Wall Following Sensor, variable voltage to IR LED. - Page 2 - Electronic Circuits Projects Diagrams Free

arhi · 15th May 2008, 11:21 AM

about the "pivoting motor mounted sensor" .. I do not need it

but the whole idea of my work is to have fun

and to pack as much as possible gadgets into a single product, so controlling stepper motor, servo motor and simple dc motor in same project, as much as it sounds stupid is exactly what I'm doing attm

.. all bunch of different sensors (I'm attm making "shake" sensor using piezo soundspeaker from "singing card" that I will mount there also

)

Torben · 15th May 2008, 07:25 PM

Quote:

Originally Posted by 3v0

After hearing the same think from you and Bill I went back and check again. The sharp IR distance sensors do not seem to function at distances short enough to be useful.

I did find a non-analog sensor that goes active at 5 cm. Digikey has them GP2Y0D805Z0F for $3.25 each. One could use them as electronic wiskers with one on each side of the robot. If one did a slight S path so that the sensor toggled frequently it could work. It may be hard to aquire the wall to start with.

Hi 3v0,

I may be reading the datasheets wrong but to me it looks like the digital IR sensor only toggles if something is detected between 1cm and 5 cm from the sensor, while the analog output one from the Sparkfun site gives a nice voltage curve from about 6cm up to 80cm. I don't really know what all of your constraints are in construction and cost etc but I wonder if you couldn't take care of the minimum range problem with the analog sensors by setting them not at the outside edge of the robot, but in about 2.5-3.5cm from the edge, pointing out. If you could mount them like that without getting spurious early reflections from other features on the 'bot you could simply ignore the "recessed" ~3cm and wind up with a minimum distance reading from the edge of the 'bot of ~3cm. Dunno if this is still too far for you. It just seems that with the digital one you would have to a) be close to the wall to sense it, and b) do something like the "wiggle-toggle" you mentioned to be sure you were ~5cm from the wall--and depending on the width of the 'bot (you said the maze walls are 10" apart?) having the extra range might be useful.

Again, I don't know enough about what you're doing to say any more than "this is what it seems like to me".

Oh yes--the analog Sharp sensors are a couple of bucks cheaper from Digikey, at least in Canada. It's still over 40 clams to mount two per side though; could be too pricey.

As to the ultrasound idea, well, I *have* played quite a bit with ultrasound and I while I've managed to build an ultrasonic rangefinder which works down to a few cm, I think you'll find the same issues with near objects (i.e. it will only be reliable down to a few cm) depending on what sacrifices are made in the design and below that threshold, you'll only be able to tell that there is something there, but not how far away it is. On one I've built the range is down to about 5cm but i.e. on the LV MaxSonar modules it's about 6".

Anyway, just some random thoughts. I'm interested to know what solution you do end up using and how well it works out. Have fun with the project!

Torben

arhi · 16th May 2008, 12:36 AM

btw, little bit off topic, but might be a helpful to try if you own pocketpc .. I tried it and loved it:
http://www.freewarepocketpc.net/ppc-tag-sonar.html

it is free sonar app for pocketPC .. uses audible sound (not ultrasound) and is pretty damn accurate

**3v0** · 16th May 2008, 02:45 AM

Currently I am more into exploring the technology then one specific application. There is no one robot I am building so my mind tends to wander a bit. But as I see it the most difficult task here is the close in reading.

Arhi,
Thanks for updating me on you work with IR. I agree with everything you said. I just added a digital pot socket to my prototype. Still need to wire it up and write the soft SPI code. Mostly just library calls. I am using C18 on a 18F1330. This chip can use its PLL with the internal 8MHz osc to run at 32 MHz. I only have the 10K digital pots on hand. These things are so useful that I plan on ordering the other values.

I am interested in what you are doing with US although I will be working with IR for a while yet.

