Push Button, Receive Candy (or Death)

candy-or-deathWill you be handing out candy on Halloween? Maybe you have a party to attend or kids to take around the neighborhood and can’t be home to answer the bell. You don’t want to be The Dark House With No Candy, ’cause that’s a good way to get TP’d. We’re not exactly sure what [Ben]‘s catalyst was aside from trying to avoid tempting would-be thieves with an unattended bowl on the porch. Whatever the reason, we’re happy to present Candy or Death, his gamified candy (or death)-dispensing machine.

Okay, so it only dispenses candy for now. [Ben] hasn’t quite worked the kinks out of his death ray. He designed it to sit behind a porch-facing window so it can’t be messed with. All trick-or-treaters can do is push the button and take the candy. It’s built around a cereal dispenser that’s modified to be cranked by a piece of round rod driven with a NEMA-17 stepper motor and an Arduino Uno with a motor shield. The candy slides down a length of aluminium rain gutter into a plastic stacking bin, and the whole thing is built into a nice wood frame.

A few adjustments were necessary to keep it from jamming. The dispenser’s hopper uses rubber blades to govern the flow, and he ended up removing a few and trimming the others. [Ben] has an album up of all his build pics and put his code on the gits. Stick around to see videos of the machine from the front and rear.

[Read more...]

DIY FPV Goggles Born From Necessity of Cheapness

DIY FPV Goggles

So now that you’ve built your quadcopter and can fly it without crashing most of the time, what’s next? How about metaphorically hopping into the pilot’s seat with a First Person View setup. Great idea… but the cost of the required gear can be a deal breaker. FPV goggles alone range from the low to high hundreds. [sneaky] was using his laptop screen for his FPV setup and decided to try to make is own FPV goggles.

The display is just a small LCD screen that was purchased off eBay. Craft foam board was cut, bent, glued and duct taped to form a box about the same size as the LCD screen which is also secured to the box with duct tape. [sneaky] then cut the opposite side of the box to fit his face before he lined it with 1/2″ weatherstripping foam. Staring at an LCD screen just inches from your face is sure to cause some discomfort. A Fresnel lens inserted in between the user’s eyes and the LCD reduces eye strain to make long flights tolerable. The whole assembly is then held to your noggin via a recycled ski goggle strap.

In the end, [sneaky] likes his new goggles better than his old laptop screen and sun shade setup. The goggles aren’t too heavy and he can wear them comfortably for a while. We’ve seen a DIY FPV goggle setup in the past that uses individual lenses for each eye rather than one large Fresnel lens.

Dusty Junk-bin Downconverter Receives FM on an AM Radio

2014-10-06-172237_1366x1536_scrot

This amateur radio hack is not for the faint of heart! With only three transistors (and a drawer-full of passive parts), [Peter Parker, vk3ye] is able to use a broken-looking AM car radio to receive FM radio signals (YouTube link) on 2 meters, an entirely different band.

There are two things going on here. First, a home-made frequency downconverter shifts the 147 MHz signal down to the 1 MHz neighborhood where the AM radio can deal with it. Then, the AM radio is tuned just slightly off the right frequency and the FM signal is slope detected.

The downconverter consists of a local tuned oscillator and a mixer. The local oscillator generates an approximate 146 MHz signal from an 18 MHz crystal, accounting for two of the three transistors. Then this 146 MHz signal and the approximately 147 MHz signal that he wants to listen to are multiplied together (mixed) using the third transistor.

If you’re not up on your radio theory, a frequency mixer takes in two signals at different frequencies and produces an output signal that has various sums and differences of the two input signals in it. It’s this 147 MHz – 146 MHz = 1 MHz FM signal, right in the middle of the AM radio band’s frequency range, that’s passed on to the AM radio.

Next, the AM radio slope detects the frequency-modulated (FM) signal as if it were amplitude modulated (AM). This works as follows: FM radio encodes audio as changes in frequency, while AM radios encode the audio signal in the amplitude, or volume, of the radio signal. Instead of tracking the changing frequency as an FM radio would, slope detectors stick on a single frequency that’s tuned just slightly off from the FM carrier frequency. As the FM signal gets closer to or farther away from this fixed frequency, the received signal gets louder or quieter, and FM is detected as AM.

At 5:23, [vk3ye] steps through the circuit diagram. As he mentions, these are old tricks from circa 50 years ago, but it’s very nice to see a junk-box hack working so well with so few parts and receiving (very) high frequency FM on an old AM car radio. A circuit like this could make a versatile front end for an SDR setup. It makes us want to warm up the soldering iron.

