Let's Make Robots!

Andrew - First robot

Change direction when meet wall

Hi all! First robot ever, saying it's not great would be an euphemism, nevertheless I would be very glad to get some feedback from you.

How it works : two switches on the front, when it meets a wall, andrew goes backwards and turn, then turn the other direction and goes forward again (see videos)

Controller : Arduino Uno. Structure : Knex. Direction : two front wheels turned by a micro servo. Engine : DC motor (with some knex gears), linked with 2 rubber bands to the back wheel. Electronics used : 4 transistors, 4 diodes, 6 resistors (330ohms and 10kohms), 1 capacitor.

Two interesting problems I've met and solved (oh yeah!) :

1) Making the DC motor going backward without H-bridge or motor shield (because I didnt want to buy and wait for these)

--> I made myself an H-bridge, with 4 transistors (2222A) and 4 diodes, according to the drawing I found there : http://www.electronicsteacher.com/robotics/robotics-tutorial/advanced-robotics/controlling-dc-motors.php

I used 330 ohms resistors to connect the arduino pins to the transistors' bases. 10kohms didnt let enough current flow.

Note that the DC motor is powered separately, with what look like a 9V battery but is most probably much lower because it's rechargeable but I don't know the value...

2) The circuit worked perfectly with leds in place of the dc motor, but it went mad when the dc motor was plugged

--> Apparently the dc motor was causing EMI (Electromagnetic Interferences), I read a great article (http://www.thebox.myzen.co.uk/Workshop/Motors_1.html), put a capacitor of 560 nF in parallel with the dc motor, and all the problems went magically away.




Please tell me what you think, especially about the power, I read a lot of different things about how to power properly the motors and arduino and yet I'm not sure my way is correct, the possibility of frying the card scares me a bit :s



Next project : get an IR sensor, a motor shield, put two dc motor at the back and make the robot going around avoiding obstacles without stopping. Some advices about the shield?

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I like the design, and personally, I get a huge grin when I see cheap and on hand materials used. It just makes me happy and is a credit to your ingenuity! Also, I like that you have some future plans with this base, its a fantastic starting point.


My only suggestion is that as you add more components, and therefore weight, watch that you dont put too much stress on that turning hinge. If the knex warps its gonna drive all funny. 


Great job, keep us posted and keep working on it! :)

Thanks for your encouragements, especially seeing all the awesome projects you've done.

...you have already solved some other interesting problems besides the two you mentioned. Great so see how you work on it. Go ahead. And Welcome to LMR.

This article about the electro-magnetic induction from the motor is interesting too. Nice share. Thank's.

You could add some categorisation to this robot project. So future LMRians can bump into this project more easely by i.e. browsing categories.

What a perfect example of how one should start out building robots. I am glad you had the sense to READ some literature to solve your problems. You obviously are a bit more intelligent than the average newby here. If only there was a way to convey the message in your robot post...
Also your improvisation shows you don't always have to wait for money or parts.
A hearty welcome to LMR.


Thanks for the nice comments, I feel welcome in the community!

Great Job!