Subject:
|
Re: Custom Firmware, IR Problems, and Dead RCXs (long)
|
Newsgroups:
|
lugnet.robotics
|
Date:
|
Sun, 27 May 2001 17:44:37 GMT
|
Original-From:
|
Andy Gombos <gombos_2000@!SayNoToSpam!yahoo.com>
|
Viewed:
|
1743 times
|
| |
|
|
Oh, geez, this could be bad. Could changing the firmware to reduce comm
activity fix this? It seems to be a problem of usage, not specific
firmware properties (i.e. constant data uplaoding.)
Andy
Ralph Hempel wrote:
> 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 down to this...
>
> *********************************************************
> If you use custom firmware like legOS, pbForth, or leJOS
> (not the standard LEGO firmware or any software that uses
> it, like NQC or RoboLab) you may be risking damage to
> your RCX and IR tower!
>
> If you use an unregulated wall-wart (adapter) you may
> risk damaging your RCX and IR tower.
> *********************************************************
>
> I've spent the past couple of spare weekends making some
> upgrades to pbForth, but recently my RCX and tower both died.
>
> I have a couple of theories about this and would like to offer
> them up for discussion. Please use the robotics.rcx group
> for followups so we can all follow the thread....
>
> 1. I do a lot of upload/download sequences. In fact, I've been
> developing an interrupt-driven comms library for the RCX.
> In testing the library I end up doing a ton of transmissions
> in both near and far range.
>
> 2. To conserve batteries, I use a RadioShack adapter through a
> Y cable to the tower and RCX (Obviously, I have a 1.0 RCX)
> The adapter is 273-1656A, which is rated for 800mA at 9V.
> The actual output (unloaded) is about 12 volts - near the posted
> limit for the RCX.
>
> 3. During the past few weeks, comms were becoming more unreliable.
> This caused me lots of grief as I was thinking my software was
> to blame. Finally, my tower died. I confirmed this using a
> video-camera. It can see IR and I verified the tower was
> not sending any chars. So I opened it up to see what I could see.
>
> 5. In off-line discussions with others on this list, it was pointed
> out that the far-range current limit resistor in the tower is
> only 5.6 Ohms. This would allow about 1A of peak current through
> the IREDs. Even at a 50% duty cycle for the carrier, the 500mA
> exceeds the normal operating range of the IREDs by about a factor
> of 5 if all 1 bits are being sent.
>
> 6. I discovered that the NPN drive transistor for the IREDs in the
> tower had failed - probably due to the very high current. I
> replaced it and also replaced the 5.6 Ohm resistor with a 75
> Ohm (actually 2x150 Ohms in parallel) to reduce the peak far
> range current. This repaired the tower, but now my RCX did not
> work either.
>
> 7. I opened up the RCX and found that one of the IREDs had failed
> and was an open circuit. I replaced the IRED with RadioShack
> 276-143C which is described as a high-output IRED.
>
> 8. The drive transistor for the IREDs on the RCX *does* get hot when
> doing steady transmissions from the RCX. Using the normal
> firmware should not be a problem, but extended serial comms may
> fatigue the part beyond its limits.
>
> 9. Windows 2000 on some computers may turn the IR tower to transmit
> all of the time. I think this may have something to do with the
> reports of tower failures under Windows2000. Leaving the tower
> in near-range may avoid this problem.
>
> Soooo, the upshot is that I think those of us that use custom firmware
> should be aware that we may be running the risk of damaging the RCX
> because some of the hardware may be stressed beyond the design limits.
>
> The use of standard LEGO firmware only uses the IR for relatively
> short bursts, and should not be a problem.
>
> Use of unregulated wall-warts or adapters may cause damage to the RCX
> as well.
>
> Please post any replies or comments to the lugnet.robotics group
>
> Best Regards,
>
> Ralph Hempel - P.Eng
--
See my Visual Interface for leJOS at http://lvi.sourceforge.net
|
|
Message has 1 Reply:
 | | RE: Custom Firmware, IR Problems, and Dead RCXs (long)
|
| (...) Well, yes and no. The biggest risk is when you use the tower or the RCX in high-power (far) mode for extended transmissions. I was thinking about why we have not received more posts about dead RCXs. My old pbForths (and I think legOS too) set (...) (25 years ago, 27-May-01, to lugnet.robotics)
|
Message is in Reply To:
| | Custom Firmware, IR Problems, and Dead RCXs (long)
|
| 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 (...) (25 years ago, 27-May-01, to lugnet.robotics)
|
17 Messages in This Thread:
  
 
- Entire Thread on One Page:
- Nested:
All | Brief | Compact | Dots
Linear:
All | Brief | Compact
This Message and its Replies on One Page:
- Nested:
All | Brief | Compact | Dots
Linear:
All | Brief | Compact
|
|
|
|
