RC Drag Racing Christmas Tree and Speed Trap

In the drag racing world, a Christmas tree is the post at the start line that sequentially lights up a set of yellow lights followed shortly after by a green light to tell the drivers to go, the lights obviously giving it its seasonal name. Included at the base of the tree are lasers to detect the presence of the cars.

[Mike] not only made his own Christmas tree for his RC cars, but he even made an end-of-track circuit with LED displays telling the cars how long they took. Both start and finish hardware are controlled by Pololu Wixel boards which has TI CC2511F32 microcontrollers with built-in 2.4 GHz radios for wireless communications.

In addition to the LEDs, the Christmas tree has a laser beam using a 650nm red laser diode for each car at the start line that’s aimed at a TEPT5600 phototransistor. If a car crosses its beam before the green light then a red light signals the car’s disqualification.

The end-of-track circuit has 7-segment displays for each car’s time. [Mike] designed the system so that the Christmas tree’s microcontroller tells the end-of-track circuit’s microcontroller when to reset the times, start the times, and clear the times should there be a disqualification. The finish line controller has lasers and phototransistors just like the starting line to stop the timers.

Oh, and did we mention that he also included 1980’s car racing game sounds? To see and hear it all in action check out the video after the break. If the cars seem a little drunk it’s because pushing left or right on the controller turns the wheel’s fully left or right.

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Third Person Driving IRL

It’s a dream come true: remote control of a real car. Besides being a lot of fun, a life-size RC vehicle has some practical applications, like performing rescue operations or delivering supplies to dangerous areas. For [Carter], [Dave], [Ryan], and [Sean], the dream became reality in the span of 24 caffeine-and-chicken-finger-fueled hours during an Ohio State University hackathon. They dubbed the system MagiKarpet because it sits in place of the floor mat and runs on pixies.

The plan was to control the throttle, brake, and steering of a Chevy Cobalt using a PlayStation controller. For added fun, a camera mounted high above the back bumper would provide a third-person view, and this feed would be displayed on a monitor in the backseat. Everything is controlled by an Arduino Mega. A beefy linear actuator works the brake and is attached temporarily with a band of Shapelock that slips around the pedal. The throttle is pushed by a lever attached to a car window motor. Another motor connects to the steering wheel with cables that can turn it 90° left and right. Although the build was successful, they ran into a couple of issues. But what’s a hackathon experience without a few problems?

The linear actuator was jammed for about an hour after some early testing, but they got it unstuck. The PS controller was borked, so they had to roll their own joysticks. The school wouldn’t let them actually drive it around because of safety (killjoys but we get it), so they put it up on a jack to demonstrate it for the judges. They took second place, though we can’t imagine what would have beat this. Check out the complete build video after the break.

You might remember these guys from last year around this time. They took first place at the same hackathon with Robottermilk Puncakes, a app-controlled pancake machine. Now that you’re hungry for pancakes, feast your eyes on this endless one.

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Robo Car Via 3G

[Emil Kalstø] has a pretty solid remote control car. We don’t mean a little car with a handheld remote you can drive around the neighborhood. [Emil’s] car has a camera and a cell phone so that it can go anywhere there’s 3G or 4G networking available.

The video (see below) shows the results (along with [Emil’s] little brother acting as a safety officer). The video offers tantalizing detail you might find useful if you want to reproduce a similar vehicle. However, it stops short of providing complete details.

The two batteries onboard will power the vehicle for over 20 hours of continuous use. The 30W motor is reduced with a chain drive to go about “walking speed.” There’s a Raspberry Pi with a Huawei 3G USB dongle onboard and [Emil] uses an XBox controller to do the steering from the warmth of his living room. Of course, a Pi can’t handle a big motor like that directly, so a Phidgets USB motor controller does the hard work. The software is written using Node.js.

The camera mount can swivel 230 degrees on a servo so that the operator can scan the road ahead. The video mentions that steering the car required a heavy-duty servo with metal gears (an earlier attempt with nylon gears didn’t work out).

Overall, it looks like a solid build. We hope [Emil] will share code and more details soon. If you can’t wait (and your insurance is paid up), you might have a go at an even bigger car. Surprisingly, there’s more than one example of that.

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