24 hour utc clock ebay how to#
24 hour utc clock ebay full#

Then I looked at the 200Ω resistor & 1N4148 diode (3) that are supposed to provide a trickle charge to the rechargeable battery, though the folks at BU suggest this is a bad idea. Without that resistor on SQW, I am relying on the weak internal processor pullups keep the alarm line high with:ĭigitalWrite(INTERRUPT_PIN, HIGH) //pull up the interrupt pinįortunately the pin stays high in all sleep modes and so far everything has been working with this setup (so fingers are crossed….again… 😉 ) This had me a little concerned, as that alarm line is vital to the whole design. I already had pullups on the I2C lines, so they were not needed here, but they were in a combined 4 resistor block, which meant that to get rid of the pullups on SCL and SDA, I also had to remove the pullup on the alarm line. The power indicator (1) was pretty pointless, so that was the first thing to go. Most of the parts were pretty straight forward:īut thanks to the tutorial by msuzuki777, I immediately zeroed in on a few parts on that circuit diagram that could be removed:

24 hour utc clock ebay how to#

I quickly found an Instructables post which described how to remove the battery charging circuit from a very similar DS1307 module, and then I found the datasheets and schematic for this DS3231 module over at at a site in Europe. I had a feeling that neither of these were going to be friendly to my power budget so I went hunting for the schematics to see what I could do to improve the situation. When the RTC’s arrived they had an LIR2032 rechargeable battery underneath the board, and a LED power indicator above. (and you get temp to 0.25°, although only to ☓☌ accuracy)

Or legitimate production runs which test out defective (if 10% of a run’s chips are bad, they often scrap the entire run) but someone intercepts the chips before they can be destroyed, and they resurface on the grey market. But even with all these possibilities in mind, I still have to make the Pearls as inexpensive as possible if they are going to be deployed in large numbers, and having an I2C eeprom on the board for the same money, made the temptation too great to resist. So perhaps they are counterfeit chips, which are simply pin & code compatible? I also found rumors about “ghost” shifts, where legitimate manufacturer plants/equipment are used off the clock to produce extra parts. While I waited for them to ship on the proverbial slow boat, I did some digging, because these modules were (almost) selling for less than the chip itself if I bought them directly from trusted sources like Digikey, Mouser, etc.

and I eventually bought a couple to try them out. I built the first few beta units with the DS3231 Chronodot from Macetech ( about $18 each), but I kept on stumbling across cheap RTC modules on eBay, Amazon, etc. So you could say that the most important sensor on the unit is the real-time clock (RTC), who’s alarm signal wakes the sleeping processor and begins the cascade of sensor readings. Since the Cave Pearl is a data logger, it spends most of the time sleeping to conserve power. NOTE: There is now an M variant of this chip on the market which is more resistant to vibration, but the -M is only temperature compensated to ±5ppm.

24 hour utc clock ebay full#

A ☒ppm DS3231N for less than $1? Really? And most of these boards use the industrial SN variant, which is rated for the full -40☌ to +85☌ temp range.