[time-nuts] Temperature weirdness with Thunderbolt & Lady Heather 5

Bob Camp kb8tq at n1k.org
Sat Dec 17 14:30:57 EST 2016


Do you (or your assistant) have a cell phone? Where was it when the original issue occurred? 

Yes, it’s a bit of a long shot, but I *have* seen test data messed up by the phone
in a tech’s pocket. We finally worked it out when the speaker on the test computer started chirping
as the cell phone did it’s “check into the mothership” thing. 


> On Dec 17, 2016, at 1:56 PM, Pete Stephenson <pete at heypete.com> wrote:
> On 12/15/2016 3:05 AM, Pete Stephenson wrote:
>> Hi all,
>> I have a Thunderbolt and am running Lady Heather 5. I've been seeing
>> odd drops of ~0.7 degrees Celsius that slowly recover over around 10
>> minutes or so. This has happened 19 times in the last 36 hours.
> [snip]
> Hi all,
> I'm pleased -- but a little frustrated -- to report that I've been
> unable to reproduce the issue after a few days of trying. A screenshot
> of the happy Thunderbolt as shown by Lady Heather is attached.
> At first, I thought the issue might have been a dodgy USB-to-serial
> dongle, so I connected the Tbolt directly to the computer's hardware
> serial port (which normally is connected to another device). The issue
> immediately cleared up.
> However, when I later reconnected the Tbolt to the same USB-to-serial
> adapter (which uses a genuine FTDI chip) the problem did not recur.
> The power supply is a used, Cisco power supply provided by the Chinese
> eBay vendor that sold me the Thunderbolt. My digital multimeter showed
> that the voltages provided were, while not dead-on -12V, +12V, and +5V,
> were within the specs required by the Thunderbolt's manual.
> Additionally, I probed the power pins with my oscilloscope both while
> the Thunderbolt was powered off and also when I disconnected the power
> connector. Visually, the traces appeared smooth, with no visible ripple
> or spikes. The FFT function on the scope showed no spikes or anything
> unusual between DC and 5 MHz (I didn't bother checking beyond that).
> Since the Thunderbolt had been turned off for a few months to save
> electricity, I thought that perhaps the issue only occurred when the
> unit was started after being cold. I unplugged it and let it cool
> overnight, then started it again. Again, nothing unusual. It's working fine.
> The only other thing I can think that might have caused an issue is I
> had recently connected another USB device (an Arduino Pro Micro
> programmed as an EDtracker: http://www.edtracker.org.uk/) that had been
> previously setup to use the same COM port number as the FTDI adapter.
> Although Windows should prevent (or at least warn about) such conflicts,
> it did not. It's possible that the output of the EDtracker was getting
> mixed in with the serial data from the Thunderbolt and causing
> corruption that Lady Heather interpreted as temperature and DAC excursions.
> Unfortunately, I can't seem to replicate the issue, so I'm out of ideas.
> In short: everything I can think to check seems to be ok.
> Thanks to all for the help and suggestions, but I think this issue is
> resolved for the time being.
> Cheers!
> -Pete
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