If you like to ride your bike at night you know that visibility to motorists is extremely important. For around $50 of materials and a little electronics experience you can add turn signal LEDs to any jacket or sweatshirt.

Instructables user leahbuechley (Dr. Leah Buechley) used this device to test out her Lilypad - an Arduino designed for wearables and e-textiles. In this use the Lilypad powers a set of left and right turn LEDs as well as power and switch indicator LEDs on the jacket.

To do this modification yourself you'll need a LilyPad Arduino board, an FTDI connector, power supply, LED lights, 2 push button switches, conductive thread and general hand sewing gear such as scissors, fabric glue, needles, and a fabric marker. You'll sew the LilyPad, FTDI, and power supply and test the circuits before adding the lights and sealing the electronics. You'll then program the LilyPad, plug in the battery pack, and go biking. The jacket is hand washable (after you've removed the battery back naturally).

Turn SIgnal Biking Jacket | Instructables

The heat is back. Summer is coming. The sun is out to get you—but don't lose hope. Here are our top 10 ways to beat the heat.

10. Ignore the Temperature

Heat fatigue might all be in your head. A study tested cyclists in different temperatures and found that the only ones who actually experienced heat fatigue were the ones who knew how hot it was. If you don't know, you don't really suffer from fatigue. Whether you're riding your bike or just walking around, avoid any instincts to check the temperature. If you don't know how hot it is, you'll probably feel better.

9. Keep Drinks Cooler by Freezing Water in Milk Containers

When you're bringing cold drinks out to the beach, the pool, the yard, the edge of a hellscape, or any other sunny outdoor area, you want them to actually stay cold. Ice does the trick, but transporting tons of ice can be a pain. Instead of buying bags of the stuff, just save some old milk cartons, fill them up with water, and freeze them. Because they're blocky they fit nicely in the cooler. If you need smaller blocks, just peel off the carton and crush the ice a bit. It's an easier and cheaper solution.

8. Hydrate Any Way You Can

The are a lot of hydration myths—like drinking soda doesn't help you at all or if you feel thirsty you're already dehydrated—and we've busted most of them. Water will often be your best bet when you need to stay hydrated, but it isn't your only option. If you only have soda or a sports drink, it can still help. You also don't need to drink eight glasses of whatever every single day. Just drink whenever you're thirsty and you should be in pretty good shape.

7. Beat the Bugs

When the heat wave comes, bugs often come with it. If you want to avoid these insects, there are quite a few things you can do. First, you want to make sure you're buying DEET-based bug spray because it's the most effective. You can also save yourself some cash by making your own citronella candles, outdoor torches, and bug traps. You can even ward off ants with chalk. So long as you're prepared, you shouldn't be bothered too much by the bugs.

6. Get the Hot Air Out of Your Car Fast

Every year I forget that leaving my car out in the sun makes the entire thing hot to the touch, which is especially unpleasant when you're not expecting it. While cooling off a hot car is always going to take a little time, there's a Japanese trick to get the stuffy air out fast. Basically, you open two parallel doors on your car, then open and close one of those doors repeatedly about five times. This pushes the warm air out and the cool air in. It's a really clever trick that only takes a minute. Just make sure you don't accidentally shut your hand in the door.

5. Stay Cool While You Sleep

When you're asleep, you can't actively combat the heat. You also probably have a tough time getting to sleep when you're overheating as it is. There are plenty of ways to stay cool at night so you can sleep comfortably despite the heat. For example, you can build your own air conditioner (or use an alternative method), get a cooling pillow like the Chillow, and put your sheets in the fridge before bedtime. Trial and error will decide which methods work best for you, but all will get you closer to a cool night's rest.

4. Keep Your Computer Cool

An overheating computer is a fire hazard. It's very important to keep it cool, especially in hot weather. If you don't have the best cooling system on your machine—especially if your home isn't air conditioned—you're going to want to look at getting a better one. The upcoming heat is also a great excuse to go inside your desktop and start blowing out all the dust. A cleaner computer will run a bit cooler, and it'll help you avoid a fire starting inside your case. For more tips and details on everything you need to do, check out our complete guide to keeping your computer cool.

