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Colleagues, The SRF08 was pointed verticaly to the ceeling, which was 150" away. There was also an incondescent ligth 70" away from SRF08. I expected to get the first bounce reading of 70", but it actually was 28". Although at short distances (under 10") the readings were correct. Does anybody know what went wrong? Thank you, Nick |
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Ultrasonic ranger SRF08 underestimates the distance
Started by ●June 21, 2004
Reply by ●June 21, 20042004-06-21
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Check your spec of the sonar. Its probably a 10" range finder :) Or check your math for conversion errors, or probably the bouncing surface is not hard enough to bounce a reliable pong. Maybe? Maybe not. |
Reply by ●June 21, 20042004-06-21
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Hi Nick, Without a complete circuit diagram/schematic and well commented code listing it is extremely difficult to say what the problem could be with any given project. There are at least 100 things that could be amiss. If you haven't already, go to the following website and study the hardware and software shown there. Apparently they can get that setup to work. http://www.robot-electronics.co.uk/htm/srf08bx24.shtml There is a discussion of the "technical specification" of the SRF08 at http://www.robot-electronics.co.uk/htm/srf08tech.shtml That should be thoroughly read and understood. When trouble-shooting, be methodical and only change one thing at a time. Document your results. If possible, devise simple tests for separate areas that you can verify as good. Divide and Conquer. Hope this helps, Eric ----- Original Message ----- From: Nick Alexeev To: Sent: Tuesday, June 22, 2004 2:12 PM Subject: [BasicX] Re: Ultrasonic ranger SRF08 underestimates the distance Colleagues, What is the typical distance you are measuring? My goal is to be able to sense 3-5m with the resolution of 0.1m. I did some more testing. It turns out that my SRF08 is giving accurate results at the distances less then 0.8m, but if the object (a plate in my case) was further (1-6m) the SRF08 was still reporting 0.8m. My first suspicion was that I'm actually receiving the reflections from the floor, so I lifter the SRF08 2.5m from the floor, but the output didn't change. What do you think is the problem? Nick |
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Reply by ●June 22, 20042004-06-22
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I've used this sensor, and the SRF04 before it, and it returns accurate values. It well return a distance to the nearest object it sees and the beam width is very wide. Therefore, if there is something closer within its field of view, perhaps a wall, workbench shelve, whatever, it may return that distance. Wave something around in front of the sensor and to the sides to "see" where the sonar is radiating and you will probably find the source of the return. John- >Colleagues, > >The SRF08 was pointed verticaly to the ceeling, which was 150" away. >There was also an incondescent ligth 70" away from SRF08. I expected >to get the first bounce reading of 70", but it actually was 28". >Although at short distances (under 10") the readings were correct. >Does anybody know what went wrong? > >Thank you, >Nick > |
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Reply by ●June 22, 20042004-06-22
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Check your power supplies, maybe you don't have enough power to drive
the Ultrasonic Range Finder Ping... It takes some current to do so... Do all readings return the same distance??? You might need to do a running average to get better steady readings.. Good luck. |
Reply by ●June 22, 20042004-06-22
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--- In , "Nick Alexeev" <kender_a@y...> wrote: > Colleagues, > > The SRF08 was pointed verticaly to the ceeling, which was 150" away. > There was also an incondescent ligth 70" away from SRF08. I expected > to get the first bounce reading of 70", but it actually was 28". > Although at short distances (under 10") the readings were correct. > Does anybody know what went wrong? > > Thank you, > Nick Nick, I use five SRF08 in a robot and they work very precisely. During the first tests and programming I used the I2C routines from Peter H. Anderson with no good results. I always had ranging distances shorter then the real distances. Then I start to use the I2C routines for the BX-24 from Gerald Coe (Devantech). Since I use BX- 01, I wrote specific ShiftIn and ShiftOut routines for it. They worked perfectly and the ranging are very precise. It is important that you use two pull-up resistors (1.8K) in the SCL and SDA pins of the I2C bus. As I use more than one SRF08 and very close one to the other, I can not use the general broadcast address to initiate the ranging because one SRF08 reads the echo originated from the ping of another SRF08. So I do the ranging in sequence by I2C address, firing each SRF08 alone and awaiting 0.07 seconds before reading the range. I hope this can be of help. Filippo |
