[time-nuts] FE-5680A Loop Lock Indicator

Sun Sep 22 15:06:57 EDT 2013

I have a circuit that seems to work well:
The lock indicator is a weak source but a good sink so it interfaces more
naturally with a pnp or p-channel device. Pull it up to 5V with 100K and
connect this point to the gate of a P channel Mosfet whose source is also
connected to 5V. Connect the drain of the mosfet to a LED anode and take the
LED cathode via 220 R to 0V.
This way, the sense of the indicator is correct (0n = lock) and the drive
capability of the lock signal works in your favour.

Chris Stake   

> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Bob Camp
> Sent: 22 September 2013 18:53
> To: Bob Stewart; Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] FE-5680A Loop Lock Indicator
> 
> Hi
> 
> If you want 10 ma through the LED (which should be plenty) then the
> collector resistor would be right around 1.2K
> 
> Bob
> 
> On Sep 22, 2013, at 1:32 PM, Bob Stewart <bob at evoria.net> wrote:
> 
> > D'oh, that should say "I could increase the COLLECTOR resistor to 1500
> ohms".
> >
> >
> >
> >
> >> ________________________________
> >> From: Bob Stewart <bob at evoria.net>
> >> To: Discussion of precise time and frequency measurement
> >> <time-nuts at febo.com>
> >> Sent: Sunday, September 22, 2013 12:27 PM
> >> Subject: Re: [time-nuts] FE-5680A Loop Lock Indicator
> >>
> >>
> >> Except that it doesn't work with even 1500 ohms in the base lead.  The
> LED immediately comes on and stays on.  I could increase the emitter
> resistor to 1500 ohms and get around 8.5-9ma through the LED, but I'm done
> playing with it until I get a proper box to put it all in.  This is just a
> random 3mm LED out of an HP 37203A, so maybe that has something to do with
> it?  I haven't looked at the specs.
> >>
> >> Bob
> >>
> >>
> >>
> >>
> >>
> >>> ________________________________
> >>> From: Bob Camp <lists at rtty.us>
> >>> To: Discussion of precise time and frequency measurement
> >>> <time-nuts at febo.com>
> >>> Sent: Sunday, September 22, 2013 12:12 PM
> >>> Subject: Re: [time-nuts] FE-5680A Loop Lock Indicator
> >>>
> >>>
> >>> Hi
> >>>
> >>> Circuit should be:
> >>>
> >>> 2N2222 with emitter to ground, collector to LED, base to lock
indicator
> via the 4.7K resistor. The LED is hooked to +15 via another resistor.
> >>>
> >>> If you have ~ 10 ma in the LED then the base needs less than 0.1 ma to
> do the job with a 2222. A 4.7K should be plenty.
> >>>
> >>> Alternate circuit:
> >>>
> >>> 2N2222 with base to lock indicator / no resistor at all, emitter to
> ground via a 1K resistor, collector to LED. LED to +15 via a 1.5K
resistor.
> >>>
> >>> Either one should work. Both turn on the LED when the output is high
> and off when the output is low. In order to turn on when it's high you
need
> to get an inversion ahead of the 2N2222.
> >>>
> >>> Bob
> >>>
> >>>
> >>> On Sep 22, 2013, at 12:17 PM, Bob Stewart <bob at evoria.net> wrote:
> >>>
> >>>> Hi Bob,
> >>>>
> >>>> I tried 4700 and even 1500, but they're too large.  I guess the
little
> flash of the LED at power-on is the hint that 1K is right at the ragged
> edge.  It would probably make a big difference if there was a 100 or even
> 47 ohm resistor between the emitter and the LED, but my little board is
> starting to get burnt up, wires are starting to get frayed, and it does
> work, so this cake is done.
