Junkbox switch for a switcher

On 08/24/2016 09:54 AM, dagmargoodboat@yahoo.com wrote:
> On Wednesday, August 24, 2016 at 9:36:46 AM UTC-4, bitrex wrote:
>> On 08/24/2016 07:48 AM, Winfield Hill wrote:
>>> Tim Williams wrote...
>>>>
>>>> IRF530 is fine:
>>>> http://seventransistorlabs.com/Images/Discrete_Tube_Supply.png
>>>>
>>>> "bitrex" wrote ...
>>>>> I need to throw together a ~150 volt supply at a few 10s
>>>>> of mA to test a circuit idea, but I don't have much in
>>>>> the way of MOSFETs in my junk box to build a switcher from.
>>>
>>>    The IRF530 is an old inferior part.  Someone should tell
>>>    bitrex his FQP2N60C is generally a fine part, suited for
>>>    a low-current boost supply, using a simple inductor.  An
>>>    IRF530 has too low a voltage rating for a boost converter.
>>>
>>>    bitrex may not have a copy of our new book, but Chapter 9
>>>    has 109 pages about power supplies, here's a free sample:
>>> http://artofelectronics.net/wp-content/uploads/2016/02/AoE3_chapter9.pdf
>>>
>>>    For 12V to about 150V at say 25mA, the MOSFET, will be
>>>    on about D = 1-Vin/Vout = 92% of the time (page 647).
>>>    The 12V input current will be Iout/(1-D) = 300mA.  Yes,
>>>    the FQP2N60C, with 5-ohm ON resistance, will waste 15%
>>>    of the power, but hey, it's right there in the junk box.
>>>    A 220uH inductor with 50kHz switching should work fine.
>>>
>>>
>>
>> Thanks, that's sort of what I was hoping for. I think I have some
>> suitable inductors too. I'm not big into winding transformers...
>
> You could tear up a 12v wallwart smps & run it backwards.  That'll
> get you everything you need, parts-wise.
>
> Cheers,
> James Arthur
>

Well, not _literally_ run it backwards but I take your point ;)

On Wednesday, 24 August 2016 14:54:45 UTC+1, dagmarg...@yahoo.com  wrote:
> > >> "bitrex" wrote ...

> > >>> I need to throw together a ~150 volt supply at a few 10s
> > >>> of mA to test a circuit idea, but I don't have much in
> > >>> the way of MOSFETs in my junk box to build a switcher from.

> You could tear up a 12v wallwart smps & run it backwards.  That'll
> get you everything you need, parts-wise.

as long as everything means the transformer.


NT

On Wednesday, August 24, 2016 at 4:35:55 PM UTC-4, tabb...@gmail.com wrote:
> On Wednesday, 24 August 2016 14:54:45 UTC+1, dagmarg...@yahoo.com  wrote:
> > > >> "bitrex" wrote ...
> 
> > > >>> I need to throw together a ~150 volt supply at a few 10s
> > > >>> of mA to test a circuit idea, but I don't have much in
> > > >>> the way of MOSFETs in my junk box to build a switcher from.
> 
> > You could tear up a 12v wallwart smps & run it backwards.  That'll
> > get you everything you need, parts-wise.
> 
> as long as everything means the transformer.
> 
> 
> NT

He just needed a switch, hence "everything you need," but this would
also get him a flyback transformer, high voltage switch, & a crappy
h.v. cap.

Cheers,
James Arthur

On Wednesday, August 24, 2016 at 10:15:19 PM UTC-4, dagmarg...@yahoo.com wrote:
> On Wednesday, August 24, 2016 at 4:35:55 PM UTC-4, tabb...@gmail.com wrote:
> > On Wednesday, 24 August 2016 14:54:45 UTC+1, dagmarg...@yahoo.com  wrote:
> > > > >> "bitrex" wrote ...
> > 
> > > > >>> I need to throw together a ~150 volt supply at a few 10s
> > > > >>> of mA to test a circuit idea, but I don't have much in
> > > > >>> the way of MOSFETs in my junk box to build a switcher from.
> > 
> > > You could tear up a 12v wallwart smps & run it backwards.  That'll
> > > get you everything you need, parts-wise.
> > 
> > as long as everything means the transformer.
> > 
> > 
> > NT
> 
> He just needed a switch, hence "everything you need," but this would
> also get him a flyback transformer, high voltage switch, & a crappy
> h.v. cap.
> 
> Cheers,
> James Arthur

