Hi Dwayne... > >What about Schottky's to reduce the drop in the rectification? > > Are you fighting heat or are you still trying to eek out that > last little > bit of headroom? Yes, I'm thinking about chipping out more crawl space. With conventional silicon diodes I'm getting just under 7V to the regulator input, with a need for 7.5V. (As Sid has reminded me) > If its not a headroom issue and you are using a linear > regulator, changing > to Schottky diodes just moves the heat from the diodes to the > regulator. But if you need that tiny bit of headroom and / or you are > using a switcher, Schottky diodes will improve the headroom > and reduce the > heat generated. > > How much heat is produced by the 1n400x diodes at 170 mA? > Good question - I don't know for sure, but heat isn't really the issue unless I up the transformer secondary voltage. the 12.6V CT windings still have the 7805 running pretty cool with 240 on the primary. The reason this has taken so long us that today has benn nothing but interruption after interruption..wah, wah...for sure. Looking at it now, let's see....the secondary is rated 12.6V at 230 pri. That gives me about 11.39V at 208 pri. Let's see 11.39*.636 = 7.25V Take away the diode drop and only about 6 1/2 V remain. Herein lies the problem since the 7805 requires 7.5V. It seems a diode swap to Schottky would only get me another .5V....Hmmmm still not at 7.5... OK, so while it may help improve regulation a bit, I am still thinking LDO. I am also wondering about substituting LM340's for 7805's. Would the 340's respond differently to low input V as compared to 7805's? > dwayne > > -- > Dwayne Reid > Trinity Electronics Systems Ltd Edmonton, AB, CANADA > (780) 489-3199 voice (780) 487-6397 fax > > Celebrating 18 years of Engineering Innovation (1984 - 2002) > .-. .-. .-. .-. .-. .-. .-. .-. .-. .- > `-' `-' `-' `-' `-' `-' `-' `-' `-' > Do NOT send unsolicited commercial email to this email address. > This message neither grants consent to receive unsolicited > commercial email nor is intended to solicit commercial email. > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads