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Belgium
Asked — Edited

Volts For Signal

the signal ports on the ez-b4 ,does that give volt?.when i see the tutorial from the leds,
i see they are connected to gnd and to signal ports. *blush*


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#1  
Yes, the signal pin does put out 5v, but only about 20mA (I think anyway) or so.... You have to make sure the Led you're talking about doesn't draw more that that...
PRO
USA
#3  
Most hobby class micro controllers accept /output 3.3v to 5 volts. The last time I checked ezb v3 it output 4.75 volts. If you use leds make sure 5v won't pop them , red and ir leds are lower voltage and would pop at that voltage . Water clear 5mm Blue, white, yellow, green are 3.2 to 3.7 volts average so you can get away with one of those.
PRO
Belgium
#4  
i got an orange led and yellow on 3 volts .bolt pop.
PRO
USA
#5  
You will need to pwm them or add a resistor , 100 Ohm I believe . You can also use pwm to dial back the voltage. If 100 percent on pwm is 5 volts then you probably want to dial it back to 70 percent. Or like I said you can use a resistor too. Verify what voltage it outputs with a meter to be sure. Run the voltage at the highest recommended for the led so that it doesn't look like it is blinking.
#7  
If you are putting an led from a v3 digital output to GND, you do not need a resistor. The output only puts out about 25 milliamps, it is self limited. You would need a resistor if you are putting a led between 5V and GND though. For example if you were putting a led between 5V and GND then you would take the LED voltage drop, usually 1.5 V and minus it from the 5 V. This leaves 3.5 V, divide this by 25 milliamps (.025) and you get 140 Ohms. This would be the value to get the full .025 amps or 25 milliamps for the led (full brightness). A 1 kohm would work but your led may be dim. 3.5 V divided by 1 kohms = .0035 amps or 3.5 milliamps. That's the beauty of the v3 ezb, you can just put leds on your digital outputs with no worry or calculations. Good luck.
PRO
USA
#9  
@ purple - he already explained he connected the digital out to his leds that have a max of 3 volts and both of them popped. There is no limitation of digital output amperes "current limiting circuit" , if it exceeds the 25 ma it can damage the PIC. Since we have limited specs here its probably best for him to validate the work with a meter to make sure it is best voltage for the led.

Sidenote though : I have used 5mm leds on the digital output with no problem but different components have different voltage compatibility range. His apparently are more sensitive. There are some leds meant for 1.5 to 2v range and those can pop if they get too much voltage.
United Kingdom
#10  
Always use a resistor with an LED if the LED forward voltage isn't the same as the voltage output of the pin.

The V3 outputs +5v on the signal pins. So, if for instance your LED has a forward voltage of +3.0v and a forward current of 20mA you would require a 100ohm 1/8w resistor.

To make calculations for a single LED easier there are many online calculators out there, including this one.
PRO
Belgium
#11  
i will have a look thanks
PRO
Belgium
#12  
very helpfull indeed.i was thinking to using some 30 leds.


User-inserted image
#13  
Categories -> Hardware -> How To Drive A Led Correctly From A Digital Output
This post was on 3/27/2013. This post explains why you do not need a resistor. Thanks
PRO
Belgium
#14  
where is this post to find.i can see only to 2014.
#15  
I thought the tutorial explained it pretty well.

"LEDs

LEDs come in all sorts of colors. The clear Blue, Red, Green and White LEDs make your project look great. You can connect an LED directly to the Digital Pin of your EZ-B. The Peripheral Extension cables make it very easy also!

The diagram below shows how to connect an LED to an EZ-B digital pin. The light can be controlled by using a Digital Control in ARC, or an EZ-Script command Set(). The one thing to notice is an LED connected to a digital port on the EZ-B does not need a resistor. This is because the digital ports on the EZ-B have pull-up resistors built-in."
United Kingdom
#17  
@nomad here is the topic

@Purple, by all means run your LEDs without resistor however I will always advise to correctly calculate the resistor for driving LEDs which have forward voltage of less than +5V.

The reason I always advise a resistor is purely and simply because I have burnt up some LEDs which were powered via the signal pin of the EZ-B V3. Nothing says more about requiring a resistor than a burnt out LED in my opinion. On the flip side, I have also run LEDs from the signal pin without issue. To save burning out any more LEDs I have since used and advised the use of a resistor, the cost of the resistor is next to nothing (literally, it's less than 1p for a resistor!).
PRO
Belgium
#18  
yes i understand the tutorial.but i will use some 20 leds for my project.
5 volt leds are great good link.
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