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Basic Electronics » OBDII project

February 16, 2010
by Mike
Mike's Avatar

The tutorial on the project calls for a 5k resistor.

Is that a 1/4 watt? Or is it higher wattage?

You can see the others are low wattage.

February 16, 2010
by BobaMosfet
BobaMosfet's Avatar

You can calculate the wattage you need. Use Watt's Law. Then choose the appropriately rated resistor.

P = I^2 * R

For example, let's say you are using a 5KOhm resistor with 5Volts DC.

Ohm's law says the current is:

I = E/R
I = 5/5000
I = 1 mA

So, the appropriate Watt rating for the resistor has to be:

P = .001^2 * 5000
P = .005 Watts.

A 1/8th Watt Resistor would be more than adequate.


February 17, 2010
by Mike
Mike's Avatar

Thanks BobaMosfet. Excellent tutorial.

I ordered the display and the chip yesterday, so I want to nail this down as best I can.

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