2

I am having some difficulty getting a board that has a Dallas Real Time Clock DS12C887+ to behave. Not sure if the problem is the RTC or not but am in the investigative stage and got the cross hairs focussed on it right now.

The DS12C887+ has an onboard (and inaccesible) battery that is molded in. My suspicion is/was that the battery in it is flat. I have filed two slots in the side of the RTC and exposed the battery terminals. I get 2.92V from the RTC (using a Fluke 87 III which i think is fairly accurate). Would this be sufficient voltage to reliably operate the RTC or is it a bit too low. I can piggyback a Li-Ion battery (CR2030 or equivalent 3V which actually reads 3.2v) onto the RTC by gluing a button battery holder in place and soldering a couple of pigtails to the terminals i have exposed and then cutting the existing battery out of circuit.

The manufacturers datasheet for the RTC can be found by searching "DS12885-DS12C887A.pdf". Does anyone know if 2.9V is enough to keep the RTC running reliably?

closed as off-topic by Stephen Kitt, DrSheldon, Raffzahn, another-dave, Kaz Jul 4 at 11:13

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "This question does not appear to be about retrocomputing, within the scope defined in the help center." – Stephen Kitt, DrSheldon, Raffzahn, another-dave
If this question can be reworded to fit the rules in the help center, please edit the question.

  • 1
    It would be quite helpful if you could add any information about the environment. What computer, what board, what problem you try to fix at the computer. As it stands now, this question is rather about the battery part, thus more appropriate for EE.SE than here. – Raffzahn Jul 3 at 7:37
  • 3
    looks like a EE.SE question to me. – 比尔盖子 Jul 3 at 8:56
  • I'm voting to close this question as off-topic because it's purely an electronics question, so better suited to EE.SE – Kaz Jul 4 at 11:13
4

2.9V seams like more than enough to keep it running. If you look into the data sheet you'll notice that a switch over to battery only happens below 3V.

But there's a simple solution: Buy a new one. They are about 5-10 EUR (~5-15 USD) depending on the shop you order from.

The DS12C887 real-time clocks is a rather new development (to replace DS1287) thus ready available. No need to file holes and tinker with the innards - unless your interest is the structure of this modern device - but that would be OT here on RC.SE, wouldn't it?

Not the answer you're looking for? Browse other questions tagged or ask your own question.