TreadBot

[skimask]

first one, an old board from about 2 years ago, made with a sharpie marker.. PIC16F84A robot controller

Lots of fingerprints...gotta clean those boards good before you etch. Pretty nice for a sharpie.

second one, a board i made about 6 months ago using a presensitized board and on overhead transparency.... GPS interface for robot

Lots of extra flux, but no fingerprints I can see. And again, pretty good. 90 degree corners aren't the best though once you start dealing with higher frequencies.

third one, the one for this robot, using the toner transfer method...

Get some rubbing alcohol and those soft acid brushes ( http://www.tecratools.com/pages/asso...ics/15215l.gif ) to break down and clean off the excess flux when you're done soldering. That stuff will harden up over time and eat away at everything, as well as possibly cause high resistance shorts (low resistance opens? ) over time. In that class I mentioned, they stressed to go ahead and use loads and loads of flux while you're soldering, but also to clean the heck out of it when you're done.

[dragons_fire]

youre right, the vreg im using has an output on the tab. so thats been fixed now, but i still dont think that was part of my probelm, since everything works when the pic isnt in it..

i tired taking out all the MCLR stuff so it doesnt connect to anything, and it still heats up pretty quickly.. im starting to wonder if the chip is destroyed and that causing it to heat up now, or if there is still something wrong..

in the schematic, MCLR is connected through the diode to the resistor and cap. its also connected to the prog pin. i see where you thought it connected to Vdd, but it actually doesnt.. the data sheet i have, its a notes page on page 34. page 35 has stuff about resets and shows the same wiring that i have.

when i etched this board, there is copper on the top too, and some of my pins dont match up perfectly, so there could be a short under the socket. i checked before i soldered, but i could have missed something..

im going to play around with the toner transfer, and see if i can get it any better. if not, i will probably make a new photoetched board.
so changes to the board now are:
vreg tab connected to output,
no more ground planes
MCLR stuff layed out better,
copper pads on top are gone, (except for the top traces)
.01 gap between pads and traces, .02 betweeen traces
more gap between Vdd and standoffs (Vss)

thanks for the comments on the old boards i made.. when i started, i thought the sharpie was the only way to do it, and that it needed sprecial equipment to make boards any other way. the photoetched one, was actually something called RCAP, its an autopilot for RC planes. its an opensource project, and the board layout was straight out of their website. it runs at 2400 baud, so i dont think it will have too many problems with 90 degree corners.

but i will stop typing now and go play with my toner and see what i can do..

[skimask]

i tired taking out all the MCLR stuff so it doesnt connect to anything, and it still heats up pretty quickly.. im starting to wonder if the chip is destroyed and that causing it to heat up now

All of the MCLR stuff? resistor and all?
Chip destroyed - entirely possible it's shorted internally...

when i etched this board, there is copper on the top too, and some of my pins dont match up perfectly, so there could be a short under the socket. i checked before i soldered, but i could have missed something..

I wouldn't throw that board out just yet. There's plenty you can do with an exacto knife, fix-it-jumper-wires, and a soldering gun.

so changes to the board now are:
vreg tab connected to output,
no more ground planes
MCLR stuff layed out better,
copper pads on top are gone, (except for the top traces)
.01 gap between pads and traces, .02 betweeen traces
more gap between Vdd and standoffs (Vss)

Nothing wrong with ground planes, as long as they're connected to ground! It's the unconnected ones that may cause trouble. Also, a big slab of copper under a part also makes an effective heat sink, whether it's connected to ground or not. Good calls on the rest of the notes...

it runs at 2400 baud, so i dont think it will have too many problems with 90 degree corners.

It's not the communications at 2400 baud that you'll have trouble with, it's those signals running at 10mhz+ hitting that 90 angle, causing a reflection, that reflection bouncing back on it's input and possibly pulling an input back low somewhere else, or something this or something that.
Don't forget, just because your PIC is only running 10mhz or whatever, each edge of each signal (square wave) is a small chunk of a wave of a much higher frequency (depending on how fast it rises and falls). The higher the frequency, the worse the problems. Suffice to say, 90 bad, 45 good enough, at least it's worked for me up to about 80mhz.

[dragons_fire]

i needed a little sense of accomplishment, so here it is!! it running off of an 877A with a pololu micro dual serial motor driver..

[dragons_fire]

heres the .PCB file (PCBexpress) of my board as it is right now.. if anyone is bored and wants to take a look and see if they can see anything wrong, let me know...

if you have any suggestions on how to make it better, those would be appreciated too..

i think im going to remake the board.. i like making them, its half the fun..


i had to ZIP it or else it wouldnt let me upload it...


thanks for all the help guys.. i like playing with this stuff until i can get it to work... but this time its getting a little frustrating because i cant really seem to find the problem..

[skimask]

heres the .PCB file (PCBexpress) of my board as it is right now.. if anyone is bored and wants to take a look and see if they can see anything wrong, let me know...

A lot of people, myself included, would be more than happy to have a look-see.
Could ya dump the file as a pdf or some sort of 'standard' file besides that PCBExpress file?

[mackrackit]

Skimask- PCB Express is free and a small download, turn layers on and off, nice program.

Dragonfire- by chance have you breadborded this this yet, at least the parts giving trouble? Looking at your layout now.

[dragons_fire]

well, i was thinking about a pdf, but the reason i left it as a PCB is that it will still have the layers... but here it is as a jpg


i think i will attempt a new board, i just wanna make sure everything is good before i do it...

did you watch the video???