Subject:
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Re: IR-based proximity measurement
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Newsgroups:
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lugnet.robotics.rcx.nqc
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Date:
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Fri, 9 Jun 2006 01:56:15 GMT
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Viewed:
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17079 times
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In lugnet.robotics.rcx.nqc, Mathew V. Jones wrote:
> I'm changing the subject line in the middle of the thread. Wonder what the
> server will do with that...
>
>
> I tried out Brian's "Max-picking" ping method, as well as a few other things.
> Here's a summary of what I found:
>
> 1) If the active sensor readings are averaged to improve the signal to noise
> ratio, then using SendSerial() to send 16 continuous bytes of 1's through the IR
> Comm port works better than using SendMessage to only send one byte. Not too
> surprising. I reckon the SNR is around 2-4 at best, using any of the averaging
> methods I tried.
>
> 2) If Max-picking is used instead of averaging, the SNR gets (finally!)
> adequately high, around 7-8 depending on how you eyeball it. This is a really
> great idea, and the more I think about it the more I appreciate why it works so
> well in this situation. My calibration code beeps with a pitch proportional to
> the estimate of proximity, and I can pretty much tell how far away from the wall
> the bot is just by listening.
>
>
> I put the code and some calibration figures here, if anyone's interested:
>
> http://www.physiology.wisc.edu/jones/robotics/proximity/SerialPing.nqc
> http://www.physiology.wisc.edu/jones/robotics/proximity/SendMessagePingAvg.jpeg
> http://www.physiology.wisc.edu/jones/robotics/proximity/SendSerialPingAvg.jpeg
> http://www.physiology.wisc.edu/jones/robotics/proximity/SendMessagePingMax.jpeg
> http://www.physiology.wisc.edu/jones/robotics/proximity/SendSerialPingMax.jpeg
>
> Cheers,
>
> Matt
i have downloaded the SerialPing.nqc program hoping to get an easy to use
proximity sensor. i have modified it to work with only one light sensor. but it
shows always -90 on the display. ok, sometimes -89 too.
can anybody tell me, what i did wrong? Here is the code:
/*
sensor.nqc /cr 2006 June 9 /lm 2006 June 9 / rt
proximity sensor, simply displaying a value i expect to be correlating with a
distance
derivied from SerialPing.nqc by Matt Jones, Sept 2005
*/
int eyeoff; // passive light sensor reading
int eyeon; // active light sensor reading
int epct; // 100*(active-passive)/passive
int disp;
task main()
{
// Set up sensors & IR Tx
SetSensorType(SENSOR_1, SENSOR_TYPE_LIGHT);
SetSensorMode(SENSOR_1, SENSOR_MODE_PERCENT);
SetTxPower(TX_POWER_HI);
SetSerialComm( (SERIAL_COMM_DEFAULT) ); // 2400 Baud, 50% duty cycle - tried other settings too, didn't seem to matter
SetSerialPacket(SERIAL_PACKET_DEFAULT); // plain data bytes
// initialize the 16 byte serial data buffer with all 1's. Sending all 16 bytes
in a row should give a long IR blast
int dummy = 0;
repeat (16) {SetSerialData(0, 0xff); dummy = dummy + 1;}
int avreps = 10, eo;
PlayTone( 440, 5 );
while (true)
{
eyeoff = 0; eyeon = 0;
eo = 0;
repeat(avreps) // average some passive readings
{
eyeoff = (eyeoff + SENSOR_1);
}
SendSerial(0,16); // SendSerial, here before loop seems to work best
repeat(avreps) // either average or take the maximum of several active readings ("Max-Picking", great idea suggested by Brian Davis)
{
//Either do this:
// eyeon = (eyeon + SENSOR_1); // add for averaging later
// OR do this (not both)
eo = SENSOR_1; if (eo > eyeon) { eyeon = eo; } // grab maximum
}
eyeoff = eyeoff / avreps;
eyeon = eyeon / avreps; // comment this out if grabbing maxima
// time = FastTimer(0); // Read timer at 10 ms/tick resolution
epct = 100 * (eyeon-eyeoff)/eyeoff;
disp = 100*epct;
SetUserDisplay(disp, 0);
PlayTone( 100+100*epct, 5 );
// PlayTone( 880, 5 );
}
}
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Message has 1 Reply:
 | | Re: IR-based proximity measurement
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| (...) Well, there were a couple of typos, but only one I found that was critical. If you are using a "max-picking LIDAR" method, you do *not* want to divide by the number of samples. The variable "eyeon" in your code should end up with the brightest (...) (20 years ago, 9-Jun-06, to lugnet.robotics.rcx.nqc)
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Message is in Reply To:
| | IR-based proximity measurement
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| I'm changing the subject line in the middle of the thread. Wonder what the server will do with that... I tried out Brian's "Max-picking" ping method, as well as a few other things. Here's a summary of what I found: 1) If the active sensor readings (...) (21 years ago, 16-Sep-05, to lugnet.robotics.rcx.nqc)
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