Hi Vasile, Thanks for your feedback.
2011/1/23 funlw65(Vasi) <[email protected]> > > > On Jan 23, 4:58 pm, vasile surducan <[email protected]> wrote: > > LM317 need Vin=Vout+3V to work properly. > http://www.national.com/ds/LM/LM117.pdf page5 > > > > > Your schematic is redundant, why do you need two LM317 since only one VDD > > level is used (+3V3 OR +5V)? > > use the jumper on the R8, without jumper you'll have +5V, with jumper > make > > R8 parallel with R8a so the equivalent resistor will be 390 and you'll > have > > 3V3 at the output. > OK, I see what you mean, but, in some cases, the two LM317 may not be redundant: power your PIC with 5V (Vdd=5V) but also power Xbee module with 3.3V. Cheers, Seb 2011/1/23 vasile surducan <[email protected]> > LM317 need Vin=Vout+3V to work properly. > http://www.national.com/ds/LM/LM117.pdf page5 > Ah.... I can remember having read drop voltage was 1.3V, I must have been confused again. Thanks for pointing this. Any hint for an adjutable voltage reg like this, for replacement ? > Your schematic is redundant, why do you need two LM317 since only one VDD > level is used (+3V3 OR +5V)? > use the jumper on the R8, without jumper you'll have +5V, with jumper make > R8 parallel with R8a so the equivalent resistor will be 390 and you'll have > 3V3 at the output. > OK, I see what you mean and thought about that, but, in some cases, the two LM317 may not be redundant: power your PIC with 5V (Vdd=5V) but also power Xbee module with 3.3V. But you're right, it's kind of confusing. I'm still not sure about the power supply part, and don't want to make decision in the early stage. Cheers Seb > > On Sat, Jan 22, 2011 at 6:33 AM, Sebastien Lelong < > [email protected]> wrote: > >> Hi guys, >> >> As I mentioned some times ago, I'm trying to design a new Jaluino board, >> named Jaluino Bee because it needs a name. This idea is to provide a very >> small board, very cheap, thus using SMD components. It would include a Xbee >> socket, as a standard way to plug many different communication modules (real >> Xbee/ZigBee, RF, USB, ...). I'm trying to make it as modular as possible. >> Depending on usage, user would solder require components or not. For >> instance: >> >> - use USB or not >> - crystal or internal clock >> - use 5V, 3V3, both or no voltage regulator (none could be used to >> directly power the board using batteries for instance). Based on adjustable >> vreg LM317. >> - or power the board through a serial module or USB >> - use I²C or not >> - Reset via RTS option >> - CTS/RTS option >> - connectors for pin header: plug on a breadboard (male) *or* used to >> plug potential shields (female) >> - ICSP connector >> - serial connector >> >> >> Attached is a first schematic draft. No PCB design yet, I don't know if >> all of this will fit within 5x5cm or smaller. But I guess so. >> >> Schematic is for PIC18F27J53, SOIC package, but I identified at least 2 >> other interesting chips: >> >> - PIC18F2550: quite common, USB inside >> - PIC18F25K22: for high speed application (up to 64MHz), lots of mem, no >> USB >> >> More may also fit. >> >> As for SMD design, I followed advices and used 1206 resistors and >> capacitors, as they are easier to solder. I also wanted to use SOIC package >> for MCU, easier to solder than SSOP for instance. There are a lot of >> jumpers, due to modularity. I'm hesitating: either using PTH jumpers, or >> solder jumpers. First are interesting when tinkering with the board, they >> can be always changed. But they are very tall. Solder jumpers cannot be >> easliy changed. I then figured out it may be possible to solder 0805 0ohm >> resistor over PTH jumper traces (0805 is 0.08" long, PTH space between pins >> is 0.1"). This way user can choose between a flexible, ready-to-tinker >> modules (PTH) and something more definitive (using 0 ohm resistors). What do >> you think ? >> >> Every component I'm using here seem to be easily available. But because >> it's kind of painful to source components, I may provide most of them >> (except MCU) if it appeared to be manufactured. >> >> Any advices, thoughts, feedback appreciated. >> >> Cheers >> Seb >> -- >> Sébastien Lelong >> http://www.sirloon.net >> http://sirbot.org >> > -- You received this message because you are subscribed to the Google Groups "jallib" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/jallib?hl=en.
