Euxton CE Robot Club

Just got two roboteers for this club (I think my advertising skills need improving πŸ™‚ ) and for this club, I’ve switched to using the @GeekMoore “Magical Moore” chassis to start with as its uses higher geared motors than the ones supplied with the Magician chassis which makes for easier control as the robot doesn’t shoot off across the classroom.

We are still using a WiFi enabled Raspberry Pi as the robot controller and using a remote control program (VNC) to let us program it from a class Laptop.

I just explained to the Roboteers that the robot had 2 motors and that we needed to create 2 variables called MotorA and MotorB and then just prompted Ben and Dylan to work out what they needed to do to get the robot to move. Β  I try and use this technique as much as possible – give them a hint as to what is needed and then let them run with idea and code it up.

These boys have had 3 half-terms of Scratch lessons over Y5/Y6 and have already used Shrimps (Arduinio clones) via netbooks to control LEDs etc so were pretty savvy in this respect.

By end of 1 hours session, they’d got full remote control of the bot (fwd,left,right,stop,speed up, slow down).

So next week, we’ll be hopefully moving onto using IR Line Sensors to get the bot to zigzag along a line by itself πŸ™‚ for video of bot in action

Week 2

We had another Roboteer join the club.

We added an Ultrasonic Sensor to Pi (name given to the bot) and then programmed it toΒ  turn left for 1 second if it detected an object less than 20cm in front of it.
This turned out to be an excellent concept/idea – very simple to do but very effective.

Although we didn’t do it – could be worth getting roboteers to extending their code so that the Robot turns for random amount of time or randomly left/right

Week 3
We switched over at this point to a Magician Chassis as I’d previously equipped it with line IR sensors (Hopefully I’ll get some fitted to the Magical Moore bot over the Easter hols)

The Roboteers soon understood that a black surface didn’t reflect the IR light but that white did and that they could see these changes in Scratch my monitoring Pins 8 and 10.

Since they were fully familiar of setting a motor variable to 0 to get the robot to turn, they soon worked out what was needed once we’d done some runs (the Magician Chassis doesn’t run very straight – well mine doesn’t anyway!)

I showed them if blocks and they coded it up.

Then they came up with idea of getting a pile of books at the end and using the Ultrasonic sensor to make it stop

Week 4The roboteers were very keen to get the bot to follow a line around the classroom so we tried using masking tape on the floor and changed the code so that the bot would follow a white line instead of a black one.

But the sensors couldn’t really tell the difference between the grey carpet and the masking tape so we tried painting the masking tape white and put some pieces of cardboard packing in to lower the sensors- the combination worked!Β  Dillon said what we should have had was the same mechanism he had on his pen where you turned the top and the pen nib went in and out – I call that moment one of the learning successes πŸ™‚

Due to time paint takes to dry πŸ™‚ we didn’t have time to run the tape around the class (much to roboteers disappointment) but at least we managed to get it to do this

Next time I do this club with another school, we’ll try out using white insulation tape instead of masking tape and I’ll see if that works better and make the sensor heights adjustable (by roboteers – not just me)Β  if possible

This club has been a great sucess

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7 Responses

  1. stewart says:

    Great to watch your work on the robot progress as I would also like to make a robot and use the ULN 2803 driver (or the ULN 2803 driver which seems to have 8 outputs instead of 7 but is easier to obtain from Rapid Electronic who I usually use) to drive the motors.
    Comment – I made a simple test circuit using the ULN2803 on a breadboard and it works just as expected using your ScratchGPIO program. I am very happy but have noticed that if instead I connect an LED to the Pi directly via an unprotected output pin the state is reversed. (i.e. ‘on’ becomes ‘off’) As things stand I am happy but just wondering if there actually is way to change the state of the pins if a I did decide to use extra output pins from both a ULN2003 driver and to directly connect output pins via the header directly with no driver.

    • cymplecy says:

      In my Arduino version, I have added in an “invert” broadcast detect to deal with common anode 7 seg displays so I’ll look incorporate in into my RPi version. It will just operate at global level e.g all highs/1/on will be converted to 0V and all lows/0/off converted to +3.3V. Will post when new version ready (by end of Eastor Hols at VERY latest)

  2. Hi Simon,]the link above:
    needs repair, stray http: at the end – great work though.


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