Build a simple robot help please

[myfirstrobot]

Hello,

I am hoping that someone will read this and help me. Although I deal with pcs and networks and a daily basis, I have never done any robotics until my son asked if we can build one. He is 7. I have read a few books and have a very basic understanding of how I want to proceed.
At this moment in time I do not want to use a Stamp or programmable chip.

I wonder if anyone has a cicuit diagram I could have for a breadboard based robot.
I have 2X 555 chips, 1x556 chip, 2XJR Servos (now Hacked so I can get 360 rotation, a breadboard, a host of capasitors,resistors and diodes, a base,wheels, micro switches and whiskers.

Again I want to avoid programming on my first robot so my son can understand (and me) how the electrical side works first.

All I want is a robot that will move forward until one of its whiskers hits something and then backs up and turns and then continues on its way until it hits something again.

I know I will need a stepper motor control circuit, an H bridge, a 9v supply and a 6v supply.

I just need some help with the circuit diagrams and how to combine the above.

I know I am asking for a lot but I am just hoping someone out there has done this project already and will share their experience with us.

Thank you.

David and Tyler

Hi, welcome to the FRA forum. Doesnt sound like a fighting robot to me .

We have all got to start somewhere. If all you want is for it to reverse when it hits something, turn and carry on then its quite simple. I did a similar project way back at collage but used ultrasonic sensors instead of microswitches. It simply turned left for a set time and then carried on. This used modified servos for drive. If you are planning to use the servos as drive motors then you dont need any additional circuit (H-Bridge) to drive the motor but you do need to send servo pulses to it. Thinking back to how I did it we sent the servos a 200Hz square wave for forward and 400Hz squarewave for backward. Not what the servos want but it did reverse the motor direction.

If you do want to make the whole circuit then one of the simplest ways i can think of is to have the motors on all the time (on/off switch)and when a wisker is hit it, it will switch 2 relays to reverse both motors direction and 2 555s can be used to time how long the relays are on. If one relay is on for 1 second and the other is on for 2 seconds then after 1 second it will start to turn (as only one motor has started going forwards again) and then after 2 seconds the other motor will reverse. The times can be adjusted for a specific turn angle.

Good luck

[big_nipper]

Hi, welcome to the FRA forum. Doesnt sound like a fighting robot to me .

We have all got to start somewhere. If all you want is for it to reverse when it hits something, turn and carry on then its quite simple. I did a similar project way back at collage but used ultrasonic sensors instead of microswitches. It simply turned left for a set time and then carried on. This used modified servos for drive. If you are planning to use the servos as drive motors then you dont need any additional circuit (H-Bridge) to drive the motor but you do need to send servo pulses to it. Thinking back to how I did it we sent the servos a 200Hz square wave for forward and 400Hz squarewave for backward. Not what the servos want but it did reverse the motor direction.

If you do want to make the whole circuit then one of the simplest ways i can think of is to have the motors on all the time (on/off switch)and when a wisker is hit it, it will switch 2 relays to reverse both motors direction and 2 555s can be used to time how long the relays are on. If one relay is on for 1 second and the other is on for 2 seconds then after 1 second it will start to turn (as only one motor has started going forwards again) and then after 2 seconds the other motor will reverse. The times can be adjusted for a specific turn angle.

Good luck

[drcharlie]

You have probably already completed the project by now, but my suggestion would be to use the whisker switches as a trigger input(s) on the 556(dual 555) as a (Couple of) 1 shot(s)(aka monostable mode). The output of these could be used to control (power) the 555(s) which could be set as oscilators(aka astable mode) the frequency they produce could be mixed by diodes (arrow pointing away from 555 pin 3, twards the servos) the signals would both be able to get to the servos depending on which 555 had power. Info on astable/monostable configuration and the component values needed for the frequencys can be found here http://www.see.ed.ac.uk/~kap/Hard/555/node2.htmlhttp://www.see.ed.ac.uk/~kap/Hard/555/node2.html

Good luck and have fun!