/sci/ - Science & Math » Thread #12798897

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I'll give you tree fiddy

marco@marcoacuna.com Sat 06 Mar 21:46:57 2021 No.12798897 View Reply Original Report

Quoted By: >>12798925 >>12799038 >>12799063 >>12799123

First fag to let me know why this shit is not lighting gets paypaled five bucks. I'll pay you as soon as I get it to light.
>Inb4 cus I'm a retard. Yeah but how TF do I get it to light.

Anonymous

Anonymous Sat 06 Mar 2021 21:51:03 No.12798925 Report

Quoted By: >>12798938 >>12798977

>>12798897
led is burned
change led

Anonymous

Anonymous Sat 06 Mar 2021 21:52:28 No.12798938 Report

Quoted By: >>12798977

>>12798925
OR wrong led placement
turn it 180°

Anonymous

Anonymous Sat 06 Mar 2021 21:57:32 No.12798977 Report

Quoted By: >>12798991 >>12799006 >>12799358

>>12798925
Tried a new led. Nothing.
>>12798938
Tried it both ways. Nothing.

My best guesses is the resister has to much resistence or I didn't sodder the battery to the wires well enough. If not. Im completely stumped.

Anonymous

Anonymous Sat 06 Mar 2021 21:57:37 No.12798979 Report

Quoted By: >>12798996

send BTC here bc1qrcntxwyugp44klcxn9edwjqae0my6qkgta45ty

Anonymous

Anonymous Sat 06 Mar 2021 21:59:01 No.12798990 Report

Quoted By: >>12799058

1. Do you have the flat side (cathode side) of the LED on the negative side?
2. Battery got charge?
3. Are the wires good? (Showing continuity with an ammeter)
4. Are the breadboard holes good? (Try other rows/columns, one at a time)
5. Is the LED burnt? (Try a different LED)

Anonymous

Anonymous Sat 06 Mar 2021 21:59:17 No.12798991 Report

Quoted By: >>12799005 >>12799058

>>12798977
make another photo showing where the legs of the LED are inserted in the breadboard, also make sure that the two cables are connected to the battery and that the battery is full. test with a voltmeter.

Anonymous

Anonymous Sat 06 Mar 2021 21:59:32 No.12798996 Report

Quoted By: >>12799009

>>12798979
nah paypal or nada. Oh yeah include your paypal in the name field or whatever.

Anonymous

Anonymous Sat 06 Mar 2021 22:00:57 No.12799005 Report

Quoted By:

>>12798991
still me, first poster, if everything else doesn't work I think that the positive leg of the LED is in the wrong hole OR breadboard is broken ---> change column

Anonymous

Anonymous Sat 06 Mar 2021 22:01:03 No.12799006 Report

Quoted By: >>12799113

>>12798977
What resistance is it?

Anonymous

Anonymous Sat 06 Mar 2021 22:01:58 No.12799009 Report

Quoted By: >>12799113

>>12798996
I don't have paypal so fuck it then

Anonymous

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Anonymous Sat 06 Mar 2021 22:07:37 No.12799038 Report

Quoted By: >>12799113

>>12798897
wrong hole, nigga?

marco

marco Sat 06 Mar 2021 22:10:02 No.12799058 Report

Quoted By: >>12799302

>>12798990
1. Again I tried it both ways.
2.it's a new battery that doesn't expire till 2027
3.From where to where?
4. It's one of the better breadboards
5. Tried that.

>>12798991
Led and resistor are all on row 5. It's hard to get that clearly on a photo. Getting the voltmeter rn.

Anonymous

Anonymous Sat 06 Mar 2021 22:11:03 No.12799063 Report

Quoted By:

>>12798897
>he thinks yellow electricity can light a red LED

Anonymous

Anonymous Sat 06 Mar 2021 22:12:06 No.12799067 Report

Quoted By:

just try to run a led without the resistor first

marco

marco Sat 06 Mar 2021 22:20:03 No.12799113 Report

Quoted By:

>>12799006
22 ohms i think. red red brown gold.
>>12799009
Thanks for the help my dude.
>>12799038
Looks like it in the pic but its not. the resistor is connected to black column (negative)

Anonymous

Anonymous Sat 06 Mar 2021 22:21:44 No.12799123 Report

Quoted By: >>12799317

>>12798897
Your resistor is backwards. Money please.

Anonymous

Anonymous Sat 06 Mar 2021 22:32:25 No.12799197 Report

Quoted By:

Bad breadbord, debris in bread board, debris on component leg

Anonymous

Anonymous Sat 06 Mar 2021 22:51:48 No.12799302 Report

Quoted By: >>12799358

>>12799058
3. You need to check each individual piece of wire that you are using to make connections. One of the wires may be bad. This is pretty common.
4. If moving everything to a different set of rows solves the problem then you'll know something is off with the breadboard.

You mention the resistor is 22 ohms. That means there is 1.5 V / 22 ohms = ~68 mA current going through that LED. Do you know what the LED is rated for? (Do you know the part number so we can look it up?)

But yeah I'm 90% certain this is just a connection problem e.g one of your wires is bad, or the soldering you did is bad, or the wires aren't quite in the holes all the way.

Anonymous

Anonymous Sat 06 Mar 2021 22:56:09 No.12799317 Report

Quoted By:

>>12799123
It's a common misconception that axial-lead wirewound resistors are directional. They are only directional in how you read them. They are omnidirectional as far as current flow. You can have the resistor placed in either direction and it makes no difference.

Anonymous

Anonymous Sat 06 Mar 2021 23:05:26 No.12799358 Report

Quoted By: >>12799453

>>12799302
>That means there is 1.5 V / 22 ohms = ~68 mA current going through that LED.
That's not how it works. The LED has its own voltage drop that is added to the resistor (since it is in series). Only then can you calculate the current level.

>>12798977
>I didn't sodder the battery to the wires well enough
Use a voltmeter on your battery, make sure you're still getting about 1.5v. Soldering a battery can kill it (too much heat).

But as to WHY its really not working, a red LED typically needs about 2 volts to light up. Your AA is 1.5 volts, and considering you have the resistor in series, the voltage is even less.
Use two AA's in series to get about 3V, and keep the resistor in there.

Anonymous

Anonymous Sat 06 Mar 2021 23:08:27 No.12799372 Report

Quoted By:

looks like negative side of resistor is in the wrong power rail

Anonymous

Anonymous Sat 06 Mar 2021 23:23:40 No.12799453 Report

Quoted By: >>12799536

>>12799358
Right I forgot about that. So supposing there is a forward voltage drop of ~0.7 V (?) across the LED, the current in the circuit is (1.5 V - 0.7 V)/22ohm = ~36 mA. Agreed?

Anonymous

Anonymous Sat 06 Mar 2021 23:45:47 No.12799536 Report

Quoted By:

>>12799453
>So supposing there is a forward voltage drop of ~0.7 V (?) across the LED
Red LED's are about 1.8-2.0 volts. Normal switching diodes are in the 0.7v range.
You are also assuming voltage drop on the resistor without knowing the source voltage. More batteries = more voltages = more current.
In this situation, with only a 1.5v battery, the resistor and LED are pulling pretty much no current because the voltage is too low to activate the LED.

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