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Resistors, electric, help? (Solved!)
Cptn Pants
Registered User regular
Registered User regular
So my LED cup holders have been burning out a lot lately (in my car). Well more to the point the resistor keeps failing. I'm on my last resistor from over 3 years ago and I can remember the value of the resistors OR what the LED's I'm using either. So anyway, I have a few questions.
1: Can anyone help me ID this resistor?
2: What could cause it to keep failing and what should I replace it with if this keep happening?
3: Should I get a higher value resistor or something?
Any and all suggestions will be greatly appreciated.
1: Can anyone help me ID this resistor?
2: What could cause it to keep failing and what should I replace it with if this keep happening?
3: Should I get a higher value resistor or something?
Any and all suggestions will be greatly appreciated.
Cptn Pants on
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the weird thing is that resistors don't really fail unless they're getting hot to the point where the LED would cook long before the resistor did, unless you're putting too much wattage through them. i think that's a 1/4 watt resistor, so you might want to try going up to 1/2 watt
the fact that you're cooking LEDs leads me to believe there are bigger problems at hand. is this thing plugging straight into the cigarette lighter in your car? if so, pictures of the electronics would be helpful
hitting hot metal with hammers
Where exactly did this come from? It sounds like you may have designed it yourself...?
How are you certain the resistors are dying and not the LEDs? Too much current can definitely kill an LED, but...you probably would have noticed the popping sound and the burning plastic smell. :P
Basic schematic:
_________________________
| ______[Resistor]____LED's|
| /
/ /
/ /
| |
Switch
| |
|
Battery
Basic picture, can't get a better one due to the dark and not working and such.
hitting hot metal with hammers
Awesome, thanks. I actually work at a Radioshack so I'll just snag an open pack and give them a try. So the ohms rating will affect brightness without doing any damage to the leds/wiring? (I'm not great with electricity or engineering lol)
Well, hypothetically if you put too much current through the LEDs without a high enough value resistor, it could burn out the LEDs. But given that you already only have a 56ohm resistor in there, it's unlikely that any value resistor would end up allowing too much current through the LEDs.
I get that too much voltage/amperage can do some damage but I don't get how resistors actually work to be honest. I get that they lower voltage or amperage down from one voltage to another but I don't get how the rating work on the resistors. You say that it's unlikely that any value resistor will do damage but I don't get why that is? I mean, if the wattage is right does the ohms rating not matter as much? A quick crash course in resistors from someone and I think we can call this solved.
yeah, you don't need to worry about damaging anything based on resistor value
an LED just needs a certain amount of resistance on the negative side to light up, a lack of resistor isn't going to damage the LED unless you're running more current through it than it was designed for. without the resistance it still functions as a regular diode, it just needs there to be a difference in current between positive and negative for the lighting to kick in, for reasons i admit i don't really understand
hitting hot metal with hammers
Resistors limit the current (amps). The higher the resistance, the more it will reduce the current. If you used a high value resistor (say 10megaohms) you would probably not get any light through your LEDs because the resistor would reduce the current to a point where it's not enough to light the LEDs. The watt rating on a resistor tells you how much voltage the resistor can withstand without being damaged (and possibly changing it's resistance due to excessive heat or just burning it out completely). Higher wattage resistors are physically bigger and can deal with more power.
edit:
You might want to specify that you mean in this particular case. Given a different set of LEDs or a different battery connected to them, it would be possible to damage the LEDs by using a resistor with too little resistance. Like if you take just a typical small red LED (like from a RadioShack LED grab bag) and hook it up to a 9V battery with no resistor, it will have too much current going through it and it will burn out much sooner than it would with the proper current supplied.
Gotcha, higher rating means less current getting to the leds and hence less brightness. So as long as I stick with a 56ohm or higher I'll be a-ok. Good stuff. Think I can color this solved. Thanks everyone!!
Voltage is your water source. Current is your water flow rate. Resistance is kind of like pipe diameter. If you have a lower resistance (=bigger pipe diameter) you will get a higher flow rate. Higher resistance (=smaller pipe) you get a lower flow rate.
You were right with your previous conclusion. For a constant voltage V, a higher resistance results in a lower current and vice versa.
The equation that describes this is Ohm's Law, V = I *R where I is current. Also, just a small nitpick, the rating of a resistor is generally how much power it can dissipate (power = V * I) whereas the value is how many ohms of resistance it is. Might save some confusion for you down the road.
(There are a few complications if you start looking at more complicated devices)