# How do I...

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• 06-20-2008, 03:15 PM
greenman100
yup, good catch
• 06-20-2008, 04:41 PM
Dan2008
Dang, how 'bout that!!! Good instructions if I can understand them.

So, do I use the highest actual resistance reading or the highest rated resistance (90 ohms for fuel or 240 ohms for temp/oil) from the senders to size the other resistor as in the instructions?

I might be that the rated resistance is actually the highest since that is cold/no pressure. I suppose it is always good to check it just in case though.

Thanks for all the help! I'll be ordering my brain soon so I can start playing around with it (everyone always said that if I had a brain that I'd play with it) and creating my instrument cluster in the Fusion Control Centre Configurator.

Dan
• 06-20-2008, 05:33 PM
greenman100
rated is what you want
• 06-20-2008, 05:54 PM
Dan2008
Cool. I'm sure I'll be back needing help in the software forum when I get my stuff in.
• 06-26-2008, 10:42 AM
RonS
Just a thought. Couldn't we use small hall effect current sensors? Put it inline with the sending unit. Measure the voltage and use that to get the reading. Then we could use 12 volts and not worry about voltage dividers. And if you already have gauges you could put the current sensors in. Then measure the voltage at different readings. Then you could setup your formulas to match the original gauge. It should work.
• 06-28-2008, 08:02 AM
Dan2008
Okay, here is what I have come up with.

Using an online voltage divider calculator), it looks like I need 336ohms for R1 if R2 is 240ohms, voltage in is 12vdc and voltage out is 5vdc.

This is where I really need some help and of course the kid at Radio Shack is as clueless as I am.

There are 1/8 watt, 1/4 watt, 1/2 watt and 1 watt resistors. Which do I need?

Also, I can find 330ohms and 470ohms but the calculator says I need 336ohms. Do I string multiple resistors together to come up with 336ohms or just use the 470ohm and compensate in my skin settings? Wouldn't stringing multiple resistors together introduce additional resistance?
• 06-28-2008, 11:06 AM
greenman100
pretty much any wattage would be fine, 1/4 watt is standard

330 is close enough
• 06-28-2008, 11:34 AM
Dan2008
Thanks. According to the calculator, that will provide an output of 5.053vdc and I wasn't sure whether that little of an over voltage would matter.

One other thuing I forgot to ask: I also see resistors marked as 5%, etc. Is that what I want?
• 06-28-2008, 07:29 PM
Bugbyte
Get 5%. 5% is the tolerance that the resistor has for providing the rated resistance. A 100 ohm 5% resistor will provided anything from 95 to 105 ohms. 5% resistors have gold bands as the very last band. Silver represents 10% tolerance.

The wattage only matters if you have to dissipate a lot of energy. In your application, it doesn't matter, so 1/4 watt is fine.
• 06-29-2008, 06:04 AM
Dan2008
Thanks Bugbyte.
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