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Topic: PCB design: Final step project (Read 1 time) previous topic - next topic

DragoslaV

Mar 18, 2012, 07:43 pm Last Edit: Mar 18, 2012, 07:45 pm by DragoslaV Reason: 1
Hello all,

I'm making my first PCB and I was hoping someone could help me with looking for any possible (noob) mistakes.

I'm trying to make my phone communicate with an ArduinoBT module on my motorcycle with bluetooth. Sofar I have made my schematic, applications and already tested the components with a breadboard. However to make everything small I wanted to make a breakout board. So I downloaded the Eagle files from the Arduino site and modified it to my own.

In a nutshell the functions I want:
1) Read with 8 opto-coupler if a motorcycle circuit is on (i.e. blinkers, fuel, alarm, warnings)
2) Send GPS speed to arduino and control 5 RGB led's.
3) Control the alarm/key's and engine with relay's. (i.e. turning engine on, or turning alarm on/off)

Components:
- 1x DE-SW050: 5v regulator (convert v12 into v5 for ArduinoBT)
- 1x CD4051: 8-ch. multiplex
- 8x PC817: Opto-coupler (note: actual its 2x PC847)
- 1x D-sub connector
- 8x 1k resistors
- 5x 68ohm resistors
- 1x 33ohm resistor
- 1x 12ohm resistor

The files:
- Schematic.
- Reference PCB image.
- Top layer PCB image.
- Bottom layer PCB image.
- Eagle file.

Thanks in advance any help !  :smiley-sweat:

dbvanhorn

The voltage regulator you are using is not nearly robust enough for vehicle power.  The "12V" power is very dirty and has large transients.  The good news is that there are three terminal regulators that will work in that circuit, which are automotive rated. 

Check on Digikey for automotive regulators.

MushfiqSarker

You need to make your POWER and GND traces much bigger in size. It seems like it is 10mil or 12mil right now. Make them bigger as that is the industry practice and it can handle more current that way.
Check out my site for DIY information: http://inventige.com

DragoslaV

@MushfiqSarker,
Thanks, all lines was indeed made with 12mil. I changed all the lines that have 12v running through it to an 32mil width. I hope that's better now.

Front PCB image.
Back PCB image.

@dbvanhorn
Ouch, that sounds like a serious flaw, I'm a noob to circuits (glad I got sofar :)) and I tried searching for the components on digikey but I couldn't find what you mentioned, any help for me there?

VccDood

You're going to run into problems with soldering Y0, Y1 and Y3 (and a bunch of others).  The spacing looks like it will fail the bot checks at the pcb houses and will be nearly impossible to make that fine a pitch at home with toner transfer or photo-resist.

Also, is there a reason for not using a ground plane instead of ground traces?  Creating a ground plane would simplify the design and provide a more robust circuit IMHO.

VccD


Chagrin

@dbvanhorn
Ouch, that sounds like a serious flaw, I'm a noob to circuits (glad I got sofar :)) and I tried searching for the components on digikey but I couldn't find what you mentioned, any help for me there?


I don't think any of the component sites allow searching for automotive-rated components, but you can just google for "linear regulator automotive" and get tons of hits on manufacturer sites.

The DE-SW050 is a switching regulator; while it'd be much more efficient than a linear regulator it's pretty pricy and really not warranted here with the low currents you'll be seeing.

Add a decoupling capacitor to your multiplexer IC.

To create a ground plane in Eagle use the polygon tool; draw a rectangle along the edge of the board. Right-click on the line and set the name to "GND". It won't look like it's filled in but you can click "ratsnest" to make it visible or of course you can look at the resulting files with a Gerber viewer after running the CAM processor.

Did you verify the amperage requirements of the coil of your relays that they are under 40ma? If not you'll need a transistor.

DragoslaV

#6
Mar 21, 2012, 12:19 am Last Edit: Mar 21, 2012, 12:23 am by DragoslaV Reason: 1
Thanks for the help there VccDood and Chagrin! I'm going to do a redesign, including a ground plane and more spacing. I watched a youtube video on it and I was quiet embarrassed how easy it is! :)


I don't think any of the component sites allow searching for automotive-rated components, but you can just google for "linear regulator automotive" and get tons of hits on manufacturer sites.

The DE-SW050 is a switching regulator; while it'd be much more efficient than a linear regulator it's pretty pricy and really not warranted here with the low currents you'll be seeing.

Add a decoupling capacitor to your multiplexer IC.

To create a ground plane in Eagle use the polygon tool; draw a rectangle along the edge of the board. Right-click on the line and set the name to "GND". It won't look like it's filled in but you can click "ratsnest" to make it visible or of course you can look at the resulting files with a Gerber viewer after running the CAM processor.

Did you verify the amperage requirements of the coil of your relays that they are under 40ma? If not you'll need a transistor.



I already have the DE-SW050 laying around, catching dust. Al through its not really warranted, it handles the job right? it also saves me from soldering more components to my breakout board 8)

I quickly made a new schematic for the breakout board. Did I placed the capacitors correctly like you meant to?

Once again thanks for the explanation! As you can see it the schematic; I already named everything with GND. This is going to make it a bit easier :D

Yes the relay's are safe to use, thanks for verifying that.

Chagrin


I already have the DE-SW050 laying around, catching dust. Al through its not really warranted, it handles the job right? it also saves me from soldering more components to my breakout board 8)

You might contact DimensionEngineering and ask if the regulator is suitable for use on a motorcycle. Aside from crossing your fingers and hoping it works it'd be the best way to find out. Also, since you seem to have enough space on the board, it wouldn't hurt to add a couple places for caps on both sides of that regulator as if you were using a typical linear regulator. You've got a fall back position then.

I quickly made a new schematic for the breakout board. Did I placed the capacitors correctly like you meant to?

Yes. Try to keep those caps as close to the IC as possible. Again after testing your board you might not find them necessary ... but you've got that fallback position.

DragoslaV


You might contact DimensionEngineering and ask if the regulator is suitable for use on a motorcycle. Aside from crossing your fingers and hoping it works it'd be the best way to find out. Also, since you seem to have enough space on the board, it wouldn't hurt to add a couple places for caps on both sides of that regulator as if you were using a typical linear regulator. You've got a fall back position then.

Yes, you're so right, crossing your fingers and hoping is something I really don't want to do! And there is nothing to learn from it except trail and error. I contacted DimensionEngineering and I got a very quick response (within 2 hours):

"No problem!  We have lot of those in use in cars/motorcycles.  What's nice about the units in that application is they already have capacitors on the input and output... No need for further filtering."

I guess this solves this issue now. Thanks for the help on this :)

Yes. Try to keep those caps as close to the IC as possible. Again after testing your board you might not find them necessary ... but you've got that fallback position.

Once again thanks, no thank you a thousand time :) I will put the capacitors as close as possible. When I did my redesign I will post the new PCB files here. I hope you have some time by then to watch it.

DragoslaV

Ok, here I am again guys  :smiley-fat: I really know I have more 'space' to use but I try to keep everything as compact as possible. I also downloaded the Eagle DRC rule from the PCB housing and it returned with no errors.

Did I used the ground planes right? I starred to my design for 2 hours now and I think everything is grounded now..
@Chagrin, did I placed the capacitors properly??
@all, any another mistakes?? or comments??  8)

- Schematic.

- New front PCB
- New back PCB

DragoslaV

Anyone has any comments, or is it ready for the PCB housing?  :smiley-roll-blue:

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