Author Topic: Unstable, weird readings of Sharp GP2Y0A02YK sensors (axon)  (Read 2968 times)

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Offline TomasTopic starter

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Unstable, weird readings of Sharp GP2Y0A02YK sensors (axon)
« on: January 28, 2009, 07:12:12 AM »
I've got three sharp Ir sensors on my robot atm, all connected to my axon.

The first thing I noticed is that they have a very high powerconsumption! But that problem is probably solved :) For now Ill just use my powersupply.

Anyway, Im getting some pretty weird readings off it. Right now, I am in a room with fluorescent lights (dont know if that matters or not), not much sunlight reaches the room and even if it is any light coming in its really clouded outside.

So what Im wondering about is why the readings are nonstable and from time to time highly inacurrate. Some times, for example, one or more sensors "shoots" up and gives crazy values. They tend to do a maximum value of 1904 cm, for some reason.

And if I remove one of the sensors from the ADC pins, HyperTerminal still gives out voltagereading on that specific pin, even if its not connected? This goes away if I remove all the sensors. Then the adc values are all zero. Wtf? Does what the other IR sensors read influence the voltage on other ADC pins as well?

Any tips on how making them as stable as possible? Any specific update frequency? I read (dont know where on this site) that I should update them maximum 20 times every second, is that true? I noticed when I used a lower update frequency, the sensors just sent FUBAR information back, not much sense at all.

Offline Geir

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Re: Unstable, weird readings of Sharp GP2Y0A02YK sensors (axon)
« Reply #1 on: January 28, 2009, 03:01:48 PM »
http://www.societyofrobots.com/robotforum/index.php?topic=6633.0 We just did this one  :)

A plot of the sensor readings:
http://gp2d12.russemotto.com

If you disconnect the sensor from the AD it will read strange values if you don't use a pull up
« Last Edit: January 28, 2009, 03:03:59 PM by Geir »
$50 Robot schematic http://elektro.russemotto.com

Offline TomasTopic starter

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Re: Unstable, weird readings of Sharp GP2Y0A02YK sensors (axon)
« Reply #2 on: January 28, 2009, 03:40:06 PM »
Whats a pull up?

(btw Norwegian?)

Offline Geir

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Re: Unstable, weird readings of Sharp GP2Y0A02YK sensors (axon)
« Reply #3 on: January 28, 2009, 04:58:02 PM »
A little quick here, dont worry about the pull up :)

btw: pull up/down
http://cnmat.berkeley.edu/recipe/how_and_why_add_pull_and_pull_down_resistors_microcontroller_i_o_
« Last Edit: January 28, 2009, 05:05:07 PM by Geir »
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Offline TomasTopic starter

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Re: Unstable, weird readings of Sharp GP2Y0A02YK sensors (axon)
« Reply #4 on: January 29, 2009, 05:05:28 AM »
Looks like the solution was to connect a condensator to the plus and minus part of the sharp (one for all sensors was enough for me, I think), I used a 22uF one, and it made the results more stable and precise.

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