TreadBot

[mackrackit]

Ive been playing with it a little bit, and if i move the board up about 3", everything works great... thats what makes me think its an interference problem instead of a "low voltage" thing...

To me that sounds more and more like a magnetic problem. A magnetic field will drop off something like an inverse square, RF does not. (some one will want to correct this) At least if it was RF, it would most likely carry more than 3"

A little info http://www.lessemf.com/guidelines.pdf

[dragons_fire]

so, i added a sheet of "galvanized flashing" between the board and the motors, and i bent some to make a box that fits perfectly over the PLCC socket, and it seems to help.. its still not perfect, but its a whole lot better than it was before. im going to see what i can do to shield it a little better. i also need to ad caps to the other motor, and im going to see what i can do to make some tubular shields to fit over the motors..

i have also noticed that things get worse if i ground all the shields..

i like the way its laid out right now, but i think it might help if i switch the controller and battery boards, so the PIC would be farther away from the motors. it would also lower the centre of gravity, and make the whole robot a little more stable...

i will try to play with it a little more this evening, and maybe add one more sheet under the one i already have, but idont want to raise the board too much, its already top heavy..

[mackrackit]

I forgot to mention that grounding the shields will transfer eddy currents.

You might try bending the sheet metal that is between the board and motors down over the tracks (fenders)?

With out a gauss meter the fields will be difficult to map. A compass can sometimes give you an idea.

This is a gadget I use. http://www.forcefieldmagnets.com/cat...roducts_id=100

[dragons_fire]

when i first started building this, my intention was to put the battery between the 2 motors inside the red fibreglass. because i wanted lots of capacity, and a higher voltage, i added them to the top. so now i have lots of room insid the chassis.

i will probably make tubes to go around the motors, and hopefully that will help.

I might also cast a lead "brick" to fill in the space between them to make it a little more stable on angles, and for more grip. the only problem is that i will lose some endurance because the motors will need to haul more wieght.

ive been working for the last ten days, but i get the next 4 off, and its raining like crazy here, so i should get some time this weekend to play with it a bit more.

After i get the "interference" problem figured out, i will have a video up here of it driving around. i have written the code for it to speed up, drive, sense obsactles, slow down and then turn and drive that way..

[skimask]

when i first started building this, my intention was to put the battery between the 2 motors inside the red fibreglass. because i wanted lots of capacity, and a higher voltage, i added them to the top. so now i have lots of room insid the chassis.
i will probably make tubes to go around the motors, and hopefully that will help.
I might also cast a lead "brick" to fill in the space between them to make it a little more stable on angles, and for more grip. the only problem is that i will lose some endurance because the motors will need to haul more wieght.
ive been working for the last ten days, but i get the next 4 off, and its raining like crazy here, so i should get some time this weekend to play with it a bit more.
After i get the "interference" problem figured out, i will have a video up here of it driving around. i have written the code for it to speed up, drive, sense obsactles, slow down and then turn and drive that way..

It was recently (today) suggested in another thread talking about unused pins and running motors and getting interference, etc., to occassionally reaffirm your TRIS assignments for all the pins you're using.

In other words, every once in awhile, or whenever you can spare a cycle or two, redo all your TRIS's, keep your inputs as inputs, and your outputs as outputs.

It seemed to help this other person's problem with motors, magnetics, etc., and it's only a slight software change.
Might help you too...

[dragons_fire]

well, i just noticed that thread as you were replying.. i will give it a try when i get home... the motor controller has a reset line on it that needs to be held high, so i used a pin from the pic, so i can turn it on or off if i need too, and i think hte pic is probably going low on that pin..

do i want to make all the unused (almost all of them right now) inputs or outputs?? they arent tied to ground or anything, because they will eventually be used.

and im not too worried about program space (yet), i have 24K words, and im only using about 300 words right now... i would prefer to get rid of as much magnetism and electrical noise as possible by physical means, and not just block it out with programming..

thanks for the help guys

[skimask]

the motor controller has a reset line on it that needs to be held high, so i used a pin from the pic, so i can turn it on or off if i need too, and i think hte pic is probably going low on that pin

Good idea...keep pinging that pin in your program to help force it high if need be.

do i want to make all the unused (almost all of them right now) inputs or outputs?? they arent tied to ground or anything, because they will eventually be used.

Don't really know on that. Almost anyone of them could be causing a problem. One thing is almost for sure though, if a pin is an output, it generally can't cause an interrupt.

i would prefer to get rid of as much magnetism and electrical noise as possible by physical means, and not just block it out with programming..

But the extra programming doesn't cost anything in hardware!

[SteveB]

well, i just noticed that thread as you were replying.. i will give it a try when i get home... the motor controller has a reset line on it that needs to be held high, so i used a pin from the pic, so i can turn it on or off if i need too, and i think hte pic is probably going low on that pin..

You could also try using a pull-up, and keeping the pin as input. If you want a reset, then in the program change it to an output, low, pause as needed, high, then back to input.