[royce]

So like 5 thousand other people that watch Mighty car mods, I thought, Gee I want to make an Arduino car thingo.

Unlike 4995 other people, I actually bought one and set about learning how it works and its pretty cool.

I quickly decided that trying to make a true digital climate control controller is probably a bit out of my league currently if just that it will take forever to work out what functions need to happen let alone how so decided to make a boost gauge instead.
It's all pretty easy to do the code part, google for long enough and youll get what you need making setting these up really fast, I looked around and decided to start off with another guys project and change it to suit, it seems to be easier to start with something and just keep modifying it suit your needs

So ive ended up with a display that shows boost (from a map sensor that mounts to the circuit board) Air Fuel (reading a 0-5v output from a wideband controller) and coolant temp (from the stock Swift sender, the manual tells you exactly what voltage is what)

Seeing I have an RGB display (changes colours) I decided to play with that as well and figured out how to change it based on whats going on.
The display starts out blue (cause rice)
Then changes to match the cars displays
If you are under vacuum (so being an eco warrior boring person, it goes green)
If you go above a preset boost level or temp level or if its leaner than a certain amount while under any boost the display will change red and flash

It also dims when you turn the lights on (well when a pin goes from low to high, anyone tell me a reliable way to convert battery voltage to 5v, regulator?)

Possible further additions
Swap the oil switch for a sender to display oil pressure and also output a signal for the oil light under a preset pressure (so only one sender and the ECU doesnt get upset)
Learn how to count an input and make a shift light, ill need to work out isolating the rpm signal from teh Arduino I guess.
Learn about menus and push button control to set warning values and so on on the unit



I'm no code or Electronics guru but I usually pick up simple stuff easy enough with some googling so this hasnt been to hard to figure out while still being a fun challenge, and really the amount of uses they have in Automotive stuff is amazing, I even figure it can read a digital input (pulse) drive a servo and print numbers on an LCD, its got to be possible to make a Sierra speedo that still swings the needle across the stock face but drives an odometer and a trip meter, running off a jimny or something vss and programmable for tyre size.

dodgy video coming

[murcod]

Well done!

I must dig my Arduino kit out and do something useful with it.... The software side of it was a bit off putting.

[JrZook]

royce wrote:

anyone tell me a reliable way to convert battery voltage to 5v, regulator?

If you need a supply to also power the back lit LCD you will have to use a switch mode regulator because the current draw will be fairly high, thus standard linear regs will have to dissipate wayyyy to much power and cook!

Maybe something like a LM2576-5.0 which only requires 4 external components to run.

rhinoman would probably have a better idea on some automotive spec switching regs.

[murcod]

Why make something when you can buy pre built modules dirt cheap? http://www.dx.com/s/voltage+regulator - take your pick. eg. US$2.72 delivered http://www.dx.com/p/m1201-dc-3-40v-to-1 ... lue-177634

[royce]

usb powers the arduino and everything, this is so I can feed 12v from the park light circuit into a digital pin (5v) to dim the display

or would a voltage divider work?

[droverdave]

very cool,

I did similar thing as you a few months back, although mine didn't change colors, but i did have a progress graph along the bottom half of the LCD as my "boost gauge". (in my wrx). and i kept the highest value and displayed that separately to the current value.

I too had a temperature sensor though all i was displaying was ambient air in the airbox. I really wanted to try and measure the pressure drop over the inter cooler but sort of sold the car before i got there...

Arduino is great for amateurs like me, so much code on the Internets to steal.

[JrZook]

A voltage divider will work. Just limit your input currents to a few mA and add a low pass filtering cap to it.

[suz_rolly]

Why not just use a 12v to usb adapter http://www.jaycar.com.au/productView.asp?ID=PS2016 5v 2.1amp



Can find them on ebay cheaper

[henno]

This is the sort of one I have to power my stuff in my car. Cheaper (three bucks), waterproof, 3amps, blah blah...

http://www.ebay.com.au/itm/1PC-Converte ... 51afb1df9e

[murcod]

You need something better than a voltage divider. The "tapped" voltage will fluctuate with the battery state of charge/ engine revs. The voltage will also vary depending on how much current you're draining through the divider. Basically, don't do it as you'll end up killing your Arduino!?

If a straight USB connection is what's required then what Henno posted is perfect. ( http://www.dx.com sell a lot of similar devices, but you might spend ages searching to find them- plus have to wait a couple of weeks for delivery.)

[JrZook]

So to save you crunching numbers to work out limiting current and the circuit use the following:

input -> a -> 10k resistor -> b-> arduino digital input pin

Now at node 'b' add a ~100nF capacitor to ground to form a low pass filter and also at node 'b' add a ~5.1V zener diode to ground. The zener diode will shunt excess voltage and protect the micro.

[royce]

Jnr gets it!

its not to power the thing, ive already got a big 5v supply to stash up behind the dash, its just to convert the 12v from the park light circuit to 5v (what the thing will accept as an input) so when I turn the lights on the screen dims.

[JrZook]

I get it now but I'll admit that I was a little bit miss led by the wording of your original post

[murcod]

JrZook wrote:

I get it now but I'll admit that I was a little bit miss led by the wording of your original post

Don't think you were the only person - hence the responses!

[Rhinoman]

Another double post! I spilt tea on my keyboard and I'm still trying to get the hang of the mini wireless keyboard that I stole from the TV box.

[Rhinoman]

If you simply want to convert a 12V signal to a 5V signal then feed it through a resistor and use a dual diode to clamp the signal to the power rails. You should use a big cap to take out any surges but you need to ensure that you don't violate any rise time requirements. For static protection use something like a 100V 4n7 cap on the signal input to the chassis. Presumably you are powering this from a local USB power connection, whatever you use needs to be automotive rated and you need to avoid floating grounds to prevent common mode issues.