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A question for those that might know (or have an
opinion)... I have in hand an LPRO rubidium reference
that requires 1.7 amps at 24 volts while the oven
warms, dropping to 500ma while it runs.
Can I parallel three or four 7824
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Tom C,
As Bruce notes below, the LM338K is a 5 amp job with a 35v max DC input
rating.
Just allow adequate heatsinking otherwise the 338 will "foldback" due to
over temperature.
There's plenty of on-line help to select the resi
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From: Tom Clifton <[EMAIL PROTECTED]>
Subject: [time-nuts] Parallel voltage regulators
Date: Wed, 24 Oct 2007 16:33:08 -0700 (PDT)
Message-ID: <[EMAIL PROTECTED]>
Tom,
> A question for those that might k
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Tom Clifton wrote:
> A question for those that might know (or have an
> opinion)... I have in hand an LPRO rubidium reference
> that requires 1.7 amps at 24 volts while the oven
> warms, dropping to 500ma while it runs.
>
> Can
ject: [time-nuts] Parallel voltage regulators
> A question for those that might know (or have an
> opinion)... I have in hand an LPRO rubidium reference
> that requires 1.7 amps at 24 volts while the oven
> warms, dropping to 500ma while it runs.
>
> Can I parallel three or four 7824 T
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Alan Melia wrote:
> Hi Tom I dont think you need the resistors these are current limited and the
> sense is inside the chip so the resistors dont do anything (you are thinking
> of a negative feedback effect). All that happens i
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Magnus Danielson wrote:
> It is not that hard to acheive 2 A at 24 V after all. The old uA723 and
> variants would probably do the trick good enought for you with external
> transitor(s).
>
> I recommend to at least include fold
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Tom Clifton <[EMAIL PROTECTED]> wrote:
> A question for those that might know (or have an
> opinion)... I have in hand an LPRO rubidium reference
> that requires 1.7 amps at 24 volts while the oven
> warms, dropping to 500ma wh
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Thanks for all the good feedback! Looks like the LM388
is the way I'm to go. Got to toddle off to the local
surplus shop in the morning to see what they have in
the goodie bin. If they don't have it eBay is full of
them.
Tom
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christopher hoover wrote:
>
> Tom,
>
> Most of the oven circuits will tolerate a significant sag in potential
> during warm-up as long as the supply doesn't cut out. I've often run OCXO's
> and Rb's off a "wimpy" bench supply w
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Hi Tom:
When I had that problem a work around was to parallel a battery with the power
supply (using a diode). The battery supplies the extra current while the oven
warms up. If the power supply voltage is a little higher t
single one
of these should do the job OK.
Cheers!,.Don Collie jnr.
- Original Message -
From: "Tom Clifton" <[EMAIL PROTECTED]>
To:
Sent: Thursday, October 25, 2007 12:33 PM
Subject: [time-nuts] Parallel voltage regulators
> ); SAExim
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Don Collie wrote:
> Hi Tom,
> If you really want to regulate the oven`s supply voltage, my National
> Voltage Regulator handbook shows that the LM317T will supply over 2 Amps,
> with an input/output differential of between
ussion of precise time and
frequency measurement"
Sent: Thursday, October 25, 2007 5:42 PM
Subject: Re: [time-nuts] Parallel voltage regulators
> Don Collie wrote:
>> Hi Tom,
>> If you really want to regulate the oven`s supply voltage, my National
>> Voltage Regulator
hs" <[EMAIL PROTECTED]>
> To: "Don Collie" <[EMAIL PROTECTED]>; "Discussion of precise time and
> frequency measurement"
> Sent: Thursday, October 25, 2007 5:42 PM
> Subject: Re: [time-nuts] Parallel voltage regulators
>
>
>
Show me where
sday, October 25, 2007 7:20 PM
Subject: Re: [time-nuts] Parallel voltage regulators
> Don Collie wrote:
>> Bollocs, Bruce! If National say it will do it, you can bet that it will.
>> An
>> LM338K will do the job too, but in my opinion it`s overkill, and in the
>> event of a
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Don Collie wrote:
>
> Hi Bruce,
> I`ve got the National Semiconductor Corporation Voltage Regulator
> Handbook [1982]. On page 3-3, the leftmost graph shows the LM117/217/317 as
> having its current limit, with a junction
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From: Bruce Griffiths <[EMAIL PROTECTED]>
Subject: Re: [time-nuts] Parallel voltage regulators
Date: Thu, 25 Oct 2007 13:51:47 +1300
Message-ID: <[EMAIL PROTECTED]>
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From: Bruce Griffiths <[EMAIL PROTECTED]>
Subject: Re: [time-nuts] Parallel voltage regulators
Date: Thu, 25 Oct 2007 17:42:51 +1300
Message-ID: <[EMAIL PROTECTED]>
> Don Collie wrote:
> > Hi Tom,
> >
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This may be a bit late in this [strangely contentious] discussion, but
I have to ask why you need to regulate the heater voltage? If the
voltage varies, the control loops will adjust accordingly. Unless the
input voltage is hi
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The simple answer is if the heater supply in unregulated, and the
supply changes, it will take a little while before the heater control
loop can compensate. While this is happening, the oven temperature
will be slightly wrong,
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Magnus Danielson wrote:
> From: Bruce Griffiths <[EMAIL PROTECTED]>
> Subject: Re: [time-nuts] Parallel voltage regulators
> Date: Thu, 25 Oct 2007 17:42:51 +1300
> Message-ID: <[EMAIL PROTECTED]>
&g
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There is a concept in temperature control called feed-forward.
