heads on display digital car speedometer cartoon

#Heads on display digital car speedometer cartoon free#

Take a look at the little animation below. The faster the car goes, theįaster the cable turns, the quicker the magnet spins, the bigger theĮddy currents it generates, the greater the force on the speed cup,Īnd the more it's able to pull the pointer up the dial. Rotating very far so it just turns a little bit instead, pulling the How? The currents actually make the speed-cup rotate in such a way that it tries toĬatch up with the spinning magnet.

They're electric currents, and they're moving in an electricalĬonductor inside a magnetic field, another law of electromagnetism says they will create motion. So the currents just swim about uselessly in swirlingĮddies-we call them eddy currents for that very reason. Speed cup have nowhere to go: there's nothing to carry their powerĪway. (the kind that makes electricity for your home in a In effect, the speed cup turns into a kind of electricity The spinning magnet creates aįluctuating magnetic field inside the speed cup and, by the laws ofĮlectromagnetism, that means electric currents flow inside the cup as How does it all work? As the speedometer cable rotates, it turns Jones, July 26, 1904, courtesy of US Patent and Trademark Office (with colors added for clarity). Artwork from US Patent 765,841: Speedometer by Joseph W. This very early example, dating from 1904, used a 'centrifugal' mechanism to move its needle later designs switched to electromagnetism. A small wheel (red), driven by a disc (orange) attached to one of the car's front wheels (gray), spun a cable (green) that snaked up to the speedometer (blue). The speed cup is attached to the pointer that moves up and down the speedometer dial.Īrtwork: Until about the 1960s, virtually all speedometers used a combination of mechanical power and electromagnetism. The speed cup are not connected together: they're separated by air.

#Heads on display digital car speedometer cartoon free#

The speed cup, which is also free to rotate, though restrained by aįine coil of wire known as a hairspring. The magnet rotates inside a hollow metal cup, known as When it rotates, it turns a magnet inside the speedometer case at the

Rotates, so does the other-even though the cable is long and bendy.Īt the top end, the cable feeds into the back of the speedometer. TheĬable is a bit like a mini driveshaft: if one end of the cable Speedometer by a long, flexible cable made of twisted wires. The shaft that turns the car's wheels is connected to the Motion? The answer is to use electromagnetism! How do we convertĬontinuous, spinning motion into intermittent, flickery, pointer Pretty tricky: the wheels are racing around but the pointer, someĭistance away, merely flicks back and forth. Spinning wheels to the pointer in some clever fashion. Wheels rotating at a certain speed and we want to know, with a simple Here's what we want out of our speedometer. Practical solution: the eddy-current speedometer. Harder it must have seemed in the early days of motoring, back inġ902, when German engineer Otto Schulze invented the first Rate of rotation? Even that problem isn't simple. If we know how big the wheels are, we can thenįigure out the speed fairly easily. What we really need is a way of figuring out how fast the car's Photo by Lek Mateo courtesy of US Air Force. Some speed guns use LIDAR (reflected laser light) instead of radar (which uses reflected radio waves). Lamp-posts and buildings and waiting for the reflections to comeīack-but that's an awful lot of bother! Isn't there a simpler way of Now in theory weĬould all have radar guns mounted in our cars, shooting beams out at The gun figures out how the beam has beenĪffected and, from that, calculates your speed. Your car reflects the beam back again, modifying The radar gun (handheld or mounted inside the speedĬamera) shoots an invisible electromagnetic beam at your car at the Side of the road, you'll probably be aware that they use radarīeams to check speeds. If you've seen traffic cops (or speed cameras) by the Know as a motorist is your instantaneous speed: the speed What we're talking about here is average speed what you need to Only a speedometer can tell you your actual speed at any given moment. But that doesn't tell you anything about your speed on the way, because you might have traveled by different routes or paused your journey. Okay?Īrtwork: To find your average speed from A to B, you could divide the distance between them by the time it took you. and I'll divide theĭistance I've gone by the time it took. How fast were you going sir? Erm, pull me over again in aĬouple of hours, when I get to my destination.

That much help, especially if a police officer is asking you Measuring your average speed after you've traveled is not actually So if you go 200 kilometers and it takes youįour hours to do it, your average speed is 50 kilometers per hour.

Speed is very simply defined: it's the distance you travel dividedīy the time you take. If you've read our article about motion, you'll know that