watch?v=aLkkAsrSibo He measures three sensors, the HC-SR04, HY-SRF05 and US-015.

He points out a number of interesting facts - the angles they will work at, how they work when a sound doesn't return, how multiple sensors can effect each other (the sound from one can be picked up from another - this might be important if you have a bunch of kids doing this in the same area) and how temperature effects the speed of sound.

You might find it helpful. Love the writeup!


#10

Thanks Paul for the link.
It's a great video especially as it enables people to see the various waveforms on a scope