Subject:
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Re: Interfacing Sharp's GP2D02 Distance Sensor to the RCX
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Newsgroups:
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lugnet.robotics, lugnet.robotics.rcx
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Date:
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Sun, 21 Jan 2001 22:45:35 GMT
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Original-From:
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Ralf Krause <nospam.krause.ralf@web.AVOIDSPAMde>
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Viewed:
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1042 times
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Hi,
I asked this problem a few weeks (or months??? ... I don't know a what time
...) but nobody could help. I got the same following answer
".... the sensor takes 35 mA and this is to much for the RCX ..."
but I couldn't understand this at this time. Until now since I really tried
to connect my own sharp sensor GP2D12 to my own RCX. My thoughts were the
same like anybody else (... or most of yours ...) thought about this problem
...
Micheal Gasperi wrote that the sensor input has an active sensor mode and
that thisone could drive an sensor power input with 8 volts ond with 30 mA.
It's right that the RCX has 8 volts if you turn on the active sensor mode
(that's the mode for the Lego light sensors or the Lego rotation sensors).
But you can't get enough power to drive the GP2D12!!
Therefor I 've done some tests with my RCX and a lot of resistors.
--------------------------------------
Table: RCX with new batteries (6 * 1.55 V = 9.3 V)
R U I P = U * I
‡ V mA mW
- 8.0 0.0 0.0
4700 7.5 1.6 12.0
2200 7.4 3.4 25.2
1000 6.5 6.5 42.3
820 5.5 7.9 43.5
680 5.5 8.0 44.0
560 5.2 8.7 45.2
470 4.5 9.3 41.9
330 3.5 10.5 36.8
220 2.8 12.0 33.0
sensor type light sensor
sensor mode Raw
---------------------------------------
This table shows that its impossible to get 35 mA with the power of 5 V from
the sensor input of the RCX. I think you can get 6 or 8 mA but then the
power gets down.
Yes, the RCX can drive motors with 100 or 200 mA but it can do so with its
outputs and not with its inputs. If you want to drive a GP2D12 (or something
else) you should do it with an output. If you only need to have two motors
with your robot then yo have one output for driving your hungry sensors with
electric power.
Take four diodes 1N4148 or 1N914 for connecting the output to get correct
polarised voltage. Then you need a 100 uF and a 78L05 and a 100 nF to get
stabilized 5 V voltage for the sensors. With this interface you can really
drive sensors with 100 mA or more. You program has to switch the output on
with full power because setting smaller power would result pwm (power with a
phase of power down ... and this is not dc power) at the output.
And it 's nice to see the robot is stopping 20 cm in front the wall ...
The GP2D12 is a distance measuring sensor with an infrared emitting diode
and a signal prossessing circuit. It enables to detect objects without any
influence on the color of reflective objects, reflectivity, the lights of
surroundings.
It has an output analog voltage with is detecting distances from 10 cm (3.1
volts) to 80 cm (0.6 volts). I 've done the connection to the input of the
RCX with the general purpose analog interface of Michael Gasperi ... the
second one with the opamp.
.../gasperi/gpa.htm
Michael, please tell me how you can write that the power can " ... provide
30 mA of power to operate other sensor electronics." As I 've tested it
seems that you can't do so ... or I am totally wrong ...??
I hope to get a lot of questions and answers about this sensor problem and
my tests ...
Ralf
ps
Peter's creation needs two outputs, one for the power and the other for the
handshaking protocol ...
http://www.inchlab.com/gp2d02_interface.htm
on 2001-01-12 00:41, John Barnes at barnes@sensors.com wrote:
> Unless I am missing something here, the Sharp range of IR distance sensors
> all have power consumptions in the 35mA range, which prohibits their use with
> the RCX unless you resort to using external power packs.
>
> How do you propose getting around this problem?
>
> JB
>
> > In lugnet.robotics, Ram Meenakshisundaram writes:
> > > Hi,
> > >
> > > Here is a link on how to hook up the GP2D02 to the RCX =
> > > http://www.inchlab.com/gp2d02_interface.htm It seems to be overly =
> > > complicated. Not to put down on Peter's creation as I think it was =
> > > ingenious, but there must be a easier way to do this instead of =
> > > compromising an input & an output port...
> > >
> > > Ram
> >
> > Hi Ram,
> >
> > I don't know an easier way of using GP2D02 but why don't you use the GP2D12
> > instead ?
> > It has an analog output.
> > You don't have to analyze any serial protocol.
> > And as the lego light-sensor has a driven light source, it should be
> > possible to drive this sensor too.
> >
> > you can find a datasheet at :
> > http://www.sharp.co.jp/ecg/NewProducts/sensor/gp2d12.pdf
> >
> > Rainer
--
____________________________________________
Ralf Krause
Bertha-von-Suttner-Gesamtschule Dormagen
Marie-Schlei-Strasse 6
41542 Dormagen
Germany
http://www.shuttle.schule.de/ne/bvsdormagen
mailto:nospam.krause.ralf@web.de
delete nospam. to get my real email address
____________________________________________
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