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

Angus not.again at btinternet.com
Mon Sep 23 00:56:12 UTC 2013 

Hi,

A lot of indicator outputs on oscillators and other things are completely or primarily pull-downs, just like some microcontroller pins.

The problem with surplus stuff like this that don't come with exact datasheets for their options is that you have to work out for yourself how it's configured, etc. If it does not look like a proper TTL or CMOS output (especially when loaded a little) it's worth checking to see if it is a pull down.
Sometimes they're just weird (or faulty!). It all depends what they were designed to connect to.

I find low current LEDs are useful to give some indication with minimal loading to reduce the chance of any complications, since you never know what else is going on. A while back there was some discussion of the pps output on some 5680As not working because of the lock indicator pin being pulled down too much.

More info at
http://www.ko4bb.com/dokuwiki/doku.php?id=precision_timing:fe5680a_faq
if you have not already seen it.

Angus.



From: "Bob Stewart" 
To: "Time Nuts" 
Sent: September 22, 2013 10:12 PM
Subject: Re: [time-nuts] FE-5680A Loop Lock Indicator

I hadn't thought of using a pullup resistor.  I'd have to get out the calculator to see if it's worth it, though.  It's only taking a load for a minute or two till it locks, so I don't think it's a problem.

Bob





>________________________________
> From: Chris Stake 
>To: 'Discussion of precise time and frequency measurement' ; 'Bob Stewart'  
>Sent: Sunday, September 22, 2013 2:06 PM
>Subject: RE: [time-nuts] FE-5680A Loop Lock Indicator
> 
>
>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  wrote:
>> 
>> > D'oh, that should say "I could increase the COLLECTOR resistor to 1500
>> ohms".
>> >
>> >
>> >
>> >
>> >> ________________________________
>> >> From: Bob Stewart 
>> >> To: Discussion of precise time and frequency measurement
>> >> 
>> >> 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 
>> >>> To: Discussion of precise time and frequency measurement
>> >>> 
>> >>> 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  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 
>> >>>>> To: Discussion of precise time and frequency measurement
>> >>>>> 
>> >>>>> 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  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 
>> >>>>>>> To: Bob Stewart ; Discussion of precise time and
>> >>>>>>> frequency measurement 
>> >>>>>>> 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 
>> >>>>>>>> To: Time Nuts 
>> >>>>>>>> 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 
>> >>>>>>>>> To: Bob Stewart ; Discussion of precise time
>> >>>>>>>>> and frequency measurement 
>> >>>>>>>>> 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" 
>> >>>>>>>>> Sent: Saturday, September 21, 2013 6:10 PM
>> >>>>>>>>> To: "Discussion of precise time and frequency measurement"
>> >>>>>>>>> 
>> >>>>>>>>> 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 
>> >>>>>>>>>>> To: Discussion of precise time and frequency measurement
>> >>>>>>>>>>> 
>> >>>>>>>>>>> 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 
>> 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 
>> >>>>>>>>>>>>> To: Discussion of precise time and frequency measurement
>> >>>>>>>>>>>>> 
>> >>>>>>>>>>>>> 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 
>> 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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