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[DPRG] Black masking tape

Subject: [DPRG] Black masking tape
From: rten at new.metronet.com rten at new.metronet.com
Date: Wed Feb 26 17:29:01 CST 2003

I made a line sensor from a pair of IR proximity sensors and I found that
distance from the tape was critical to good results. This is almost surely
the case for any sensor type used for line following.

On Tue, 25 Feb 2003, Dave Hylands wrote:

> Another secret to getting good readings from the Lego sensors is to get them
> as close as possible to the ground. I've seen some robots where the sensors
> are 1/2" from the ground, and this is too far to get good readings. The
> sensor should be on the order of 1/8" for good results.
> --
> Dave Hylands
> Vancouver, BC, Canada
> http://www.DaveHylands.com/ <http://www.davehylands.com/>
> -----Original Message-----
> From: LJGeib at aol.com [mailto:LJGeib at aol.com]
> Sent: Tuesday, February 25, 2003 9:00 PM
> To: miner at centtech.com; dprglist at dprg.org
> Subject: Re: [DPRG] Black masking tape
> Go ahead and use the electrical tape. I have done a bunch of tests for the
> PDXbot events and I think you will find that there is plenty of contrast. Of
> course it depends on the background color and the sensors you are using.
> At PDXbot, we use a white Melamine. Under these circumstances, I get very
> high contrast with the MKII sensors. These are the QRB1114 or QRB1113
> sensors, which work in the IR spectrum. Using a 10 bit ADC, white readings
> are over 950 (Out of 1024), and black readings are well under 100, (most
> readings around 40-70) so there is plenty of room for threshold tuning. I
> also have tested the old MKII sensors, which used a LDR and a red LED, and
> the results were similar. You milage may vary, but I still think the
> contrast will be high.
> I don't Know much about the Lego sensors, but I'd be surprised if they
> couldn't detect this difference.I've tested several black PVC tapes, both
> electrical and plumbing, and they were all pretty close to each other. I do
> Know that some Lego folks have reported some problems with shiny Melamine
> washing out the contrast, so make sure to sense at an angle to the surface
> and not directly down on it.
> As a sidelight, colored elecrical tapes (green,red, yellow, etc. test out as
> nice greyscale alternatives. Of course, how you place you sensors on the
> robot will be important. you may wnt to insure that refections from stray
> sources are not a factor.
> Larry
> In a message dated 2/25/03 7:50:41 AM Pacific Standard Time,
> miner at centtech.com writes:
> Worst case I can try black electrical tape but I'm
> guessing it's too shiny (reflective) to give enough
> contrast for the LEGO sensors.
>         - Dan

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