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Reply by ●June 22, 20042004-06-22
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Colleagues, What is the typical distance you are measuring? My goal is to be able to sense 3-5m with the resolution of 0.1m. I did some more testing. It turns out that my SRF08 is giving accurate results at the distances less then 0.8m, but if the object (a plate in my case) was further (1-6m) the SRF08 was still reporting 0.8m. My first suspicion was that I'm actually receiving the reflections from the floor, so I lifter the SRF08 2.5m from the floor, but the output didn't change. What do you think is the problem? Nick --- In , "basicxgroup" <pardini@g...> wrote: > --- In , "Nick Alexeev" <kender_a@y...> wrote: > > Colleagues, > > > > The SRF08 was pointed verticaly to the ceeling, which was 150" > away. > > There was also an incondescent ligth 70" away from SRF08. I > expected > > to get the first bounce reading of 70", but it actually was 28". > > Although at short distances (under 10") the readings were correct. > > Does anybody know what went wrong? > > > > Thank you, > > Nick > > Nick, > > I use five SRF08 in a robot and they work very precisely. During the > first tests and programming I used the I2C routines from Peter H. > Anderson with no good results. I always had ranging distances > shorter then the real distances. Then I start to use the I2C > routines for the BX-24 from Gerald Coe (Devantech). Since I use BX- > 01, I wrote specific ShiftIn and ShiftOut routines for it. They > worked perfectly and the ranging are very precise. It is important > that you use two pull-up resistors (1.8K) in the SCL and SDA pins of > the I2C bus. As I use more than one SRF08 and very close one to the > other, I can not use the general broadcast address to initiate the > ranging because one SRF08 reads the echo originated from the ping of > another SRF08. So I do the ranging in sequence by I2C address, > firing each SRF08 alone and awaiting 0.07 seconds before reading the > range. > > I hope this can be of help. > > Filippo |
Reply by ●June 24, 20042004-06-24
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Thanks. My schematic is almost the same as in your link. Almost... I didn't have a separate fat 5V regulator, and as soon as I added it, the ranger started to work properly. Nick --- In , "eserdahl@" <eserdahl@p...> wrote: > Hi Nick, > > Without a complete circuit diagram/schematic and well commented code listing it is extremely difficult to > say what the problem could be with any given project. There are at least 100 things that could be amiss. > > If you haven't already, go to the following website and study the hardware and software shown there. > Apparently they can get that setup to work. > > http://www.robot-electronics.co.uk/htm/srf08bx24.shtml > > There is a discussion of the "technical specification" of the SRF08 at > > http://www.robot-electronics.co.uk/htm/srf08tech.shtml > > That should be thoroughly read and understood. > > When trouble-shooting, be methodical and only change one thing at a time. Document your results. > If possible, devise simple tests for separate areas that you can verify as good. Divide and Conquer. > > Hope this helps, > > Eric > ----- Original Message ----- > From: Nick Alexeev > To: > Sent: Tuesday, June 22, 2004 2:12 PM > Subject: [BasicX] Re: Ultrasonic ranger SRF08 underestimates the distance > > > Colleagues, > > What is the typical distance you are measuring? > > My goal is to be able to sense 3-5m with the resolution of 0.1m. > > I did some more testing. It turns out that my SRF08 is giving > accurate results at the distances less then 0.8m, but if the object > (a plate in my case) was further (1-6m) the SRF08 was still reporting > 0.8m. My first suspicion was that I'm actually receiving the > reflections from the floor, so I lifter the SRF08 2.5m from the > floor, but the output didn't change. > > What do you think is the problem? > > Nick > |