Toben,
I have a sharp distance sensor (fairly sure it is GP2D12J0000F) that measures from 10 to 80cm. The voltage goes up as you close to 10cm and then drops for distances less then 10cm so it is fairly useless in close. I have it mounted on the front of a robot. So far I have only successfully used it to avoid walls and objects.

If one used a maze with tall walls one could (as suggested mount the IR sensors facing across the top of the robot. I am not sure I want tall maze walls. I have a few chunks of 2x4 that I arrange to build quick and dirty mazes. Do not want to go to 2x6. Maybe place them ahead of the robot body and have them look past each other.

The GP2Y0A21YK0F is a better sensor in that it works as close as 6cm. Mouser has them on back order for 3 months. I can not be sure but they may list soon-to-be-stocked items at a discounted price to get a few sales prior to getting the shipment. The GP2D12J0000F was cheap and back ordered, when they became a stocked item the price went from $8 to $10. It will be interesting to see if it happens again.

I seen an article on the web where a guy took the PCB off the sharp sensor and added a spacer to change the focal length. Shortened the range. I can find it if anyone is interested.

arhi · 16th May 2008, 03:01 AM

with maze, I believe that IR will do the proper job (with variable resistor) and give pretty good resolution as all your wall's will be made of same material. If you add one simple light probe at the top of the bot to compensate for ambient light, i believe you can achieve steady and accurate resolution. The thing that I spent too much time on is "focus" .. I took data sheet too literal so assumed that 40 or 60 degree angle of IR radiation from IR LED is "absolute" .. it is not

so I had whole bunch of interference in the early stages. After trying to "focus" the light using different materials (cardboard, plastic ...) that I believed not to be transparent, I finally ended up using aluminum tubes. Longer the tube, better the results. I also placed IR Receiver at the end of one (bit larger) tube to focus the receive side too. The "focus" might not be the right word here (yup, English is my 3rd language

) but I bet you understand what I mean.

Torben · 17th May 2008, 07:46 AM

Quote:

Originally Posted by 3v0

The GP2Y0A21YK0F is a better sensor in that it works as close as 6cm. Mouser has them on back order for 3 months. I can not be sure but they may list soon-to-be-stocked items at a discounted price to get a few sales prior to getting the shipment. The GP2D12J0000F was cheap and back ordered, when they became a stocked item the price went from $8 to $10. It will be interesting to see if it happens again.

Try DigiKey--at least the Canadian site lists the GP2Y0A21YK as in stock. Still $10.71 CDN a pop though.

Quote:

I seen an article on the web where a guy took the PCB off the sharp sensor and added a spacer to change the focal length. Shortened the range. I can find it if anyone is interested.

That sounds interesting. Don't take time from the project but if you come across the link again I'd love to read it.

Torben

Torben · 17th May 2008, 07:49 AM

Oh yes--another reason I agree ultrasonic might not be great for a maze: unless you tuned things down quite a bit I'd think you'd get crazy reflection problems. There would be pings bouncing everywhere in such a confined space. It would probably be possible to deal with that but I don't know if it would be worth it.

Torben

[Edit: I know ultrasonic isn't really what you're looking at; I'm just spewing thoughts as they come.]

**3v0** · 17th May 2008, 11:50 AM

The sharp sensor mod to reduce range is at
GP2D15 Shorter Range Modification

I also ran into Field (electric, capacitance) sensors which are interesting but do not have a use for at this time.

