Subject:
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Re: Custom Firmware, IR Problems, and Dead RCXs (long)
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 29 May 2001 14:29:05 GMT
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Viewed:
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434 times
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I don't understand all the problems about blown IR-LEDs and don't believe anyone will ever see 1A flowing through his IR-LED's.
My experience:
I'm doing contiunuous data transfers for hours in long range mode, with fresh batteries I measure 100 mA peak IR-LED current in long range mode (Hiroki Shirakawa measured the same value);
No problems at all (9V alkaline battery in IR tower and NiCd batteries in RCX).
Some other points to concider:
- The nominal forward voltage is 1.5V @ 100 mA and increases to 3V @ 1A (specifications from SFH485)
- The oscillator is started / stopped at every bit change (not a good idea), the startup time of the oscillator could be a problem ?
- Normal duty cycle is only 25% ( 0.5 for 38 kHz modulator and 0.5 for bit balancing)
- If you're look at the specs of 9V alkaline batteries they all go to a maximum of 100 mA
So the only ways to blow up the IR-LED's is in my opinion are:
- use of wrong netadapter, too high voltage or too low internal impedance
- bad starting oscillator (maybe due to not-bit-balancing software ?)
For who's interested, I've put all my personal notes about the IR tower (including schematics from John Barnes, Hiroki Shirakawa, keeping tower alive and battery-less IR-tower) on my webpage
http://baserv.uci.kun.nl/~smientki/Lego_Knex/Lego_electronica/IR_tower/IR_tower.htm
Ralph Hempel wrote:
> The following information is my own opinion and not
> endorsed or verified in any way by LEGO.
Stef Mientki
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Message is in Reply To:
 | | Custom Firmware, IR Problems, and Dead RCXs (long)
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| The following information is my own opinion and not endorsed or verified in any way by LEGO. That being said, I think that now is the time to relate some experiences I've had over the past couple of months with my RCX and IR tower - and it boils (...) (23 years ago, 27-May-01, to lugnet.robotics)
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