> -----Original Message----- > From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf > Of Tom=E1s =D3 h=C9ilidhe > Sent: 27 June 2008 16:24 > To: Microcontroller discussion list - Public. > Subject: [PIC] Three AA's instead of two > = > = > So let's say I use three AA batteries instead of two, giving me 4.5 V. > = > I can put the 4.5 V straight into the PIC without a problem. > = > Should I use the 4.5 V to power the driver chips? > = > As people have already mentioned, the driver chips I'm using have > darlingtons inside them, so I'm wasting power. Would I be better to > replace the driver chips with individual transistors? If so can someone > suggest suitable through-hole transistors to use? MOSFET's maybe? > = > Or perhaps is there a driver chip out there that doesn't waste so much > power? > = > Does anyone know approximate average values for the milliampere hours of > AA and AAA batteries? I've looked at a few datasheets but strangely most > of them don't mention it... and for the few that do mention it, there > seems to be massive variation (e.g. from 500 mAh to 2.7 Ah). > = > I went to the Duracell website (they're a popular brand of battery in my > country) and I still couldn't find out what the capacity was of their AA > and AAA batteries. It took me all of 20 seconds to find this (even with their crappy Flash web= site): The capacity of zinc carbon and alkaline cells is extremely dependant on th= e current drain, so you won't find a single mAh number. However, that data= sheet gives all the information you should need to be able to predict an ap= proximate life given the current consumption of your project. Note that 0.8v per cell is taken as the end of life point in this case. Wi= ll your project actually work at 2.4 volts? If not then without a switchin= g regulator you will not be able realise the full capacity of the cells. Regards Mike =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D This e-mail is intended for the person it is addressed to only. The information contained in it may be confidential and/or protected by law. If you are not the intended recipient of this message, you must not make any use of this information, or copy or show it to any person. Please contact us immediately to tell us that you have received this e-mail, and return the original to us. Any use, forwarding, printing or copying of this message is strictly prohibited. No part of this message can be considered a request for goods or services. =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist