"Help!" for: Electronics

[Roadkiller]

Wow, so no one want's to answer my question. Screw it anyway, I figured it out myself after three days of no reply.

Good for you! And now that you've learned something that apparently not many people here know, you should share it with the group.

 

[Plasma Code]

Good for you! And now that you've learned something that apparently not many people here know, you should share it with the group.

Very well. The reason one needs a resistor is because some objects cant handle a large current produced by the electromotive force. That being said, we don't want to overpower an LED with a high current. The reason resistance exists in the first place is because the electrons are bouncing off of atoms while they're being transfered through a circuit due to potential difference (voltage). Electrons keep going because they're being attracted by the negative terminal, however it's an ordeal because energy is lost when electrons hit the atoms.
As far as wiring in parallel and in series, it's best to wire in parallel because when one LED is disconnected (for whatever reason), the other will not be effected (assuming you're wiring two or more LEDs). Also, when you wire in series, you have multiple resistance that adds up and just puts strain on the electrons. In parallel, the current is broken up into paths. So for resistance in a series, you have the equation: Req=R1+R2+R3... and for parallel you have the equation: 1/Req=1/R1+1/R2+1/R3... If you do the math in regards to any circuit, you'll find the resistance in parallel for two resistors has a smaller ohm value as apposed to two resistors in a series.

And if you wire in parallel, in theory, you don't need to have a resistor on each branch of the circuit. I haven't tested it out, but the math seems logical. Example bellow:

And yes, I can combine two or more resistors to get a precise value. If I need 100 Ω (keep in mind this is an example), and I only have 50 Ω resistors, I can add two of those and it won't be an issue.

 

[M071]

Wow, so no one want's to answer my question. Screw it anyway, I figured it out myself after three days of no reply.

Check you PM I will send some web sites I use that are much more helpful for electronics

 

[ventrue]

[...] Electrons keep going because they're being attracted by the negative terminal [...]

And if you wire in parallel, in theory, you don't need to have a resistor on each branch of the circuit. I haven't tested it out, but the math seems logical. Example bellow:

To be precise, while the direction of electric current is by definition from plus to minus, electrons actually move in the opposite direction and are attracted by the positive side of a battery.

Also, wiring LEDs in parallel as shown by your example is a bad idea. LEDs are semiconductors and as such, their resistance changes with temperature. That means, if you hook an LED up to a battery, a current will flow, it'll get warmer, as a result its resistance will drop and the current will increase, generating even more heat. That's bad all by itself, because it means that any single LED with no current limitation will literally work itself to death.
Now in your example, there is a resistor that limits the overall current, but obviously that is too much for a single LED and since no two LEDs are exactly the same, it's actually possible that most of the current will flow through only one of them. That particular LED will then burn out (see above), and while the other LED will at that moment still be working (which is what you had in mind when you said "it's better to wire [lights] parallel than series", which is actually true, but for light bulbs), it'll have to take all of the current from then on and as a result will burn out as well.
If you want to wire up multiple LEDs, either do it in series with a current limiting resistor for the whole row or do it in parallel with a separate resistor for each LED. Which way is right depends on what current and voltage you have available. For wiring in a row you need a larger voltage, and for wiring in parallel you need a larger current.

 

[BlueSol]

How about two bright, green LEDs, one at the top pointing down to light up the lower half of the diamond and one at the bottom pointing up to light the other half?

Easy and cheap, i love it. Thanks I'll throw up a picture of it when it's completed on my s-III page.

 

[Plasma Code]

To be precise, while the direction of electric current is by definition from plus to minus, electrons actually move in the opposite direction and are attracted by the positive side of a battery.

Also, wiring LEDs in parallel as shown by your example is a bad idea. LEDs are semiconductors and as such, their resistance changes with temperature. That means, if you hook an LED up to a battery, a current will flow, it'll get warmer, as a result its resistance will drop and the current will increase, generating even more heat. That's bad all by itself, because it means that any single LED with no current limitation will literally work itself to death.
Now in your example, there is a resistor that limits the overall current, but obviously that is too much for a single LED and since no two LEDs are exactly the same, it's actually possible that most of the current will flow through only one of them. That particular LED will then burn out (see above), and while the other LED will at that moment still be working (which is what you had in mind when you said "it's better to wire [lights] parallel than series", which is actually true, but for light bulbs), it'll have to take all of the current from then on and as a result will burn out as well.
If you want to wire up multiple LEDs, either do it in series with a current limiting resistor for the whole row or do it in parallel with a separate resistor for each LED. Which way is right depends on what current and voltage you have available. For wiring in a row you need a larger voltage, and for wiring in parallel you need a larger current.

Site was down for a while. Anyway, you say wiring in parallel is bad because the resistance changes with temperature, but if that's the case, wiring in series will have the same effect, no? I actually have an equation for that: ρT=ρo[1+α(T-To)]. But I think I understand what you're saying about resistivity in parallel. Now let's say I need a resistance of 200 Ω for the whole circuit, and I have two LEDs. Will I simply apply one, 100 Ω resistor to each LED in the parallel connection?

Check you PM I will send some web sites I use that are much more helpful for electronics

Thanks mate, I'll take a look at those.

 

[ventrue]

you say wiring in parallel is bad because the resistance changes with temperature, but if that's the case, wiring in series will have the same effect, no? I actually have an equation for that: ρT=ρo[1+α(T-To)]. But I think I understand what you're saying about resistivity in parallel.