3. Use the Heat to Your Advantage

When you know how heat works, you can use it to your advantage. To do that, all you really need is a basic understanding of thermodynamics. Then you'll know how to use heat to open jars more easily, how to dress to stay cooler, and how to keep your house from turning into an oven. It's science you can use!

2. Understand Sun Screen

Sunscreen doesn't actually work the way you think. First of all, most of them don't do anything and so you're wasting your time. If you're not buying a sunscreen that contains both zinc oxide and titanium dioxide, you're wasting your money. You also need to make sure you understand what an SPF rating is. SPF isn't like a sunscreen power level, but rather what determines how long the sunscreen will last before you need to reapply it. To better-understand SPF and learn about how sunscreen actually works, check out this infographic.

1. Learn Your Body's Cooling Spots for Temperature Reduction on the Quick

We all know that cooling off involves coming into contact with something cooler than ourselves (like The Fonz), but that personal temperature reduction can happen a lot faster if you know your body's quick cooling spots. Your neck and wrists are two of the best, but the top of your feet and insides of your ankles work, too (plus a few others). Just focus your ice pack, or whatever you're using too cool yourself, on those areas and you'll beat the heat in no time.

Photos by Liz Mc, dr_relling, Joost J. Bakker, alterfalter (Shutterstock).

A lot of new cars have fancy cameras on the rear bumper to help you parallel park. If your car doesn't have that feature, DIY blog Mad Science has put together a tutorial to roll your own sensor system with an Arduino.

The build is incredibly simple and you only need a ping sonic range finder, Arduino, a buzzer, and just a few wires. The sonic range finder emits a sound wave that tells you when you're close to obstacles behind your car. When you're too close to an object the buzzer sounds. If you're not so good at parallel parking or you just want a warning when someone's tailgating you this should help. Find the full guide to making it for yourself over on Mad Science.

Make These Sonics Distance Sensors for the Bad Driver in Your Life | Mad Science

Dear Lifehacker,
I've spotted some amazing deals on Craigslist, but I also know people sometimes get screwed (out of money!) on Craigslist. How can I weed out the scams from the legit listings and make sure I get the best buys?

Signed,
New Craigslister

Dear NC,
Craigslist is a terrific resource for nabbing great deals on everything from furniture to bicycles to electronics—but it's also full of duds and scams. Although not all listings on Craigslist are fraud attempts, it's smart to take extra precautions when buying from any stranger online (whether on Craigslist or eBay or another buy-and-sell site). Here are a few things you can do before and during the sale to make sure you don't get ripped off.

While Searching: Watch Out for Red Flags in Craigslist Listings

The risks: getting suckered out of your money, giving up personal info to a scammer, and losing your faith in humanity

How can you spot a Craigslist scam? Many of them feature the same telltale signs:

• An abundance of spelling and grammatical errors. A typo here and there is forgivable, but when a listing is riddled with poor English, it's an indication an overseas scammer posted the ad using automated translators—or the person behind the ad just doesn't care about the listing. Either way, you probably want to stay clear.
• Generic product photos. Look for real photos instead of the typical product pics or photos found elsewhere on the web. It's hard to believe the seller actually has the item in question if he's using PR photos.
• Ad posted in multiple places. Sellers are only allowed to post their ad in one city. If you see the same ad posted word for word in a distant city, that's a huge red flag. You can search all Craigslist sites at once with previously mentioned Search All Craig's or more recently highlighted Craiggers. Search Google for the ad wording to see if it's been posted elsewhere or check the Craigslist Scammers blog dedicated to just this purpose.
• Too good to be true. The biggest telltale sign of a Craigslist (or other) scam is if the ad promises a ridiculously good deal. When you're buying from sellers seemingly desperate to get rid of their used stuff, it's hard to know what's a true offer or just bait for your personal info. Know what your product is selling for (see below) and, if you have any doubt, pass on it.

Craigslist offers other common sense rules to avoid scams, including only meeting in person for local listings, never wiring any money, and never giving out any personal or financial information.