> >>>>
> >>>> Bob
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>> ________________________________
> >>>>> From: Bob Camp <lists at rtty.us>
> >>>>> To: Discussion of precise time and frequency measurement
> >>>>> <time-nuts at febo.com>
> >>>>> Sent: Sunday, September 22, 2013 6:31 AM
> >>>>> Subject: Re: [time-nuts] FE-5680A Loop Lock Indicator
> >>>>>
> >>>>>
> >>>>> Hi
> >>>>>
> >>>>> If you trace out the chip that drives the lock indicator it's got
> some sort of strange gating in it's supply pin. That gets you even less
> output than you would expect from a CMOS gate. I would not count on it
> putting out more than 1 ma at 5 volts. A 4.7K resistor to the 2N2222 base
> should be about right.
> >>>>>
> >>>>> Bob
> >>>>>
> >>>>> On Sep 21, 2013, at 10:34 PM, Bob Stewart <bob at evoria.net> wrote:
> >>>>>
> >>>>>> Thanks for the heads-up, Bob.  I'll do it the next time the iron is
> hot.  Fortunately, it's only on for about a minute or so, then there's no
> drive from the FE-5680A.  Is 3ma really that big a deal?  I know squat
> about CMOS gates.  I guess it is pulling the voltage down by 25%, though.
> >>>>>>
> >>>>>> Bob
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>> ________________________________
> >>>>>>> From: Robert LaJeunesse <rlajeunesse at sbcglobal.net>
> >>>>>>> To: Bob Stewart <bob at evoria.net>; Discussion of precise time and
> >>>>>>> frequency measurement <time-nuts at febo.com>
> >>>>>>> Sent: Saturday, September 21, 2013 9:24 PM
> >>>>>>> Subject: Re: [time-nuts] FE-5680A Loop Lock Indicator
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>> Bob,
> >>>>>>>
> >>>>>>>
> >>>>>>> I would bump that base resistor up a lot higher, to load the FE-
> 5680 less. The PN2222 has enough gain it only needs about 0.3 mA base
drive
> to work as intended. You'd get that with a 10K base resistor.
> >>>>>>>
> >>>>>>>
> >>>>>>> Bob LaJeunesse
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>> ________________________________
> >>>>>>>> From: Bob Stewart <bob at evoria.net>
> >>>>>>>> To: Time Nuts <time-nuts at febo.com>
> >>>>>>>> Sent: Saturday, September 21, 2013 10:02 PM
> >>>>>>>> Subject: Re: [time-nuts] FE-5680A Loop Lock Indicator
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> Hi John,
> >>>>>>>>
> >>>>>>>> Thanks for the response.  I managed to cobble something up with
> >>>>>>>> LTSpiceIV, and get it to work.  And for me, that's saying
> >>>>>> something!    Here's what I wound up with:
> "http://www.evoria.net/AE6RV/GPSstd_PLL/LED-driver.png", where V2 is the
> Loop Lock Indicator.  The PN2222 shorts out the LED until it goes into
> lock, then the LED comes on.  It does give a short pulse when power is
> first applied and things are equalizing.  Even with a 1K resistor, the
4.2V
> from Lock signal is pulled down to 3V.
> >>>>>>>>
> >>>>>>>> And here's a pic of my Rb standard on it's temporary home with
the
> LED on a scrap of breadboard:
> >>>>>>>> "http://www.evoria.net/AE6RV/GPSstd_PLL/Rb.standard.png".
> >>>>>>>>
> >>>>>>>> Bob
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>> ________________________________
> >>>>>>>>> From: jmfranke <jmfranke at cox.net>
> >>>>>>>>> To: Bob Stewart <bob at evoria.net>; Discussion of precise time
> >>>>>>>>> and frequency measurement <time-nuts at febo.com>
> >>>>>>>>> Sent: Saturday, September 21, 2013 6:58 PM
> >>>>>>>>> Subject: Re: [time-nuts] FE-5680A Loop Lock Indicator
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>> Yes, but put an isolation resistor between the output and the
> >>>>>>>>> base of the transistor, something between 3K and 5K should
> >>>>>>>>> work. The LED will light upon power on and extinguish when lock
> is achieved.
