Go Down

Topic: Did i ruin my adapter? (Read 210 times) previous topic - next topic

Tolicim

The project is simply an ledstrip(WS2812B) with an external power source.
Now since these strips can suck up quite a lot of amps i could not power the needed length with simple USB so i bought an adapter for it that is 5V-6A.

I had the test set up for a small piece and was connecting up the female socket for the adapter which made a 1 second short-circuit (i did see a spark at the connectors).
Now since the led on the adapter was still burning i hoped it would be fine so i checked with a multimeter and it gave me a 5.2V reading.

However when i connect this to the strip then all the wiring gets very hot but the strip does not light up.
If i power it through the board or a double battery-pack then it does light up.

DrAzzy

That the *wiring* gets hot indicates a short, or near short.

That the LED strip works, indicates that there's nothing fundamentally wrong with the strip.

You said there was a short and you saw a spark? Did you see two wires that shouldn't be touching touch, or did you infer that there was a short from the spark? (that is not a solid conclusion, as you can get a spark with any moderately heavy load, and the spark won't occur if you quickly and smoothly connect the wire, even if there is a short)

I don't suppose the power supply is wired backwards, and the protection diodes in the WS2812B's are miraculously surviving and preventing damage to the LEDs by bringing down the power supply before they fail?

I'd also investigate physical problems with the connector. Because you seem to have an apparently working power supply, and an apparently working LED strip, yet combined they don't work.
ATTinyCore for x4/x5/x61/x7/x8/x41/1634/828/x313 megaTinyCore for the megaavr ATtinies - Board Manager:
http://drazzy.com/package_drazzy.com_index.json
ATtiny breakouts, mosfets, awesome prototyping board in my store http://tindie.com/stores/DrAzzy

DVDdoug

#2
Aug 16, 2019, 09:52 pm Last Edit: Aug 16, 2019, 09:52 pm by DVDdoug
Quote
I don't suppose the power supply is wired backwards...
That's a good guess! 

Your multimeter will show polarity.  Make sure it shows the same as the battery...

Quote
Now since the led on the adapter was still burning i hoped it would be fine so i checked with a multimeter and it gave me a 5.2V reading.
Are you measuring 5V with the LEDs connected?   

A multimeter can be misleading because the power supply could  be noisy/spikey or it could be putting-out AC or a combination of AC & DC and a meter won't always show that.   Try switching your meter to AC.   It should read (nearly) zero.   But try that with the battery first to make sure your meter reads zero (on the AC range) with pure DC.

Tolicim

#3
Aug 16, 2019, 11:14 pm Last Edit: Aug 16, 2019, 11:16 pm by Tolicim
Hey thanks a lot for the replies! i am very new to the electronics scene so pretty unsure about things sometimes.

It seems i did have it wired up wrong, the DC 2.5 connector has a long and short leg and since there was no written indication of a +/- i figured the long leg had to be + since it works that way with LED's and capacitors as well.
Unfortunately i did not know i could just measure the polarity with the multi-meter.

So now wiring it up correctly does stop the wires from getting hot but it still does not light up.
To be more exact the voltage actually seems to be 5.36 and that is measured from just the connector so it is not wired up to the strip.

The schematic on that strip says 3.5V/5.3V so i guess the protection is just kicking in because of the tiny little extra bit of voltage it is getting?
I thought that if it was getting too much voltage it would just be too bright and get destroyed that way, i didn't know it has a protection against that.

Edit: the short-circuit is because i tested the connection with alligator clips and those accidentally touched eachother for 1sec.

DrAzzy

Generally on connectors, if leads are different length, the ground lead is longer, as this guarantees ground makes contact first, which is more likely to be the safer order of connections.

Are you sure that the LEDs still work? Ie, they weren't damaged the second time you hooked up power backwards?

I didn't think those LEDs had protection against excessive voltage (I would expect they'd just burn out, or maybe burn out when left on full brightness due to heat).

0.06v over maximum isn't much - but it may be too much. A high-current schottky diode in series with the +5v supply would knock the voltage down by about 0.3v; just make sure you get a schottky diode rated for the max current the LEDs can draw.
ATTinyCore for x4/x5/x61/x7/x8/x41/1634/828/x313 megaTinyCore for the megaavr ATtinies - Board Manager:
http://drazzy.com/package_drazzy.com_index.json
ATtiny breakouts, mosfets, awesome prototyping board in my store http://tindie.com/stores/DrAzzy

TomGeorge

#5
Aug 17, 2019, 03:06 am Last Edit: Aug 17, 2019, 03:07 am by TomGeorge
Hi,
Welcome to the forum.

Do you have a DMM?
If not, look to purchasing an inexpensive one.

This would have saved your adapter as you WOULD HAVE tested the plug before using it.

Lesson learnt;  Do not make connections with the power ON.

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

Tolicim

#6
Aug 17, 2019, 01:25 pm Last Edit: Aug 17, 2019, 01:28 pm by Tolicim
Thanks for the welcome, i do got a cheap little multi-meter but was not aware that i could measure polarity with it so that's very handy to be aware of now.

Well i don't know why it didn't work yesterday with the correct wiring but today it miraculously does work!
I think the wiring might have just been a bit loose or maybe i need a better breadboard.
Anyways thanks a lot for the tips, i can now proceed to get my case ready and solder that puppy up! :)

Paul__B

Well i don't know why it didn't work yesterday with the correct wiring but today it miraculously does work!
Extreme good luck!  :smiley-eek:

Go Up