Subject:
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Re: sensors input
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Fri, 1 Jan 1999 17:33:21 GMT
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Original-From:
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FTHOMPSON9@nomorespamAOL.COM
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Viewed:
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1167 times
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michael,
The parallel combination of resistors is the recprical of the sum of their
recpricol values.
Req = 1 / ( 1/R1 + 1/R2 + 1/R3 + ...)
Your 16 LED resistors combine to make
Req = 1/( 16 x (1/82)) = 5.125 ohms. So your LEDs are drawing just under 1
Amp. (Remember there is a small (about 0.5V) voltage drop across the LED
itself.
The parallel combination of your 16 Sensor resistors is
Req = 1/( 16 x (1/120,000)) = 7500 ohms, a little easier to support. The
voltage drop across the sensors is expected to be much larger than 0.5 Volts.
I would suggest that you take another look at the problem you are trying
to solve. See if one LED can support several sensors, or if a single sensor
set will work with a much larger LED resistor. Otherwise I suggest that you
find another supply for the LEDs. Another idea to consider is to make the
LEDs flicker (at something near 40 kHz, then design an AC amplifier for your
sensor circuit. You might find a much better performance.
Good Luck,
Pherd
In a message dated 98-12-30 14:10:08 EST, you write:
<< hi everyone,
i have tried to configure a set of sensors used for sensoring the wall in
the maze.
the circuitry of each of the sensors is:
+5V +5V
----- -----
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\ \
/ /
R1=82 ohm \ \ R2=120Kohms
/ /
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------- |/
IR emitter \./ |\ IR receiver
----- |
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--- ---
GND GND
the IR sensor is sharing the same +5V source and the same ground. but when i
assembly 16 of them together, the habdyboard will immediately switch to
reset mode. so i tried to troubleshoot by only connecting the digital sensor
port and it works. but after about 2mins, the HB switch to reset mode again.
the same situation happen when i tried with the analog port only.
i like to know what is wrong and how to solve. could it be the wire is short
or the circuitry is faulty? or could it be the HB cannot supply enough
current to the sensors ?
please help! i am really at my wits end.
michael
>>
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