Question Help Choosing Resistor

[antonyjlawlor]

Hi,

I am trying to figure out which type of resistor I need to be able to achieve 120c as per the image attached. I know the reference voltage is 5v and that the voltage after resistance is introduced 0.28 and that the resistance I need is 1.18kohms (1180ohms) - i'm pretty sure it's not as easy as just picking up any 1.18k resistor so hoping you guys can help - not too clued up on ohms law and resistor banding etc.

Thanks,

 

[kanewolf]

To get 1180 ohms, that is most likely 3 or 4 resistors in series. 1000 ohm + 100 ohm + 80 ohm (if you can find one) or 75 ohm + 5 ohm ... That is plus or minus the tolerance of the resistors.

 

[antonyjlawlor]

To get 1180 ohms, that is most likely 3 or 4 resistors in series. 1000 ohm + 100 ohm + 80 ohm (if you can find one) or 75 ohm + 5 ohm ... That is plus or minus the tolerance of the resistors.

What about the banding around the resistors etc? i have a bunch of them, some have r next to the number.

 

[Spinachy]

Resistors can only handle a certain amount of CURRENT - be sure that you get ones rated for the amount of current that will be flowing in your circuit.

 

[kanewolf]

What about the banding around the resistors etc? i have a bunch of them, some have r next to the number.

The banding tells you the value of the resistor and the tolerance -- http://www.resistorguide.com/resistor-color-code/ You might find an 1180 ohm resistor. They CAN be made in any value. "Standard" value resistors will be more limited.

 

[AllanGH]

With 4 - band color coding:
1KΩ = Brown Black Red, with a Brown for 1% tolerance
180Ω = Brown Grey Brown, with a Brown for 1% tolerance
If these are going into a 5 Volt reference circuit, just use 1/4 Watt resistors and you'll be fine.

 

[antonyjlawlor]

Thanks guys