Hi Tom,
Actually, no-one has. And come to think of it, maybe that's the root of the
problem. I have the resistors lying on their sides right under the OCXO on the
opposite side (bottom) of the PC board. Any air circulation is going to make
them weave and wobble a bit in value. I'll have to
li...@rtty.us said:
> A 7805 has a *rated* temperature coefficient of 2 mv / C. Most parts do way
> better than this. The problem is knowing if you have a good part or not. On
> a 5V part, your reference could be running 400 ppm/C. Since the divider has
> no impact on this number, it over-rides wh
I am not sure if anyone else mentioned this, Placing the parts against the
oscillator with a little thermal epoxy under a small piece of foam so they are
at least partially "ovenized" should really help.
Thomas Knox
> From: li...@rtty.us
> Date: Fri, 31 Jan 2014 22:36:46 -0500
> To: lajeune.
Hi
If you attenuate the DAC 100:1 to 1000:1 before it hits the OCXO, the DAC does
not matter much. That may sound like a crazy ratio, but it is indeed possible
with some of these OCXO EFC ranges. They can have a *lot* of swing.
The reference is an LTZ1000, they run about $50 in single piece lo
Must be military prices. If using 5 PPM resistors in the build a reference much
better than that isn't needed, especially if the temperature is somewhat
controlled, like time nuts do. A commercial 3 PPM/C part, the LM4140A, is $4.54
each in singles. At 2.2uV p-p it's reasonably quiet as well.
C
On 1/30/2014 7:50 PM, John Miles wrote:
Exactly, for unity gain you'd design for +6 dB and series-terminate the
output with 50R. Good for capacitive loads as well as isolation.
Do you run it in inverting or non-inverting configuration?
I've only used the non-inverting configuration (figure
Any idea what the usual temperature coefficient is for the VRef output of the
OCXO? I looked under the Trimble label of my spare and found: DOC2127 and
44/1416. The one I have installed is probably the same.
>
> From: Bob Camp
>To: Bob Stewart ; Discussion
Hi
A 7805 has a *rated* temperature coefficient of 2 mv / C. Most parts do way
better than this. The problem is knowing if you have a good part or not. On a
5V part, your reference could be running 400 ppm/C. Since the divider has no
impact on this number, it over-rides what ever you do with th
Don't underestimate the effect of resistors being at different
temperatures. The tempco isn't linear at all, so your drift caused by
ambient temp won't be the same at the different resistors. It is best to
have them at the same value!
I'd been experimenting quite some days to find a reasonable sol
Around $25.00 to reproduce the final result. The cost goal for me to make it
work is considerably more elastic. It's a project that I'm having fun with.
There is no commercial market.
>
> From: "ewkeh...@aol.com"
>To: time-nuts@febo.com
>Sent: Friday, Janua
What is your cost goal?
Bert Kehren
In a message dated 1/31/2014 3:19:50 P.M. Eastern Standard Time,
b...@evoria.net writes:
I'm trying to put something together that is generic enough for the guys
on the VE2ZAZ GPS Standard board, but that will be relatively free of
temperature issues.
Joe-
You might be on to a good idea. If I could use a pair of optical sensors to
watch the escapement wheel when winding, then I could count any movement in
either direction or no movement at all and know how much to slew the timing
pulses say over the next hour or two to get the clock back on
Hi Bob,
Do you think that maybe the oven current difference when the temperature
changes could be at the root of this? To me, it seems like this started when I
put the divider in. Before that, drift might have been hidden due to the lower
resolution, I suppose. In any case, Mouser has my mon
Hi
If you are going to attenuate the EFC *and* center it up around 3V you will
also need a voltage reference. Even a good one has a TC. You also have oven
current running in the ground pin which contributes to voltage issues (oven and
EFC share a common ground). Past that, you have thermocouple
As to what the specs are on this oscillator, I couldn't say. I have two of
them. The one in my GPSDO wants about 2.101V for 10MHz. The other one wants
about 2.6V (from memory). So that pretty much limits my options to a divider
and a summing device to bring the EFC back up for the oscillator
Count the period where the counterweight is disconnected from the
movement using a microswitch and then program the controller to speed up
the clock to make up the difference until the next time the clock needs
to be rewound.
Sort of like the way my bank just recalculated my escrow fund:-)
--
Is the op amp just a unity gain buffer or does it have any gain setting
resistors that might be adjusted?
I'm just wondering if you could tailor the gain to reduce the swing rather
than require the oscillator to effectively require a larger swing.
The 344310-T is likely to have come from a
Hi:
The Zendulum uses a magnetic ball as the pendulum (it rides on a curved track rather that from a string like the first
version) and there's a coil in the base.
Each pass over the coil causes the coil to output a pulse that drives a circuit that in turn sends a power pulse to the
coil repell
Hi Volker,
Thanks for the ideas. The resistors are all within a short radius of each
other. I hadn't thought about bundling them all together. I suppose I could
epoxy them together as a last resort. I've got some EPF foam, so I could try
putting that on the board right against them. In fac
I'm trying to put something together that is generic enough for the guys on the
VE2ZAZ GPS Standard board, but that will be relatively free of temperature
issues. Yeah, I know: an impossible task. The precision of the GPSDO is
probably not in the same league as what this board is used to. The
Brian your clock will be running. I can assure none of our CS, RBs or me
will be.
Not sure how I will break, but those pesky things called capacitors,
resistors and semiconductors will.
