In the last post I was playing with 4Tronix's Bit:Bot. In this post I will show the initial experimentation with an artificial neuron controlling the Bit:Bot to follow the edge of a line (it follows the left-hand side of the line).

The neurons (well two separate ones, S1 and S2) are produced using weighted sums - summing the weights x inputs [ right-hand sensor (rs) and left-hand sensor (ls)] plus a bias for each neuron in this case w[0] and w[3].

net=w[0]+w[1]*rs+w[2]*ls

net2=w[3]+w[4]*rs+w[5]*ls

If weighted sum >=0 then its output 1 otherwise 0

if net>=0:

s1=1

else:

s1=0

if net2>=0:

s2=1

else:

s2=0

What actual causes S1 to be either 1 or 0 is all defined by a set of weights w (three for the first neurone, S1, three for S2).

w=[0,-1,1,-1,1,-1]

Converting the outputs of the two neurones S1 and S2 into actions is shown below.

if s1==1 and s2==1:

forward(40)

elif s1==0 and s2==1:

forward(30)

right_turn(10)

elif s1==1 and s2==0:

forward(30)

left_turn(10)

elif s1==0 and s2==0:

backward(40)

The functions for forward, right_turn, etc are defined elsewhere.

At the moment the movement is a bit rough and it is a little simpler to build a version that follows the centre of the line; this approach though, works with thinner lines.

To change the function of the system, change the values in w; for example to produce one that follows the centre of the line just change w (I will leave that to someone to work on). The complete code is shown below.

Code

**from microbit import ***

**import neopixel, random, array**

w=[]

w=[]

def forward(n):

def forward(n):

**pin0.write_analog(551)**

**pin8.write_digital(0)**

**pin1.write_analog(551)**

**pin12.write_digital(0)**

**sleep(n)**

**def backward(n):**

**pin0.write_analog(551)**

**pin8.write_digital(1)**

**pin1.write_analog(551)**

**pin12.write_digital(1)**

**sleep(n)**

**def right_turn(n):**

**pin0.write_analog(511)**

**pin8.write_digital(0)**

**pin1.write_analog(511)**

**pin12.write_digital(1)**

**sleep(n)**

**def left_turn(n):**

**pin0.write_analog(551)**

**pin8.write_digital(1)**

**pin1.write_analog(551)**

**pin12.write_digital(0)**

**sleep(n)**

**w=[0,-1,1,-1,1,-1]**

while True:

while True:

**ls= pin11.read_digital()**

**rs= pin5.read_digital()**

**net=w[0]+w[1]*rs+w[2]*ls**

**net2=w[3]+w[4]*rs+w[5]*ls**

**if net>=0:**

**s1=1**

**else:**

**s1=0**

if net2>=0:

if net2>=0:

**s2=1**

**else:**

**s2=0**

**if s1==1 and s2==1:**

**forward(40)**

**elif s1==0 and s2==1:**

**forward(30)**

**right_turn(10)**

**elif s1==1 and s2==0:**

**forward(30)**

**left_turn(10)**

**elif s1==0 and s2==0:**

**backward(40)**

All opinions in this blog are the Author's and should not in any way be seen as reflecting the views of any organisation the Author has any association with. Twitter @scottturneruon

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