Arduino data-logger shield HW problems  - Page 1
Forum section: electronics / beginners

author: nikkoaki
author_rank: Newbie
timestamp: December 18, 2016, 06:36:25 pm
content: Greetings everyone!I will start by saying that i'm a newbie and i'm just starting to learn so please don't be shocked if i say something that makes no sense. Also, as you might have seen, my english isn't great either.Well, some weeks ago i bought a fake chinese Arduino data-logger, pretty much a clone of the adafruit one (https://learn.adafruit.com/assets/9094the original revision, not the B one). It works great, the problem is that the RTC battery only lasts a couple of days if the shield is disconnected from power.I remember measuring the current from the coin cell at the time when the device was disconnected and the multimeter actually measured a pretty high value that according to a quick calculation would give approximate 2 days (but since my multimeter is garbage, i just thought it was giving a wrong value). Another thing i noticed was that when the shield was off and not attached to the arduino, the power LED on the shield was actually glowing very faintly and it would turn off when i inserted the SD card.Anyway, i had two busy weeks and had to put it aside. Today, i took some time to play with it and sure enough the battery is flat.I don't consider myself good enough to make this kinds of statements but as far as i can tell, the RTC part of this shield is connected exactly like the adafruit one.I tracked the traces, checked continuity between different pins/components and measured some voltages. I'm feeding 3.3V from another arduino to the batt pads because i don't have another fresh battery.. Here is what i found:The positive pad from the battery only goes only place : the VBAT pin on the DS1307 RTCVoltage between battery pads: 3.27VVoltage between GND and 5V: 1.47V (This pretty much means that the power LED, the 3.3Volts Regulator, the SD card and every single sensor i have connected are receiving that voltage (which is also going back to the arduino) that seems to be "leaking" through the VCC pin on the RTC).Checking some reviews on amazon on this shield shows that more people have this problem but i also remember seeing someone complaining and he had an adafruit one.Here is a close-up of the RTC:Apart from this, everything works fine.Any kind of help would be welcome, thanks!

author: madires
author_rank: Super Contributor
timestamp: December 18, 2016, 07:01:37 pm
content: Fake DS1307?

author: nikkoaki
author_rank: Newbie
timestamp: December 18, 2016, 08:40:00 pm
content: Quote from: madires on December 18, 2016, 07:01:37 pmWell, damn.. didn't even think about that. I couldn't find much about the behavior of fake DS1307's.. it seems to change depending on how much they suck.Trying to find a cheap one on ebay to replace it will probably result in me receiving another fake.I do have a DS3231 connected to a raspi.. i don't know if it's fake or not but it does work well, i guess i can use that one for a while.It's a shame because i bought the shield so i could have everything on one pcb with no wires running around.. i got what i payed for.Thanks.

author: madires
author_rank: Super Contributor
timestamp: December 18, 2016, 08:52:16 pm
content: No need to throw away the shield. Simply get a DS1307 from a known distributor and put that one onto the shield. If everything is fine then, you know for sure it was a fake chip.

author: nikkoaki
author_rank: Newbie
timestamp: December 18, 2016, 09:07:34 pm
content: Quote from: madires on December 18, 2016, 08:52:16 pmI thought about that but those listings for 5 pieces at 0.83€ free shipping are definitely fake. I just checked my local robert mouser and they do sell it for 2.68€ . Let's see how good i am at soldering this small..Other option is to use the PCF8523 which is used on adafruit's rev.B board and seems to be pin compatible but a bit harder to find and low prices.Thanks again.