Oh, and a PWM controller, too.  --ja

On Thursday, 25 August 2016 03:15:19 UTC+1, dagmarg...@yahoo.com  wrote:
> On Wednesday, August 24, 2016 at 4:35:55 PM UTC-4, tabbypurr wrote:
> > On Wednesday, 24 August 2016 14:54:45 UTC+1, dagmarg...@yahoo.com  wrote:
> > > > >> "bitrex" wrote ...
> > 
> > > > >>> I need to throw together a ~150 volt supply at a few 10s
> > > > >>> of mA to test a circuit idea, but I don't have much in
> > > > >>> the way of MOSFETs in my junk box to build a switcher from.
> > 
> > > You could tear up a 12v wallwart smps & run it backwards.  That'll
> > > get you everything you need, parts-wise.
> > 
> > as long as everything means the transformer.
> 
> He just needed a switch, hence "everything you need," but this would
> also get him a flyback transformer, high voltage switch, & a crappy
> h.v. cap.

It gets him 200v or 400v low beta low current transistors, a reservoir cap that's too small by far, etc.


NT

Michael A. Terrell wrote...
>
> How about a cheap Boost converter module?  $12.12 USD
> DC-DC-12V-24V input to 100V-250V output @ 70W
> <http://www.ebay.com/itm/131675760033

 Too bad those are only available shipped from China.
 That includes the Amazon sellers of this nice item.


-- 
 Thanks,
    - Win

Winfield Hill <hill@rowland.harvard.edu> wrote:
> Michael A. Terrell wrote...
>>
>> How about a cheap Boost converter module?  $12.12 USD
>> DC-DC-12V-24V input to 100V-250V output @ 70W
>> <http://www.ebay.com/itm/131675760033
>
>  Too bad those are only available shipped from China.
>  That includes the Amazon sellers of this nice item.

China is the main and soon the only source of electronics modules.
Local stocking went out even before local manufacturing, so what
do you expect?

On Thursday, August 25, 2016 at 3:38:47 AM UTC-4, tabb...@gmail.com wrote:
> On Thursday, 25 August 2016 03:15:19 UTC+1, dagmarg...@yahoo.com  wrote:
> > On Wednesday, August 24, 2016 at 4:35:55 PM UTC-4, tabbypurr wrote:
> > > On Wednesday, 24 August 2016 14:54:45 UTC+1, dagmarg...@yahoo.com  wrote:
> > > > > >> "bitrex" wrote ...
> > > 
> > > > > >>> I need to throw together a ~150 volt supply at a few 10s
> > > > > >>> of mA to test a circuit idea, but I don't have much in
> > > > > >>> the way of MOSFETs in my junk box to build a switcher from.
> > > 
> > > > You could tear up a 12v wallwart smps & run it backwards.  That'll
> > > > get you everything you need, parts-wise.
> > > 
> > > as long as everything means the transformer.
> > 
> > He just needed a switch, hence "everything you need," but this would
> > also get him a flyback transformer, high voltage switch, & a crappy
> > h.v. cap.
> 
> It gets him 200v or 400v low beta low current transistors, a reservoir cap that's too small by far, etc.
> 
> 
> NT

The switches are always MOSFETs these days, IME, all sized for 220VAC
inputs.  Haven't seen a BJT ever.

The reservoir cap's value is fine for 10mA, but ESR is poor.

Still, for $1 at the thrift store he gets a good switch, pre-fab
magnetics, and a PWM chip if he wants it. That's not bad.

Cheers,
James Arthur

On 08/25/2016 06:49 AM, Winfield Hill wrote:
> Michael A. Terrell wrote...
>>
>> How about a cheap Boost converter module?  $12.12 USD
>> DC-DC-12V-24V input to 100V-250V output @ 70W
>> <http://www.ebay.com/itm/131675760033
>
>   Too bad those are only available shipped from China.
>   That includes the Amazon sellers of this nice item.
>
>

And my junkbox switcher is already up and running!  ; )

"Jasen Betts" <jasen@xnet.co.nz> wrote in message 
news:npqstn$4j2$2@gonzo.alcatraz...
>> (Hint: superglue is a key disassembly tool...)
>
> Huh? Superglue for dissasembly - how does that work?
> Some sort of solvent I could understand, but glue?

Think diagonally. ;-)  You'll likely break as many cores as not, during 
disassembly... the final step of disassembly is partial reassembly. :^)

Super glue is just fine for redoing fractured cores.  The fracture is 
usually simple and rough, so superglue adds little gap, and the pieces align 
accurately.  You only need to avoid fractures on super-high mu cores 
(>5000?), where even that little gap will spoil the inductivity a bit.

Tim

-- 
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: http://seventransistorlabs.com