Arduino gauges

[Fraser64]

So I was going to redo the dashboard on my spit and add a few extra gauges, oil pressure, analogue clock, voltage and so on.

Then I found the price of Smiths gauges and thought OUCH.

So I am now starting to think more modern and about using an Arduino wth an OLED display and push button selector to cycle through the different readings.

 I have found a pressure transmitter for the oil that outputs 0 - 5 volts depending on pressure which should be straight forward to use and I am guessing the standard water temperature sender works on resistance varying with temperature.

Since an Arduino can only handle 5 volts maximum and I only have a fairly basic understanding of electrical engineering to read the cars 12 volt supply I would need to use some kind of diode to drop the voltage (I'm still looking into this!)

Anyone done anything like this before? It looks like a promising idea.

 

[mpbarrett]

I have a couple of Arduinos (and a PIC based controller) in my Herald.  Easy to read the battery voltage by feeding the battery voltage thru a potential  divider to drop the voltage down to the input range of the Arduino A/D I would also add a bit of smoothing (capacitor) or software averaging to take out any noise. Also  a Zener diode to protect it from spikes, the 12V supply in a car can be quite noisy and will go above 12V when the battery is being charged.
Take care with the power supply to drop the supply voltage down to 5V, make sure there is plenty of decoupling. Also use the watchdog timer so that if (when..)  the Arduino software crashes it will restart properly. 
Finally the OLED display are nice and bright but you need to monitor the car lights line so that you can dim the display at night time when the lights are on...

Nice project, I did try to build one into a standard gauge housing but you end up with a very small display, but 4D now make circular displays now. https://4dsystems.com.au/products/ulcd-220rd bit bigger than 52mm.

Mike

[Colin Lindsay]

10 hours ago, Fraser64 said:

So I was going to redo the dashboard on my spit and add a few extra gauges, oil pressure, analogue clock, voltage and so on.

Then I found the price of Smiths gauges and thought OUCH.

Why not buy second-hand? Some good ones out there.

https://www.ebay.co.uk/itm/24v-Electrical-Gauges-52mm-Oil-Pressure-Oil-Temp-Fuel-Temp-Volt-gauge/292749567116?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D20131003132420%26meid%3Db60300f71ed94126a02800171a9c27fd%26pid%3D100005%26rk%3D5%26rkt%3D12%26mehot%3Dco%26sd%3D323843505776%26itm%3D292749567116%26pmt%3D1%26noa%3D0%26pg%3D2047675%26algv%3DSimplAMLv5PairwiseWeb&_trksid=p2047675.c100005.m1851

[Pete Lewis]

and for repairs refurg your originals  http://www.jdo1.com/other_services.html   can be worth a look 

Pete

[poppyman]

Also we are coming up to show season, there is a lot of choice between new and second hand as well  

Tony.

[Fraser64]

Thanks Mike and all.

As much as I like the look of Smiths gauges they take up a lot of space I could use for other stuff.

I'm thinking of moving the petrol and water temp onto the Arduino and putting the display into the radio slot, also moving the heater controls to a digital system controlled off the Arduino freeing up the space in the centre console and probably fitting a more modern touchscreen type music system in its place......

 

Moving into the modern era.

[hugh]

7805 5v regulator for supply

[NonMember]

23 minutes ago, hugh said:

7805 5v regulator for supply

I thought Fraser wanted to move into the modern era 😛

[dougbgt6]

18 minutes ago, NonMember said:

I thought Fraser wanted to move into the modern era 😛

So he bought a Triumph Spitfire! 

db

[Colin Lindsay]

Don't knock it, it could have been an MX5....

How about one of these all in one jobbies?

https://www.carbuilder.com/uk/compact-all-in-one-digital-instrument

 

[Richard C]

On my boat I use a buck-boost converter to provide a stable 5V to digital instrumentation and logging (rpi based). It works, and on the boat it copes with the sudden voltage drop caused by starting the engine after sailing. They are cheap from online sources, and the only drawback is possible RFI with audio equipment which can be dealt with in the usual ways. I am a bit concerned that a failure mode might put 12V on the output, so the addition of a zener diode and fuse might be appropriate. I'm not that concerned. In general, these switch-mode devices are far better at providing dc-dc conversion than 78xx series regulators, and neccesary for higher current loads,

[NonMember]

A buck-boost is probably overkill for this application - a straight buck converter should cope with drops down to 6V during starting and you're unlikely to be able to start if it goes below that. Audio equipment will pick up the "RFI" line noise (it's probably only marginally RF unless you go for a fancy high-spec device, and even then it's LW) but a few additional capacitors may help. I don't think a zener is going to protect much if the high-side FET fails short - you'd need something that will crow-bar the full quick blow current of the fuse, like a zener+thyristor combo or a big MOV.

You'd probably get away with a linear regulator for an Arduino but you definitely want a buck type for the demands of a Raspberry Pi.

[Fraser64]

I only have a basic understanding of electronics but dosn't a buck converter just step down a voltage to a single output voltage?

I would like something to take the place of the Smiths voltage gauge with the Arduino so if the car is 12 volts and on charging increases up to around 14-15 volts then I am looking for some way of 'dividing' that varying 0 - 15 volt signal by 3 to bring it down to between 0 - 5 volts that the Arduino can handle.  If the car is producing 11.5 volts the arduino will recive 3.83 volts (11.5 / 3).

[NonMember]

The discussion of buck converters was in relation to the power supply requirements of your Arduino (or Raspberry Pi), which is normally 5V. Some Arduino's have an on-board regulator to provide that, and you may be able to connect the power input directly to the ignition switch (via a fuse, probably). But note, only "may", because the regulator they provide may not withstand the large voltage spikes sometimes present on car electrical systems, and may not sufficiently filter the mid-frequency spike noise from the ignition.

For voltage monitoring purposes, all you need is a resistor divider - 10K from ignition switch to the input, 4K7 from the input to ground. For extra protection, a Schottky diode from ground up to the input and input to 5V (so they're both reverse-biased in normal use but will conduct on a load dump) should prevent any damaging voltages hitting the Arduino ADC on a load dump.

[SpitFire6]

Hi,

 buy a Buck converter from AliExspress.

Very few reasons would make me chose otherwise.

No harm with a MOV + fuse if you want to protect anything expensive from damaging volts & don't mind paying for it.

Cheers,

Iain.