How Do Dash Cameras Work?

Can you just use your phone as a dash cam?

how dash cameras work
Dash cameras work differently from other cameras. Douglas Sacha / Moment Open / Getty

While it is technically possible to use virtually any recording device as a dash camera, there are a number of reasons that you should consider buying a purpose-built dash cam instead of hacking something together.

There actually are a handful of important factors that set dash cameras apart from other portable and handheld recording devices; all of which make dashboard cameras easier and more convenient than the other alternatives.

You may never catch a video of someone's tire flying off, a fellow driver setting his vehicle on fire at the gas station, or a meteor falling to the earth, but a properly set up dash cam can come in really handy.

How Does a Dashboard Camera Work?

In order to really see what sets purpose-built dashboard cameras apart from general purpose devices, it’s necessary to understand how dash cams actually function. Unlike general purpose recording devices, dashboard cameras tend to be no-frills affairs that often lack fancy bells and whistles like power switches and recording controls in favor of rock-solid performance day after day.

In fact, a prototypical dashboard camera consists of only a handful of basic components:

  • A video camera: This is the one thing every single dash cam needs. The camera is how it captures the action.
  • Hard-wired power inputs: You can run a battery-powered dash cam in your car if you really want to, but then you have to worry about taking it out to charge it. Wire it directly into your vehicle's electrical system, or plug it into the cigarette lighter, and you're set.
  • Built-in or removable solid-state storage media: It's fine to use a dash cam that has built in memory, but it's better if the memory is removable. Choose a dash cam that accepts micro SD cards and save yourself some headaches.

Function follows form in the case of dashboard cameras, so you can probably get a pretty good idea of how they work by looking at that sparse list of components.

Without an on/off switch, a dashboard camera is typically wired into a circuit that is only hot when the ignition key is in the start or run position. For added security, and a small risk of your battery going dead, you can also wire the camera into a circuit that's hot at all times.

Without any sort of recording controls, dashboard cameras are typically designed to record continuously whenever they are powered up. Others have a security option to record only when they sense motion. With that in mind, you can see how these simplistic devices are designed to automatically turn on and start recording each time a car is driven without the need for any input or interaction from the driver at all.

This can be contrasted with general purpose portable recording devices. Although you can use virtually any recording device as a dash cam, you will have to turn it on and set it to record every time you get in your car. If you imagine a scenario where it slips your mind one day, and you just happen to get into an accident, then it should be easy to see the draw of a purpose-built device.

What Happens When the Storage Fills Up?

If you’ve ever used a portable recording device like a cell phone, digital camera, or anything else, then you’ve probably seen what happens when the storage media fills up. The device stops recording right then and there, and you have to either free up some space or insert a new memory card if you want to keep recording.

On the surface, it seems like this would be a huge issue with dashboard cameras. They record all the time, so you would expect them to fill up pretty fast. Even if you use a huge SD card for storage, it’s going to fill up eventually, right? And who wants to fiddle with memory cards while driving.

This is actually the other area where a purpose-built dashboard camera tends to really shine in comparison to the alternatives. Unlike general purpose recording devices, a dashboard camera will typically be designed to automatically overwrite the oldest files on its storage media if the media fills up.

This is a feature that would be horrible if it was baked right into a digital camera or an iPhone since it might accidentally delete something you really wanted to keep, but it works great for surveillance and sousveillance devices.

Do Viable Dashboard Camera Alternatives Exist?

If you don’t want to hard-wire a camera into your car’s electrical system, or you just can’t afford one, then there are viable alternatives. It’s important to remember that these alternatives do lack the convenience features that are built into dashboard cameras, but that may be a trade-off you’re willing to deal with.

For instance, there are apps that can turn your iPhone, Android device, or another smartphone into a dashboard camera, although these still aren’t truly “set and forget” solutions.

In most cases, you have to mount your phone when you get in the car, open the app, and then activate it when you start driving. The one place where the best dash cam apps work just as well as dedicated hardware is that they are designed to automatically overwrite old footage as the storage fills up.

You can also use another recording device, like a camcorder or a GoPro, but then you have to deal with issues like a power source, remembering to turn the device on, and even manually switching out memory cards.