A Mobile Radio Power Controller

October 10, 2014 by Brian Benchoff 24 Comments

[Pete], a.k.a. [KD8TBW] wanted to install his Yaesu radio in his car. From experience, he knew that having a radio in a car inevitable led to leaving it on once in a while, and this time, he wanted a device that would turn his rig on and off when the key was in the ignition. He ended up building a mobile radio power converter. It takes the 12V from the car when the alternator is running, and shuts everything off when the engine has stopped.

The Yaesu radio in question – an FT-8800 does have an automatic power off feature, but this is a terrible way of doing things. There is no way to turn the radio back on, and the radio must be left in a non-scanning mode.

In what he hopes to be his last design in EagleCAD, [Pete] whipped up a board featuring an ATtiny85 that measures the voltage in the car; when it’s ~14V, the alternator is working, and the radio can be switched on. When it drops to ~12V, it’s time to turn the radio off. It’s a great project, and with the 3D printed case, it can easily be shoved inside the console. Video below.

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Carpool DeVille: The World’s Fastest Hot Tub

July 14, 2014 by Eric Evenchick 27 Comments

Back in 1996, a group of engineering students at McMaster University set out to build a fully functional hot tub housed in a working car. They chopped up an abandoned 1982 Chevy Malibu and converted it into The Carpool.

That group of students graduated, and began work on the Carpool DeVille. Six years later, they’re ready to take it to Bonneville Salt Flats to claim the title of “world’s fastest hot tub.”

There has been some substantial modifications to the vehicle to make the Carpool a reality. A custom fibreglass tub was built to drop into the passenger compartment, and heat exchangers were added to the stock engine system to heat the water. The plumbing and pumps for the tub reside in the truck, while the original V8 engine is up in the front. A custom air suspension system allows them to carry the massive volume of water. There’s even a marine throttle to control gas and brake from the driver’s seat in the tub.

The folks behind the Carpool DeVille ran a Kickstarter to fund their race costs. The campaign is over, but you can still check out the story and pictures of the conversion. Since it was a successful campaign, we’re looking forward to seeing this custom vehicle out on the salt flats.

Visualize Vroom With This RGB LED Tachometer

July 7, 2014 by Kristina Panos 6 Comments

[Pete Mills] recently bought the all-new Ford Fiesta, which offers impressive fuel economy over that of his Jeep. He soon figured out that he has real time access to a wealth of engine and chassis data through Ford’s OpenXC platform and used it to build blueShift, a neopixel tachometer. The car already has a tach, but this one is more visual, can be seen in periphery, and is just plain fun.

In case you hadn’t heard, the OpenXC platform is Ford’s consumer key to the kingdom of OBD2 treasures. It unlocks the magic through its Vehicle Interface, which plugs into the OBD2 port and translates the CAN bus messages to OpenXC format. These messages are packaged into JSON format and can be sent over Bluetooth or Ethernet/Wi-Fi to an Android, Python, or iOS device.

[Pete] went with Bluetooth and used a BlueSMiRF with an Arduino Pro Mini. He derives power from the car’s on-board USB port, but has future plans to use the OpenXC VI port. blueShift reads the RPM data and displays a green trail as the engine revs up. At the peak revolution, it shows a red LED. This one is sticky and will persist for the lesser of three seconds or the time elapsed to a new positive RPM. [Pete] is also reading the headlight status of the car. As soon as they come on, the RGB LEDs dim to avoid blinding him at night.

[Pete] wanted to make an enclosure more finished-looking than a Tupperware box. He nearly detoured into 3D-printer design, but ended up putting together a Prusa i3v and came up with this RAM mount-compatible enclosure. His fantastic write-up and code are on his blog, but you can make the jump to see a short demo and a full explanation video. You can also make smart brake lights or even create art with OpenXC.

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Measuring Car Engine RPM Via The Cigarette Lighter

June 10, 2014 by Mathieu Stephan 57 Comments

Sometimes we forget how many things we can do with a simple oscilloscope. In this video [Ben] uses one that Tektronix lent him to measure his DeLorean engine RPM. By checking the car main ~12V voltage one may notice that the voltage spikes occurring are directly related to the engine speed, as they are created by the inductive kicks from the ignition coils. Obviously the multiplication you have to do to get the RPMs from the number of spikes per second depends on your engine configuration (flat 4, v6…).

The method that [Ben] used was to search for high amplitude spikes on the (AC coupled) car 12V Fast Fourier Transform (FFT) to get a reliable measurement given the many electrical noise sources present in his car. At the end of his video, he however mentioned that it could still be possible to get a good measurement with a simple voltage comparator and a high enough voltage reference.

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