Hello, I have an arduino mini pro, and I need to connect 2 leds, 5mm, in parallel, on a single digital pin.
there is some danger that the arduino burn?
and if I connect to 4 digital pin, connecting 2 LEDs per pin. What happens?
Make sure each LED has it's own resistor.
Make sure the total current per pin is less than 20ma.
Example
LED forward voltage drop is 2 volts (you will have to check yours)
Each LED will have 10ma flowing through it. 10ma+10ma=20ma
Therefore 5V(supply)-2V(LED) / .010 amps = 300ohms.
Use the standard value of 330 ohms.
Each LED needs a 330 ohm series resistor.
Naruto128:
Hello, I have an arduino mini pro, and I need to connect 2 leds, 5mm, in parallel, on a single digital pin.
there is some danger that the arduino burn?
Each pin can provide 20mA.
If each LED draws 10mA (or less) then you're OK.
(ie. you need a resistor on each LED, try 330 Ohm).
fungus:
Naruto128:
Hello, I have an arduino mini pro, and I need to connect 2 leds, 5mm, in parallel, on a single digital pin.
there is some danger that the arduino burn?Each pin can provide 20mA.
If each LED draws 10mA (or less) then you're OK.
(ie. you need a resistor on each LED, try 330 Ohm).
http://arduino.cc/en/pmwiki.php?n=Main/ArduinoBoardProMini
DC Current per I/O Pin 40 mA
each LED is the 20mA 5mm voltage :3v
40 is the absolute maximum.
If you use 40 you stand the risk of damaging your contoller.
20 is the safe operating current.
5-3=2 2/.01 = 200. Use 220ohm.
You could put two in series (if they're red, yellow, green).
You could have two red LEDs in series with a 220? resistor and have that same network in parallel for a total of 4 red LEDs from one output, around 15mA total.
The devil is in the details.
(details, details, details - it's all about details)
Naruto128:
fungus:
Naruto128:
Hello, I have an arduino mini pro, and I need to connect 2 leds, 5mm, in parallel, on a single digital pin.
there is some danger that the arduino burn?Each pin can provide 20mA.
http://arduino.cc/en/pmwiki.php?n=Main/ArduinoBoardProMini
DC Current per I/O Pin 40 mA
From the Mega328 datasheet (written by the people who make the chips):
Naruto128:
Absolute Maximum RatingsDC Current per I/O Pin ............................................... 40.0 mA
This is a stress rating only and functional operation of the device at these or other conditions beyond those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability
My recent experience with LEDs is they are very very visible even at very low currents of less than 10mA. Unless you need to see (for example) system status from across the room, go with a bigger resistor and tiny current. I've used 1k and still had adequate light.
On my DFR0009 LCD panel, the power LED is blindingly bright: I stuck a piece of card over it and the light coming out the sides is more than adequate as an indicator.
JimboZA:
My recent experience with LEDs is they are very very visible even at very low currents of less than 10mA. Unless you need to see (for example) system status from across the room, go with a bigger resistor and tiny current. I've used 1k and still had adequate light.
Yep. The idea the LEDs MUST run at 20mA is ridiculous. 20mA is for flashlight builders or when you want to see things in direct sunlight. Or when you're multiplexing and have a very low on:off ratio. Or when you bought some "old-stock" LEDs on ebay that turned out to be from the 1980s.
For "status indicator" LEDs you can get away with 1mA or even less. I built a gadget yesterday and put a 10k resistor in it because a 4.7k resistor was too bright. You could run dozens of those off a single Arduino pin.
my leds are 20 mA, white.
I've tried to put leds in Original chamnel using ws2803 18,
in groups of two. and the arduino digital pins using 6.
These lights only 8 LEDs at a time. I'm using two attached battery of 4500mA 18650 in series
and only lasts 6min.
All this mounted on a bicycle wheel, will the amount of wires That the battery lasts so little?
that's why I wanted to put two LEDs per digital pin to put fewer wires
and the battery last longer, but you say I would burn the arduino is.
I'm frustrated.
I'm doing something like.
