Subject:
|
Re: RCX has a fast clock, was Re: Rolling ball clock revisited
|
Newsgroups:
|
lugnet.technic, lugnet.robotics
|
Date:
|
Wed, 8 Dec 2004 14:08:54 GMT
|
Viewed:
|
173 times
|
| |
|
|
> I suppose that this problem comes from bad capacitor loading of the crystal used
> on RCX. Crystals need to see some capacitance to oscillate at the right
> frequency, generally in the 10 to 30pF range. Even if PCB traces themselves
> bring some capacitance, there is no added caps on RCX PCBs (see
> http://www.brickshelf.com/cgi-bin/gallery.cgi?f=38746), this should be enough to
> explain the problem.
As David Ward suggested me, the oscillator is most probably equipped with a
ceramic resonator with built-in capacitors. This explains the low precision of
the clock (tolerance for ceramic resonators is in the 1% range while for
crystals it is in the 0.01% range). Resonators are cheaper too ;o)
Philo
|
|
Message is in Reply To:
15 Messages in This Thread:
  
 
- Entire Thread on One Page:
- Nested:
All | Brief | Compact | Dots
Linear:
All | Brief | Compact
|
|
|
|
