Yep, injection locling works just fine
Don
----- Original Message -----
From: "paul swed" <[email protected]>
To: "Discussion of precise time and frequency measurement"
<[email protected]>
Sent: Sunday, August 08, 2010 7:37 PM
Subject: Re: [time-nuts] Regulating a pendulum clock
Now I will get myself in a lot of trouble.
Why wouldn't a constant pulse at a 2 sec interval essentially lock the
pendulum after a bit.
If the pulse is always there and occurs just after the mid swing. I
suspect
you do need to adjust current with a pot to get things settled. But
essentially open loop.
I have often thought about tinkering exactly like this if I ever ran
across
a nice clock like the one at television network TVA in Montreal that used
to
run network time. Unfortunately they would not part with it.
Good luck
On Sun, Aug 8, 2010 at 7:22 PM, Bruce Griffiths
<[email protected]>wrote:
Mere fast blow fuses aren't usually precise enough to protect transistors
against over current unless one uses rather large transistors.
Overcurrent protected drivers are available and readily designed/built.
Protection against di/dt transients due to external events is also
advisable.
Minimising the parts count isn't necessarily conducive to improved
reliability when external hazards aren't taken into account.
Merely resonating the coil without other filtering doesnt necessarily
lead
to low EMI when driving it with a voltage waveform having high edge slew
rates.
Some edge filtering to control the current flowing in the load
capacitance
is also advisable.
Bruce
Don Latham wrote:
fast blow fuse, resonate the coil to the pwm frequency. Parts count
small,
tinkering in software instead of breathing lead fumes or whatever
noxious
stuff the Europeans have forced us to use...
Don
Bruce Griffiths
No protection against external shorts or other undesired events.
Extensive analog filtering to avoid creating an effective radiator of
noise may also be necessary.
Simple analog techniques are probably simpler/cheaper once the
necessary
filtering and protection are included.
Bruce
Don Latham wrote:
Hmmm lemme see. I think I'd use a 12 volt supply and two transistors
driven by two outputs on my Arduino,basic stamp,picaxe or other
whizzie.
I'd then implement a PID controller essentially using the 1 sec pulse
from
the pendulum and the 1 sec pulse from my Rb, satellite receiver,
crystal
clock, or whatever. The appropriate output pin will be brought to
ground,
and the other driven as a pdf with the rate given by the pid loop.
Temperature and even pressure corrections can be applied within the
gizzie
software. External parts, minimum. Opportunity to play with tuning,
maximum.
Don
Bruce Griffiths
J. Forster wrote:
You are picking very unimportant nits.
If there were a small noise spike from the opamp, it'd goose the
pendulum
a tiny amount. That would be corrected on the next swing.
Heuristic analysis of this type is counter productive.
You are turning a trip to the corner store into an Apollo Moon
Mission.
Reliability is paramount in a circuit that may be required to work
for
decades.
BTW, since the =drive does not to be bipolar, one of the NPN and PNP
transistors can be deleted. They never turn on. So you are left with
two
opamsa, =each with a simple emitter follower.
The original request was for a bipolar drive.
The lack of short circuit protection is poor design practice when
driving an external load.
-John
==============
Bruce
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