RoboSavvy Forum

SRF04 Sonar

2006-12-01T16:56:26+01:00

Hi. I was just wondering if any of you can help me. I am working with the srf04 sensor for a university project. I have hooked it up to an oscilloscope and everytime i fire it it returns an echo pulse of 36ms(no object detected) irrespective of weather theres an object in its path or not. I really dont understand why its doing this! If anyone has any ideas, i would be very greatful of your suggestions. Adam

Statistics: Posted by Adam — Fri Dec 01, 2006 4:56 pm

SRF04 Sonar

2006-03-30T18:00:20+01:00

ucrobots wrote:
I think Robobasic has a bug where they can't service the timer fast enough, or, as others have said, there is a false trigger happening...

I fully agree that RoboBasic has a bug.

If you call the SONAR() twice the measurement results are nearly stable and it will read any object down to 2200µs/5.8µs/mm ~ 380mm.

So I hope Hitec will fix the bug.

Just to update you all I have raised a call with Robonova Support in germany - they have updated me to day and they are still looking into the issues with the Sonar. No conclusion as yet but we can hope.

As I hear more I will update the posts

Pev

Statistics: Posted by Pev — Thu Mar 30, 2006 6:00 pm

SRF04 Sonar

2006-03-29T15:45:23+01:00

I think Robobasic has a bug where they can't service the timer fast enough, or, as others have said, there is a false trigger happening...

I fully agree that RoboBasic has a bug.

If you call the SONAR() twice the measurement results are nearly stable and it will read any object down to 2200µs/5.8µs/mm ~ 380mm.

So I hope Hitec will fix the bug.

Statistics: Posted by ucrobots — Wed Mar 29, 2006 3:45 pm

SRF04 - Yep, it's flaky

2006-03-29T07:20:28+01:00

Hi all,

This forum has been great to get me started and see where some of the pitfalls are. It's nice when you beat your head against the wall to know that others have the same problem.

I can confirm that the sonar is really flaky.
1. It consistantly gives a reading one out of every 3 pings if pointed to and object the right distance away.

2. It will NOT read any object closer then 5-6 feet (at least mine doesn't)

3. Once you get it pointed at an object 6 feet away, it's fairly steady.

I think Robobasic has a bug where they can't service the timer fast enough, or, as others have said, there is a false trigger happening...

I plan to try I2C next... It doesn't look promising... I hate bit-banging I2C!

Statistics: Posted by Guest — Wed Mar 29, 2006 7:20 am

SRF04 Sonar

2006-03-16T19:16:51+01:00

Well I have had a chance to see if I could get the Sonar to stop firing all the time. I basically cut the roboBasic code down to this:

GOTO AUTO
FILL 255,10000

LCDINIT

MOTOROFF 10
MOTOROFF 11
'================================================
MAIN:

PRINT "Working "
GOTO MAIN

That is the entire program I downloaded. Guess what - the sonar still fires all the time GGGGRRRRRR. Not sure that there is a way to stop it firing now.

Pev

Statistics: Posted by Pev — Thu Mar 16, 2006 7:16 pm

SRF04 Sonar

2006-03-16T18:49:49+01:00

Subpilot

it's in the robobasic manual in the sonar section. It refers to the Sonar ports and links them to the DIO ports - it's a table on pages 133 and 134.

Pev

Statistics: Posted by Pev — Thu Mar 16, 2006 6:49 pm

SRF04 Sonar

2006-03-16T18:22:22+01:00

Pev, BTW, where did you find info on where the sonar ports were? I didn't see anything in the documentation.

Statistics: Posted by subpilot — Thu Mar 16, 2006 6:22 pm

SRF04 Sonar

2006-03-16T15:24:25+01:00

I have seen the same problems. You can't switch off the servoports if they are used by commands like "Move G6A x,y,z...
But PWM 0, 1, 2 or OUT 32,1 (ADPort 0) works. So I hope these ports could be used to trigger the sonar sensor.

ulli

Statistics: Posted by Guest — Thu Mar 16, 2006 3:24 pm

SRF04 Sonar

2006-03-16T09:59:28+01:00

I tried the same things to turn off the output but had no luck either. Have a quiet weekend planned so will have another go from scratch and thanks for the comment on the power line. I know I was playing a bit on the edge - really must sort out a regulator for this robot, all my others have them lol

Pev

Statistics: Posted by Pev — Thu Mar 16, 2006 9:59 am

SRF04 Sonar

2006-03-16T00:54:53+01:00

I hooked up my SRF04 and see some problems. First off the readings are not consistant like Pev had seen. I put a scope on the trigger line and see that the module is getting a 1.5mSec wide pulse every ~13mSec without calling a sonar command. I think the problem may be that the servo output is enabled on the ports the sonar is using. I'm going to look into it.

EDIT:

I am sure that the fact that the 3024 trigger channel is constantly sending pulses is screwing things up. I can't seem to disable the output. I also see that the echo receive line is configured as an output by default (because it's set up for a servo) This causes the SRF04 output to be dragged down (bus contention). As soon as you issue a sonar command the line apparently switches to an input but the continuos triggers keep happening. I tried:
MOTOROFF 10
MOTOROFF 11

and also tried:

PWM 10, 0
PWM 11, 0

No go. Hope somebody (Pev) else can sort this out.
I'm going to try to give my I2C sonar module a go.

Statistics: Posted by subpilot — Thu Mar 16, 2006 12:54 am

SRF04 Sonar

2006-03-15T07:57:26+01:00

Pev, I just noticed that you are running the SRF04 off the servo bus voltage. The SRF04 is only rated to 5V and the servo rail can be quite a bit more.

Statistics: Posted by subpilot — Wed Mar 15, 2006 7:57 am

SRF04 Sonar

2006-03-13T13:50:58+01:00

Yes it is - sorry my raving colour blindness doesn't help

Pev

Statistics: Posted by Pev — Mon Mar 13, 2006 1:50 pm

SRF04 Sonar

2006-03-12T23:09:15+01:00

The BLUE wire you ref to in the text??? Is it Purpley ?

Statistics: Posted by rep001 — Sun Mar 12, 2006 11:09 pm

SRF04 Sonar

2006-03-10T11:53:51+01:00

LIke the knee idea - need to ponder that one
The other thought I had was to take a leaf out of the KHR-1 book and rep-lace his head with a servo, then mount the sensor on that. That would atleast allow for a pan motion to check more than one distance before moving.

Pev

Statistics: Posted by Pev — Fri Mar 10, 2006 11:53 am

SRF04 Sonar

2006-03-10T01:02:18+01:00

What about putting the SRF04 inside the wrist? You could have him do a scan by waving his arm around. Or maybe mount it on the front of the knee. I think that stays clear.

Statistics: Posted by subpilot — Fri Mar 10, 2006 1:02 am