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31  Using Arduino / General Electronics / Re: 8bit shift register 74HC595 - Power up 16 leds ! on: November 14, 2012, 10:26:48 am
thanks a lot ! i will follow your advises , thanks !
32  Using Arduino / General Electronics / Re: 8bit shift register 74HC595 - Power up 16 leds ! on: November 14, 2012, 10:10:39 am
EDIT :
parallel wiring will make 595 to draw 20 + 20 mA total 40 mA and it can draw 35mA max per pin... so it will be damaged... So attachment isnt really the way to go...

That's why I calculated the resistor you need assuming you drive them at 17mA each or a bit less. Don't worry that the LED forward voltage is quoted at 20mA, they will light up at much lower currents.

i can see.... you suggested 100Ω and the site below suggests the same but with a different wiring... i will follow your plan with 2 100Ω , 1/led and not 1 100Ω for 2 leds...

http://ledcalc.com/#calc

clicking at parallel leds and filling 5V , 3.3V , 20mA and 2 leds , it gives "Circuit's current consumption" 36.2mA with 100Ω resistor
33  Using Arduino / General Electronics / Re: 8bit shift register 74HC595 - Power up 16 leds ! on: November 14, 2012, 08:35:30 am
Thank you both , i will go to buy one of them , i need only one capacitor , 5V pin of 595 and GND pin , not from leds ! i understood it right ? About the circuit i think this is the way to go (attachment) thanks  a lot for the help ! all of you !

EDIT :
parallel wiring will make 595 to draw 20 + 20 mA total 40 mA and it can draw 35mA max per pin... so it will be damaged... So attachment isnt really the way to go...

Wiring in series , will make them dram total 20mA but needs the double voltage... It cant be done because 595 works with 5V , or i missed something....
34  Using Arduino / General Electronics / Re: 8bit shift register 74HC595 - Power up 16 leds ! on: November 14, 2012, 07:34:38 am
can you draw it somehow in order to understand where to put the second resistor ? i understood what you said !

See attached. The Sparkfun page for those LEDs says their forward voltage is 3.4V, so 100 ohm resistors will give you (5 - 3.4)/100 = 0.016A or 16mA per LED (actually a little less because of the output resistance of the 74HC595).

Don't forget to include a 0.1uF or greater decoupling capacitor between the Vcc and ground pins of the 595.

So 270Ω is pretty much , i have to other resistors but thats not a problem , i can play with them and if its too dim i will buy 220Ω or less ohm resistors , i will use a ATX power supply so my GND will be from there, the capacitor is still required ?

Very good answer thanks a lot !
35  Using Arduino / General Electronics / Re: How many A requires my project ? on: November 13, 2012, 06:29:07 pm
If i buy a simple pc power supply and turn it on by connecting black and green wire together (common power supplies colors for this trick) , the 5V from the red (common 5V cable) will be safe enough for my project leds servo sensors lcd etc ??? I show a lot of guides , some of them made it so easy as i described it and some other followed the hard way soldering resistors etc to their power supplies , it will work as simple as connecting black and green cable ? thanks !

It will automatically power up the arduino , so after the black-green connection is made (maybe i put a switch there) it will have load at no time.
36  Using Arduino / General Electronics / Re: 8bit shift register 74HC595 - Power up 16 leds ! on: November 13, 2012, 05:38:55 pm
If they have different brightness, you should do it the correct way and supply a seperate resistor for each led.

can you draw it somehow in order to understand where to put the second resistor ? i understood what you said !
37  Using Arduino / General Electronics / Re: 8bit shift register 74HC595 - Power up 16 leds ! on: November 13, 2012, 04:20:40 pm
Finally i took these leds https://www.sparkfun.com/products/529 they have better brightness and im thinking something like the attachment... i think it will work ??? I will light only 1 pin per time , 1 pin = 2 leds...

38  Using Arduino / General Electronics / Re: 8bit shift register 74HC595 - Power up 16 leds ! on: November 13, 2012, 12:16:43 pm
Quote
I have to find out what resistors i will need for blue leds in order to work with your example

I typically use 330-390ohm resistors - no point in calculating them out so precisely - your eyes perceive brightness logarithmically and will have a hard time to tell them apart once they light up reasonably.


thanks for mentioning this , the only reason i want to calulate them is in order not to exceed 35mA per 2 leds
39  Using Arduino / General Electronics / Re: 8bit shift register 74HC595 - Power up 16 leds ! on: November 13, 2012, 11:58:58 am
If you run the LEDs at 17mA or less, you can connect two of them + series resistors to each output of a single 74HC595, without exceeding the 35mA pin rating. And if you are only lighting up one pair at a time, the total current will be below 35mA too, keeping you within the 70mA total current rating.

