| General > General Technical Chat |
| Ban of non-rechargeable batteries |
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| Nusa:
No, he's right, some times there is clearly an idiot involved in the engineering. The cheap TM-904C thermometer that's been around for years uses a 9V battery*. The 9V battery goes to a 3.3V regulator, which then goes to the switch that turns the device on/off. Two problems: a) using a 9V battery for a 3V device is just stupid, and b) the switch is on the wrong side of the regulator, so the battery goes flat in the drawer after a few weeks, even if switched off. The fix was actually quite simple: replace the 9V with 2 AAA batteries (existing battery compartment is large enough) and bypass and remove the regulator from the circuit. Actual draw of the circuit without regulator is very small, so batteries will last for many months, even if left on. Lo-battery indicator comes on at 2.3V *These days you can buy a 3V version instead, but the 9V version is still available. Originally, 9V was the only option. |
| Raj:
--- Quote from: james_s on July 04, 2020, 05:07:27 pm --- --- Quote from: Raj on July 02, 2020, 07:57:42 am ---out wall clocks having AA, I'm slowly replacing them with my own PoE IoT (local network) clocks cause the standard quarts clocks are too inaccurate for my taste (they go off by 5 minutes every month, donno why so much deviation. --- End quote --- That's odd, do you have wide temperature swings in your house? I have a few different quartz clocks and they typically hold to far better than that, maybe a few minutes at most in a year. --- End quote --- Could be...I have no central AC Some clocks have direct sunlight falling on them through the window while others are in air conditioned room but they all deviate hugely from the internet based clock. I guess it's as expected with clocks that I actually got for free with heavy appliances. |
| james_s:
Sunlight falling on the clock controlled by a quartz crystal will definitely affect the accuracy. The clocks built into large appliances often use the mains frequency as a timebase so the accuracy of those will depend on the electrical grid. |
| tooki:
And long term, the electrical grid is extremely accurate. |
| james_s:
--- Quote from: tooki on July 05, 2020, 09:07:24 pm ---And long term, the electrical grid is extremely accurate. --- End quote --- It is in much of the world, but not everywhere. Most of the old Soviet digital clocks used a crystal timebase for that reason. The person with the clocks is in India, I have no idea how stable the power grid frequency is there. |
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