Let's Make Robots!

Drumbot

 
Drum on stuff

Final Update:

Welp drumbot was interesting, I got him to the point where he could approach, align, and drum on objects, but shortly thereaftrer the gears stripped on one of his GM10 stick motors when the stick got stuck on something.  *sigh*  In any case, DrumBot is finished, and his components are now being reclaimed for a rebuild of igor :-).  Pics of that coming soon-ish.

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This is the makings of my drumming robot.  I know, I know, it's been done again and again, but hey I guess Fritsl started a craze :-)  Anywho, I am using a stripped down toy tank chassis as the base, an Arduino for the brains, a solarbotics L298 board to drive the tread motors and a custom SN754410 board I made to control the sticks, which are very much like the ones from LDM, GM10's with 1/4" aluminum tubing.  For the sonar, I am using a parallax PING.  I am still figuring out exactly how I want it to go together, but this is the basic bits of it....

IMG_0836.jpg

IMG_0830.jpg

UPDATE: 10/4/2008 -

I got some time in with the glue gun today, and got DrumBot mostly assembled.  I wrote a quick test program to test out my wiring, and the servo, the PING, and the 2 drumsticks work great.  The drive motors work, however the arduino resets if I engage the both at once.  I suppose I will have to have a secondary motor power pack or something after all :-/

Anyways, once I work that out, Drumbot will be ready to roll, or maybe it's ROCK N' ROLL :-)

DrumBot_001-1.jpg

 

11/3/2008

So indeed he is underpowered, there is apparently quite a voltage drop due to the L298.  I will have to pick up a small maybe 2xAA holder and piggy-back it with the other batteries

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Nice project. How did you connect the ultra sonic ping))) to the arduino?

 

Its regulated. I think i should take the routerobotologist suggested and buy a more resiliant chip. 

Another clue mentioned was that the h-bridge operates fine at 7.2 volts, but gets warm at 13.8 volts. The motor winding resistance will be the same in either case. As an estimate, say the motors are pulling 360 mA (for easy math) from the 7.2v. That would give the motor resistance to be 20 ohms (ignoring transistor losses) by the V= IR changed to V/I = R formula. So if you increase the voltage to 13.8v, the motor coil will always be 20 ohms, the current becomes 690 mA from the formula V/R=I. That 690 mA is above the continuous current rating of the L293D, which would be a good reason why it is heating up.

Is there some device you are wanting to add to the tank base that requires 12 volts? If not, why not just use the 7.2 volt pack?

 

Theres nothing that needs that much power, the reason i wanted to use the 13.8v supply was so that i could get some decent programming time without being restricted to however long the battery lasts. My plan was to use a long cable i have from some garden lighting to feed power to him permanently. 

 

I may have to rethink my  strategy though and just buy another power supply that is adjustable.  

When i use it with a 7.2v battery its fine, but i have a 13.8 power supply that i have been trying to get it all working with. Its when i use that that things go wrong.

 

http://www.maplin.co.uk/Module.aspx?ModuleNo=231

 

thats the power supply, its the M20W one.  I am using a regulator with it too. 

 

Im stil new to all of this, ive tried measuring amps and current but im somewhat baffled by it all. I kinda get it but then i cant apply what i think i understand of it all.  

is the 13.8 power supply an unregulated wall power supply? If so without a load it is likely supplying 15-16 volts and the amperage is too high.

Have you had any problems with the l293?

 

 Im trying to power two motors with mine and it keeps overheating. 

Might need an L298 (here or here) or bigger, any specs on the motors? Measuring resistance  across the motor terminals while turning slightly can get you a number to use with Ohms Law for stall current draw.
What are you using to power it? Are you using it on a project board or did you sodler something? Could be a short... They do get warm when you use them.
cool base !!!! it realy makes the robot look good!