V over I/O?

jessef · Posted: Wed May 10, 2006 3:33 pm Post subject:

depending on the current that the motor draws you may need a bigger transistor. recently I did a project for an EE class where we built a motor controller of sorts for a RC car and we started out with the same transistor listed in the schematic. but the motor required more then the max of 500mA that the transistor required so it broke and made a horrible smell.
I think that the flickering problem might be solved by adding a resistor and capacitor some where in the circuit to average out the wave. a motor should be fine because it has a greater averaging effect then the LED.

Ephi · Posted: Wed May 10, 2006 6:48 pm Post subject:

I added a bigger transistor for the motor!
and now I have a TI tranporter!
its funny, but I drove it with the ti on boart against a wall Confused

....booooooooooooooooooooooooooooooooooom...
and the ti cover is now broken Crying or Very sad

but I know where to get a new one! Wink

jessef · Posted: Wed May 10, 2006 9:24 pm Post subject:

if you wan't you'r car to react to it's enviornment you have to have a coprocessor to take care of the I/O stuff cause the calc only has 2 I/O lines.

Ephi · Posted: Thu May 11, 2006 1:37 pm Post subject:

oh, i don´t want to build a very good car. it was only a test!

I tryed to add a capacitor but it does not work Crying or Very sad

here my schematic:

jessef · Posted: Thu May 11, 2006 7:00 pm Post subject:

I can't see you'r schematic. you probably had the capacitor in series whith the LED. it should be in parallel whith the LED, I think. series definantly won't work. We haven't covered capacitors in school so far so I don't know much about them or what value you might need.

Ephi · Posted: Fri May 12, 2006 5:14 pm Post subject:

sorry, I have some problems with the picture...

I try with the capacitor...

Ephi · Posted: Tue May 16, 2006 5:49 pm Post subject:

the capacitor dont works...

have you any other idea?

jessef · Posted: Fri May 19, 2006 4:22 pm Post subject:

well their are 2 approaches that I see:
1) "the LED changes state too fast so it needs to be slowed down some how." this was the point of the capacitor I am not sure what else you can do.
2) "the software is too slow it needs to be spead up." if you make the peiod small then the LED may flicker less but then you have fewer brigtness levels. you could also put the code in a loop instead of an inturupt but this would make it harder to have stuff going on in the backround.