Send your shipping address and what zener you want.
The price is RIGHT.

  *
  |  __O    Thomas C. Sefranek  WA1RHP@ARRL.NET
  |_-\<,_   Amateur Radio Operator: WA1RHP
  (*)/ (*)  Bicycle mobile on 145.41 MHz PL 74.4

ARRL Instructor, Technical Specialist, VE Contact.
http://hamradio.cmcorp.com/inventory/Inventory.html
http://www.harvardrepeater.org

> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Matthew Brush
> Sent: Wednesday, June 02, 2004 3:02 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: [EE:] Transformerless PS w/o Zener?
>
>
> Hello all,
>
> I'm making a current monitor for the mains power line.  I plan on
> using an electrical outlet as an enclosure (probably plastic).
> Not that it matters, but in case anyone is interested, I'll be
> using a PIC16F876A w/ one of those nifty Allegro current sensors
> (so cool BTW) and a 3 digit 7seg. LED scrapped from a PC case.
>
> Anyway, I remember there was a discussion recently about
> transformerless power supplies on the piclist.  I have found
> several similar schematics on the net for this scheme.
>
> Here's my question, is there any way to make it work without the
> Zener diode?  Not that it's hard, but I'm trying to make this
> thing using stuff I already have, and I don't have any Zener
> diodes (damn Canadian RadioShack is going to the dogs).  I know
> they're probably like $0.15 at digikey, but then there's the min.
> order fee $5.00 and then shipping $8.00 so a handfull of zeners
> would cost me almost $15.00.  I really don't have enough money
> right now to order more stuff to make it worthwhile.
>
> So is there any other way of doing this, like maybe a resistor
> divider or some such thing, fed into a regulator?  I really don't
> need much current, just enough for the pic to wake up, take a
> sample and go back to bed (and then the LEDs), maybe less than
> 100mA?.  Do any of you gurus know any good tricks on the cheap
> that'll do this?  Or should I just hack up a Wall Wart and use
> that transformer (might fight into the outlet box)?
>
> Another quickie, can I use a little 600:600 audio transformer
> from a telephone to provide some isolation with the
> "transformerless" power supply?
>
> In the meantime, I'll be routing through some scrap circuit
> boards from telephones and VCRs to see if I can find a suitable
> Zener diode.
>
> Thanks ahead of time.
>
> MJ Brush
>
> --
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>
>

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