It’s Kite Aerial Photography season, people. Let’s get this ish started. Today I bought a camera, and as soon as I got home, I tore it apart. The goal was simple: get in, solder a few wires, and get out before I screwed things up completely. And that’s exactly what I did… sort of.
Ok, so I didn’t tear it apart; I was actually more careful while taking this camera apart than I’ve ever been while taking anything apart before. After all, digital cameras aren’t cheap, and I’m not about to go out and buy a whole new camera if I wreck this one. Right off the bat I knew that there would be two beasts lurking inside the tiny, unassuming black box I had just brought home: 1) wire tapes, and 2) a very large capacitor. Wire tapes, for those who don’t know, are my arch nemesis when it comes to electronics. They’re little tiny tape-like things inside most popular electronics today, and they have a bunch of tiny wires in them. Tiny wires break. Tiny wires breaking ruins the device they’re in. Tiny wires, breaking, make me angry. The plan was just to be super careful and hopefully not break any wire tapes. The other beastie, the very large capacitor, is something I’ve never had trouble with before, but I’m always leery of just in case. And just so I don’t leave you in suspense: this time, it gave me trouble. The capacitor bit me.
I’ve taken this camera apart about four times so far. Each time I realized that the wire tape that controls the buttons wasn’t plugged in properly, so I had to take it apart and try again. But to test the buttons, you have to turn the camera on, and you have to press the buttons. When pressing the buttons you occasionally take a picture, and when you do that you sometimes trigger the flash. Now let’s dive into a some of electrical fundamentals for a second here (I’ll keep the physics babble to a minimum, I promise.) It takes a lot of power to make the flash in your camera do anything useful. Since many cameras aren’t powered by more than 4 volts or so (that’s not a lot,) there has to be a way to get a ton of power to the flash in a really small amount of time (maybe a few hundred microseconds or so.) This is done with a capacitor, which stores energy over a period of time and then dumps it all out when you tell it to, which is how a tiny digital camera has enough power to drive a bright flash. Now in case you hadn’t guessed: the little metal projections protruding from the bottom of the capacitor are not something you want to touch. In fact, it’s a good idea to avoid these things like the plague. The capacitor in your camera will give you a hefty shock. The one in the back of an old tube TV will either kill you, throw you back a few feet, or both. So from all this build up, you can probably tell what I did…
I touched it. I didn’t mean to, but I did. See, once you use the flash once, the camera charges the capacitor in case you need it again. But if you turn the camera off, there’s no point in discharging the capacitor because you don’t get to reuse that power. Well I forgot this fact, and while tinkering with one of the stupid wire tapes I felt a shock in each of my middle fingers, my muscles jolted, and a voice in the back of my brain said, “YOU IDIOT! You touched the terminals on the capacitor!!!” Before I ever realized what was happening I had thrown down the camera and jumped backward. It hurt. And it scared the crap out of me. Not literally.
Now, an ordinary person would have called it a night, and maybe abandoned the project all together, but I’ve dealt with electricity before, and I know that when handled properly it’s nothing to be afraid of. So I dove back in, being careful this time to only touch the camera with one hand at a time. Little did I know that the capacitor had two other terminals which were fairly close together near where I was holding it; I shocked myself again. There was less juice this time, but it still hurt. Fortunately I didn’t shock myself again.
Until I did, and this time I’m not even sure where it came from, but I decided to just give up and go to sleep. I disconnected the battery after the first shock, and apparently the capacitor had enough power to shock me three separate times and scare me each time. The moral of the story: electricity is dangerous, kids. Don’t be stupid.
Update: If you want to work with big capacitors safely, you have to drain them first. To do that, you should measure the voltage between the two terminals with a volt meter, and then calculate the required resistance to drain the capacitor without burning out the resistor. The resistance you need is given by: R=V^2/W where V is the voltage across the terminals of the capacitor, and W is the wattage rating of the resistor. Those tiny brown resistors with the colored bands that most of us hobbyists use are 1/4 Watt resistors. Round up on your resistor value. I usually connect each probe on my multimeter to a lead on the resistor and touch the capacitor terminals with the probes so I can watch the voltage decrease. It will probably take 15 minutes or so.
You could probably just short the two terminals, but this way is much less violent.
PSA: If you are ever going to work with a large capacitor (or any sort of high voltage,) make sure that you only work near it with ONE HAND. If you use both hands, the current will ark from one hand to the other, passing through your heart, and could potentially stop your heart. There has to be a lot of voltage to do that, but it’s not worth the risk.