Beginner questions about led matrix and motors

I got my Arduino recently and I am about to order my first parts but I have some questions first

  1. Do I need a motor driver shield to drive stepper motors or other motors? If I do, which one would you recommend? I see on the arduino website that there are libraries to control servos and steppers so why would I even to spend so much money on a shield?

  2. For my first bigger project I am planning to build a simple tetris game that is played on a 8x16 led grid. I don't want to spend $30 on an RGB matrix so I am planning to buy 2 Red-Green matrices from sparkfun. So my question is what all do I need to run these 2 matrices? I think I need just 3 shift registers, but I am not sure if I need to use resistors, transistors, or other ICs. I see people use a lot of different ICs for shift registers and sinks and it makes me confused. :frowning:

  3. Again for the led matrix, I am pretty sure I need the shift registers to scan through each LED by giving power to a column and ground to a row. My question is do I need another IC to do the multiplexing or is a software based multiplexing of powering on and off each led sufficient so no flicker is visible? It worries me because there are 128, and if I keep scaling up this would I eventually need an IC to do the multiplexing? (say 16x16)

Any help is appreciated!

I guess I was hoping for a simple answer to my motor question and it now appears that there is no simple answer without picking the exact motor I want. It also appears additional ICs are necessary to work with motors because of their high voltage and current demands. I guess I will try to read more and figure it out myself.

Also, do you recommend any particular led matrix tutorials that use shift registers?

Would this work for the transistor?: Darlington Driver 8-Channel ULN2803 DIP - COM-00312 - SparkFun Electronics

I was basing the parts list from Wise time with Arduino: Introducing the "Dual bi-color LED matrix shield"...

Can you explain why you need a high power shift register and a normal shift register? And also my a transistor is necessary. I didn't think LED needed that much power.

why you need a high power shift register and a normal shift register?

I couldn’t see the two types in that schematic. In general you are over stressing a logic device if you drive a LED from the pins. An LED takes about 20mA which is a lot for some forms of logic. Some people wrongly use a normal shift register to drive LEDs but this is over stressing the part. However as the parts don’t immediately fry they think they are “getting away with it” which they probably are, but there are implications for long term reliability and component life time.

Would this work for the transistor?

Yes these are quite good for pulling down or sinking current. Just beware that although any one channel can sink 500mA theirs is a limit on a total of about 650mA being sunk by this chip at any time.

And also my a transistor is necessary

A transistor allows you to switch more current than a logic output.

but there are implications for long term reliability and component life time

Mike, what do you estimate the life time of the 74HC595 shift register to be, when in “normal” use?
How much shorter, percentage-wise, do you think the life time would be if the Io current is 20mA (limit being 25mA)?

I can't really follow his circuit. He appears to be using common emitter devices (595 and 2803) for both the row drivers and the column drivers

I use common cathode LED matrices. The 595s drive the columns (connected to LED anodes). The rows are sinked by the 2803, one by one.
I think one good measure for the potential reliability of the circuit is the amount of heat is dissipates. My dual LED matrix board has been functioning continuosly on my desk for close to half year now, with ICs pretty cool (temperature-wise).