Teensy 3.0 RC car

[Pedvide]

Hello!

I'm building a RC car using Teensy as its "brain". I started learning electronics only a few months ago, so although I've come very far I still have some problems, specially since today I killed my third Teensy 3.0.....

I'm going to show you some pictures and then I'll talk about the problems:

General view from above:

Back side: teensy, motor driver, RF receiver and some leds:

Front side: led bar, ultrasonic sensor and voltage regulator.

RF remote controller, outside view:

RF remote controller, inside view:


I hope everything is commented well enough.
The code for the car's teensy and the transmitter teensy is:
View attachment racecar_RF.ino
View attachment control_RF.ino

So why did I kill three beautiful Teensies (Teensys?)?
I connected the first one to 8V power..... it was disappointing that it didn't smoke or burn or something.
The other two I'm not sure, I think that when I drive the car and crash it into a wall some cables become loose, and shortcircuit something, but I'm never sure of what happens.
This last time the only cable that was disconnected was the SPI data cable (yellow), on the front side. Is it possible that the cable touched some part of the shift register at 5V and burned the Teensy? Or can't the teensy withstand a crash (it wasn't going that fast, and it has a bumper on the front)?

The main problem that I have apart from the teensy is power.
I know that I have to have at least two different power lines, one for the Teensy (nokia Lithium battery) and the other for the motor and servo (4.85V 6600mAh battery pack). The problem is that the motor needs more voltage. I don't know exactly how much as it doesn't say anywhere on the motor, but I think I remember this thing needing around 6 alkaline batteries (12V). That's why I have the voltage regulator taking the 4.85V from the battery and stepping it up to 8V (is it very inefficient to set it higher), but the problem with this is that when the motor starts to run the voltage drops around 2V, so that the 4.85 power line goes to 3V or so, and the ultrasonic sensor stops working (it needs 5V, not 3,3V).
I have bought two 1000 mAh 7.4V lithium batteries (I have a camera charger that suits them) that I intend to use for the motor exclusively, so I'll use the voltage regulator to step up the nokia battery to 5V, so that the ultrasonic sensor can work (I don't know what to do with the servo, maybe another nokia battery....).

The other problem is with the RF receiver. I think it catches a lot of interference from the motor when it's running, so I should shield it somehow. Maybe some tinfoil between the motor and the battery? (the motor is directly below the battery, with a 1 cm gap approximately).

This is my project with its problems! Now, so you don't think this doesn't even work I'm going to show you some videos:
https://www.youtube.com/watch?v=egTxoewQK7c
https://www.youtube.com/watch?v=hkOYBLEO75c

If you look into the other videos I've posted in youtube you'll see that at an earlier stage this thing was controlled by a TV remote using a IR sensor. I have the code for that if somebody is interested.

Do you have any ideas or thoughts about my problems?
Thanks,

Pedro.

 

[stevech]

Congratulations!
No doubt you've learned a LOT doing this.

the radio issue: Be sure its power source is either on a different battery or has special regulation and filtering. And beware ground loops and so on.
Then, the question is what sort of radio did you choose? Frequency, modulation method, error detection and correction, etc.
The best is to use an 802.15.4 radio like the XBee Series 1 (ONE, not 2), in peer to peer mode (no PAN). That gives you spread spectrum, error correction, addressing, and so on, without you coding all that.

 

[Pedvide]

Thanks a lot for the info. Right now I'm in the process of moving to another flat, so I've already packed the RC car.
But before doing that I made some changes to the wiring regarding the ground of the motor power (thanks to this link http://www.epanorama.net/documents/groundloop/in_circuit.html). Now, instead of flowing to the breadboard with the Teensy, it goes directly to the ground of the big battery, so I expect less current to be flowing near the Teensy. I've also changed the power for the motor driver so that now it's powered by the big battery as well. When I get back to this I'll move the led bar and the shift register so that they are powered by the nokia battery.

I've looked into this XBee thing and it's awesome! One question though, is it enough to buy just two modules and feed one of them the joystick position and the other will receive it somehow? or do I need to buy the USB programmer?

Also, directed to other people as well: why did the Teensies die? If I put some diodes on the outputs from the teensy will that protect them against shortcuts?