I'll even make it easy for you. 
Here they are on Aliexpress. Displays soldered on:
Displays socketed:
(They have doubled in price since Covid. I always cite the cheapest listing. )
Those are actually a favourite display of mine.
BTW don't try to cascade those without bypassing the diode on the back. Else each cascaded module runs on 0.7V less voltage than the one before it, until it's all gone. 
Not sure what they were thinking...
reversed polarity protection maybe?
It's not in the right position for that. It's set up more like backflow protection... but from what? It's incredible but I guess it must be to prevent people from connecting input wires to the output terminals... incredible because they're clearly labeled. Oh, well.
Beyond the fact that you really only need backfeed protection on the last unit in the chain. There should be a set of pad right there for a 0 Ohm resistor to bypass it.
I think maybe the backfeed protection is intended for a single unit. You might assume that a user who even knows how to chain, would know how to connect them properly. I completely agree about the bypass pad idea, but I just went across the diode with a wire jumper.
thank you all for your thoughts!!
the MAX7219 seems amazing! but it also seems like total overkill and very expensive for a 4-digit display. i'll keep it in mind if i ever need more digits.
but for my current needs, the 4-digit TM1637 modules seem perfect for the price. i think i'll pick up a few of those. too bad it seems difficult to find a good source for just the TM1637 chips
Hi,
If you use the controller to do the multiplexing, any extra work you get the controller to do will slow the multiplexer down, thus introducing flicker.
If you use a MAX7219 it will do the multiplexing for you, so any change in code or speed of your process will not introduce flicker.
No it isn't if you look at code simplicity, and that you do not need to tread carefully with your code to prevent digit updates and multiplexing flicker.
How much do you want to spend on a 4digit 7 seg display?
I think you will find it is almost as cheap to use a MAX assembly with the displays fitted, than it is to make a 4digit display and wire it to your controller.
Tom.. 
Oh?
https://www.aliexpress.com/item/32797764127.html
and many other vendors...
No, anything else is "underkill" and going to cause you a lot of problems. Did you really dislike the prices of the modules that I linked? They seemed quite affordable to me even at twice what they used to be!
I like the modules that integrate a microcontroller (or MAX7219) and 7-segment displays on one PCB - way easier to use! I've seen microcontroller ones with a simple serial interface which is as friendly as it can get really.
1 Like
- MAX7219
- HT16K33
- TM1637
but honestly, I don't know why you think a MAX7219 (module) is "expensive". They are sold for more or less for the same price...
The clone bare LED modules with no driver IC, just pins, cost barely less, sometimes more than the modules including a driver IC. What you get from the higher end manufacturers is better PCB quality, more variety (for example available LED colours), and online documentation and support.
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