Ximimark 5Pcs I2C RTC DS1307 AT24C32 Real Time Clock Module for AVR ARM PIC SMD for Arduino

All 5 worked without issue and hold time reliably. I'll also say out of the three rtc modules I tested this one sipped the least amount of energy by a surprising difference, I'll be ordering more.

This is a great DS1307 RTC with 4kB EEPROM that I mated with an ESP-WROOM-32 to create a recording voltmeter. Works as expected. The clock on mine runs about 12ppm slow (-1 sec/day) which I compensate in software.The DS1307 is designed for 5V but runs fine at 3.3V due to the backup battery having a voltage divider that lowers the power fail trip point. The divider runs down the battery faster than without it. The EEPROM works fine. Originally, I tried a DS3231 RTC with (purported) internal crystal, but the generic version had erratic accuracy, losing one hour every ten hours. The beauty of the DS1307 is that the 32.768 kHz crystal is external and can be verified.This assembly appears to be a clone of the Gizmo TinyRTC I2C Module.By the way, the GND pins are connected to the ground plane on the back side and to appropriate circuit points. The PCBs I received were not defective and did not require modification.

Poor clone design but works with a simple modifications. The GND pins on both headers are not connected to anything. You will have to run a jumper wire from ground to the side of C2 shown in my picture or pin 1,2,3, or pin 4 of U3. Technically, pins 1-3 of U3 should not even be connected to GND on the PCB. They should be connected to -VBAT along with pin 4 of U2. If you plan on daisy chaining these together remember to run another ground jumper to the header on the other side since it's floating as well. Anyways, the reason I gave these 3 stars is because they were $7 for 5 boards, keep time well, and seem to work of 3.3V or 5V.

3 out of 5 are bad straight out of the package. Do NOT buy these RTC modules. Obviously, no quality control (i.e. they were shipped bad from manufacturer). Seriously, 60% failure! Never again!

As described- Not sure what I'll do with 5 of them lol

Had some trouble in the beginning with this board, online they said the crystal case should be grounded. Bought this DS1307 board in 2022. So I'm not sure if product was updated since. Tested it with Arduino DS1307RTC library example sketches and seemed to work.

I haven't yet compensated for it in software like was suggested by another review, but will look into that.

You may have read that some time ago people reported the PCB connection error that needs to be corrected by wiring ground using a piece of wire. Well, that is still the case. Depending on your application the low price and need for immediate repair may be appealing or not.

El producto llegó tal cual en la foto, su empaque lo protegió durante el camino y no pude esperar más o menos. Recomendado.