Sunday, 16 September 2018

Less is More

Sputnik 0.1 has been stripped down completely to make way for Sputnik 0.2

As you can hopefully see from the comparison above, it's much smaller and lighter. The purpose of this build was to test out the 4tronix RoboHat motor controller, paired with a power supply of 2 x 18650 Lithium Ion batteries. 

The RoboHat powers the Raspberry Pi from the same power source it uses for the motors, so we can do away with the heavy USB Powerbank from the previous build. We also don't need the L298N Dual H-Bridge controller. 

The RoboHat is working well, although the terminal blocks for the motors are way smaller than the L298N controller, so we had to use some separate terminal blocks we had in the toolbox to wire the motors to and then have a jumper wire from those to the RoboHat. 

The software now starts up when the Raspberry Pi is powered up - we really need to add a shutdown button to the controller - at the moment we can connect using ssh from a mobile phone to shutdown without wheeling out the laptop. 

We've also added an LED that flashes whilst waiting for the controller to pair, and then goes solid when the pairing is complete.

I had a bit of a panic when one of the terminals broke off a motor. Managed to solder the wire onto the remaining tiny bit of terminal that was sticking out - not sure how long it will last - but I'll be getting new motors and wheels soon.

It's a bit jumpy when turning but suspect that'll also improve with different wheels.

The next step is to build a proper chassis so my sons can start practising their driving skills, and we can fine tune the remote control software and we can sort out where to place all the electronics.

Lesson's learned from this build:
  1. When screwing a jumper cable into a terminal block - don't clamp the plastic surround. We have discovered these don't conduct electricity very well. 
  2. Screw the hat onto the Raspberry Pi. Two minutes of driving and the hat came loose from the GPIO pins. 
  3. Don't immediately blame the motor controller when it doesn't work straight out of the box. (See point 1).
  4. Robot building is fun - but takes much longer than you think. 

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