All controlled by our little friend the computer I suppose.

See Post_4 here : https://forum.arduino.cc/t/driving-mechanical-car-speedometer-using-arduino-controlled-motor/1171960/4

… then follow your nose

MichaelG.

I have certainly seen stuff on Arduino using these but I don’t have a link to hand.  Google is your friend.

If there was no advantage in electronic speedos, they wouldn’t exist.   Actually they provide many opportunities, starting with being cheaper to make, and more accurate and reliable than the electromechanical type.

But the first important advantage is the electronic type doesn’t need a long spinning bowden cable threaded between gearbox and  dashboard.   Admittedly not difficult to fit speedo cables to private cars, but long cables are a serious nuisance in large vehicles.

The advantages above mostly benefit manufacturers, but there are customer goodies too.   The electronic type measures speed, distance, calculate acceleration and understand the information.  As hard braking and fast acceleration on public roads both indicate a bad driver – boy-racer, or drunk – it’s helpful to highlight them on the display.   More.  The speedo can be integrated with the Engine Management Unit,  tyre pressure and anti-skid systems.   My speedo reminds me of service intervals.  Sad to say we live in a somewhat dishonest world, so it’s good they’re difficult to clock, or replace in order to mislead second-hand purchasers.

I know mechanical engineers find it hard to believe, but electronics are orders of magnitude more reliable than mechanisms.   Almost always best to ditch mechanical options if a job can be done electronically.

Dave

Since all the car systems now are digital and software based it would be logical to just have a digital display of a speed number calculated in a computer.  It’s just these pesky humans that still like to see needles on dials so they needed some way to make them.

Didnt they try the digital speedo on a super astra and everyone moaned they couldn’t see the direction it was going and really big nos as well, a bit like DVMs and analogue meters!

I’d have thought it a lot simpler for the electronics simply to produce a voltage or current proportional to speed, then the display is just an analogue or digital V or A meter.

Back when you could easily fix cars yourself you got 35 mpg on a good day and you had to service them every 6000 miles. I can still do an oil and filter change every 10000 and there are no points, and I get 55 mpg on a good day. Even in the 70s instruments we’re built into the plastic dashboard, so good luck fixing them. I’m now on my 4th car with a ECU, the previous 3 all did 150000 miles plus without changing the clutch. Compare that with my Vauxhall Viva which did well to get 20000 before I discovered the van had the same assembly except the friction material was a lot thicker. OK changing the clutch was easy, but I’ll take the hit not to have to spend the weekend on my back under the car. I could go on, SWMBO has a Hillman Imp when we met, I spent a lot of time under that, potentially a nice car, but not properly developed. I had a VW Beetle, OK it was reliable, but the handling was absolutely awful, and performance wasn’t startling. Heating system was prone to leaking CO into the car as well since it relied on blowing air over an exhaust heat exchanger.

I know a good supplier of rose tinted glasses