After our CDG security debacle in February, where the French confiscated the kids’ Nerf guns due to their foam-dart plane-downing properties, I promised to find them some treats as replacements.
First up was Sibéal, who indicated interest in RC cars. Rather than spending a fortune and discovering she didn’t really like them, I ordered a €21 kit from DX in China. It’s a very simple 4WD, 4-motor, two layer kit with no electronics or controls at all. The idea is that you add an Arudino, some form of motor control and some form of remote control yourself. (Note that brown stuff is a paper coating!)
The pics on DX have the motors backwards, so our first session was a complete flop as we tried to attach them and the wheels.
In the second session, we put them all on the right way round and screwed the two layers together. It looked great and we wired some batteries to one motor to make sure it worked ok.
I installed some of the Adafruit simple test code and then the two of us wired up the 4 motors. All of them spun. In random directions A quick re-wiring and they all spun slowly the same way. After re-reading the code and trying a few different things, I got it running full speed. It’s pretty quick.
Then disaster struck a few days later as some over enthusiastic kids drove it at full speed into a wall and shattered the lower plastic layer. Tons of metal brackets and epoxy resin later and it was stronger, stiffer and better than ever.
Last night we focused on bling and added some Lego and a teddy.
I didn’t like using 8 rechargeable AA batteries and they took up a lot of space so I investigated proper RC Car batteries. HobbyKing seems to be the best site online for this kind of stuff so I ordered a 2200mAH Turnigy battery and charger from their UK store. I used an old PC ATX PSU to provide 12V to the charger.
Due to HobbyKing’s high delivery charges outside of the UK, I used Parcel Motel for the first time. Great service which provides you with a UK address and a collection location. Shipment from the UK last Friday arrived in Topaz on the Bandon Rd, opposite Dunnes on Wednesday.
As LiPo batteries can be killed by over-discharging, I’ve also ordered a low-battery alarm from their HK store. And finally I grabbed some of the right XT-60 connectors from an eBay seller in Donegal. I’ll report back on battery life.
Next up is a remote control. We’re starting with an Elecfreaks Joystick Shield.
It’s very simple to program and has a connector for an NRF24L01 2.4GZ Transceiver. I’ll have to solder the other transceiver on to the motorshield as it doesn’t expose expansion pins at all. Then I’ll create a simple directional control protocol to run over that link.
Once that’s done, we’re going to investigate line-following code and ultrasonic obstacle detector code.
So far she loves it and her main questions is whether it’ll be faster than Fionn’s i-racer.
Whilst the cost of all the parts is adding up to be more than just buying a full RC kit, the great thing here is that once she tires of the car, we have a ton of re-usable tools/parts to build whatever we want next.