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I'm a bit new to electronics
what i need is .76ohm and .42ohm resistance added to two different projects on vout.
as far as i can see they don't make/have any of those over at radio shack (yes i know they are way over priced)
so how can i go about putting two resistors in series to accomplish this?
would be nice to run out and pick w/e i need up today.

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it's a small heating element, very simular to the build of a light bulb.

i don't seem to be able to find 0.76ohm or 0.43ohm resistors online via radio shack.
when looking for the ohm do you take off the 0. and just get 76ohm?

being that i don't know to much about all this, can a diode work for this also?

any help on reducing this output, such as what i should buy or where to buy it would be great.

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No 0.76 Ohm is 76 Ohm divided by 100.

You need to round to standard values as audioguru told you.

RadioShack are expensive and only stock a limited range of components, go to a real component supplier such as DigiKey.

The resistance probably won't change much when the voltage is reduced.

Assuming a resistance of 3.2R and a power supply voltage of 5V you'll need a 0.5 Ohm resistor to drop the voltage to 4.5V and 0.75R to drop to 4.2V; the resistors will need to be rated to at least 0.5W and 0.84W respectively. You could make these values by connecting two resistors in parallel, 1 Ohm for 0.5 Ohm and 1.5 Ohm for 0.75 Ohm.

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No 0.76 Ohm is 76 Ohm divided by 100.

You need to round to standard values as audioguru told you.

RadioShack are expensive and only stock a limited range of components, go to a real component supplier such as DigiKey.

The resistance probably won't change much when the voltage is reduced.

Assuming a resistance of 3.2R and a power supply voltage of 5V you'll need a 0.5 Ohm resistor to drop the voltage to 4.5V and 0.75R to drop to 4.2V; the resistors will need to be rated to at least 0.5W and 0.84W respectively. You could make these values by connecting two resistors in parallel, 1 Ohm for 0.5 Ohm and 1.5 Ohm for 0.75 Ohm.


the last part sort of confused me
do i need two .5ohms and two 1.5, then connect the two .5 for 4.5 and then connect two 1.5 for 4.2v?
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I'm not sure what you're asking.

I calculated the values of 0.5R and 0.75R using the potential divider formula:


http://en.wikipedia.org/wiki/Potential_divider#Resistive_divider_2

R1 = series resistor.
R2 = 3.2R the heating element.
VOUT = 4.5V or 4.2V the voltage across the heating element,
VIN = 5.2V the supply voltage

If you don't have 0.75R and 0.5R resistors, they can be made by connecting two 1R or 1.5R resistors in parallel.

Use the resistors in parallel formula and you'll see what I mean:




If all the resistor values are the same, you can simply divide the value by n, in this example connecting two 1.5R resistors in parallel gives:
1.5/2 = 0.75R

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I'm not sure what you're asking.

I calculated the values of 0.5R and 0.75R using the potential divider formula:

3db7631c0aa17b19db461b8e30aa41de.png
http://en.wikipedia.org/wiki/Potential_divider#Resistive_divider_2

R1 = series resistor.
R2 = 3.2R the heating element.
VOUT = 4.5V or 4.2V the voltage across the heating element,
VIN = 5.2V the supply voltage

If you don't have 0.75R and 0.5R resistors, they can be made by connecting two 1R or 1.5R resistors in parallel.

Use the resistors in parallel formula and you'll see what I mean:
301px-Resistors_in_parallel.svg.png
dc55458c0154c67e7e8eed2b2e5b835a.png
e1d6c77805c0245d311b04e4e2c8e9b3.png

If all the resistor values are the same, you can simply divide the value by n, in this example connecting two 1.5R resistors in parallel gives:
1.5/2 = 0.75R


my question is do i take a single 1ohm for 4.5v and add to that one a 1.5ohm for 4.2v
like i said, i'm not someone that knows enough about electronics.. at least to the point to figure out that math formula or what to series with what.
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