Would be nice if you could provide a circuit diagram from a cad package such as EAGLE as this would make it a lot easier to read the circuit. ************************************************* Roy Hopkins rdhopkins@ihug.co.nz ************************************************* ----- Original Message ----- From: "Jim Tellier" To: Sent: Monday, January 26, 2004 1:55 PM Subject: Power Supply question... > Hi Analog wizards! > I've put together a little power supply that is intended to supply 24VDC > for some solenoids (operating current about 250mA), as well as the +5VDC for > PICs and misc logic (about 300mA estimated). > Here's my crude ASCIIMATIC... > > /-------------\ /---------\ > | FULL- | + A 24VDC | LM317T |2 B > ()---------| WAVE |--------+---------| POS. |---------+-----> > 5VDC > 18VAC | BRIDGE | - | 1| REG. | | > ()---------| |--+GND | \---------/ | > 1.5A max \-------------/ | | |3 | > | === 4700uF +-----\/\/\----+ > | | | 220 | > | | / | > | | \ | > --- --- 5K /<---+ === > 2500uF > - - \ | | > / | | > | | | > | | | > --- --- --- > - - - > Notes: "A" and "B" also have 10K bleeder resistors to > - as well as .1uF and .01uF bypass caps. > > Here's the question: Point "A" drops to about 23V under the solenoid load. > But point "B", with no load other than the 10K bleeder, drops about 0.25V > when point "A" is so loaded. The PICs that I'll be using, IIRC, have an > acceptable supply voltage range of 4.0-5.5V, so I don't think this poses a > problem in an "absolute" sense, but I wonder about the PIC's tolerance of > sporadic fluctuations of this magnitude, even if it's within acceptable > limits. One of the (3) PICs being powered by this +5 will actually be > switching the 24V to the solenoid, via power MOSFET. > Anyone see potential problem here, or am I worrying needlessly? I "could" > put another LM317 on the 24V node if I really need to, but ...? > Thanks!! > Jim > > > > -- > > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > > > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.566 / Virus Database: 357 - Release Date: 22/01/2004 -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body