This has probably been done to death on the blogs but I was inspired by the born 2 craft site. Mine needs a bit of work in the code but I generally prefer to do something from scratch by myself after seeing an idea. Mine is also a bit larger as it is veroboard.
Design
The parts are all hacked off of other dead RC toys and boards, ATTiny85 is the only thing I paid for, makes me happy. The system uses a small LiPo striped from crashed mini RC helicopter, nice and light. The board layout was worked out in building, working around the socket as it was meant to be a 8 pin PIC proto-board.
The wheels were made from ABS sheet, using a circle template at 23mm. Using the four centre marks on the diameter I drew between opposite ones to get the point to make a hole for the shaft, I used a dividers point and checked every now and then to see the fit, just push on with reasonable pressure.
I used marine silicon to create a tread. This is done by running two strips along ABS sheet at the distance of the wheels, and roll back and forth.
The battery is charged by a full spec LiPo balance charger through the headers, the switch is moved towards the header toput in charge mode.
Some build pics, some:
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| Underside |
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| Front View |
Hardware
The design of the circuit is similar to the born 2 craft, but I made some modifications.
I added the flyback diodes to the two motors, I skimped on those to begin with as there was not enough space, but after changing the transistors for both motors I added them. The PCB layout is my design.
- Transistors are BC817-40
- Diodes are 1N4148
- ATtiny85/45
- Small model motors
- 0805 resistors
- LiPo 3.7v
- Switch SPST
- Wheels: ABS, 23mm dia.
- Some copper wire, varying thickness
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| Schematic |
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| PCB |
Code
/*
Tiny Bot: an LDR based light following robot, or avoidance bot
if you switch the drive function around.
Hardware is based off the Light Bot by born 2 craft
TODO:
Add IR control
Clean up code
##############################
Written by:
Reece May
rev1 12/15/14
https://ziggyelectronics.blogspot.com
You may use the code and modify it as long as you keep the above
and make edit notes bellow and put it on github here:
https://github.com/ReeceM/Tiny-Bot.git
*/
#define Rmtr 1
#define Lmtr 0
#define Rsens 3
#define Lsens 2
#define drive_time 100
int Rav, Lav = 0;
void setup(){
pinMode(Rmtr, OUTPUT);
pinMode(Lmtr, OUTPUT);
pinMode(Rsens, INPUT);
pinMode(Lsens, INPUT);
}
void ADread(){
Rav, Lav = 0; //clear the average to prevent errors
for(int q = 0; q < 20; q++){ //loop to create average
Rav += analogRead(Rsens);
Lav += analogRead(Lsens);
}
Rav /= 19;
Lav /= 19;
}
void drive_RIGHT(){
digitalWrite(Lmtr, 0);
digitalWrite(Rmtr, 1);
delay(drive_time);
digitalWrite(Rmtr, 0);
delay(drive_time);
}
void drive_LEFT(){
digitalWrite(Rmtr, 0);
digitalWrite(Lmtr, 1);
delay(drive_time);
digitalWrite(Lmtr, 0);
delay(drive_time);
}
void loop(){
ADread();
if(Rav < Lav){
drive_RIGHT();
//drive_LEFT(); //use this to avoid light
}
ADread();
if(Lav < Rav){
drive_LEFT();
//drive_RIGHT(); //use this to avoid light
}
}
Links
https://github.com/ReeceM/Tiny-Bot.git
