jeb Posted April 2, 2007 Report Posted April 2, 2007 hello,i want to do a very small midibox (just a few pots and a small1 line LCD) : is it possible to take a 9v battery (accu) insteadof a transformer ?how long will such a battery last ? thanxjeb Quote
lylehaze Posted April 2, 2007 Report Posted April 2, 2007 Yes, it should work.The best way to tell how long it will last is to try it.It will only cost you a 9 volt battery to find out.If you want to make it last longer:make sure the LCD backlight is OFF.Experiment with using an Low Dropout Regulator.Turn off as many LED's as possible.Another good way to lower power consumption is toreduce the clock frequency, but then all your timingand Baud rates would be wrong, so that's probably nota good idea.Personally, I think the first time the battery went lowin the middle of something important, I'd probablyget mad enough to change it back to normal power.Have Fun,LyleHaze Quote
dj3nk Posted April 3, 2007 Report Posted April 3, 2007 you could also use some lion accumulators from mobile phones. You can easily find some with a big charge. Quote
kris Posted April 3, 2007 Report Posted April 3, 2007 yea make it a rechargeable battery then you could make it last as long as you want more cells etc regards kris Quote
Screaming_Rabbit Posted April 3, 2007 Report Posted April 3, 2007 Check the LowPower PIC. - Same type but it got "LP" somewhere within the type-number.Search the forum, there have been several threads about this.Greets, Roger Quote
bill Posted April 3, 2007 Report Posted April 3, 2007 I use LIPO batteries from Radio Controled modelism, they load quickly, and stay pretty long ;) You should try them, they are not that exensive, and you can play for hours. Quote
Lall Posted April 3, 2007 Report Posted April 3, 2007 Hi all,Experiment with using an Low Dropout Regulator.If the input voltage remains unchanged then the Low Dropout will not bring any gain as the difference between its input voltage and output voltage will remain unchanged as well.In order to have a gain from a LDO, the input voltage must be reduced by the amount that the LDO makes you win compared to classic linear regulator.Another option is to use switching power supply. They have very good efficiency factor and as there's no audio in this box, noise they can generate is not that crucial.you could also use some lion accumulators from mobile phonesYou have to watch out that it seems to be a complicated subject, you must use specialized chips to do lion battery recharging if you want it to work. Look at Linear Technology, Analog Devices or TI portfolio for this matter...One thing I've leared lately about these batteries is that they normally have (some don't) some integrating electronics preventing wrong use of the battery. Without this protection, the battery could litteraly burn and as I've been said, there's not really anything that can stop this fire... (sounds like a nice experiment too ;))Best regards,Lall Quote
lylehaze Posted April 3, 2007 Report Posted April 3, 2007 @Lall,You are correct that a Low Dropout regulator will dissipate the same amount of power as a regular one. What you may have missed is that a 9 volt battery will not stay at 9 volts for its entire life span.I just checked the datasheet for a TI 7805 regulator. It has a 2 volt dropout, so as soon as the nine volt battery drops below seven volts, you're finished.A Low Dropout regulator would allow you to continue working the battery until the remaining voltage is lower than that.A switching regulator is the best choice, absolutely!@Screaming Rabbit The LP series of chips allows the user to run lower voltages IF they drop the operating clock frequency. 4.2 volts is the lowest safe operating voltage at 40MHz, same as the non-LF part.LyleHaze Quote
Lall Posted April 3, 2007 Report Posted April 3, 2007 Hi LyleHaze,A Low Dropout regulator would allow you to continue working the battery until the remaining voltage is lower than that.Indeed, you're right. From the lifetime point of view, LDO will help, very good point. I thought you were having power consumption in mind...Best regards,Lall Quote
kris Posted April 3, 2007 Report Posted April 3, 2007 id say youd be better sticking with lithium polymer batteries from radio controlled models as these are some of the most efficient batteries for the money and also a lcd without back light regards kris Quote
Lall Posted April 3, 2007 Report Posted April 3, 2007 Actually, the (very valid) point about the backlight makes me rember about the following thread about LCD screen saver: http://www.midibox.org/forum/index.php?topic=7779.0That would be a kind of inbetween compromise... :)Best regards,Lall Quote
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