Distance measurement using HC-SR04

[TomasS]

Hi

I would like to do a project using a HC-SR04 for distance measurement. Anybody who has done a similar project who would like to share a program example for this?

BR

Tomas

[Benj]

Hi Tomas,

That looks like a great little module. May have to get one myself and have a play

Not done anything with these but looking at the sample PICaxe code it looks quite straightforward.

Here is some simple psudocode I came across for driving the device.

symbol trig = 3 ‘ Define output pin for Trigger pulse
symbol echo = 6 ‘ Define input pin for Echo pulse
symbol range = w1 ‘ 16 bit word variable for range

main:
pulsout trig,2 ‘ produce 20uS trigger pulse (must be minimum of 10uS)
pulsin echo,1,range ‘ measures the range in 10uS steps
pause 10 ‘ recharge period after ranging completes
‘ now convert range to cm (divide by 5. or inches (divide by 14.
‘ as picaxe cannot use 5.8, multiply by 10 then divide by 58 instead
let range = range * 10 / 58 ‘ multiply by 10 then divide by 58
debug range ‘ display range via debug command
goto main ‘ and around forever


You could output the start pulse and then use say a timer interrupt to time the period for the pulse to return.

[TomasS]

Hi Ben

That looks like a great little module. May have to get one myself and have a play

Not done anything with these but looking at the sample PICaxe code it looks quite straightforward.

That's a nice site, indeed

Here is some simple psudocode I came across for driving the device.

symbol trig = 3 ‘ Define output pin for Trigger pulse
symbol echo = 6 ‘ Define input pin for Echo pulse
symbol range = w1 ‘ 16 bit word variable for range

main:
pulsout trig,2 ‘ produce 20uS trigger pulse (must be minimum of 10uS)
pulsin echo,1,range ‘ measures the range in 10uS steps
pause 10 ‘ recharge period after ranging completes
‘ now convert range to cm (divide by 5. or inches (divide by 14.
‘ as picaxe cannot use 5.8, multiply by 10 then divide by 58 instead
let range = range * 10 / 58 ‘ multiply by 10 then divide by 58
debug range ‘ display range via debug command
goto main ‘ and around forever


You could output the start pulse and then use say a timer interrupt to time the period for the pulse to return.

Looks nice - I must try to "translate" this into Flowcode

[Benj]

Give it a go and post up your Flowcode program if you get stuck and we should be able to help you get this device up and running.

[TomasS]

Give it a go and post up your Flowcode program if you get stuck and we should be able to help you get this device up and running.

Thanks. I'll do that
The module has now been bought - $3.41 including shipping, so I await it's arrival and will return after this!

BR.

Tomas

[medelec35]

The module has now been bought - $3.41 including shipping

Wow that sounds like a bargain!
hope it's all going to work for you.
With all the experts on here, (and me of course ) I'm sure we would be able to get a working project for you.
I have already started working on ultrasonic range finder. Not sure on the distance it will work up to yet.
If successful I can post the flowchart.

Martin

[JohnCrow]

Ive played with the SRF05 (which is the same pin out as the SRF04) ranger using the projects in Bert van Dams Flowcode book which work well.
These were done in FC3 but certainly worked fine in FC4 (Not tried them in FC5 but should work).

Im currently trying an SRF10 which is a lot smaller than the SRF05 and uses I2C bus, but so far ive not been able to get it to work properly. :(Need to have another look at this project soon)

[TomasS]

The module has now been bought - $3.41 including shipping

Wow that sounds like a bargain!
hope it's all going to work for you.
With all the experts on here, (and me of course ) I'm sure we would be able to get a working project for you.
I have already started working on ultrasonic range finder. Not sure on the distance it will work up to yet.
If successful I can post the flowchart.

Martin

Hi Martin

Yep! Ebay is the place to find the stuff
I'm pleased ´to find all you experts on here - for sure!
Sounds great - maybe we can compare solutions, when I receive my version?

BR.
Tomas

[medelec35]

pulsin echo,1,range ‘ measures the range in 10uS steps
pause 10 ‘ recharge period after ranging completes
‘ now convert range to cm (divide by 5.8) or inches (divide by 14.8)

Hi Ben. I have started working on my own ultrasonic detector, but was a bit puzzled about range of 10us and the distance.

Since sound travels at approx 343.2 metres per second in dry air at 20 deg C
then 1meter it takes 1/343.2 = 2.01ms
so if divide by 100 then sound takes 2.01ms/100 = 29.14uS to travel 1cm
Divide by 2 then it takes 14.57 to travle in 0.5cm

But if going by lots of 10us then after say 100 lots of 10us distance will calculate at 100/5.8 = 17cm
But at a distance of 17cm, i believe sound will take 17*29.14 = 495us and not 1ms?

Therefore would be divide by 2.9 and not 5.8?

I could be wrong of course?


Edit :Ahh logically worked it out.

Ben that is correct. because its an echo, it will take twice as long since the distance is double. to the overall calculation has to 1/2 the distance hence 5.8 and not 2.9
At least I have worked out the reason. lol


Martin

[TomasS]

Ive played with the SRF05 (which is the same pin out as the SRF04) ranger using the projects in Bert van Dams Flowcode book which work well.
These were done in FC3 but certainly worked fine in FC4 (Not tried them in FC5 but should work).

Im currently trying an SRF10 which is a lot smaller than the SRF05 and uses I2C bus, but so far ive not been able to get it to work properly. :(Need to have another look at this project soon)

Hi John

I'm actually feeling a little stupid at the moment since I actually have this book on my shelf, but I did not see that it had a project with the ultrasound sensor - I will look into that!

BR.

Tomas

[medelec35]

I'm pleased ´to find all you experts on here - for sure!

I wasn't including myself in the expert list

Sounds great - maybe we can compare solutions, when I receive my version?

Sure, as you can see from my post above, I have already started, and querying the calculations.
Has to be right

If I can get it working OK,will post flowchart in the tips section.
I will also post on here a link to it.

I have a busy weekend, but I will try to complete as much as I can.

I actually have this book on my shelf, but I did not see that it had a project with the ultrasound sensor - I will look into that!

If you go to this website:
http://www.elektor.com/extra/microcontr ... 1368.lynkx
You can download the flowchart (by Download the complete package).
Flowchart can be found in Chapter5, section 5-3

Martin

[TomasS]

I'm pleased ´to find all you experts on here - for sure!

I wasn't including myself in the expert list

Sounds great - maybe we can compare solutions, when I receive my version?

Sure, as you can see from my post above, I have already started, and querying the calculations.
Has to be right

If I can get it working OK,will post flowchart in the tips section.
I will also post on here a link to it.

I have a busy weekend, but I will try to complete as much as I can.

Sounds great! I'll look forward to it

I actually have this book on my shelf, but I did not see that it had a project with the ultrasound sensor - I will look into that!

If you go to this website:
http://www.elektor.com/extra/microcontr ... 1368.lynkx
You can download the flowchart (by Download the complete package).
Flowchart can be found in Chapter5, section 5-3

Martin

Done!