ACCLR8N

Lots of good info on this site, but I'm not finding specifics on what people did, how it looked and how it worked. I'm sure a lot of you college kids will find this overly obvious, but it might help out one or two other people. More importantly somebody will pipe up "are you an idiot?" and prevent me from making a mistake.

This is a dash gauge display for my kit car. '87 Firebird chassis, '95 Trans Am drive train, K1 Evoluzione body. Don't worry about reliability, few believe this car will ever actually see the road. I have V4 Fusion Brain and the balance of my order should arrive any day with connectors and temp sensors. I'm running this on a Toshiba M200 touch screen laptop (I may never need dedicated carpc, see above). Been using Gimp to create png images for MDX. More on my car can be seen at http://www.cardomain.com/ride/2234824

First up, battery voltage: 0-18V battery range. I'll be connecting a 3K ohm 1/4watt resistor to a switched 12V power source. That will be connected to both a FB AIN and a 1K ohm 1/4watt resistor. The 1K ohm will be grounded to the car. I've read they should be kept under 1K. I thought bigger meant less current constantly flowing off the battery when I placed my order. Feel free to explain that.

Next, Fuel level: Original GM 0-90 ohm sensor. I'll connect a FB 5V out to a 51 ohm 1/4watt. The 51 ohm will be connected to the FB AIN then a 2.2 ohm and the signal wire from the fuel level sender. Should give me a 0.2V-3.2V reading.

Oil pressure: Original GM 0-90 ohm sensor. I'll connect a third FB 5V out to a 51 ohm 1/4 watt. The 51 ohm will be connected to the FB AIN, a 2.2 ohm and the single wire on the oil pressure sensor. Should give me a 0.2V-3.2V reading. Autometer 2246 3 wire 5V sender would be easier to get PSI values from, but they are $100. I'll try and figure out the math for the one wire.

Water temp: My plan is to drill out the existing water temp sensor and epoxy a 3 wire FB store temp sensor into the housing. Plug it into the FB.

Going to buy some more resistors...

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2k1Toaster

Resistor values are fine and really anything less than 400KOhms-800KOhms will work fine. Generally, we like 1k to 10k range.

Also with using a 10ohm powered off the FB, you could be drawing a ton of current worst case scenario and depending on everything else in your system, that much could make it unstable. If that happens, you may need a separate 7805 to power one or both of them.

Sounds like you have a grasp on what you are doing, and the skin screenshot looks great so far!

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ACCLR8N

Edited first post with higher 12V battery voltage resistor values, corrected oil pressure values. Increased resistor values for fuel and oil pressure gauges to reduce current.

Alternator check light I'm going to replace with a relay to deal with the 12V reversing polarity. I trust there is no issue connecting FB 5V out directly to the AIN for on/off input.

The service engine light goes to ground but can have up to 0.5V when not activated. I was thinking 5V out, 100K, AIN & 10K voltage divider connected to a diode and the signal wire.

ACCLR8N

I've had some success. The gutted and epoxied in water temp sensor is working. I clipped off the capacitor as was suggested for over 105*C.
Voltage gauge is working with some tuning to match my multi-meter reading.
Alternator light with relay works after trial and error with resistor values.
Check engine light worked as planned though values are lower than expected.
Oil sensor seems to work, but I have either a bad sender or no pressure. Ordered replacement sender.
Outside temp was plug and play.
Chickened out on rotation images in MDX and went digital. Created a large numbers font for speedo because the existing verdana got blurry.
Need to order more input cables and a couple frequency-to-voltage converters. Will need at least one more FB to run all my idiot lights.

Questions: The empty ports are reading at least 0.2V. Port0 is pulling 0.96V from somewhere pegging out my tach with nothing hooked to it. Where are the free electrons coming from?
I contacted the FB guys about a quote modifying their Freq-to-V board for more resolution. While I wait for a reply, has anyone located something off the shelf elsewhere? My math says 1V will be 132MPH and 8600RPM if I hook up the FB converters.

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greenman100

You can zero out the unused ports with a jumper from "-" to "AN". They red voltage because the PIC microprocessor really only has one analog to digital converter, and it switches from port to port. There is some residual charge in the internal sample and hold capacitor.

Sorry we haven't had a chance to respond to your email, but we can modify those boards for the price of parts. Email us with exactly what you want.

ACCLR8N

Every once in great while I get lucky. New oil pressure sender working! Wife thought I passed out in car as I sat watching my gauges. Wondering why I couldn't use another one of these senders for fuel pressure? Worst case fire and explosion. Can't think of a material that would survive hot oil but not cool gas at same pressures.

I'm going to try tapping MAP sensor signal wire (0.2-4.9V) directly for vacuum boost gauge on second FB. I've finished skinning idiot lights and gauges for my dash except odometer. Only suggestion I've gotten was flames when speed hits 88 mph (just got Back to the Future reference).

Got quote today for modified Hz to V boards. Need more parts!

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2k1Toaster

You know that looks great!

I do wish you share your skin for others, I am sure they would appreciate it.

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ACCLR8N

Thanks. Welcome to it.

Get anywhere on read/writing variable data to a file? Just starting to ponder an odometer. 100mph, 4000 pulses per mile: 111.111Hz. Usually slower.

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greenman100

Contact the mfgr. Some sensors are interchangeable, some are not. Gasoline breaks down certain rubbers.

RonS

You have a PM..

ACCLR8N

Frequency boards are in. RPM is connected to port 0, port 1 is set aside for speed. Virtual screen is showing 0 to 0.01V with key on engine off. There seems to be a lot of interference when the engine is running and ports 0 & 1 parallel each other. I shorted port 1 AIN to the ground as suggested and that lowered the read out but they still both bounce the same 0.2V with engine running. The tach multi-image is slow to rev, and the port spikes over 3 volts when I let off the gas. Moving the USB around seems to alter the tach. Open to suggestions.

greenman100

Multi image slow to react: you probably have averaging turned on.

It sounds like there's insufficient filtering for your tach signal. Where are you grabbing it from? What's its peak to peak voltage like? Have you put an o-scope on it?

ACCLR8N

Nope, averaging is false and history is set to zero. I'm hooked to the feed from the PCM to the gauge cluster. No gauge cluster of course. Don't own an ocilloscope.

greenman100

Are the unmodified boards any better?

0.2v is 5% of full scale, which should be what, 250rpm? it's far from ideal, but might be the best that can be done at this (hobbyist) level.

turbochris

I have a 95 LT1 and I get all kinds of data out of the OBD port. I use Datamaster.

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