In this case you would sample the supply line with an inverting
amplifier and use it to increase the oven drive signal as the
line voltage decreases. The goal is to
se time and frequency measurement"
Sent: Friday, October 26, 2007 12:29 PM
Subject: Re: [time-nuts] Parallel voltage regulators
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>
> The simple answer is if the heater supply in unregulated, and the
> supply change
ime-nuts] Parallel voltage regulators
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>
> Magnus Danielson wrote:
>> From: Bruce Griffiths <[EMAIL PROTECTED]>
>> Subject: Re: [time-nuts] Parallel voltage regulators
>> Date: Thu, 25 Oct 2007 1
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Don Collie wrote:
>> Bruce
>> I don`t think the higher current created when a fuse is used instead of
>> near-instantaneous current limiting is "alleged", but rather a real problem
>> that can cause damage further down the lin
day, October 26, 2007 1:21 AM
Subject: Re: [time-nuts] Parallel voltage regulators
> There is a concept in temperature control called feed-forward.
>
> In this case you would sample the supply line with an inverting
> amplifier and use it to increase the oven drive signal as the
>
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Considering the efficiency and easy availability of switchmode
supplies these days, I would never bother with a linear regulator
in a new design.
For instance national has a series of switch mode regulators (LM25xx)
which just
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Poul-Henning Kamp wrote:
> Considering the efficiency and easy availability of switchmode
> supplies these days, I would never bother with a linear regulator
> in a new design.
>
> For instance national has a series of switch mo
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>Poul-Henning Kamp wrote:
>> Considering the efficiency and easy availability of switchmode
>> supplies these days, I would never bother with a linear regulator
>> in a new design.
>>
>> For instance national has a series of
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Switchmode regulators really are risky for use in a low
noise environment. Even if you can reduce input and
output conducted noise to acceptable levels, the
opportunity for magnetic coupling from the inductor
to adjacent wiring
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Pete wrote:
> Switchmode regulators really are risky for use in a low
> noise environment. Even if you can reduce input and
> output conducted noise to acceptable levels, the
> opportunity for magnetic coupling from the inducto
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J.D. Bakker wrote:
>> Poul-Henning Kamp wrote:
>>
>>> Considering the efficiency and easy availability of switchmode
>>> supplies these days, I would never bother with a linear regulator
>>> in a new design.
>>>
>>> For
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In a message dated 10/26/2007 14:59:29 Pacific Daylight Time,
[EMAIL PROTECTED] writes:
>> That is a recipe for disaster if one wants a really low noise oscillator.
>> This is particularly true if one is a beginner.
>> R
urday, October 27, 2007 10:07 AM
Subject: Re: [time-nuts] Parallel voltage regulators
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>
> I do have some experience with temperature controlled ovens. I found that
> a
> long term plot of the temperat
bject: Re: [time-nuts] Parallel voltage regulators
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I do have some experience with temperature controlled ovens. I found
that a long term plot of the temperature while using an unregulated
supply on the oven heater showed
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This has been a fascinating and educational thread! I
have always been aware of noise coming from switching
regulators - just have Argo or Speclab look at your
laptop's sound card with "no input" signal and there
is plenty to l
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Tom Clifton wrote:
> This has been a fascinating and educational thread! I
> have always been aware of noise coming from switching
> regulators - just have Argo or Speclab look at your
> laptop's sound card with "no input" sign
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Don Collie wrote:
> Great idea!!,Don C.
>
Now all you need is a current limited bypass switch to protect the load.
Such a switch is relatively easy to implement.
Bruce
___
electrolytic].
...Don C.
- Original Message -
From: "Bruce Griffiths" <[EMAIL PROTECTED]>
To: "Discussion of precise time and frequency measurement"
Sent: Saturday, October 27, 2007 1:57 PM
Subject
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Don Collie wrote:
> I`ve always wondered about noise from batteries - please tell us more
> Bruce!! [also wondered about noise from the electrolytic action of
> aluminium, and tantalum electrolytic capacitors, and wondered
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Don Collie wrote:
> I`ve always wondered about noise from batteries - please tell us more
> Bruce!! [also wondered about noise from the electrolytic action of
> aluminium, and tantalum electrolytic capacitors, and wondered
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Bruce Griffiths wrote:
> Don Collie wrote:
>
>> I`ve always wondered about noise from batteries - please tell us more
>> Bruce!! [also wondered about noise from the electrolytic action of
>> aluminium, and tantalum elec
y measurement"
Sent: Saturday, October 27, 2007 7:26 PM
Subject: Re: [time-nuts] Parallel voltage regulators
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>
> Bruce Griffiths wrote:
>> Don Collie wrote:
>>
>>> I`ve always wondered
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In message <[EMAIL PROTECTED]>, "Don Collie" writes:
>); SAEximRunCond expanded to false
>I`ve always wondered about noise from batteries - please tell us more
>Bruce!! [also wondered about noise from the electrolytic acti
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From: Tom Clifton <[EMAIL PROTECTED]>
Subject: Re: [time-nuts] Parallel voltage regulators
Date: Fri, 26 Oct 2007 17:19:45 -0700 (PDT)
Message-ID: <[EMAIL PROTECTED]>
> ); SAEximRunCond expanded to false
>
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