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Cap's across the motor may help, but it's probably the result of the frequency of your PWM. What is the freq anyways? Maybe we can help you come up with something a bit higher so you can't hear it (but your dog will go nuts!!!).Originally Posted by dragons_fire
Last edited by skimask; - 17th April 2007 at 23:07.
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could be from the PWM, im using a serial motor driver, to keep things simple.. so i cant "easily" change the freq. its not the "hearing" noise im worried about, its the static (snow) on the tv. im just worried that it may affect my circuit since the motors are only going to be an inch from the board..
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The noise showing up on the tv shouldn't affect the motors (ever noticed when you run a blender in the kitchen that the tv in the living room goes nuts?).
Can you 'scope the PWM to the motors or put a meter with a freq reading on it?
Any reason why you're using serial motor drivers? Other than it's already done and one less thing to worry about...which is handy...
And I just thought of something. You said the gear ratio is something like 298:1. All that noise is probably just regular motor noise. How do the motors sound on straight DC battery type power?
Which reminds me...where did you get the tracks? I've been wanting to build another R/C lawnmower and want to drive it with tracks instead of tires...
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im using them because they are already done... all i need to do is output a serial command, and the motors drive...
example command:
serout2 motor, motorbaud,[$80,0,lfwd,speed]
$80,0 are commands for the driver. lfwd is left forward. and speed is one of 128 speeds
i send one command and the motor driver keeps it at that speed until i tell it to change.. lots less for the PIC to worry about..
im jsut worried about the "electronic" noise affecting the PIC and other stuff on the board...
my tracks are probably a little small for you... the "tiles" on the floor are 6 inches across, so my tracks are tiny... they came from a tamiya dozer kit, it was the leftover track parts. each side has 3 pieces of track connected together...
when i get home, i will upload a picture of the tracks on one of my other toys... they would be almost perfect for a lawnmower, except that they would rip up all the grass!!!!
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heres pictures of my tracks on my bigger robot... (its not really a robot yet, its controlled my RC right now... ) theres a 9v battery on top for a size reference...
this link is for the programmer im using.. its wired almost the same as mine, except they dont have the cap.
http://www.melabs.com/images/icsp1.gif
reading about what they say about ICSP, i need to modify my board some more.. it looks as though i need to connect AVdd and AVss too, and it says i need to pull PGM low with a 100k resistor. i also forgot a cap across the vreg.
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You're right on everything you mentioned so far. AVdd and AVss NEED to be tied to Vdd and Vss during programming only. During normal ops, they can be seperated. And pulling PGM low is a good idea (in my mind) whether you are using HV-ICSP or LV-ICSP, maybe throw a jumper in there or something for future 'optionability'.
And put .1uf cap's across every chip, every Vdd/Vss pair, heck throw a couple extra in there when a power or ground trace runs for a few inches without one, if you've got the room for it whether you actually plug one in or not. It'll save you future headaches and give you extra spots to pull a power or a ground.
Since you are wanting to redo your boards, you might want this hint...
For a couple of years now, every time I design a board, I put extra via's on every trace/signal/line/whatever, whether I actually use them or not. Doesn't matter where I put them, I just put them wherever they can fit, and they don't have to be double-sided via's. This way I leave myself a load of future re-config options. I can cut a trace here or there and install jumper wires if I want (or more likely, fix a screw up!).
And those tracks...that's a good idea. I didn't think of putting cleats on chains like that. How well do the chains track over the sprocket when the bolt heads hit the teeth on the sprockets?
Motor drivers - can't argue with that...
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my problem with this board, is that i rushed into it, without fully thinking things through, and doing my research.. now that i have done some research, snd thought about this board more, i feel more confident that its going to work.. im also going to omit the pads in the top that arent being used (pcbexpress automatically makes pads on the top and bottom of holes). i have been thinking about the 90 degree angles all evening (ive been installing IPTV all evening, and even using staples that hold the wires snug can destroy the signal.. wires need to have a certain radius for each corner, and cant be kinked...) so i angled some traces so they have 45 degree bends now..
i will upload another copy of the board later, to see what people think..
if you look closely to the sprockets, some teeth are actually cut out to make clearance for the bolt heads. imworking on changing that design too. i think im going to use only one chain for drive, and make some kind of wheel to support the otehr side. the chains dont stay on well now, because it was almost impossible to make both sprockets line up perfectly... i also want to say, its driven by 2 windshield wiper motors, with 3 x 8.5A 12V sealed Gell cells. one for each motor, and one for the headlights.. we have lots of old coal mines and caves around, so its meant to be able to explore them...
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