> >>>>>>>>>
> >>>>>>>>> John  WA4WDL
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>> --------------------------------------------------
> >>>>>>>>> From: "Bob Stewart" <bob at evoria.net>
> >>>>>>>>> Sent: Saturday, September 21, 2013 6:10 PM
> >>>>>>>>> To: "Discussion of precise time and frequency measurement"
> >>>>>>>>> <time-nuts at febo.com>
> >>>>>>>>> Subject: Re: [time-nuts] FE-5680A Loop Lock Indicator
> >>>>>>>>>
> >>>>>>>>>> Hi Bob,
> >>>>>>>>>>
> >>>>>>>>>> I hooked the big voltmeter up to it, and it shows +4.2V out for
> about a minute, and then goes to 0. Looking on the web, it seems like I
can
> use that to drive a 2N2222 and put the LED and dropping resistor in the
> collector path with the emitter to ground? Does that sound right?
> >>>>>>>>>>
> >>>>>>>>>> Bob
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>>> ________________________________
> >>>>>>>>>>> From: Bob Camp <lists at rtty.us>
> >>>>>>>>>>> To: Discussion of precise time and frequency measurement
> >>>>>>>>>>> <time-nuts at febo.com>
> >>>>>>>>>>> Sent: Saturday, September
> >>>>>> 21, 2013 4:12 PM
> >>>>>>>>>>> Subject: Re: [time-nuts] FE-5680A Loop Lock Indicator
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>> Hi
> >>>>>>>>>>>
> >>>>>>>>>>> Those readings sound a lot more like a CMOS gate output than
> some sort of open drain / open collector discrete driver.
> >>>>>>>>>>>
> >>>>>>>>>>> Bob
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>> On Sep 21, 2013, at 4:43 PM, Bob Stewart <bob at evoria.net>
> wrote:
> >>>>>>>>>>>
> >>>>>>>>>>>> Hi Bob,
> >>>>>>>>>>>>
> >>>>>>>>>>>> It's rather curious. Using my handheld DVM in the diode
> >>>>>>>>>>>> scale, I get a reading of 448 in one direction and 458 in
> >>>>>>>>>>>> the other with it off and cold. In the 2K ohms scale, I get
> >>>>>>>>>>>> 561 and 562 ohms. Later on, I'll pop the top off again and
> >>>>>>>>>>>> take a pic so I can expand it and look at it. For what it's
> >>>>>>>>>>>> worth, my DDS board is 2 revisions earlier than the one
> >>>>>>>>>>>> Matthias Bopp
> >>>>>> modifies here
>
"http://www.dd1us.de/Downloads/precise%20reference%20frequency%20rev%201_0.
> pdf"
> >>>>>>>>>>>>
> >>>>>>>>>>>> Bob
> >>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>>>>>> ________________________________
> >>>>>>>>>>>>> From: Bob Camp <lists at rtty.us>
> >>>>>>>>>>>>> To: Discussion of precise time and frequency measurement
> >>>>>>>>>>>>> <time-nuts at febo.com>
> >>>>>>>>>>>>> Sent: Saturday, September 21, 2013 3:00 PM
> >>>>>>>>>>>>> Subject: Re: [time-nuts] FE-5680A Loop Lock Indicator
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> Hi
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> As far as I know the lock output is a CMOS output that will
> drive a couple of ma. There are so many variations that yours may indeed
be
> an open collector and good to +15 volts.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> Bob
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> On Sep 21, 2013, at 10:55 AM, Bob Stewart <bob at evoria.net>
> wrote:
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>> The instructions I got with this Rb said that you could
hook
> an LED through a 5-10K resistor to the +15 supply and get a lock
> indication. I'm using a 10K resistor and the LED lights as soon as it's
> powered up from cold. Is the loop lock indicator circuit broken or is it
> just another strange option for these things? I saw on one site that if
you
> do it this way it prevents lock, but mine seems to lock OK with or without
> the voltage.
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> Bob - AE6RV
> >>>>>>>>>>>>>> _______________________________________________
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