Thanks for the reply! So you're saying best bet would be to pass the ADC circuits output to the arduino, and essentially let it replicate the signal to the ecu, and also controly lcd? Could I use the power stepdown circuit built into the ADC to power the arduino as well, or should I put in a seperate one?

Sorry for the basic type questions, Im not sure where I could find the information, and I've not take any electronics classes

 

Yes. You're in essence making a "homebrew" ZT-style gauge.

You should have plenty of power from either of the regulators. I would run some basic load tests (everything on/testing voltages with a controlled FlexFuel sensor input at a few levels/EverClear 195 works great!) just for the heck of it.

No problem on the Q's. Me neither

 

In doing some of the reading...it appears the Arduino should not effect the signal...I hope.

It has no way to output a true analog signal, only a PWM signal, so a filter would be needed....almost seems like excess crap starting to build up.

The input is supposed to be 10Mohm impedance, so it shouldn't effect the signal I would hope. I will try to do some testing once I get everything together...and teach myself some programming language. Wish I had payed attention in that class in college HA!

 

there is no solution for Evo 9 ?

 

If you read the thread you will find the answer is no. Wanna step up and make a patch for the 9?

 

I finally got my order from Futurelec. I didn't realize they were in Australia until after I did the order LOL.

I am extremely busy with work at the moment so it may be some weeks before I can dedicate any time to building the circuit.

 

Futurlec short shipped me one 25v 1uf capacitor. Locally I can get 50v 1uf capacitors but they are not tantalum. Is there any issue with using these?

 

No issue with the 50V non-tantalum. The reason for tantalum is that is allows a small capacitor size. You should check the tolerance on the 1uF that you can source locally, which should be no more than +/- 5%. If you have a digital voltmeter that you can measure the F value of a few, take it and select the one that is closest to 1uF.

 

Thanks. I bought two already. I will test them an see how close they come.

 

I note that everyone recommends putting the ethanol sensor in the return line, after the regulator. On my car it will be easier to put the sensor before the regulator. I am wondering if there is a durability issue with subjecting the sensor to 70+ psi of fuel pressure (base pressure plus boost pressure).

 

does this do the same thing as this?
http://proefi.com/info/product-list/flex-fuel/

 

yup.

 

Well I have completed my circuit but it is not working

When I power it up without connecting the sensor I get 4.98v at FF out and 4.38V at FF+, 0V at ECU. When I plug the sensor in with free-air, I get 4.87v at FFout but I GET 3.25V at FF+ and still get 0V at ECU.

In my haste to test this I initially interchanged FF out and FF + so I don't know if I damaged anything there.

I have double checked my circuit connections and don't see anything wrong and I used a socket to avoid damaging the chip. I did note when building this that heat builds up extremely quickly in the LM317 and LM7805 when soldering so I am wondering if any damage occurred there.

I am going to take it step by step, starting with checking the LM317 and LM7805.

 

What are you using to power the circuit? If you use a fully charged battery at +14V, FF+ should be close to 12V. Sounds like you have a problem with the LM317. Are the pins the wrong way around? Check the orientation of input (pin 3) and adjust (pin 1). It's easy to get them mixed up - don't ask me how I know .

The output from the FF sensor is a 50Hz pulse. If this is what you mean by FFout I don't know how you can measure the voltage without an oscilloscope. If you are talking about the voltage on FFin without the sensor connected, it should be just the pull up voltage of 5V from the LM7805, so 4.98V looks OK.

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I just spotted an error in the PCB schematic for the LM317. I've corrected the original in post #173. Here it is again for reference.

 

Thanks for responding. I did it according to the incorrect schematic so hopefully that is the only problem. I will correct it and report back.

BTW, I know the sensor puts out a frequency but I don't have an oscilloscope. I measured the voltage at FF out anyway incase the voltage has some significance.