When You've Found an Item to Buy: Vet the Seller and Know Your Product

The risks: wasting your time buying a fake or a broken item or something other than what you're expecting; paying too much for it

Let's say you found what looks to be a legit deal—the photos are unique and the listing doesn't look like typical Craigslist scams. Now it's time to ask some questions and find out more about the seller and the item.

Ask detailed questions about the item you want to buy over multiple emails or calls. Does the laptop come with all the installation CDs and has a virus scan been done on it recently? For an apartment rental, what's included in the rent or what amenities are nearby (you can verify this with Google Maps)? What problems or issues with the item has the seller had? Why is this person selling the item? What's the exact model number of the item? Asking questions like this not only gives you more information about the product, it verifies the seller has firsthand knowledge of it.

For whatever you're buying, also look up ahead of time common problems with the item and how to spot a fake. Google "common problems with [X product]" or "how to spot a fake [X product]" to find the right questions to ask and things to look for when testing out the item in person (see below). You can also check for recalled items at several government sites.

Look the seller up. Search the seller's email address and phone number on both Craigslist and Google. Look up the seller's name on Facebook and White Pages services (see if the address matches, too, if you're given one).

Check if the price is right. Although a lot of items on Craigslist may be great deals, sometimes the prices really don't make sense. In a Priceonomics study, people sold their used TVs on Craigslist for 14% less than the same TV was selling new, but a 30% discount for headphones. The 14% discount, Priceonomics says, isn't enough of a deal for the hassle of possibly buying a dud. Sellers, apparently, were pricing their items based on the original prices they paid—not the market value at the time, which made them price their used TVs too high. Check out price guide Pricenomics to find acceptiable price ranges and recommended used prices. You should also check the going prices for that specific model/item on Amazon and other retailers. Want an even better deal? If you're ready to haggle, use the 15-to-20 percent rule to find a more reasonable price (sellers may be adding in this haggling price too).

At the Exchange: Meet Safely and Inspect the Item

The risks: getting robbed or physically hurt; not noticing problems or missing features until after you've parted with your money

Ready to buy? Now comes the most anxiety-ridden part: the exchange.

Meet in a public location, such as a bank or coffeeshop. Craigslist says meeting in person will help you avoid 99% of scam attempts on the classifieds service. Meeting face-to-face can still be risky though, so to avoid the chance of being robbed, meet in a public place—preferably one with lots of witnesses and security cameras. A bank lobby, Gizmodo suggests, is perfect because you and the seller can withdraw and deposit cash without having to carry it around. If a bank lobby seems too odd to conduct your personal secondhand buying business, a hotel lobby, busy gas station, coffeeshop, or similar location would work (and these also usually provide ATMs for easy access to cash). (Note: Buy & Flip advises not using a parking lot, mall, or fast food restaurant because people aren't actually paying attention there. I think Starbucks or Barnes & Noble may be perfect because of how busy these locations are and you have outlets for testing electronic items.)

Bring a friend. Go with a friend or family member for additional protection. He or she can also help you evaluate the item in question.

Kick the tires. Make sure you test everything and try using the product before you pay for it. For a used computer, check the ports, make sure you have the license keys and admin account information, confirm the battery life is what's expected and all the specs match, and look for things like massive dust buildup. Before you buy a cell phone, make sure it can be activated by verifying the electronic serial number or ESN with your cell phone provider or at CheckESNFree. If you're buying a car, make sure all the paperwork is available (registration papers, titles, and maintenance information) and look for other stolen car signs. If it's got a plug, plug it in to see if it works. Push all the buttons, and try all the features.

After all your sleuthing and research, hopefully you'll end up with a proud purchase.

Love,
Lifehacker

P.S. See our Definitive Craigslist Guide for the Recession and How to Avoid Getting Scammend When Buying or Selling Online for even more advice. Or share your tips and experience with us in the comments.

Have a question or suggestion for Ask Lifehacker? Send it to tips+asklh@lifehacker.com.

Photo remixed from an original by bioraven (Shutterstock)