EE Times Under The Hood - October 8, 2007 - (Page 70) under the hood: COMPUTERS & GAMING www.eetimes.com • www.techonline.com RC car is fraught with design trade-offs BY RICHARD NASS I n its basic form, this looks like a fairly simple, straightforward design. However, as most of you know, very rarely is there anything simple about a design. In this case, the object of the teardown was a remote-controlled car, not unlike lots of remote-controlled cars used by kids all over the world. The end product, a Maserati, was manufactured by Nikko of Japan, one of the world’s largest manufacturers of such products. What made this toy different from other remotecontrolled cars is that it could be controlled by a Motorola iDEN mobile handset, in addition to the traditional remote. A separate module that holds the wireless capabilities is plugged into either the standard remote or the handset. By plugging into the handset, the car gives the user feedback, like speed and direction. The concept was conceived in February 2004 by Steve Bozzone, an engineering manager at Motorola who formed a small team to create a prototype that summer and led the project through to shipping. The car was developed as part of an iDEN promotion for Nextel, a sponsor of NASCAR racing, so the first design was done both as a Maserati and a NASCAR vehicle. A few key parts The car’s pcb basically contains two key ICs from Freescale Semiconductor: a 13192-4534 wireless transceiver and a M9S8GT60 microcontroller. Freescale and Motorola’s iDEN division have a longstanding relationship (both groups were part of Motorola at the time). The Maserati was one of the first end products to use the chip set. The remote control contains a PIC microcontroller from Microchip that was chosen for two reasons: It cost less than others that were available, and the engineer who designed the remote knew the architecture. While the 2.4-GHz transceiver is capable of running a ZigBee stack, the designers opted for a proprietary wireless protocol that allowed them to use an MCU with less memory. “Looking back, we might have been better off going with ZigBee,” said Bozzone, “but it was pretty early in the ZigBee days. Going with ZigBee would have made it compatible with other devices. And now a more integrated part is available, so rather than use two ICs, it could be done with one. That would have cost less.” Dealing with the slump The biggest design challenge had to do with a “voltage slump.” Typically, remote-controlled cars are designed 70 Electronic Engineering Times, TechOnline | October 8, 2007 http://www.eetimes.com http://www.techonline.com
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