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[Reply #15 on:]

the transistor is used to stop the charging... why a spec. lipo charger when only working with a single cell and not a battery?

as for the gps... i live i a flat where the outer wall is brick and inner wall is concrete i have once some time ago tried gps inside and could only get a valid fix if the damm thing was just up to the window or just outside...

[Reply #16 on:]

LiPo cells want to charge using constant current, until they reach 4.2 volts (typical -- check specifics for your cell), at which point they want to stay at constant voltage.
You will need a current sense method (such as a small high-watt resistor with an opamp across it to an analog in pin) and a voltage sense method (to know when it gets to 4.2V.)
Most LiPo cells come with protection built in against over-charging, but if you use this to "control" charging, you'll significantly reduce the lifetime of the cell. In fact, for best lifetime, you don't want to charge the cell entirely to full, but stop somewhat short.

[Reply #17 on:]

been thinkering for some days, maybe nimh cells instead?

[Reply #18 on:]

as for the gps... i live i a flat where the outer wall is brick and inner wall is concrete i have once some time ago tried gps inside and could only get a valid fix if the damm thing was just up to the window or just outside...

The GPS will still keep track of time, but unless it does get a fix occasionally, it'll drift just like the RTC.

[Reply #19 on:]

That's why i ruled it out, the reception at the window is poor enough as is

Thats why i thought of NTP, The signal is plenty strong and and i should be able to move the alarm clock to any location within wifi range..

i had a look at this post: http://arduino.cc/forum/index.php/topic,8505.0.html and its somewhat close to what i want except that it pulls the alarm times from a server and also the time. this makes it dependent on haveing a server running all the time so not so great in the end.

but i guess i could use the debounce routine for each button... but then again my programming skills are to bad for me to figure out how to set/store an alarm time

in the learing section i did find how to connect to an ntp and get the time of that... http://arduino.cc/en/Tutorial/UdpNtpClient

oh well anyway time to go to bed... will thinker on with this

[Reply #20 on:]

but then again my programming skills are to bad for me to figure out how to set/store an alarm time

No need to reinvent the wheel. The Time library

http://www.arduino.cc/playground/Code/Time

has alarm routines built into it; you just have to tell it what you want to do. From the alarm example readme:

Code:

Here is how you create an alarm to trigger a task repeatedly at a particular time of day:
  Alarm.alarmRepeat(8,30,0, MorningAlarm); 
This would call the function MorningAlarm()  at 8:30 am every day.

Chris

[Reply #21 on:]

thanks a lot...

think only step left is to input the alarm time itself. have a few ideas i need to thinker with during the day