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15th May 2008, 11:21 AM	(permalink)
arhi	about the "pivoting motor mounted sensor" .. I do not need it but the whole idea of my work is to have fun and to pack as much as possible gadgets into a single product, so controlling stepper motor, servo motor and simple dc motor in same project, as much as it sounds stupid is exactly what I'm doing attm .. all bunch of different sensors (I'm attm making "shake" sensor using piezo soundspeaker from "singing card" that I will mount there also ) __________________ http://www.it4um.com

16th May 2008, 12:36 AM	(permalink)
arhi	btw, little bit off topic, but might be a helpful to try if you own pocketpc .. I tried it and loved it: http://www.freewarepocketpc.net/ppc-tag-sonar.html it is free sonar app for pocketPC .. uses audible sound (not ultrasound) and is pretty damn accurate __________________ http://www.it4um.com

16th May 2008, 02:45 AM	(permalink)
3v0	Currently I am more into exploring the technology then one specific application. There is no one robot I am building so my mind tends to wander a bit. But as I see it the most difficult task here is the close in reading. Arhi, Thanks for updating me on you work with IR. I agree with everything you said. I just added a digital pot socket to my prototype. Still need to wire it up and write the soft SPI code. Mostly just library calls. I am using C18 on a 18F1330. This chip can use its PLL with the internal 8MHz osc to run at 32 MHz. I only have the 10K digital pots on hand. These things are so useful that I plan on ordering the other values. I am interested in what you are doing with US although I will be working with IR for a while yet. Toben, I have a sharp distance sensor (fairly sure it is GP2D12J0000F) that measures from 10 to 80cm. The voltage goes up as you close to 10cm and then drops for distances less then 10cm so it is fairly useless in close. I have it mounted on the front of a robot. So far I have only successfully used it to avoid walls and objects. If one used a maze with tall walls one could (as suggested mount the IR sensors facing across the top of the robot. I am not sure I want tall maze walls. I have a few chunks of 2x4 that I arrange to build quick and dirty mazes. Do not want to go to 2x6. Maybe place them ahead of the robot body and have them look past each other. The GP2Y0A21YK0F is a better sensor in that it works as close as 6cm. Mouser has them on back order for 3 months. I can not be sure but they may list soon-to-be-stocked items at a discounted price to get a few sales prior to getting the shipment. The GP2D12J0000F was cheap and back ordered, when they became a stocked item the price went from $8 to $10. It will be interesting to see if it happens again. I seen an article on the web where a guy took the PCB off the sharp sensor and added a spacer to change the focal length. Shortened the range. I can find it if anyone is interested. __________________ search engine for electronic parts Junebug USB PIC programmer kit., USB Bit Wacker, Homepage The 15 Minute Printed Circuit Board! (+drill time)

16th May 2008, 03:01 AM	(permalink)
arhi	with maze, I believe that IR will do the proper job (with variable resistor) and give pretty good resolution as all your wall's will be made of same material. If you add one simple light probe at the top of the bot to compensate for ambient light, i believe you can achieve steady and accurate resolution. The thing that I spent too much time on is "focus" .. I took data sheet too literal so assumed that 40 or 60 degree angle of IR radiation from IR LED is "absolute" .. it is not so I had whole bunch of interference in the early stages. After trying to "focus" the light using different materials (cardboard, plastic ...) that I believed not to be transparent, I finally ended up using aluminum tubes. Longer the tube, better the results. I also placed IR Receiver at the end of one (bit larger) tube to focus the receive side too. The "focus" might not be the right word here (yup, English is my 3rd language ) but I bet you understand what I mean. __________________ http://www.it4um.com

17th May 2008, 07:49 AM	(permalink)
Torben	Oh yes--another reason I agree ultrasonic might not be great for a maze: unless you tuned things down quite a bit I'd think you'd get crazy reflection problems. There would be pings bouncing everywhere in such a confined space. It would probably be possible to deal with that but I don't know if it would be worth it. Torben [Edit: I know ultrasonic isn't really what you're looking at; I'm just spewing thoughts as they come.]

17th May 2008, 11:50 AM	(permalink)
3v0	The sharp sensor mod to reduce range is at GP2D15 Shorter Range Modification I also ran into Field (electric, capacitance) sensors which are interesting but do not have a use for at this time. __________________ search engine for electronic parts Junebug USB PIC programmer kit., USB Bit Wacker, Homepage The 15 Minute Printed Circuit Board! (+drill time)