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Battery Back up for RAM

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  • joshbensadon
    Hi Lee, Remember I told you I put in battery backup for my 2101 s? I just didn t remember where the schematic was for this. Well, as I was going through my old
    Message 1 of 9 , Jun 3 8:29 PM
      Hi Lee,

      Remember I told you I put in battery backup for my 2101's?
      I just didn't remember where the schematic was for this.
      Well, as I was going through my old ELF file, I found the schematic, it was right there in Joseph Weisbecker's article, part 2! PE Sep-1976, pg 39. Using a 9V Battery and a 5.6V Zener diode.

      So how long do you figure my memory would have stayed with a 9V Battery?


      PS. It was fun going through my old file, I found a lot of little notes I made while constructing my ELF. The CPU cost me $13.88 back then! Too bad I didn't date the actual year I constructed the ELF, but I am guessing it was 1979.

      Cheers,
      Josh
    • Mark Graybill
      Wow, that was a great price if it was 79. I was paying about $20 apiece for 1802s till late 80 or 81, I think. -Mark
      Message 2 of 9 , Jun 3 11:38 PM
        Wow, that was a great price if it was '79. I was paying about $20
        apiece for 1802s till late '80 or '81, I think.

        -Mark
      • joshbensadon
        ... Yes, it was a great price. On my old notes, I had called and searched for the cheapest cpu from 3 places. That was the cheapest, the others were selling
        Message 3 of 9 , Jun 4 4:33 AM
          --- In cosmacelf@yahoogroups.com, Mark Graybill <saundby@...> wrote:
          >
          > Wow, that was a great price if it was '79. I was paying about $20
          > apiece for 1802s till late '80 or '81, I think.
          >
          > -Mark

          Yes, it was a great price. On my old notes, I had called and searched for the cheapest cpu from 3 places. That was the cheapest, the others were selling for $17 and $19.95

          There was a lot of great competition back then, not much "Price Fixing".
          Let's all jump in my time machine and go back eh!
        • Lee Hart
          ... Probably not all that long. If your 2101 s draw 25ma each, that s 50ma. A 9v battery s capacity is probably no more than 500 milliamp-hours, which would
          Message 4 of 9 , Jun 4 9:41 AM
            On 6/3/2012 10:29 PM, joshbensadon wrote:
            > Hi Lee,
            >
            > Remember I told you I put in battery backup for my 2101's?
            > I just didn't remember where the schematic was for this.
            > Well, as I was going through my old ELF file, I found the schematic, it was right there in Joseph Weisbecker's article, part 2! PE Sep-1976, pg 39. Using a 9V Battery and a 5.6V Zener diode.
            >
            > So how long do you figure my memory would have stayed with a 9V Battery?

            Probably not all that long. If your 2101's draw 25ma each, that's 50ma.
            A 9v battery's capacity is probably no more than 500 milliamp-hours,
            which would support a 50ma load for 10 hours.

            Now if you used the 2101L it would be longer. And if you used the CMOS
            5101, the 9v battery would last almost its shelf life!

            --
            Humanity is acquiring all the right technology for all the wrong reasons.
            -- R. Buckminster Fuller
            --
            Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart at earthlink.net
          • joshbensadon
            I honestly can t remember, but I think I got at least until the next day. Probably as the battery died, the current dropped when the battery got very low.
            Message 5 of 9 , Jun 4 3:10 PM
              I honestly can't remember, but I think I got at least until the next day. Probably as the battery died, the current dropped when the battery got very low. Well, there's nothing for it but to hook up those old RAM chips and give it a try!

              Does anyone want to wager when the RAM will change? Might be a fun lottery game?

              --- In cosmacelf@yahoogroups.com, Lee Hart <leeahart@...> wrote:
              >
              > On 6/3/2012 10:29 PM, joshbensadon wrote:
              > > Hi Lee,
              > >
              > > Remember I told you I put in battery backup for my 2101's?
              > > I just didn't remember where the schematic was for this.
              > > Well, as I was going through my old ELF file, I found the schematic, it was right there in Joseph Weisbecker's article, part 2! PE Sep-1976, pg 39. Using a 9V Battery and a 5.6V Zener diode.
              > >
              > > So how long do you figure my memory would have stayed with a 9V Battery?
              >
              > Probably not all that long. If your 2101's draw 25ma each, that's 50ma.
              > A 9v battery's capacity is probably no more than 500 milliamp-hours,
              > which would support a 50ma load for 10 hours.
              >
              > Now if you used the 2101L it would be longer. And if you used the CMOS
              > 5101, the 9v battery would last almost its shelf life!
              >
              > --
              > Humanity is acquiring all the right technology for all the wrong reasons.
              > -- R. Buckminster Fuller
              > --
              > Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart at earthlink.net
              >
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