Clever 8x8 matrix wiring , but ...


According to this Instructables, there is a neat way that we can hide the jumpers underneath the component.
Now, my class of 20 students has only the official Arduino starter kit with small breadboards. I wonder, where to place the 8 current-limiting resistors? There seems to be no rows or columns left to place the resistors. The alternative would be to forgo the resistors and see what happens?
Also, as a side note, TInkercad does not have a matrix component, so it is really difficult to try out online. We can try it out by using two breadboards, but my goal is to use one breadboard only, since that's what's in the official kit.
Any thoughts on this?

Thank you.
Here is the link again: Connect an 8x8 LED Matrix to a Small Breadboard : 6 Steps - Instructables

these LEDs modules are available in blocks of 4 pieces for a bargain:

including a proper LED driver IC, the max7219. You can split these PCBs and can use the 4 modules separately if necessary. Explain your pupils the protocol of this IC, how to use HW-SPI, concentrate your lessons on how to design pattern, how to iterate through nested for loops, make animations withou delays... concentrate on the software side, but don't do a multiplexing with resistors and FETs on the UNO if it can be done so easily with the max7219 for this LED module. For a quick start - there are several libraries available for the MAX7219 also.

noiasca kind of beat me to it. :grinning:

It is not entirely clear what is the value of connecting a matrix directly to an Arduino. I suppose it is a way of introducing the concept of a matrix and then to the concept of multiplexing. Note that to directly connect the matrix to the Arduino with a view to multiplexing, you use 1k resistors, not 220 or 330 Ohm.

Our point is that this is very much an interim step. Once you explain multiplexing, you immediately move on from using the Arduino to perform the multiplexing, it is just not a practically useful approach. Coding the MAX7219 is itself a valuable exercise in the use of shift registers (while multiplexing a matrix using 74HC595s would be a serious sidetrack) and you can then move on to the much more exciting applications of the matrix displays for dynamic games or text presentation.

Persisting with driving the display directly form the Arduino would be tedious at the very best. :astonished: