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Ds-1302

MikeSMikeS Posts: 131
edited 2004-11-04 05:03 in BASIC Stamp
I am wanting to add some short-term back up to a DS-1302 time keeping chip. Documentation refers to a "super cap". Is this a large value electrolytic or a special memory backup capacitor? Also I am not sure if I understand how to configure the trickle charge circuit with the diode and resistor. Is it between the two Vcc pins or between one of the pins and ground?

thanks

Comments

  • NewzedNewzed Posts: 2,503
    edited 2004-11-01 16:04
    Why not just add a backup battery.· They are inexpensive and last about 7 years.

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  • allanlane5allanlane5 Posts: 3,815
    edited 2004-11-01 18:32
    A 'Super-Cap' is a high-internal Resistance, high-capacity (1 or 2 Farad) capacitor. It's not your normal capacitor. Its purpose in life is to provide battery-backup for RTC (real-time clock) chips like the DS1302. I believe a 'fully charged' super-cap will run the chip for a week. You *must* buy a 'Super-Cap' if you want to do this. 'Normal' capacitors are entirely un-suitable.

    On the other hand, a CR2032 3 volt coin cell will run the RTC for over a year -- and will last for 5 years, if the power never goes off. Something to think about.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2004-11-01 21:42
    I agree with Sid and Allan...I have 2 projects that have been running a DS1302 using a Battery as a backup...Keeps the code and the circuit simpler.· Besides, it only uses the backup when the main power fails.



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  • MikeSMikeS Posts: 131
    edited 2004-11-02 19:21
    After thinking about it ....you guys are right. I'll go with the battery.

    Thanks for your responce.
  • lrohnlrohn Posts: 33
    edited 2004-11-04 05:03
    If a CR2032 is used as a battery backup, would you connect it to VCC1 and disable the trickle charger circuitry?
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