My arduino gauge project

@nightrunner84 can you run your spare under that tank?

nightrunner84 said:

Are you using the GM oil pressure sensor for the fuel pressure

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I’m using an exhaust back pressure sensor from a 7.3 powerstroke, they go up 40psi and will read vacuum too.

Pulled a bunch out of the wreckers, not all of them were good though, 7.3 ones are 1/8” npt, 6.0l and 6.4l are some flare thing and can read pressures up to 75-80psi. The bottom right is a map sensors for a 6.4L which is an o-ring seal with metric threads and reads up to 75-80psi

dgr said:

@nightrunner84 can you run your spare under that tank?

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I'm going to make a bracket to carry the spare under the rear tank. It'll hang a little low, but the plan is to drag a 5th wheel long distance with my kids. I WILL have a spare.

Sorry it's been a while. I got the permanent circuit built, and it seems to work. Still need to add two more data fields, one for pressure, and one for temp. Here is the board I made from Ifrythings drawing. The trans temp field is missing the powered portion because, as he said, the temp sensor in the trans can be tapped.







Also, I found this bezel on Thingiverse. It'll be going into the overhead console I'm building.



Also, intercooler......

ifrythings said:

The readings bouncing all over the place is from the lack of averaging, lack of a low pass filter into your ADC or could be exactly what your fuel pressure is doing. On my truck the fuel pressure waves around about 1 PSI and a non-dampened mechanical gauge shows the same thing.

For the lowpass filter try this circuit below. This also protects your ADC input incase the sensor wire shorts to battery voltage.

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What a great project! Super handy advice. Quick question in the diagram you have 10nF and 100nF caps, I'm having a hard time sourcing such small ones. Where do I find them?

I get most of my parts from digikey and for prototyping most of it comes from old electronics. You should be able to find them on amazon and eBay also.

ifrythings said:

I get most of my parts from digikey and for prototyping most of it comes from old electronics. You should be able to find them on amazon and eBay also.

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Found some! I find digikey indimidating, way too many choices. Did you make all your own low-pass filters? If I wanted to pass all 8 gauges through to a MEGA are there any off the shelf LPF that could make my soldering job easier? I read that using a 47K resistor is best for 12v systems as it "guarantees" the board won't see excess amps even in an voltage spike. Is there a reason you used a 10K rather than something larger?

thanks again for all the super informative posts!

The values are what I reversed engineered from a few different ford computers, as far as I know there isn’t any premade filters.

The 10k resistor will easily handle the sensor wire being shorted to battery indefinitely, in the data sheet most pins can handle vcc+(0.3v to 0.5v) so say 5.3v max input to the Arduino, 10k protection resistor and the sensor wire shorts to battery say 15v. (15v - 5.3v)/10k=0.97mA that the Arduino esd diode has to handle. Most mcu’s esd diodes are rated for 1mA continues, short term could be 10mA for a second or two (datasheet should tell you all this stuff, this is just off the top of my head).

In my mind, if ford thinks these values are good to protect the mcu from fatal damage then it should be good for us to use and same for the filter values, no point in redesigning something that works.