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Hi friends..... plz help me.... i am working on a small project using 89S52,Keypad,lcd,MOSFET IRF9540N, and 7805 IC. 7.4 v Lipo battery. my concept is to turn on and off LCD with the keypress from keypad. Am using 7805 to step down voltage to 5v and then 5v is being supplied to 89s52 and MOSFET source pin. Mosfet drain pin is attached to LCD and gate pin to port 3^5. lcdis straight away grounded. Lcd is attached to port 1. my code and circuit works well.... but the problem is the battery gets drained in 10-12 hours even if lcd is in off state. At initial stage have kept my lcd off... and when button 1 is presses from keypad the lcd goes on and again if keypad is pressed its goes off.. so for that i have put port3^5 pin which is connected to MOSFET gate...low at initial stage to keep the lcd off... and port3^5 high when button 1 is pressed.... i have also low all the signal pins port1 which is connected to lcd.... but even then my battery gets drained.... dont know what is it that is conauming my power....
You must read the datasheet for your selected (you did select it, didn't you) processor, and figure out if it works for your task or not.
But some other processors are much better suited for low-power battery operation.
Some processors requires a number of mA or more when doing nothing. Some other processors can get get work done while consumig some uA.
You must figure out how many mAh capcacity your battery has, and how many hours you need to be able to run on that battery. That will tell you the avearage current consumption for your device. Remember to subtract the number of hours you want the LCD running times the current consumption of the LCD when figuring out how much energy that is left for the processor.
There are 8051 chips specifically intended for low-power use. And a number of ARM Cortex chips can run at very low power levels. Microchip has PIC processors in their nanoWatt series. Texas Instruments also have chips that can run a clock for 10 years from a button cell. So there are much processors to chose from. But a processor shouldn't be selected until you have written down all your needs.
There are, of course, ways to save current with your processor too. Turn off all power to it with one more FET, until someone presses a button. But it might not be a good route. Need to know how long it has slept? Add external RTC - most external RTC also has alarm function so you can decide to wake the processor every minute or every hour or however often you like. But it's work-arounds not needed with some other processors.
There are 8051 chips specifically intended for low-power use. And a number of ARM Cortex chips can run at very low power levels. Microchip has PIC processors in their nanoWatt series. Texas Instruments also have chips that can run a clock for 10 years from a button cell. So there are much processors to chose from. But a processor shouldn't be selected until you have written down all your needs. don't forget SILabs, they have some very frugal '51's
yes... ypu r right.... but have already done with this chip.... and i cant change anything now because of my time target... have to complete it as soon as possible..... Have also done power down mode.... 89s52 also moves to power down mode but the problem is the same.... PCON |=0x02..... Plzzz help me
U DISABLE ALL CLOCK AND POWER CAN GO TO 50MW
WHAT POWER FET DO U USE?
so, if micro disables all clocks it goes to MegaWatt, better have a fire extinguisher ready
"WHAT POWER FET DO U USE?"
Didn't you real the first post, where the FET model was mentioned? Or did you spend all your time making sure the CAPS LOCK key got properly stuck in SCREAM mode?
and i cant change anything now because of my time target show the value of reading datasheets before designing
Prio 1: Figure out requirements Prio 2: Select components that can fulfill the requirements Prio 3: Design with the selected components Prio 4: Debug and evaluate the design
A large number of projects are started with "I use this component because we use it in an existing product" or "because I know it" or "because I have an evaluation board for it". A large number of projects fails - or have to limit the final functionality - because the "smart short-cut" wasn't so smart. Sometimes the selected component actually fulfills the requirements, but still fails because it's old and suddenly have the end-of-life date announced.
A traditional view on design is that the cost increases with a factor 10 for every stage later a problem is found. That's why it's really bad economy to skip the early requirements analysis and the careful selection of what components to use.