Shop OBEX P1 Docs P2 Docs Learn Events
Which BS is best for battery operation? — Parallax Forums

Which BS is best for battery operation?

basicstampedebasicstampede Posts: 214
edited 2004-10-19 12:26 in BASIC Stamp
Hello.· I want to do some data logging in a remote location, and the Stamp must use 9V battery.

The test will last for several months, measuring humidity & temp.·(Sensiron·sensor).

What is the best Stamp for·this purpose (needs to be cost power consumption and high memory space)?

What other strategies do you recommend to make battery last longer?

Use BS2pe or BS2 with external EE?

Any inputs from those who have done similar battery-operated projects would be appreciated.

Thanks.

Comments

  • Tracy AllenTracy Allen Posts: 6,664
    edited 2004-10-18 18:02
    The BS2pe is the best bet for data logging. In SLEEP, it draws about 50 microamps on the average, which with a 450 milliamp hour 9V battery would come out to ~375 days of battery life. The question then will be how often the Stamp has to wake up to take readings. The full operating current of the BS2pe is ~16 milliamps. So, I figure it could be awake for about 10 seconds per hour and still meet your 6 month goal with a 9V, 450 mah battery. It takes about 2 seconds to get a reading from the Sensirion, so that means the Stamp could take about 5 readings per hour, if it does not have other time-consuming program chores. The BS2pe is also the champ when it comes to memory available for logging. It has 32kbytes total, a small fraction of which will be used by your program.

    www.emesystems.com/BS2pe.htm

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Tracy Allen
    www.emesystems.com
  • basicstampedebasicstampede Posts: 214
    edited 2004-10-18 18:29
    Tracy,

    Thanks for your info.· Frequency of data collection is flexible.· I was thinking taking a humidity and temp. reading every 1 minute (but every 10 min. would also be fine)...as you can see, it is not critical.·

    What is the best way to put the Stamp on sleep, then wake it up every 10 minutes?·

    How do I do this?· Is there an external RTC chip that can "interrupt" every 10 min. (or every 1 minute)?

    And do I need a BS2p or pe since they have interrupt capability?·

    Or is it possible to wake a stock BS2 that is "sleeping" via external signal (assuming RTC gives such signal)?

    Thanks.
  • Tracy AllenTracy Allen Posts: 6,664
    edited 2004-10-18 19:33
    You probably do need a real time clock chip, like the DS1307 or something like that. It does not need an interrupt. You just need to read the time from the RTC and have the Stamp calculate how many seconds remain until it needs to make its next reading. Say it is 597 seconds. Then SLEEP 597. The Stamp wakes itself up. That will give quite good sync with clock time, never off more than a couple of seconds.

    The BS2pe has lower current consumption than the BS2p, so it is more suited for remote data logging. The BS2pe has a lot more eeprom space to store data, which recommends it over the BS2 for that purpose, too.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Tracy Allen
    www.emesystems.com
  • K de JongK de Jong Posts: 154
    edited 2004-10-18 21:37
    Hi,

    Maybe you can save some more power by switching ON and OFF the Sensiron sensor from a Stamp output pin.

    Take look at the power consumption and supply voltage requirements of the Sensiron to see if this is a feasible option.

    Klaus
  • basicstampedebasicstampede Posts: 214
    edited 2004-10-19 11:46
    Tracy, Klaus, thanks for your inputs.

    Reading your comments, I wonder if I really need a RTC chip.· Can I just use SLEEP (perhaps repeatedly) to wake up periodically and take reading every 10 minutes (shutting down Sensiron afterwards)?

    Do you see any issues with my strategy above?

    Thanks.
  • K de JongK de Jong Posts: 154
    edited 2004-10-19 11:51
    Hi,

    If you want to analyse the readings afterward you will need some markers for time and date in your recorded data. Otherwise you end of with lots of numbers and you will have no idea when they are taken smile.gif.

    I would put in an RTC for sure !!

    Klaus
  • allanlane5allanlane5 Posts: 3,815
    edited 2004-10-19 12:26
    You should know that the BS2 (any flavor) 'sleep' function is not really accurate. Over 10 minutes, it MAY be accurate to within a few seconds, but that's about it. If you want 'real' clock time, use 'Sleep' to wake up the BS2, then read the RTC chip to find out what 'Real' time it is.

    If you must take the samples 'on-the-tick', then you can have 'sleep' wake the BS2 a little early, read the RTC until the 'tick', then take your data reading. But that's the only way to get accurate time out of a BS2.

    Having said that, many people have not found this to be much of a limitation. A DS1302, with crystal and CR2032 battery, is around $5.00, and takes up very little real-estate (it's an 8-pin chip, after all).
Sign In or Register to comment.