Putting more LEDs per pin will not save any battery life. The amount of wire (unless you have hundreds of feet) will not affect battery life. If you want longer battery life, you have two choices:
More batteries.
Dimmer LEDs.
tylernt:
Putting more LEDs per pin will not save any battery life. The amount of wire (unless you have hundreds of feet) will not affect battery life. If you want longer battery life, you have two choices:More batteries.
Dimmer LEDs.
I was doing some calculations and approximately total
having a length of wire, 216 inches or 5.5 meters.
I think if this affects battery life, you say?
Long continuous lengths of wire have resistance, which will "lose" energy to heat. You can use this chart and calculator to estimate how much wire loss you are experiencing:
My guess is it's not significant unless you are using a very fine gauge wire.
tylernt:
Long continuous lengths of wire have resistance, which will "lose" energy to heat. You can use this chart and calculator to estimate how much wire loss you are experiencing:My guess is it's not significant unless you are using a very fine gauge wire.
I'm using wire network
Cat5 is typically 24AWG. Plug that in to the calculator along with your amperage, you're probably less than 1?, which is insignificant.
What amperage are you running each LED, and how many LEDs are you lighting?
I have 24 leds 5mm 20 mA, color, white, light but only 8 per time.but only eight LED lights
two batteries, Ultrafire 18650 4200mah 3.7 v Li-ion Rechargeable Battery,
connect in series.
only lasts me about 6 min, approximately
Let's do the math.
Your batteries are 7.4V (nominal, cells actually go from 4.2V charged to 3.6V discharged) and your LEDs are being supplied with 5V, so we need an apples-to-apples comparison. We do this by using milliwatt-hours. (milliWatts = milliAmps x Volts.)
Your batteries hold (a theoretical) 31,080mWh (4,200mAh x 7.4V) of energy.
Your LEDs consume 100mWh/ea (20mA x 5V) or 800mWh total when lighting 8 at a time.
Your batteries should theoretically power this load for 38.85 hours. Of course, we are ignoring the fact that 4200mAh batteries don't really store 4200mAh (yes, Virginia, manufacturers lie), that the Arduino's CPU and associated USB-serial and other hardware is consuming probably 20-40mA, that the current-limiting resistors for the LEDs dissipate some power as heat, and that the linear voltage regulator is "wasting" some of that power as heat. I'll just do some hand-waving because I'm too lazy to do all that math, but the long and short of it is, you should be getting at least 10 hours out of a 18650 Li-ion battery.
Either your batteries are terrible quality, or they are damaged, or your charger isn't properly charging them, or you're wasting massive amounts of power somewhere.
When you say 20mA, do you mean you are using a series resistor to limit each led current? What value is that resistor?
If you light 8 LEDs allowing 20mA each you end up consuming 160mA: a 4200mAh battery should be able to power such LEDs for 4200/160 = 26,25h, more than a day, continuously...
The fact you are connecting the batteries in series is not going to increase the pack capacity but its voltage. Anyway, I believe those batteries aren't performing not evenly near that capacity, they are well known for being trash: did you buy them from China for cheap?
While writing another post came in which uses watts in its math and represents a better explanation of the battery capacity mismatch with your results.
Another possible explanation about the battery behaviour is you didn't disconnect them when they reached their minimum value of 3.6V. If you discharge LiIon or LiPoli below their minimum value your batteries get damaged and they won't store much charge any more. If you go higher than their max they turn into fireballs...
Their voltage level must be monitored while charging or discharging to avoid such nasty things to happen.
May be you just left them connected without any protection/shut down circuit: I don't know if those batteries have a built in protection circuit...
I have understood that batteries, the discharge limit is 2.7v.
batteries said to have a protection circuit for discharge and loading.
also, I'm monitoring the batteries with the arduino.
LEDs are connected with a 50 resistecia ohnm
I think as you say, these are junk bateris.
that they would recommend me batteries last me at least 7 continuous hours.
other things, the LEDs turn on and off so fast, it makes
batteries can discharge faster?
Naruto128:
other things, the LEDs turn on and off so fast, it makes
batteries can discharge faster?
Not appreciably. Like .01%, if that.