Yesterday I have finally received the jumper wires I've been waiting for and have connected the binary LED clock to the Raspberry Pi
At first, when I turned on the Pi, I immediately saw that something was wrong because one of the LEDs was always on, even when the ULN2003s were not inserted into their sockets, so clearly there was a short somewhere. It took me about half an hour to find it and fix it. After that, to my great enjoyment, the whole thing started working exactly as expected
So the first version of the project is completed! Thank you all very much for your help, I could not have done it without all the useful information that I have learned from you on this forum. I will post a nice video about it soon. It will take a few days because I want to do a nice video, with explanations, etc, not just some low quality amateur stuff. Be patient, it's coming
A few things worth mentioning:
1. Although I have followed Gordon's advice and have removed the serial lines from /boot/cmdline.txt and /etc/inittab, when the RPI boots up, 3 or 4 LEDs are on. It doesn't bother me much, I just wonder why this happens.
2. As I have stated earlier, I've designed the circuit to deliver 5 mA max to each LED (by adding 390R and 760R resistors to the LEDs) and I have also connected 10K variable resistors in series with the normal resistors in order to be able to limit the current going through the LEDs to 0.5 mA or less. The purpose of this was not just not to waste current, but also to be able to reduce the light of the LEDs so much that I could sleep next to the clock. Well, I have graciously failed
even when the 10K variable resistors are turned to their max setting (10K), the light of the LEDs is still much too powerful in the dark
I guess modern LEDs are extremely efficient. Not much I can do about it now without un-soldering components (which I don't want to do), but for the second version I'm going to experiment and find out exactly how much resistance is required to dim the LEDs as much as possible.
1. For the next version of the circuit I plan to add components which will make it possible for the clock to automatically dim itself depending on the sensed ambient light intensity. I know that this can be done because you guys have told me that it is
Can you please explain what component needs to be added where in order to achieve this? Let's say that I'd like 2 mA to pass through each LED in strong daylight and 0.1 mA at night. I'm also thinking that the clock's own light (generated by the LEDs) might influence the behavior of this automatic dimming so it needs to be taken into consideration.
2. I'd like to measure the total current consumption of my current circuit. I plan to do this by disconnecting the 5V or 0V pin from the RPI and connecting a multimeter in series, between the RPI's 5V (or 0V) pin and the clock's 5V (or 0V) pin, with the multimeter set to small current measurement mode. This is the correct way to do it, right?