Are there any benefits or not, of joining 8 LED's up to 1 resistor or via 8 single resistors.

Most circuits until a few years always showed any 8 bit chips each being monitored by a single LED and a single resistor. But it seems some circuits now show the 8 less being commoned up through a single resistor.

Ok it reduces the component count, but are there any other benefits or downsides to either way.



OR

 

The drawback of using 1 resistor is that the current will not be shared equally.

Eight resistors is preferable.

 

The CD4022 circuit is perfectly valid (if using a High output to drive the LED), since only one LED will be on at any one time, whereas with the HC595, more than one LED could be on, so each should have its own resistor.

 

Hi gray,
Your first circuit, showing a 10meg resistor, is optimistic.
E

Update:
If you want your LED 1 through LED 8 's to illuminate in sequence, note that the IC pin assignments in fig 1 are incorrect.,

 

Thanks for your inputs.

I think a single LED with a single resistor.

If the one common resistor blows for any reason, you have no indication at all.

Many thanks

 

since 4022 and 4017 have 1 of N outputs, in other words, only one LED will draw current and single resistor is fine.
if there is anything else to consider is supply voltage, because when sharing one resistor, LEDs that are off are not really "off", they are reverse biased. many LEDs have low reverse breakdown voltage (like 6V). so if you are using higher supply voltage, you may want to use individual resistors or at least test your LEDs.

 

I have to agree with that if only a single LED will be lit only a single resistor is needed.

Ron

 

Careful if you run the 4022 from a high voltage, as there will be a reverse bias on the LEDs that are OFF, and LEDs don't like reverse bias.