Let's Make Robots!

2Deckard

mrate's picture
obstacle avoiding
Cost to build: 
$150
Weight: 
200 grams

2Deckard v0.1

2Deckard v0.1

Hi everybody!

First of all, I want to thank all of you guys who's robot projects and blog entries make this site such an amazing place! You all ignited my passion for robotics! I've dedicated my life to computers and programming and this is a really cool way of connecting it with the real world :-)

This is my very first robot called 2Deckard and is far from done but I really feel like sharing my first steps :-) The robot is driven by Arduino Uno, it has 2x 3V DC motors controlled by SN754410 IC (in combination with one 74HC04 hex invertor IC), two TM70145 wheels and one TM70168 gearbox form Tamiya, and SRF05 distance sensor attached on servo. There is also an IR detector that will be used to switch robot modes by TV remote control (right now I've got some problems with detecting signals from remote, I've made it work when the motors are disconnected but as soon as I plug them in I'm recieving a lot of noise... but since there is just one mode at the moment it doesn't bother me so much :-) ).

As a power source I use one 9V battery (for Arduino, servo and sensor) and 4x AAA alcaline battery (for motors). I'm planning to switch to rechargable batteries because the alcaline ones are drained pretty fast (especially the 9V one).

Right now it's just a prototype with lots of wires hanging from solderless board :-) One of the planned improvement is to create custom PCB that would be used as an Arduino shield (I know there is a lot of similar projects on the web but I would like to try making my own version).

So far the robot is moving around the room and avoiding obstacles. It seems that it's "navigating" quite well and it made it's way out even from a dead end of room. I have in plan to add line following (such a popular "hello world" of robotics :-) ) and maybe some other cool stuff, like aiming a poisoned darts throwing cannon :-) For a line following I'll use QRD1114 attach to the PATA cable that is taped to a gearbox on the front (one of many nice ideas I saw while wandering on LMR :-) ). One pair of QRD1114's will maybe end up as wheel encoders. There is so much more I would like to improve, still there is 6 analog inputs and 7 digital I/O left :-)

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mauricio's picture

Hello guys,

Nice bot :-)

Thanks a lot for the hints on noise, it will be very useful in my small bot...

I have one question: does it make difference between placing the capacitors near the motor or near the 754410?

It seems much easier and Im very tempted to solder them directly on the PCB but I have no idea if it will impact the filter efficiency...

Which place is better?

 

Geir Andersen's picture

As a 9V battery is a pack of 6 thin AAAA batteries it's not really for anything that draws some current.

http://en.wikipedia.org/wiki/Nine-volt_battery

mrate's picture

I'm planning to switch to 9V NiMH 200mAH rechargable battery, or maybe for some NiMH battery pack. It would be nice to have one battery source for both the logic and the motors.

ignoblegnome's picture

You might want to give this tip on voltage regulation a read. It is a great resource that I refer back to often.

http://letsmakerobots.com/node/3880 

mrate's picture
Great resource, thanks! From what I know the Arduino has it's own 5V power regulator, so it should be all right to use 7.2 or 9V NiMH battery and connect it right to Arduino and (through some power diodes or voltage divider) to DC motors. I'm thinking about switching the original 3V DC motors that came with Tamiya gearbox with some low current 6V ones, because the original motors take 2.1A (per motor) when stall, which is quite a lot.
ignoblegnome's picture

Another approach is to run the 3V motors at 5 or 6V and use PWM. If you stay away from full duty cycle, you probably won't kill your motors. ; j

Geir Andersen's picture

Hi and welcome to LMR

You probably already know this, but adding some small capacitors on the motors will remove lot of the noise. 

  1. Take two capacitors and twist them together.
  2. Scratch a spot on the motor between the two terminals.  Using soldering iron apply some solder.  Then solder the twisted end of the two capacitors to the spot on the motor case.
  3. Take the other end of the twisted pair of capacitors and insert one end to each motor brush terminal.
  4. Place a third capacitor between each motor brush terminal.

http://www.superdroidrobots.com/product_info/motor_wiring.htm

Great looking robot by the way!

 

ignoblegnome's picture

Hey Geir, that is an interesting link. Have you ever tried using shielded cable and the ferrite rings on your motors in addition to the capacitors? Looks a bit extreme, but I'm sure that it might be worth it for some applications.

Geir Andersen's picture

Hey ignoblegnome.

No I have never tried that solution but it seems to make sense :-)
They even sell small shielding kits http://www.superdroidrobots.com/shop/item.aspx?itemid=387 but the price was a bit high :-)

ignoblegnome's picture

Another technique I have used is to twist the motor leads. This makes a twisted pair, which in theory should reduce noise. I have never done any testing to see if it is effective, since I don't own an oscilloscope.