Hi,
My first post and my first PCB design. What is the best image type file to post on this forum so I can get some advice on the PCB layout and the circuit design?
Thanks
Your best bet is to upload the sketch (the .fzz file, upload is 7th icon from the left in the reply menu.) That gives us the complete sketch to check over.
Peter
Yep, it worked fine. Your circuit passes DRC (in pcb view Routing->Design Rules Check) so should be fine I expect. You could eliminate the via by routing that trace on the top layer but it shouldn’t really matter that much.
Peter
Thankyou for that. Next test is getting the board manufactured.
It should be OK, assuming the connections are correct. I’m a little concerned that one of the parts (looks like the MK42D Interface) has unusually small holes:
(this is from the gerber drill.txt file.) T101 is likely the via and should be small, but T108 which looks to be the MK42D is only 0.028in which is fairly small (an IC is typically 0.030in for comparison.) The Pololu A1 that it appears to be based on has 0.030 holes so it may be OK (a 0.1in header has a 0.038in hole typically.)
; NON-PLATED HOLES START AT T1
; THROUGH (PLATED) HOLES START AT T100
M48
INCH
T1C0.086614
T100C0.035000
T101C0.015748
T102C0.038194
T103C0.030000
T104C0.031497
T105C0.036000
T106C0.037639
T107C0.042000
T108C0.027559
T109C0.040000
Other than that the gerbers look fine (displayed here in gerbv)
Peter
I used the polu board to get the pin spacing as the interface board is a substitute for the motor control board (the stepper motor has a controller attached to the motor so it has an adapter connection instead). I will be using female header pins to plug the interface board in to so I assume the header pins will need to have 0.030in holes so I will change them to that.
Ooops. I should have asked how I edit the hole sizes.
thanks.
PCB TT version 2.1.fzz (22.9 KB)
I made some changes to the arduino pins in the code so the via hole is now removed. I still need to edit the hole sizes for the interface, how do I do that?
John
To edit the hole sizes you generally need to edit the part (which isn’t easy.) If you need a header you are likely best to replace the motor driver with a header from core parts like this:
the header will have the appropriate 0.038in holes by default (and save you some space on the board.)
Peter
PCB TT version 3.1.fzz (23.4 KB)
Modified as advised. Thanks Peter. I am waiting for the stepper motor to arrive from China. When it arrives I will need to check the spacing of the plug board pins against the headers position. Can the Fritzling system produce a 1:1scale printout of the PCB?
John
Yes, export as an image should do the trick I believe. .
Peter
Printing via “File → Print” should do it. It will either produce a PDF or directly send it to your printer, depending on your system settings. If it is not to scale (and your system does not apply any additional filters, like printing two pages on one) then this would be a bug.
Hi, I have modified the design further but I have a problem with the schematic. The diode at D1 is as per the circuit I have taken from a working example on the internet which is accepted as the standard method of taking a DCC signal to an Arduino. The problem is that the connecting lines are non polarised as the DCC system supply switches like an AC supply even though it is DC. So the schematic produces ratlines that are not correct and if I delete them the tracks on the PCB also get deleted. I cannot find a non polarised connector on the parts list which would solve this issue . Is there a way around this?
This what I want
This is the pcb with crossing track connections that I would like to not have crossing.
If I change the tracks on the PCB to non crossing it defaults to the schematic I posted previously
The best bet is for you to upload the sketch (the .fzz file, upload is 7th icon from the left in the reply menu) so we can see the actual circuit in Fritzing and see what may be wrong. Pictures are basically useless to diagnose problems. That said I expect you have diode D1 reversed in either the breadboard or pcb views and those connections have reflected as rats nest line in schematic from the error in the other view.
Peter
That PCB does not seem to have crossing traces. The one trace color is on the top of the board, the other on the bottom. To see one at a time, you can turn off display of the other.
I uploaded the standard design schematic for a DCC signal input circuit (by Dr. Geoff Bunzig) above in a previous post. The Fritzing schematic follows exactly that design for the diode (I think) and it is the fritzing schematic that wants to add ratlines where there should not be ratlines. I have tried reversing the diode on schematic and pcb but the problem just moves to a different point which is why I have ended up with the PCB as it is now. The PCB layout should follow the fritzing schematic. I think I have the diode on the pcb and on the fritzing schematic as it should be in accordance with the standard design DCC input signal circuit.
The issue is the connector blocks are polarised and the DCC input signal is not even though it is a “DC” input. When I measure DCC voltage I have to set my multimeter to alternating DC otherwise I get half the true voltage indicated. This is standard for a DCC system as per the NMRA standard for DCC. A single pin screw connector component would solve the issue but I can’t find one in the fritzing parts list. There must be a single pin screw connector available?
The bottom line is to remove the two pin screw connector component and just leave the through holes but that is not very elegant.
Here is the uploaded .frz file.
PCB TT version 3.5.fzz (39.8 KB)
Hi microMerlin. The crossing traces on the PCB are fine and will work. But they need not be like that. Having the traces like this is the only way I can get rid of unwanted ratlines on the schematic as the connector is polarised and the input is not. The circuit I am recreating from Dr Bunza has non polarised DC inputs.
I can live with if there is no practical solution available it but there must be a better solution and there must be single pin connectors available that would solve the polarisation issue.
