Subject:
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rcx power circuit
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 6 Dec 2001 20:15:58 GMT
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Original-From:
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Mathias Uhr <uhr@STOPSPAMmathias.net>
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Reply-To:
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uhr@/SayNoToSpam/mathias.net
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Viewed:
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635 times
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hi list again!
thanks a lot for all your replies to my postings about
accu pack and power plugs!
since i already got my ordered 1.0 rcx's today (thanks rob!)
and now own all versions of the rcx, i disassembled them
all to have a look at the power circuit.
here are the results:
- rcx 1.0 (with power plug)
* the two inputs (plug and batteries) are completely
independent. there isn't even a direct ground connection
between them.
* the external power source is rectified with a bridge
rectifier (4 diodes), filtered with 6 caps of 330uF each
and then stabilized with a voltage regulator ic.
* the positive pole of the battery input is protected with
a diode against batteries put in the wrong way.
* the internal batteries don't get disconnected when
an external power plug is inserted - at least not
mechanically.
- rcx 1.5 (mine says "1.0" on it, but has no power plug)
and rcx 2.0
* the rcx 1.5 and 2.0 versions seem to have an identical
circuit.
* the sophisticated stabilization circuit is omitted (no caps,
no regulator, no rectifier diodes and no plug of course).
* instead, there's a big cap (1000uF) and a ferrite "ring"
on the battery input (probably for some kind of filtering
if someone still connects an external power source).
* i couldn't find a diode behind the positive battery pole.
* the piezo beeper sits where the 6 caps have been in
1.5, no longer under the display.
conclusions:
- the rcx 1.0 (with power plug) is the one to get!
it has a great power circuit. lego is obviously cutting
costs by omitting all these parts in rcx 1.5 and 2.0.
if - as reported - you can use 2.0 soft- and firmware
for the 1.0 as well, there is no reason to use something
else. get as much of those sturdy oldies but goldies
as you can!
- because of the rectifier circuit in the 1.0, the polarity
of the external power plug doesn't matter, you can
even attach an ac source (which i tested) and even
more than 12v (which i didn't test, don't sue me!).
i wouldn't recommend this though, cause the regulator
ic would then probably produce too much heat.
- for my "accu pack application", this means that it is
perfectly safe to attach an accu pack (or any other
power source) of up to 12v to the external power plug
of an rcx 1.0 along with normal batteries in the brick!
it has, however, to be tested first, which ones get
consumed quicker.
for charging, the accu pack can remain connected, as
long as the charger's voltage doesn't rise above 12v.
but i still recommend to disconnect it from the rcx...
pfhh, long post. hope nobody got bored or pissed...
greetings
mat
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Message has 3 Replies:
 | | Re: rcx power circuit
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| (...) FYI - I ran my RCX1.0 for a while with a 12V DC adapter. The RCX has "9-12V" printed above the plug. One day I thought I check my DC adapter and found it was actually putting out 18V! Needless to say I stopped using it, but I had been running (...) (23 years ago, 6-Dec-01, to lugnet.robotics)
| | | Re: rcx power circuit
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| On Thu, 2001-12-06 at 12:15, Mathias Uhr wrote: <snip> (...) This is more likely to act as a buffer to prevent the voltage from sagging on the CPU when you're running the motors. This is always a pronlem when motors and CPU are run off a common (...) (23 years ago, 7-Dec-01, to lugnet.robotics)
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