Resistors caps diodes OH my!

rotarypower101 · 04-28-2006, 08:40 PM

Hey guys I am trying to build a small 12 volt reg and need some details before putting it together.

Referring to this thread
http://www.mp3car.com/vbulletin/general-hardware-discussion/73989-need-very-small-12volt-regulated-ps-60-ma-min.html

Wondering if it matters which way I place a resistor in a circuit?
Does it matter, or are these components not determinant on direction?

I think a cap does, is this correct? And which way does it go?
Is it white band on positive voltage?

And I am 99.9% sure the zener diode does.
White band to positive side correct?

I have the diagram, but am unclear as to which direction to place the components.

I also would like to ask, because the guys that helped me find the components said it would be fine to substitute some of the components with similar components,

1 Will it be alright to run a 10 ohm 2 watt resistor in place of the 1 watt?
2 Will it be ok to have 47 uf 16v caps?

I am looking now trying to find references that will answer these questions, but it seems so basic everything skips the reference of direction or polarity of components.

corchulio · 04-28-2006, 08:56 PM

Yea resistors can be placed any way round its ok. With caps the cylinder shaped capacitors (electrolytic) have to be placed in a specific way they are always marked with arrows or -ve signs pointing to the nevative. Or he shorter wire is the nevative. With the resistor i think if you increase it to 2W the zener might not keep up with it since its rated at 1W

rotarypower101 · 04-28-2006, 09:39 PM

Ok this all seems good, I think

So just wait until I get a 10 ohm 1 watt then?

What are the effects of a 2 watt rather than a 1watt (the guy that got me those seemed pretty confident those would work) but I trust you guys more than some guy just trying to get me out the door.

Also just to confirm, the cap rated at 16V is alright?
I think I have seen this as a standard, just want to make sure.

Thanks for the time and help!

e30_droptop · 04-28-2006, 11:24 PM

You can use the 2 watt resistor instead of the 1 watt. Essentially, the wattage is a measure of power that is disappated. Power can either be disappated in two ways. Heat or Light. In this case, heat. As the resistor "drops" voltage across it there will be a buildup of heat from this action. Dont thing , OH my god the heat is going to burn down my car or my house. The heat is a natural byproduct of running the circuit.
The rating of wattage on the resistor tells one how much heat can be disappated safely without the resistor being subject to failure. The 2 watt resistor can just dissapate more heat if needed. This is a good thing.

If anyone has any contrary viewpoints feel free to voice them.

rotarypower101 · 04-29-2006, 12:56 AM

Good to know.

Question then, why did/do they have resistors in many increments ranging from 1/8 – 2 watts?

Would these others not just be superfluous if the only reason is how much heat one can give off safely?

What would be a reason or circumstance that you would want a smaller range for failure?

nameeri · 04-29-2006, 01:50 AM

Power is a rating based on OHM's Law. V=IR, or P=IV or P=I^2R. So, A resistor thats rated at 2W can run more current through it, thus using more power, but its still dependant on its resistance.

mushin · 04-29-2006, 12:57 PM

Quote: Originally Posted by rotarypower101

Good to know.

Question then, why did/do they have resistors in many increments ranging from 1/8 – 2 watts?

Would these others not just be superfluous if the only reason is how much heat one can give off safely?

What would be a reason or circumstance that you would want a smaller range for failure?

Cost and size. Higer rated resistors are physically larger, and cost more. Which is a waste if you don't need the higher rating.

e30_droptop · 04-30-2006, 08:21 PM

Quote: Originally Posted by rotarypower101

Good to know.

Question then, why did/do they have resistors in many increments ranging from 1/8 – 2 watts?

Would these others not just be superfluous if the only reason is how much heat one can give off safely?

What would be a reason or circumstance that you would want a smaller range for failure?

Have you ever seen one of those large 2 watt resistors being used on a surface mount PCB? The answer is rarely if ever. Take a look at your average PCB and you will see these tiny little chip resistors. Those cannot disappate much power, but they really dont need to so for the sake of miniturization they are small just like the rest of the components.

Take one of those 2 watt resistors and solder it inside your cellphone and you would hardly have room for much else! : ) hahahahah

e30_droptop · 04-30-2006, 08:22 PM

Quote: Originally Posted by nameeri

Power is a rating based on OHM's Law. V=IR, or P=IV or P=I^2R. So, A resistor thats rated at 2W can run more current through it, thus using more power, but its still dependant on its resistance.

Ohm's law rocks!

JimmyFitz · 04-30-2006, 11:17 PM

Quote: Originally Posted by e30_droptop

Ohm's law rocks!

ELI the ICE man is cool, too.

adaminc · 04-30-2006, 11:39 PM

I like ELI the ICE man better, because you can turn it into a song, like me and a friend did once during a very boring electricity class! It was very... country mountain folk songish.

...man i'm a geek