[GPS_Standard] -5 to +5 Voltage Source

[Dave]

I used the LT1054 on mine. It has the advantage of being able to take up to
15V input and give a regulated -5V output at up to 100mA  It doesn't suffer
the internal series resistance issues of the 7660 where the output drops
with load. An example of my using it is at http://g4fre.com/10gpa.htm

Dave

G4fre

-----Original Message-----
From: GPS_Standard [mailto:gps_standard-bounces at mailman.qth.net] On Behalf
Of Zack Widup
Sent: 15 December 2014 03:23
To: gps_standard
Subject: Re: [GPS_Standard] -5 to +5 Voltage Source

The VE2ZAZ design includes a 5 volt positive regulator on the circuit board.

To get a negative 5 volts I've used the simple 7660, etc. design that
just requires a few capacitors. Positive 5 volts in (brought from the
7805 on the circuit board) produces -5 volts out. The current demand
for this circuit is well within the specs of a 7660 or a 7662. I have
some other circuits that will supply quite a bit more current at
negative 5 volts. I think the TC962 is one device. The LT1072/1172 is
another.

73, Zack W9SZ


On 12/13/14, Dave Platt <dplatt at radagast.org> wrote:
>
>> I'm having difficulty understanding how to create the proper voltage
>> source
>> for the VE2ZAZ control board, -5 to +5 volts.  Any suggestions?
>
> There are several approaches.
>
> If you start with a single-voltage supply (say, a +12 or +24 - whatever
> your oscillator requires) you can add an additional regulator to get a
> clean +5 supply for the board's oscillator-control output.  Since you
> only need a small current, a simple 78L05 regulator and a couple of
> filter caps would be all you need.
>
> The -5 is more difficult.  The most straightforward way is to use a
> commercially-made or home-made power supply with both positive and
> negative outputs... say, a +/- 15 (these are relatively common) and then
> use a negative voltage regulator such as a 7905 to regulate the -15 down
> to -5.
>
> You could buy a kit such as the Chaney C6895 from Electronics
> Goldmine... this has three variable output voltages (positive and
> negative up to 15 volts, at 400 mA, and positive up to 21 volts at 1
> ampere).  This might be your best bet, if 1 amp is enough to run the
> oscillator with its heater and the main VE2ZAZ input - the two
> low-current outputs could be set to +5 and -5 and provided to the VE2ZAZ
> output circuit.
>
> It *is* possible to start with a single-voltage DC supply, and generate
> positive and negative voltages from it.  It's a bit tricky.  One
> approach is to use a switching-type "inverting regulator" to create the
> negative voltage.  Alltronics has a +12 in, -5 out (Astec AA7600), $8
> for two.  These switching inverters might not be a great solution for a
> GPSDO where you want really low noise, though.
>
> Another approach is to start with something like a 24-volt DC supply,
> and use a 7805 linear regulator to create an "artificial ground" (which
> then becomes the "GND" power input to your VE2ZAZ board).
>
> If I were you I'd probably look for a multiple-output DC power supply...
> Electronics Goldmine, Alltronics, All Electronics, Marlin P Jones are
> all good on-line vendors to check.
>
> And... as an out-of-the-box possibility - although your HP oscillator
> has a -5 to +5 tuning range, there's no law that says you have to
> actually *use* the whole tuning range.  You could have the VE2ZAZ board
> put out a tuning voltage between 0 and 5 (so no negative supply
> required) and use the HP oscillator's "FREQ ADJUST" trimmer to
> rough-tune the oscillator so that it's right about on-frequency when the
> VE2ZAZ is feeding a mid-scale output (2.5 volts) to the oscillator's
> EFC input.
>
> This would let you get away with just positive power supply voltages to
> the oscillator oven, oscillator input, and VE2ZAZ.
>
>
>
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