[Read more...]

Hacking out of Necessity — Fixing Your Own CPAP Machine

Fixing a CPAP machine

One of our avid readers named [Felix] suffers from sleep apnea, and needs a CPAP machine in order to not suffocate while he sleeps — After a recent power-outage, his machine broke, so he decided to try his hand at fixing it.

A CPAP (Continuous Positive Airway Pressure) machine ensures people suffering from sleep apnea breath throughout the night, by preventing their throats from closing. As a medical device, they tend to be super expensive, which is why [Felix] wanted to try fixing his (at least until he gets a new machine covered by insurance).

Upon opening up the machine, it was easy to see the problem: the circuit board was completely fried. Luckily, the machine is pretty simple. It has a brushless DC motor (12V), and two chambers with air filters, along with an air pressure sensor. Since the motor is brushless, it’s not quite as simple as just hooking it up to a power supply. It had a whopping 8 separate leads.

[Read more...]

Raspberry Pi Bluetooth Receiver for your Car Stereo

RasPi Car Audio

The ability to play music in your car over a Bluetooth connection is very handy. You can typically just leave your phone’s Bluetooth module turned on and it will automatically pair to your car. Then all you have to do is load up a music player app and press play. You don’t have to worry about physically tethering your phone to the car every time you get in and out of the vehicle. Unfortunately Bluetooth is not a standard option in many cars, and it can be expensive to buy an aftermarket adapter.

[parkerlreed] built his own solution to this problem using a Raspberry Pi. He first installed arch Linux on his Pi. He also had to install pulseaudio and bluez, which is trivial if you use a package manager. He then modified some of the Linux configuration files to automatically bring the Pi’s Bluetooth adapter online once it is initialized by the kernel.

At the end of the boot sequence, the Pi is configured to automatically log in to a virtual console as [parkerlreed's] user. The user’s bashrc file is then altered to start pulseaudio in daemon mode at the end of the login sequence. This allows the Pi to actually play the audio via the Pi’s sound card. The Pi’s stereo output jack is then plugged into the vehicle’s auxiliary input jack using a standard audio cable.

The Reddit post has all of the configuration details you would need to duplicate this setup. [parkerlreed] also includes some commands you will need to setup the initial pairing of the Raspberry Pi to your smart phone. Be sure to watch the video demonstration below. [Read more...]

Helix Turning Tool Born From Necessity

helix turning tool

Sometimes while working on a project there comes a point where a specialized tool is needed. That necessary tool may or may not even exist. While [Fabien] was working on his DNA Lamp project he needed to bend a copper wire into a helical shape. Every one of us has wrapped a wire around a pencil and made a little springy thing at some point. While the diameter may have been constant, the turn spacing certainly was not. [Fabien] came up with a simple gizmo to solve that problem.

The tool utilizes an 8mm rod that will ensure the ID of the helix is indeed 8mm. We’ve already discussed that was the easy part. To make certain the turn spacing is not only consistent but also of the correct amount, a wooden frame is used. The frame has holes in it to allow the 8mm rod to pass through. Adjacent to those rod holes are much smaller holes just a bit larger than the copper wire that will become the helix. These holes are drilled at an angle to produce the correct turn spacing. [Fabien] figured out the correct angle by taking the desired turn spacing distance, helix diameter and wire diameter and plopping it in this formula:

[Read more...]

Bare Bones Arduino IR Receiver

TV Remote

Old infrared remote controls can be a great way to interface with your projects. One of [AnalysIR's] latest blog posts goes over the simplest way to create an Arduino based IR receiver, making it easier than ever to put that old remote to good use.

Due to the popularity of their first IR receiver post, the silver bullet IR receiver, [AnalysIR] decided to write a quick post about using IR on the Arduino. The part list consists of one Arduino, two resistors, and one IR emitter. That’s right, an emitter. When an LED (IR or otherwise) is reverse biased it can act as a light sensor. The main difference when using this method is that the IR signal is not inverted as it would normally be when using a more common modulated IR receiver module. All of the Arduino code you need to get up and running is also provided. The main limitation when using this configuration, is that the remote control needs to be very close to the IR emitter in order for it to receive the signal.

What will you control with your old TV remote? It would be interesting to see this circuit hooked up so that a single IR emitter can act both as a transmitter and a receiver. Go ahead and give it a try, then let us know how it went!

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