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battery backup for Prop-Proto-USB bds — Parallax Forums

battery backup for Prop-Proto-USB bds

karlikarli Posts: 16
edited 2010-01-22 15:39 in Propeller 1
··· Hello, fellow time keepers,

··· I'm using several Prop-Proto-USB bds(dark-blue) for 24Hr[noparse][[/noparse]365day]
timer applications. It lets me set the ON and OFF times down to the second
per day or per year.
alas...even if saved in EEprom it'll lose its real time reference when the power
flickers or goes down.

The Proto-USB bds are powered by standard 9-->12V DC wall plug-in modules.
I'm currently using a missing pulse detector setup for 60Hz·· to switch in (fast !) an
external set of· of 6- D-Batteries during pulse misses, brown-outs, power loss,etc;
I wanted to keep this timer design simple; so, no DS1302 clock IC or alpha-numeric
display is being used.
I'm using only a few LEDs to monitor the "00" sec WWV beep to check up
on 5Mhz xtal drift and then push a Zero-Set Push button to synch up the time.

I scanned DiscoverCircuits.com to see if in their vast circuit repertoire they might
have something more compact or elegant.

has anyone dabbled in this battery backup application as well ?
please let me hear from you; ·Thanks
· karl[noparse][[/noparse]i]
·

Comments

  • Miner_with_a_PICMiner_with_a_PIC Posts: 123
    edited 2010-01-19 21:41
    Karli >> Provided that all the D-Cells in series (minus the diode voltage drop, best to use this as a buffer) have a slightly lower voltage than the input power supply even when fresh you could forego the niffty 60Hz power out detection system and opt for to have the batteries in parallel with the power supply. The catch is that a diode MUST be used to prevent charging of the batteries when the "external" power is available. The voltage constraint will help to prevent discharge of the batteries during normal external powered operation. The advantage is simplicity and a rock solid switch-over and back.

    so battery connection scheme >>> power_in_ground- |-Bat1+|--|-Bat2+|--|-Bat3+|--|-Bat4+|--|-Bat5+|--|-Bat6+|--->|----power_in+

    ex. suppose V battery fully charged is 1.6V (yes they can be higher than 1.5, use a multimeter) then we have (1.6V * 6) = 9.6V ...the power supply should be 9.6V or higher (when fully loaded).

    I have never used this but it should work...try it.
  • Brian RileyBrian Riley Posts: 626
    edited 2010-01-20 04:31
    Miner_with_a_PIC said...
    Karli >> Provided that all the D-Cells in series (minus the diode voltage drop, best to use this as a buffer) have a slightly lower voltage than the input power supply even when fresh you could forego the niffty 60Hz power out detection system and opt for to have the batteries in parallel with the power supply. The catch is that a diode MUST be used to prevent charging of the batteries when the "external" power is available. The voltage constraint will help to prevent discharge of the batteries during normal external powered operation. The advantage is simplicity and a rock solid switch-over and back.

    so battery connection scheme >>> power_in_ground- |-Bat1+|--|-Bat2+|--|-Bat3+|--|-Bat4+|--|-Bat5+|--|-Bat6+|--->|----power_in+

    ex. suppose V battery fully charged is 1.6V (yes they can be higher than 1.5, use a multimeter) then we have (1.6V * 6) = 9.6V ...the power supply should be 9.6V or higher (when fully loaded).

    I have never used this but it should work...try it.



    Years ago I used almost that exact circuit ( mine was 8 x D-cells and a 13.8V supply) to back up a Terminal Node Controller (TNC) at a ham radio digital node site. It worked through two dozen power outages over a three year period with one change of batteries. It should work here, considering the Prop's power drain, you might even get away with AA batteries, C's for sure.

    cheers .... BBR

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    cheers ... brian riley, n1bq, underhill center, vermont
    The Shoppe at Wulfden
    www.wulfden.org/TheShoppe/
  • Toby SeckshundToby Seckshund Posts: 2,027
    edited 2010-01-20 11:04
    I have used two 2AH Li Ion cells for 8.4 to 7.4 volts into the 5 volt reg and 3.3 volt reg. The 8.4 Volts·is set by a 1 Amp limited reg (via a diode) so that the batts are topped up, without too vicious a rate, and will take over the supply seemlessly. Assuming that the Prop bit takes less than 1 Amp the difference is available as a charge.

    The cells do not require any balancing as the 1 Amp (max) is quite kind to the sort of punishment they got in the laptop.Make sure that you put a fuse in the battery lead, this will save charging faults, and more likely, frazzled Prop bits. Batteries show little mercy!

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Style and grace : Nil point
  • lockadoclockadoc Posts: 115
    edited 2010-01-21 21:55
    What I'm going to do is to remove an emergecy light power supply and use its 6 volt battery to supply power.
    this way I'm running off the battery all the time, and if power goes out the prop will not miss a beat.

    Bill S
  • karlikarli Posts: 16
    edited 2010-01-22 15:39
    Thanks to all who have responded !
    battery backup can have a host of nuances, from heavy-duty, like you , "lockadoc" suggested to just bridging the first
    sign of power-interruption and then having a minute to shut down. In my timing applications, I wanted something
    really, simple, portable, light-weight, compact, etc, and it only needs to keep the prop-USB bd clock going when
    I'm out of town for a few days. When I'm at home and the power goes down I can easily do a reboot with the correct
    time/date stamp. I'm also using one Prop-USB bd for a window blinds controller which changes the angle of the slats
    in the morning and then again at night. Another one is used in a telephone answerer application.
    thanks again,
    karl
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