Monthly Archives: November 2013

Prototype lifter arm

I added a prototype lifter arm to my robot yesterday. It needs re-doing (it’s unreliable and heavy) but it works for now.

I’m using a new motor driver circuit for it as I burned out the SN754410 motor driver I was using, the lifter motor seems to peak briefly at about 1.5 amps when starting to lift the arm, and that’s out of the chips range. I stayed up late making a new motor control circuit with a L298N that can provide a lot more power.

Here is the robot picking up 12 ping-pong balls. I was driving, Morwenna was filming:

Here is the same run seen through the on-board camera. Almost all of the run was done watching the live feed rather than watching the robot itself:

Here is the paper strip-board design for the L298N circuit.


Testing the circuit out on breadboard:


The finished circuit. You can see it bolted to the back of the robot in the video.


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First robot remote driving test

I programmed some remote control software using a Golang receiving program on the robot and a ruby control client using my gamepad ruby gem and an xbox1 controller. It worked OK. It was a bit jerky, there’s no PWM so no acceleration, it’s either go or stop; anything not totally rigid on the robot wobbles. Also the position of the camera doesn’t show enough of the robot so it’s hard to get a real idea of where the robot is.

I was filming, the robot was being controlled my my wife, Morwenna, from upstairs.

The robot is also prone to shed a track if the “half turn” is used too much, that is one track forwards or backwards, the other one stationary. I can fix this in software if I can work out a way to do PWM on the robot that doesn’t run the Raspberry Pi CPU.

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