Yes it will. But there will be no other way for the current than through both LEDs, regardless of their resistance. If you wire them in parallel, the current can and will choose the easiest path (i.e. the LED with the lowest resistance). Mostly, anyway, there's a formula for that, too. Somewhere

Now let's say I need a resistance of 200 Ω for the whole circuit, and I have two LEDs. Will I simply apply one, 100 Ω resistor to each LED in the parallel connection?

You need to decide on how to wire this first and then determine the necessary resistance per LED, not for the whole circuit.

For example: If you had a 9V power supply and two 2.5 V LEDs rated for a current of 20 mA, you'd need a resistor with exactly 200 Ω if you wired them in a row: U=9V-5V=4V; I=20mA; U=RI→R=U/I=4V/0.02A=200Ω. If you took those same LEDs and and wired them to the same power supply in parallel, each "branch" would still get the full 9V, but only suck up 2.5 instead of 5 V. So you'll not only need two resistors instead of one, but they'll also have to have a higher resistance (same equation, new R=325Ω).

 

[Plasma Code]

Yes it will. But there will be no other way for the current than through both LEDs, regardless of their resistance. If you wire them in parallel, the current can and will choose the easiest path (i.e. the LED with the lowest resistance). Mostly, anyway, there's a formula for that, too. Somewhere



You need to decide on how to wire this first and then determine the necessary resistance per LED, not for the whole circuit.

For example: If you had a 9V power supply and two 2.5 V LEDs rated for a current of 20 mA, you'd need a resistor with exactly 200 Ω if you wired them in a row: U=9V-5V=4V; I=20mA; U=RI→R=U/I=4V/0.02A=200Ω. If you took those same LEDs and and wired them to the same power supply in parallel, each "branch" would still get the full 9V, but only suck up 2.5 instead of 5 V. So you'll not only need two resistors instead of one, but they'll also have to have a higher resistance (same equation, new R=325Ω).

I see now. Wow, much thanks. And for clarification, when an LED says nV, that's describing the amount of voltage it sucks up, correct?
I hope I didn't sound douchey earlier as well.

 

[Claws61821]

Is there a reliable way to safely install gear within our armors that requires pos-neg-grd?

 

[thatdecade]

The reason we wire the LEDs with one resister per LED is to maximize the current through each LED. They will be brighter and last longer, with less math. lol

 

[thatdecade]

Is there a reliable way to safely install gear within our armors that requires pos-neg-grd?

The batteries that we us are generally safe to touch (under 12V). It is good practice to cover all bare wiring with electrical tape. It's a bit more plasticy and stretchy than regular tape.

If you have exposed wires and someone splashes water one you, you may get a little tickle. This is harmless for most people (no heart problems).

 

[DonaldDarko3]

Can you hot glue EL Wire? I'm planning on using it to light up the eyes on my NCR Veteran helmet. I want to glue it in position on the inside of the helmet. Also, how tough would it be on my eyes inside the helmet?

 

[thatdecade]

I've never done it personally, but a quick search says it should be ok. I still wouldn't go over board on the heat, may discolor the el wire.
http://www.thebestcasescenario.com/forum/showthread.php?t=2554

 

[Spartan 215]

Hey Adam. Newbie here. My suit is complete, and now I'm just here learning how to trick it out.

I've been stressing over the lights and electronics. Watched your lighting tutorial. Made the whole process WAY less intimidating. Thanks.

I know you said you're no electronics expert... but did you wire a few of the lights together? Or do you just turn them on one by one? Just curious as to if there's some sort of fancy rigging you've got going on there.

 

[thatdecade]

Hey Dustin. Newbie here. My suit is complete, and now I'm just here learning how to trick it out.

lol, I fixed it for you

The lights in the video linked in my signature is Adam's. Minimal modification was done on the reading lights. Each light has it's own battery and switch.

 

[Jona]

Hi, my brother is building a GUNGNIR helmet and wants a camera and screen to put in his helmet so he can see. He is planning on using just
a camcorder and taking it apart because we are limited on money. Is there a better way of doing this?

 

[thatdecade]

Yeah, a hidden slit so he can see.

I don't think this can be done cheaply. You can connect a video camera up to a pair of video goggles. Can find them used on eBay for ~$100.

If you know what your doing, maybe, maybe, you can use just a camcorder or not even have to take the camcorder apart. You need a camcorder that has an eyepiece viewfinder, not a 2-3 inch LCD display.

The eyepiece has optics that allows you to focus on the image at a minimum distance.

 

[Jona]

Yeah, a hidden slit so he can see.

I don't think this can be done cheaply. You can connect a video camera up to a pair of video goggles. Can find them used on eBay for ~$100.

If you know what your doing, maybe, maybe, you can use just a camcorder or not even have to take the camcorder apart. You need a camcorder that has an eyepiece viewfinder, not a 2-3 inch LCD display.

The eyepiece has optics that allows you to focus on the image at a minimum distance.

I have suggested a hidden slit and other ways like that but he is pretty set on some sort of electronic device. I will definately check ebay for some good camcorders, thanks for the advice.

 

[Thyjos]

I made my full armor and of corse I want to put leds in it,but thats no problem for me.

I only have one question: where shall I put the batteries?
Is it better to buy one large(i could put it into my backpack) or to use a single battery in any party of may armor???

thank you for your answers!

 

[Plasma Code]

I would use a battery for each part of the armour just so you can avoid a complex circuit. And you wont be as limited.