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Topic: leds And resistors (Read 1 time) previous topic - next topic

GreyArea

Showing my ignorance again...

I know a resistor is necessary to protect LEDs from blowing. However I noticed on my breadboard that the resistor I was using made other LEDs further down the line much dimmer.

Is this normal and is there a way to get around it? Should I not be using different rated LEDs on the same circuit perhaps?

groundFungus

#1
Feb 01, 2018, 12:29 pm Last Edit: Feb 01, 2018, 12:31 pm by groundFungus
We don't know how the circuit is wired.  We don't know the values of the resistors.  We don't know the types of LEDs.  Without more information, I don't see how we can give an intelligent answer.   It does not sound normal.   How to fix it depends on what it is supposed to do.  We don't know that, either.



TomGeorge

Hi,
What are you using as a power supply?
Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?

Can you post a picture of your circuit layout please?

Thanks.. Tom.. :)
Everything runs on smoke, let the smoke out, it stops running....

GreyArea

Ok yes apologies for all the above.

I have one green "traditional" led that it was suggested I use a 400-1000 ohm resistor in line with to protect. I'm using a 1k resistor. Sorry I don't have the ma rating for the led but I do remember the resistor suggestion accurately. I'm really just using it as an indicator to show thepower is on.

Further down the line are 8 ws2812b LEDs, wired onto individual breadboard breakers. It is these that appear dimmer than before I put the green led and resistor in.

Power is 5v, coming from an Arduino Trinket which is itself powered by @ rechargeable battery pack (like a phone charger). I've also used a bench power supply (it actually says 6v on the dial) To power everything on the breadboard. When I do this I just take the data from port 8 on the Arduino, I disconnect the power...but I get the same dimming effect.

Sorry as you'll have gathered from my odd question I don't do circuit diagrams yet...but I think I've answered all the requests for info ( that I should have included in the first place!)

Though even without the info your comment of "it doesn't sound normal" is reassuring...

DVDdoug

Quote
Further down the line are 8 ws2812b LEDs, wired onto individual breadboard breakers. It is these that appear dimmer than before I put the green led and resistor in.[/qutoe]Further down the line are 8 ws2812b LEDs, wired onto individual breadboard breakers. It is these that appear dimmer than before I put the green led and resistor in.
Something is wired wrong.   Or, are you sure that's a 1K resistor?  


If you have a multimeter check 1K resistor.  And, check the power supply voltage to the ws2812b's...  It shouldn't change when you connect the green LED.

TomGeorge

Hi,

Can you please post a picture of your project so we can see your component layout?

Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?

Thanks.. Tom.. :)
Everything runs on smoke, let the smoke out, it stops running....

tinman13kup

Quote
Further down the line are 8 ws2812b LEDs, wired onto individual breadboard breakers.
It would probably be a real good idea to post a picture of the circuit you have because the quote above really doesn't make much sense. Do you have any idea what the limitations are of the trinket 5V regulator? I/O pins?

Tom
It's not a hobby if you're not having fun doing it. Step back and breathe

slipstick

I'm still trying to work out what "individual breadboard breakers" might mean.

Steve

TomGeorge

Sorry as you'll have gathered from my odd question I don't do circuit diagrams yet...but I think I've answered all the requests for info ( that I should have included in the first place!)

Though even without the info your comment of "it doesn't sound normal" is reassuring...
Now is a time to start, you are in troubleshooting mode now and you need to help us understand your circuit.
At least some pictures will help.
Do you have a DMM?
Thanks..Tom.. :)
Everything runs on smoke, let the smoke out, it stops running....

GreyArea

These...

https://www.adafruit.com/product/1312

I just use eight of them, wired exactly as in the pic here (but obviously another four) to test lighting patterns...the "ordinary" led is between the power rail of the breadboard and is just there to indicate I've remembered to connect power for when I get my Trinket programming wrong (often, see "newbie") and the WS 2812 b LEDs don't light up at all.

I noticed when I added the led and resistor, the ws2812bs seemed dimmer. The led and resistor are in series, on the +5v line, before any other components.

TomGeorge

#10
Feb 02, 2018, 01:08 pm Last Edit: Feb 02, 2018, 01:09 pm by TomGeorge
The led and resistor are in series, on the +5v line, before any other components.
Hmmm thats open to interpretation.
  • you have the led and resistor in series, one end of the series is connected to +5V and the other end of the series is connected to gnd.

OR
  • you have the led and resistor in series and you have disconnected the 5V from the WS2812 and placed one end of the series pair to +5V and  the other to where the +5V was connected.


Please a picture of your component layout or a hand draw circuit.

Tom.. :)
Everything runs on smoke, let the smoke out, it stops running....

wilfredmedlin

the "ordinary" led is between the power rail of the breadboard
You can't be between one thing.

So one end of the led and its resistor is on the power rail; where's the other end?





Please .... a hand draw circuit.
I don't do circuit diagrams
Keep Calm and call 0118 999 88199 9119725...... 3

GreyArea

#12
Feb 04, 2018, 10:03 am Last Edit: Feb 05, 2018, 10:04 am by GreyArea
Meant to say between power rail...and any other components. Ok, talk about careful what you wish for...

rubbish diagram here.

Yes I'm sure the 1k resistor is really1k. Can remember the led said use 400 to 1k as protection, but can't remeber spec. Ws2812b LEDs are dimmer with green resistor in-line. Green line on drawing from Arduino to ws2812b is just data in. Arduino on usb power (not shared with power pack powering ws2812b LEDs).

All I can say about the diagram is...sorry. Reason for hesitancy is that while I can control my Parkinson's well enough to solder, drawing and handwriting not so much. I know. Odd. It's an unpredictable bugger of a condition as anyone who has it will tell you.

Grumpy_Mike

If you have wired it up like that it is a great way to damage your WS2812 LEDs. This is because the data signal from the Arduino will be much higher than the supply applied to the WS2812s.

WTF are you trying to do?

At over 100 posts you should know how to post an image or at least know to read the how to use this forum sticky post.

slipstick

That diagram is fine and perfectly explains the problem. Your LED and resistor should not be inline IN the 5V line. Putting them there effectively "uses up" most of the 5V before it gets to the WS2812Bs.

If you just want to know that the 5V power is on then the LED and resistor should be connected between 5V and ground. Though if you want to know that the 5V is actually getting to the WS2812Bs they should be connected AFTER the switch.

Steve

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