Solder on battery holder for Real Time Clock
The battery holder is quite easy to solder firmly. The sheet metal of my holders is quite thin and can be heated up very well with the soldering iron. So I first applied solder to the two little feet left and right on the underside. Then I put the battery holder on the board, pressed it with my index finger and heated one of the two feet until the solder melted and was really liquid. With my Jetson Nano there was already solder on the pads which melted and so I connected the first foot to the PCB. With the second foot I proceeded immediately.
The battery holder looks soldered on as shown below.
Now the appropriate batteries are still needed. I bought CR1225 batteries.
Note new board version
I have received messages again and again that the Jetson Nano does not keep the time even if the battery is soldered on. This is due to a new board design and a simple diode is needed or a capacitor that can be charged. If a diode of the type BAT54H is installed, a battery can be used again because then the charging current does not come back to the battery via the diode. If a super capacitor is installed, it can be charged. In this case a jumper must be soldered instead of the diode.
The following picture explains how the diode must be installed to be able to use the battery described in this article.
Insert battery and check Real Time Clock time
The CR1225 fits very well in the battery holder. The battery sits firmly and cannot slip out. You don’t have to do much more than that and the Jetson Nano can be switched on. The following picture shows my Jetson Nano from below with the battery inserted.
The exciting question now is, of course, whether everything works out. I have booted the Jetson Nano and have displayed the time of the RTC with the following command.
The time of the system itself and the time of the real time clock can be seen clearly. Both clocks run synchronously with the difference that the RTC and the system time depending on the country setting, in my case for Germany 2 hours, run offset.
I then shut down the Jetson Nano and left it there overnight. Before the next power on I removed the USB WIFI dongle so that the operating system has no possibility to download the current time over the internet.
The result was an absolutely accurate time of my system. I am now very satisfied with this and can also convert my other Jetson Nanos. Very nice is that I did not have to make any settings on the operating system and the RTC worked directly.
Most of the time I had to spend to understand how to equip the Jetson Nano with a Real Time Clock (RTC). When I understood that the Jetson Nano is already equipped with a Real Time Clock and that the board has the connectors for a power supply of the board with a small battery I bought the appropriate brackets. I was still a bit worried about the soldering but it worked surprisingly well. So I needed about 10 minutes to solder the brackets.
I am very satisfied with the result and it is just great that I can now use the RTC of the Jetson Nano for little money. Finally my Donkey Cars don’t loose time anymore when I accompany IT trainings with the cars without internet connection or record training data for me outdoors.
Click here for the first part (NVIDIA Jetson Nano Real Time Clock (RTC) – Part 1) of my two reports.