my first PCB Designing problem/confusion. urgent help required.

[Qaisar Azeemi]

Hi;

i have had a confusion when i started pcb designing and made my first pcb. the same circuit that was working on breadboard, or on vieroboard is not working on my designed PCB :-( i am new to pcb designing, My question is that is there any specification with the Routes and lenghts of routs in the pcb layout. i mean should i have to take care with the width of traces and spacing between the traces? if yes then how i come to know that how much width length and other specifications i have to measure for each device?

i have designed a single layer pcb and check the routes many times and also continuity of routes with ohmmeter. and i am using Proteus for design.

Any help will be highly appreciated.

Best Regard;
Qaisar Azeemi

 

[keith1200rs]

What frequency and impedances are involved? If you are working with nA or very high frequencies the I would expect differences but normally it would be the breadboard which doesn't work.

Keith

 

[RetroTechie]

My question is that is there any specification with the Routes and lenghts of routs in the pcb layout. i mean should i have to take care with the width of traces and spacing between the traces?

Absolutely... you should make sure that:

• The voltage drop caused by current through a track doesn't affect the function of your design.
• The current through + track DC resistance doesn't cause a track to overheat / burn up. That is: for average current / voltage. For pulsed currents you can often ignore, but not when pulses last long enough and/or peak currents are very high.
• The distance between tracks isn't so small that electricity will 'jump' to/from a track beside it.
• The impedance of each track is low enough not to interfere with the function of your circuit. That highly depends on the type of circuit you designed.
• Parasitic capacity between tracks isn't too high as to affect the function of your circuit.
• For tracks carrying AC mains voltage (and methods used to connect those to components outside the board), no safety rules are violated.
• Overall you have the shortest possible routing. Possibly with priority given to a few specific connections.
• The overall board surface used is as small as possible to minimize cost(s) of producing a board.
• Components on the board have enough room when everything is assembled.
• Components which get hot, have some space around it to allow for cooling.
• Components which need a heatsink, are located such that this heatsink can be attached.
• Tracks aren't so thin that a 3rd party can't manufacture the board, or (when you do it yourself) tracks disappear in the etch bath.
• Track-track spacing isn't so small that the tiniest speck of dust will cause a connecting bit of copper to remain where you didn't intend.
• There's enough copper around a hole to be able to actually solder components onto (and provide some mechanical support to their wires).
• Etc, etc.

Summarized: just post circuit diagram + layout here, in ordinary graphics format so readers don't need PCB design software installed to have a look (but providing some way to determine physical size of PCB elements), and invite comments. For example in "Hobby circuits" or "PCB routing software" section.

Then other users of this forum will probably tell you where you've gone wrong. ;-)
Expect a number of design changes before everyone thinks the layout is okay...

 

[Qaisar Azeemi]

Thank you very much mr retro;

how can i find the impedance of tracks?

following are the images of my schemetic and layout. it was working fine on bread board but fail to work on designed PCB.