# What value of resistance to put between the output of a 74hc595 and the LEDs?

I'm going to start a project to make an array of LEDs using the shift registers 74HC595, I've seen many tutorials and it's not really difficult using the Arduino plataform.

The situation is as follows: in the tutorials they put a resistance between the outputs of the 74HC595 (Qx) and the LEDs , but in each tutorial the resistance varies (between 200 and 575 Ohms).

Then the question would be: if feed with 5V to 74HC595 (the same power as the Arduino) and the resistance that I put between its outputs (Qx) and the LEDs is lower (let's say 200 Ohms), the LEDs will light brighter than if I do it with resistors with higher values (let's say 500 Ohms)?

• What does the 74HC595 datasheet say about maximum current per output and maximum current for the entire IC? The Texas Instruments datasheet uses 560 ohms per LED on the Typical Application page. Aug 27, 2018 at 19:43
• @VE7JRO, the OP is asking, using a lot of words, if a 200 ohm series resistor will produce brighter LED output when compared to a 500 ohm series resistor. Aug 27, 2018 at 19:47
• I know the Ohm´s law, I just asking for experience, I Live in Cuba and is very dificult to me order pieces (when I buy them I have to wait almost 4 month to get them); so, when I order I try to order "things" that I would know that will work, I ask for this reason. Sorry Aug 27, 2018 at 19:48
• They say 25mA per output. Aug 27, 2018 at 19:51
• no need to apologize .... then you should be asking about what @VE7JRO mentioned in the above comment .... can the 74HC595 handle the load when all the LEDs are on? Aug 27, 2018 at 19:53