Multiple LED's without Arduino?

Hello,

I am curious is there a way to blink/flash 9 LEDs at different rates without an Arduino?

mDSP:
I am curious is there a way to blink/flash 9 LEDs at different rates without an Arduino?

Yes, there are many. You could use 555 timer chips, one for each led. But this would be a more complicated circuit than if you used an Arduino.

Why do you not want to use an Arduino? Size/cost? You could use an Arduino to develop the circuit, then once you have it woking, use the Arduino to program the sketch into an ATtiny chip. An ATtiny84 should have enough digital pins for 9 leds.

Paul

Hello Paul,

thanks for the answer. Yes, its a problem of size and also of power consumption. I was hoping there would be a single chip which would make ti with different resistors/capacitors

An Arduino Pro Mini is quite small.
.

LM556 is a dual 555. Two at a time.
You don't have to use the entire board, you can just used the chip
with a resonator or crystal.
Dwight

A tiny84 would certainly use less power than a full Arduino. For flashing a few leds, it could run at 1MHz. But it will be your leds that use almost all of the power anyway, so it won't make a dramatic difference to battery life. Other components will be minimal. At least you need a 0.1uF bypass cap, a 10K pullup for the reset pin, and a series resistor for each led.

Attiny84 is the same size chip as a 556, but you would need 4 or 5 556 to flash your 9 leds independently, and many more caps and resistors.

You can get LEDs with a built in resistor and flashing circuit for the ultimate in size reduction.

Grumpy_Mike:
You can get LEDs with a built in resistor and flashing circuit for the ultimate in size reduction.

Hi Grumpy_Mike

do you recommend any particular brand? Store?

I need to place the 9 Leds in an installation in a librady so there are two factors that are importand

  1. Security (fire danger)
  2. longevity of battery

How long can a battery hold on a ATtiny switching on and of 9 small LEDS?

It is important to be able to control the precise frequency of blinking (individually for each LED)

Thanks
mDSP

If you want precise frequency, then you need a controller for the frequency.
How many mA do you want to drive each LED with? There are super bright LEDs out that are just blinding at 20mA, they can be driven with just 2-3mA and plenty bright enough.
If you have a 3xAA battery pack, they have about 2500mAH capacity. 9 LEDs at 3mA x 50% ontime = 13.5mA draw, a bare processor (such as Attiny2313) with crystal will draw maybe another 15mA draw = 28.5mA draw, so the battery would last ~ 80 hours. Use a 3xC or 3xD battery pack for even longer life.

You say it is important to control the frequency of each. Does is mean that they have to be synchronised as well, because if you do not use an Arduino even if they operate at a precise frequency they will drift out of phase with each other.

Thank you CrossRoads and Grumpy,

Yes frequency has to be precise but it will be different for each led. Let's say one will flash 12 times per minute another 19 times per minute another 3 times etc.

It will be very sparse light effect. So phasing is not a problem but precision is required.

I know how to do it with Arduino, and your advice for ATtiny is great. I was thinking that maybe it could be possible without a controller (to avoid power consumption)

I was hoping also to be able to set it and run maybe for 1-2 years before a battery needs to be replaced.

Best
mDSP

"I was hoping also to be able to set it and run maybe for 1-2 years before a battery needs to be replaced."
Only if it was a really big battery. You can use a slower system clock, 1 MHz (vs 8 or 16,) that will save on processor power, or put the processor to sleep between LED IO changes, wake up once a second from an RTC module alarm (separate battery backed power from coin cell) see if anything needs changing (data stored in an array perhaps) then go back to sleep.
Powering the LEDs is what will ultimately be the large power draw.

I will try on sleeping approach. But realistically, with small LED and sparse blinking (lets say something is flashing approx every 10 seconds) at short flashing durations (like 100 ms) with a ATTiny and a 3AA battery pack how much time can I expect?

maybe I can really reach one year?

mDSP

Do the math like I did. total on time ( number of flashes x flash duration) x current draw while on.
9 LEDs with different number of flashes.
Add them all up.
Size of the LED doesn't matter - it's the current draw when it's on that counts.