So, the weather is getting better and it is time to bring the outdoor toys back to life!
One of my toys is New Bright’s Mud Slinger Jeep Wrangler, which I got cheap in a returned toys sale. For the fun of it, I opened the case of the remote control and probed around with an oscilloscope. Some of my findings I documented on a page in my Wiki.
The remote control’s insides make a rather cheap impression, but it contains a 40 MHz quartz oscillator, which can be observed oscillating, when a remote control button is pressed, at several locations on the board, e.g. on the top pin of transistor Q1.
In the scope capture we can see 28 complete sine waves in 13.8 divs with 50ns/div, making for a frequency of 40.6MHz.
The antenna’s solder point is also showing continuous activity, while a button is pressed. The time resolution is now 1ms/div:
Surprisingly, for every button the same sequence seems to appear. The oscilloscope used was rather cheap, so I didn’t manage to trigger to the transmission start (or to the same point within a sequence twice for that matter). But all buttons initiate transmission sequences consisting of alternating four long and four short 40MHz bursts, and all are ending with four short bursts.
All buttons have a different effect on the car, so there must be a difference in the signal. Maybe the oscilloscope resolution wasn’t high enough to see that difference time-wise or maybe there is a difference in the sequence itself, that’s not seen due to the small time window monitored.