Let's Make Robots!

I'm getting sick of Sharps --Is there something better?

Alright, this is it... I am anti-sharp distance sensor. I spent over a week fighting noise on the power side which screwed with my RF reciever. I have fried them because thier pin-out does not match the configuration of a servo connector or the picaxe 28x board. Thier numbers jump all over the place. Now it seems that all four of the ones I have are "worn-out". By that I mean this:

I added a .1uf cap to deal with noise and now it seems they won't output anything without the cap attached. My picaxe will not sync while even just one sensor is plugged in. On top of that, all of them are spitting out a measurement of 50 or so when looking at infinity and the total sensing distance is down to about 10 or 12 inches maybe less. I am sick of dealing with these silly things and do not want to spend more money replacing the ones I have.

The Problem:

I have to have a minimum of 3 sensors on Walter to deal with his width. A SRF05 centered on a servo is a given thus leaving the needed sensors to catch the corners and sides. I have looked at other sonar systems (the ones with just the single black emitter (SRF02?) and even thought about just spending the bucks on 2 more SRF05's. The issue is (especially with the "single emitter" (which fire constantly)) is interference from sensor to sensor. In many instances I will have 2 sensors firing almost directly forward and the ultrasound from one will screw with the readings of the others. (All 3 sensors must be able to turn via servo). I have looked into some of our fellow LMR'ers IR distance systems but I just can't seem to get the distance I need.

What the hell can I do here?!?! Does anyone know of an upgraded Sharp? Is there a quality IR distance sensor out there? Something? Maybe a 180 degree sensor that does not have to be swept with a servo? 

Oh, and I don't have a lot of cash. 

For the love of God, help.


Just had a thought:

Has anyone tried any of the home made IR distance sensors with a lens or two to increase distance/ sensitivity? --Maybe I should experiment a bit...

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I have the same problems you have although I haven fried any sharps yet. My main problem is the instability of the readings. Sometimes they are rock steady and then, for no apparent reason, they start bouncing up and down without any servo or motor activity that would cause the interference.

I've been looking for a good, affordable, narrow beamed sensor with a range of about 1 meter for a couple of months and I haven't found it yet. The only device that comes close is a professional laser ranger, but those things are very very expensive.

I suspect that all those home brewed IR sensors will not be any better than the sharps. I haven't seen anyone get a 1 meter range. The ultra sonics do well, but like you said: they interfere with each other and they have a rather wide beam.

Maybe we should make this into a challenge: Find/build a range sensor that beats the Sharps in max range, narrow beam and stability for under $25.

The corner sensors I need swivel from straight forward to 90 degrees to the side. When forward they cover the blind side (as the main sonar is sweeping right, the corner sensor swings in) and to the side they are for wall detection. Overall, I would like to see them kicking in at about 18" but at a absolute minimum, I would need about 12". But then again, at 12" the robot would have to comit to a major direction change -the futher the distance of the sensor, the more porportionate the direction adjustment can be.
How much distance do you need it to cover? You may be able to use the LED method, but it wouldn't get a lot of distance and callibrating it for different ambient light could prove troublesome.