Almost every piece of test gear I have picked up as broken was due to one
form or another of some cap. being bad.
Sorry, missing picture...
Am 31.01.2014 20:47, schrieb Volker Esper:
> Here's how to place the divider resistors. The picture is from 1992, I
> didn't use SMDs then. But the results are promising at a very low price.
>
>
> Isolierband = insulation tape
> wärmeleit. Kern = thermoconducting core
>
>
Thanks for all the ideas and replies. Let me see if I can address all
points in just
one e-mail.
1) The clock(s) in question are very costly and to modify them in any way
would
instantly kill the value. These are part of history collection in 100%
original condition.
2) These clocks wind with a
Here's how to place the divider resistors. The picture is from 1992, I
didn't use SMDs then. But the results are promising at a very low price.
Isolierband = insulation tape
wärmeleit. Kern = thermoconducting core
The picture shows two examples, the left one if you need three
resistors, the righ
The ratio tempco is the point! It's hard to design a divider yourself,
since temperature differences between the two divider resistors is the
problem.
Resistor networks with very low ratio tempcos are fairly expensive. I
don't know your budget and how far you want to go. If you want to try it
your
It's hard to be sure without knowing the characteristics of the DAC ouput
and the oscillator EFC, but if you're only making a one off I wonder if it
might perhaps be possible to simplify that arrangement to just a potential
divider using selected values and being fed from the DAC and tapped
Not know much about the clock in question... ...how about replacing
the weight and cable with an endless cable and motor to constantly
'pull' on the thing... You might have to remove a few parts, but may
be able to make the changes so you can always restore the clock to
original condition later
The escapement wheel needs to have a little torque on it so it will turn as
the pendulum swings.
Regards.
Max. K 4 O DS.
Email: m...@maxsmusicplace.com
Transistor site http://www.funwithtransistors.net
Vacuum tube site: http://www.funwithtubes.net
Woodworking site
http://www.angelfire.com/e
Thank you.
Regards.
Max. K 4 O DS.
Email: m...@maxsmusicplace.com
Transistor site http://www.funwithtransistors.net
Vacuum tube site: http://www.funwithtubes.net
Woodworking site
http://www.angelfire.com/electronic/funwithtubes/Woodworking/wwindex.html
Music site: http://www.maxsmusicplace.
wa1...@att.net said:
> I think the best I can do is to use the basic design from the article that
> David noted and will have to adjust the clock once a week after winding.
How far off does it drift while you are winding?
I haven't wound a pendulum clock since watching my grandfather (and maybe
I just realized that I have a pot in the mix. I see one on Mouser with
25PPM/C, so I suppose I'll try that. Here's the circuit I'll use with the
replacements. What I have in there now has the values of R3, R4, and R5
multiplied by 10 and R2 is 3.9K. I suppose it won't matter so much for the
Hi Nigel,
I didn't give any thought to thermal issues when I bought the resistors.
They're just standard carbon composition. I see some metal film resistors with
a temp coefficient of 5 PPM/C, so I'll get some of those and put them in.
thanks,
Bob
>
> Fro
Jellybean resistors can have a tempco in the 100s of PPM per degree C. Some
precision resistors are as low as 25 PPM/C while really good resistors can be
had at 5 PPM/C. Better yet look for a resistor array where part tracking is
called out. Some arrays get below 5 PPM tracking so the division r
The problem is certainly real enough.
What you're seeing is a drift of approx 2500ppm, and Vishay shows the
temperature coefficient of their standard carbon film resistor, for example,
to
be approx 200ppm per degree C for a value of 20K.
If yours is carbon film this would imply your measur
Tom thanks for your continuing contributions to the science and history of time
and frequency. Your passion and knowledge set a high bar for both amateurs and
professionals that can help motivate each of us toward our own goals. The
ability to both educate and motivate is indeed a rare gift.
Be
I put a divider network in the EFC line of my GPSDO to restrict the OCXO range
to 2Hz. Now I'm seeing heat-related drift that wasn't apparent before. I put
a 20K resistor from the same strip on my 3456A, and the warmth of holding it
between fingers moves it by about 50 ohms. What type of resi
Brian,
It would seem that while you are winding the clock, the pendulum could be
measured by the use of the same coil that syncs it. That way you would
sense the run down and over a short period after the clocks been wound
speed up to re-align the tick.
I could imagine a coil below the pendulum and
Tom,
Very enjoyable talk. One small non time related quibble. Ray and
Charles Eames were not brothers; Ray was Charles Eames (Eames Chair etc)
wife and a co-collaborator on many projects. PBS has a documentary of
their work and life together.
http://www.pbs.org/wnet/americanmasters/episode
Le 31 janv. 2014 à 06:06, Brian, WA1ZMS a écrit :
< snip>
>
> "Modern" pendulum clocks have a modified gear drive where the
>
> escapement is still being driven while the main wheel is being advanced
>
> to wind the weight cable. Not the case for 200+ year old clocks.
>
>
It is not so much t
Mike-
Yes, I was wrong. The idea of constant driving power was around. Sadly most of
these early American tall clocks with often sand filled weights used a simple
design since as you noted cost was important and raw metals such as brass was
hard to produce locally and often imported from Europe
If you take the link in the original message (it is a youtube
presentation), the player on that page has an option to open the video
in Youtube.
Anyway, it goes here:
http://www.youtube.com/watch?v=MT2reYXPvGg
On 1/30/2014 8:30 PM, Max Robinson wrote:
Tom. Could you give us a link to the u t
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