Fuel sender wiring help

[whensparksfly]

I'm fitting a fuel gauge to a car tank attached is the diagram so I'm not used to resistors he said to use for the r1 a 260 the (r3 is the guage)
ohm I can seem to find one

 

[Seadog]

It's not a preferred value. You can use a 270 Ohm and a 10 Ohm in series to achieve that value.

 

[whensparksfly]

I wondered why I couldn't find them thanks

 

[MoreWellie]

You can use a 270 Ohm and a 10 Ohm in series

not if you are trying to make 260, you have just made a 280 ohm resistor

260ohm is available, do you know what power rating you need?

edit: ignore the question easy to work out

 

[MoreWellie]

or to be fairer to @Seadog , near enough 260 ohms

261 ohm https://uk.farnell.com/vishay/mrs25000c2610fct00/res-261r-1-600mw-axial-metal-film/dp/9466401

it all depends how accurate you want to be, if the 12v shown is just the car battery then the fuel display will vary with engine speed (as the voltage changes) which is why dashboards often have a small regulator in them to reduce the 12v down to something stable for the gauges

edit: do mount the resistor on something like a bit of veroboard (stripboard) as it won't handle vibration just stuck on the end of the cable

 

[voipio]

A 260 ohm resistor will be dissipating around 750mW when the tank is empty, at 13.8V nominal supply voltage, so needs to be rated at least 1 Watt.

 

[Seadog]

not if you are trying to make 260, you have just made a 280 ohm resistor

Whoops, I misread the value. I saw 280