I think its the best solution because i already have the 74HC595 , so the important think is the resistor to provide the 2 leds 17mA and my system will be safe enough ! Then I have to find out what resistors i will need for blue leds in order to work with your example
40  Using Arduino / General Electronics / Re: 8bit shift register 74HC595 - Power up 16 leds ! on: November 13, 2012, 11:42:32 am
So i can do 2 things !

Use 2 74HC595 chips to control individually 16 leds and just ligth 2 of them together (programmatically)

or

Use 1 TPIC6B595 chip to control 16 leds , connected at pairs !

Is that correct ?

probably i will need external battery supply for my leds because 5V DC wall supply wont be enough for 2 blue leds ! thanks for mentioning this
41  Using Arduino / General Electronics / Re: 8bit shift register 74HC595 - Power up 16 leds ! on: November 13, 2012, 11:23:28 am
The 75HC595 is not ideal for driving LEDs because it is rated for 70mA total Vcc or ground current. That's just under 9mA per pin if you are using all 8. If you exceed the 70mA rating, it's unlikely to fail immediately, but don't expect it to last very long.

so these 2 tutorials are not so accurate ? http://bildr.org/2011/02/74hc595/ , http://www.arduino.cc/en/Tutorial/ShiftOut , do you suggest replacing with something like this ? https://www.sparkfun.com/products/734

True, there are better options that function the same, for example the TPIC6B595.

______
Rob

its the same wiring as the chip i have now , but it can provide more current to each pin right ?


My questions are: why do you always light a red and a green led at the same time? There are yellow leds, too.
Won't you like to be more flexible ? Control all 16 individually, use parts allowing to light them in parallel?
 

I want to simulate water flow , so i want 16 blue leds at two rows light as i said , 2 at a time , not all together. Sorry for messing with colors i didnt know it makes any difference !


"Won't you like to be more flexible ? Control all 16 individually, use parts allowing to light them in parallel?" 

How ? i dont mind if lighting them up is programmatically or hardware done. i just want to ligth 2 of 16 leds each second !


How i will know what resistors i will need  ?  Im using 5V power supply ! , one tutorial uses 180Ω and the other  220Ω
42  Using Arduino / General Electronics / Re: 8bit shift register 74HC595 - Power up 16 leds ! on: November 12, 2012, 10:55:24 pm
Quote
i dont want to power them up one after other, i want to power up the 1 red an green at the same time
Despite the fact that one SR is located after the other using two shift registers has no affect on when the LEDs light or in what order. That's entirely up to your program.

You send 16 bits to the 2 SRs, nothing happens to the LEDs however until you toggle the latch pin. Then they all change at the same time.

______
Rob

so you say to make the "3. Add a second set of LEDs." of http://www.arduino.cc/en/Tutorial/ShiftOut and instead of putting leds at one row , put them at two , and ligth shift registers at the same time ?
43  Using Arduino / General Electronics / Re: 8bit shift register 74HC595 - Power up 16 leds ! on: November 12, 2012, 09:10:35 pm
1 2 3 4
- - - -      GREEN
- - - -      RED

All leds are off , 1 second , GREEN and RED les of column 1 are ON , next second , column 1 is OFF , column 2 is ON , next second , column 3....

did you understand ? i think its the last sentence of your post ! smiley
44  Using Arduino / General Electronics / Re: 8bit shift register 74HC595 - Power up 16 leds ! on: November 12, 2012, 08:56:36 pm
thanks for answering , i dont want to power them up one after other, i want to power up the 1 red an green at the same time , you game me an idea to use 2 chips in order to do this , but my thought was to make it with one chip , do you know if i can do this ? thank you so much !
45  Using Arduino / General Electronics / 8bit shift register 74HC595 - Power up 16 leds ! on: November 12, 2012, 08:32:54 pm
Hello i bought this chip https://www.sparkfun.com/products/733 and i found tutorials to make it work with 8 leds and i was wandering if i can make it work with 16 leds ! im using basic blue leds (20mA each)

tutorial with 8 leds http://bildr.org/2011/02/74hc595/

i want to make something like this with 16 leds :

- - - - - - - -
- - - - - - - -

2 first leds ligth together , off , 2 second leds ligth together , off , 2 third.....
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