The 74HC595 is just a shift register.
I’d like to visualize what is being shifted out and preferably using a single LED.
I think the brightness will change depending on the number of leds on… but assuming that I’ve got enough ohms to hold all 8 I’m not going to blow them.
I tried this and have some thoughts for future users.
It works and saves alot of time.
As predicted by Bob above, more LEDS HIGH causes brightness of the set to drop.
The single resistor value you use makes a real difference. You want it as high as you dare so the logarithmic effects of the distance square law kicks in and the differences in brightness is minimized.
If you’re going to do this I recommend using the same color LED for all. Different colors already need different ohms and the added unevenness starts to make the product look “unfinished”.
This would be perfect if your goal is to maintain a consistent amount of lumens from the board (just changing where the light is coming from).
For the record, I even though I tried it I did end up choosing to give each of my LEDs it’s own resistor. The result was much better and allowed me to use many colours.
A few dead segments in that lot. Only the green one complete. The flickering is to do with the refresh rate and the movie frame rate being different or no mathematical relationship.
Sometimes I find these forum posts amusing in the twists and turns they take.
The original question by @Pixmusix has been answered.
The introduction of Digital Clock displays by @Eddie112471 is a different question.
These use a single chip that does everything and each segment is displayed individually at a rate the human cannot detect due to persistence of vision making it look like all segments are active at the same time. One load resistor for all segments and no change in brightness. Simple and effective.
The datasheets don’t go into the internal hardware design of the chips. but I remember studying how it could be done when I was learning electronics too many years ago now.
The chips are highly dedicated to being a digital clock and are not much use for anything else.
If I was @Pixmusix I’d look at 7 segment display drivers, you program it to display what you want and the chip does all the rest. I have successfully used these kind of drivers with just LEDs. The MAX6954 would be a good starting point. This can drive up to 128 LEDs.
EDIT: The device I used was a MAX7219 driving an 8x8 LED matrix controlled by an ATMega328P…
I did run a slow motion capture on my very reasonably priced xiaomi m9 phone.
However, being a hobbyist and not really smart at that.
I can’t say for certain if I’m actually doing it correctly.
I did open up the old Goldair clock. Just because I’m curious as cats.
Yes James46717, I think you are right regarding the operation of the clock IC chip.
It’s all very dried up and the cables and connectors are a bit crispy. I main IC is a Texas Instruments (sorry I can’t seem to upload the photo). The LED display seems to go straight into the IC chip. Not many passive components about.
I looked up this datasheet…
Unfortunately it doesn’t have any circuit examples more a block diagram showing the method of operation.
It talks about using 2 parts of the AC cycle to alternative light the LED Display (page 10).
Could that be what in the above video…hmmmm…?
The TI Chip seems a common part taking on many variations in a plethora of LED clocks of the day. I think Sanyo made a variant.
Thank god this is only a pastime and not my day job!