[time-nuts] +12 Volts 1A (plus a bit) supply?
Bob Stewart
bob at evoria.net
Fri Jun 28 00:37:16 UTC 2013
Thanks for the correction Bob. I don't know what made me think it was an on/off oven. The OC-050 datasheet gives a drain of 12 watts in warmup and 4 watts in run mode, so I went with that in the post I just made, calculating the loads, etc.
Bob
----- Original Message -----
> From: Bob Camp <lists at rtty.us>
> To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
> Cc:
> Sent: Thursday, June 27, 2013 7:27 PM
> Subject: Re: [time-nuts] +12 Volts 1A (plus a bit) supply?
>
> Hi
>
> The OCXO in the TBolt has a linear controller. It drops back to about 150 to 250
> ma on the +12 line after warmup. It's been at least 40 years since I saw an
> on/off oven control in production ….
>
> Remember that the +12 feeds the oscillator circuit. The more crud on the 12
> volts, the worse the phase noise of the output. A linear regulator is a good
> idea.
>
> Bob
>
> On Jun 27, 2013, at 3:49 PM, Bob Stewart <bob at evoria.net> wrote:
>
>> Hi Hal and other responders,
>>
>> I believe that the OCXO uses an ON-OFF type of regulation. So, no, it
> doesn't use 1A all the time. Maybe I should just put an ammeter in the line
> and see what kind of duty cycle it has after it's at temperature.
>>
>>
>> I tried a 7812 regulator with a small dissipator on it. It goes into
> overheat mode almost immediately and the output voltage starts quickly doing
> down. The case does have provisions for a single TO-3 transistor conducting
> heat to the back of the case with no radiating fins. I had briefly considered
> using a zener and a 2N3055.
>>
>> I think that instead of worrying this to death, I'm just going to use a
> brick to get it together, and then if something comes up later that I like,
> I'll put that in. I did like the looks of that PT5102 but it's at end
> of life, and 1A is right at it's limit. I've given some consideration
> to seeing whether I can pull a few turns off the transformer secondary, as well.
>>
>>
>> Bob - AE6RV
>>
>>
>>
>> ----- Original Message -----
>>> From: Hal Murray <hmurray at megapathdsl.net>
>>> To: Bob Stewart <bob at evoria.net>; Discussion of precise time and
> frequency measurement <time-nuts at febo.com>
>>> Cc: hmurray at megapathdsl.net
>>> Sent: Thursday, June 27, 2013 2:24 PM
>>> Subject: Re: [time-nuts] +12 Volts 1A (plus a bit) supply?
>>>
>>>
>>> bob at evoria.net said:
>>>> The transformer gives me about 20 volts DC out. Dropping 8 volts
> at 1 amp
>>>> is just a lot of power to void with a resistor. I'd like to
> avoid
>>> having
>>>> that much waste heat in the unit.
>>>
>>> Does it really take 1A after it's warmed up?
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