RE: PIRANHA-III Power control? (fwd)

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Original poster: Gerry Reynolds <greynolds@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Sun, 17 Dec 2006 11:20:27 -0700
From: Terrell Fritz <terrellfone@xxxxxxxxxxxxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: RE: PIRANHA-III  Power control? (fwd)

Hi,

Many thanks for the responses ;-))

Figures 7 and 8 of ST's AN308 describe "pulse train" Triac firing which 
seems to be very good for really screwed up loads.

http://us.st.com/stonline/books/pdf/docs/3566.pdf

The circuit is simple and cheap ;-))  Steve Conner used a similar idea for 
his OLTC II supply but with much more control circuitry:

http://www.scopeboy.com/tesla/ol2psu.html

The best part is apparently the ST circuit is appearing in devices called 
"Router Speed Controls".

http://www.amazon.com/Grizzly-G3555-Router-Speed-Control/dp/B0000DD1R4

Some versions are less than $20 with free shipping ;-))

http://www.mlcswoodworking.com/orderstatus/html/smarthtml/pages/speedcon.html

I was about to get on till I saw this :-))))))   $12.50 is a fair price I 
guess even if the router is "sold separately" ;-))

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=43060

I am not "sure" of the circuits inside them, so I would have to get one and 
take it apart.  Also would disable the "full" switch setting which to too 
easy to hit be accident.  They are all obviously of the same design with 
different cases.  Everyone is dropping the prices on them since they are 
obviously very "cheap".  Some might be "too cheap" ;-))  But others like 
the Grizzly one are probably made pretty well.  Very convenient fuse 
location too.  Probably easy to "enhance" the fuse value if needed :o)))

So I'll see if I can pick one up today and let you know what's in it.  They 
"might" be a good "variac replacement" in general.  I would think the 
PIRANHA would be a far more pleasant load than a router so it might work 
fine.  If so, I will use the 15 amp version on PIRANHA-II

If they work, this was all waaaaay too easy ;-)))

Cheers,

	Terry