I've seen this option using LM317 on National Semiconductor site (where I tried to get free sample, with product & shipping fees, strange "free" definition...). It requires more parts (meaning more space), maybe Richard you can check this if you too think it's a good option. LM3940 is hard to find (almost nothing on eBay), it's also quite an expensive part: 1.67€ compared to 1.12€ for LM317 (farnell). On eBay, you can get 20pcs for 9$ including shipping fees ( http://cgi.ebay.fr/20pcs-LM317-Voltage-Regulator-TO-220-1-2V-TO-37V-1-5A_W0QQitemZ370253147020QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item5634ceab8c&_trksid=p3286.m63.l1177) or 5pcs for 3€ including shipping fees from a professional vendor ( http://cgi.ebay.fr/Lot-de-5-regulateurs-variables-LM317-LM317T_W0QQitemZ390088413712QQcmdZViewItemQQptZFR_YO_MaisonJardin_Bricolage_ElectroniqueComposants?hash=item5ad314d210&_trksid=p3286.c0.m14 ).
Availability and price are also important criteria... Cheers, Seb -- Sébastien Lelong http://www.sirloon.net http://sirbot.org 2009/8/31 a.faber <[email protected]> > > If the 3.3 volt regulator is hard to find, why not design it with the good > old LM317 and two resistors? > Albert > > ----- Original Message ----- > From: "funlw65" <[email protected]> > To: "jallib" <[email protected]> > Sent: Monday, August 31, 2009 11:13 PM > Subject: [jallib] Re: Jaluino next version: what could be added/improved > > > > Hi Sebastien, > > I looked again on Arduino site at their hardware specifications > starting from Nano, Diecimila to Duemilanove and Mega. All boards are > using the 5V source for powering the microcontroller and the board. If > an external source is lower than 7V can cause board instability. > The 3.3V power is provided by FTDI and can draw a maximum of 50mA. Is > provided for shield and is fragile in my opinion. > Jaluino can have a more powerful regulator. Having a 3.3V source > available for shield is a good option (very handy). > > But, if others can't easily find a 3.3V voltage regulator, the board > still can be built and used because 3.3V is only for shield use (if > required - it can be soldered later). Anybody can find a 7805 5V > regulator. > > My opinion... > > Regards, > Vasi > > > On Aug 31, 10:13pm, Sebastien Lelong <[email protected]> > wrote: > > Hi Richard, > > > > I can't guess which is the most used, which make more sens: > > > > 1. 3.3V/5V selection for board and shield, or > > 2. 5V on board and 3.3V shield with voltage adjustments... > > > > If we follow Arduino design, I think (but I'm not sure it is the same on > > all > > *duino flavors) it corresponds to just 3.3V on spare pin, that is option > > 2. > > > > > > > > > > OK, I'll try to find one of these. > > > > I've ordered more copper clad boards & more stuff on eBay, I hope to > > receive > > > > them this week so I can build this upcoming board next WE. > > > > > Lets hope the next one will be the final one for Jaluino Medium > > > homebrew > > > > Don't worry for me about building many boards, I expected this, and this > > is > > a mandatory and very important step. (and I need to see it for real to > > figure out what should be modified, etc...) > > > > Cheers, > > Seb > > -- > > Sbastien Lelonghttp://www.sirloon.nethttp://sirbot.org > > > > 2009/8/31 Richard <[email protected]> > > > > > > > > > Hello Seb, > > > > > > > Ok, I will only add 3.3V to spare pin of the power connector, but > am > > > > > afraid i will at least need to add 1 via and maybe more :-(. > > > > > > Do you mean it would be simpler if you put 3.3V selection and all the > > > > whistles about 3.3V ?... :) > > > > > Well, it is quit simple to make +5V selectable between 3.3V and 5V > > > because the traces dont need to be changed so except for serial > > > connector (this better stay on 5V) all +5V when selected on 3.3V will > > > become 3.3V so on power connector that +5V will also become 3.3V > > > (spare stays unconnected). > > > > > above is easier but if you want the main board on 5V and need only > > > 3.3V for the shield (and off course dealing with the voltage level > > > adjustments on the shield) this would be impossible. > > > > > But every time when you need 3.3V on a shield you also want to power > > > your main board with 3.3V so that you dont have to deal with voltage > > > level adjustments, well than it is the easiest way. > > > > > In my opinion is 3.3V on the spare pin of the power connector AND 5V > > > selectable between 3.3V and 5V the most flexible option (but off > > > course also the most impact on the pcb) > > > > > > OK, I'll try to find one of these. > > > > I've ordered more copper clad boards & more stuff on eBay, I hope to > > > receive > > > > them this week so I can build this upcoming board next WE. > > > > > Lets hope the next one will be the final one for Jaluino Medium > > > homebrew > > > > > > Cheers, > > > > Seb > > > > > Greetz > > > > > Richard > > > > > --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
