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Double Check my PCB for me please!

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coillah

Sun Jan 11 2009, 04:14AM

Registered Member #1517 Joined: Wed Jun 04 2008, 06:55AM
Location: Chico CA
Posts: 304

Hey guys, this is my first PCB. I am going to use FeCl to etch after ironing on the pattern with magazine paper.

Can you double check my schematic and pcb design and tell me if I did anything newbish?

Myke

Sun Jan 11 2009, 04:28AM

Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969

There is no schematic to compare it with...

aonomus

Sun Jan 11 2009, 04:34AM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

From the looks of it, its a 74hc14 based SSTC driver, that is my best guess. I'd have to comment that if you haven't etched boards before, you may want to increase the gap between ground plane and traces.

Also, consider adding mounting holes so you don't haphazardly mount your board...

And from personal experience, the 7812 regulator will need a heatsink absolutely (the 74hc14 draws next to no power, but the 2 UCC's draw a ton of power). Look at what heatsinks you have and plan the space accordingly. I believe that the tabs are connected to ground which will make heatsinking easy (ie: both can be grounded together).

rp181

Sun Jan 11 2009, 04:45AM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529

I would move the bottom trace farther away from the edge of the board.

Arcstarter

Sun Jan 11 2009, 06:21AM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

I must agree with aonomous, but the heatsink need not be too terribly big, depending on your input voltage.

Go to about 18 seconds to see the heatsink i used. I was using about 12.4(wayyyy too low) into the 12v regulator(still came out to exactly 12v) and it was a 500ma regulator. And, the dc blocking cap i used for the GDT sucked, and i had the wrong core, and the ucc's heated up much more than the tiny heatsink. After that video, the heatsink was a tiny bit warm, but not enough to cause any worry even for longer runs.

coillah

Sun Jan 11 2009, 06:50AM

Registered Member #1517 Joined: Wed Jun 04 2008, 06:55AM
Location: Chico CA
Posts: 304

Myke you're absolutely right!

I forgot to upload the schematic and because it is on another computer I wont be able to do so.

For those who cant tell, this is the exact circuit for the Steve Ward Mini SSTC driver. (well maybe exact)

here's a link to the schematic (everything up to the half bridge):
Schematic

I have a few left over heat sinks from some scrap projects, I will use those for the regulator.

Thanks for the tips, anything else?

Myke

Sun Jan 11 2009, 08:18AM

Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969

You should probably tie the inputs of your other unused gates to the positive rail (I think that's what you are supposed to do because I think that they draw more current if they are tied to ground).

HV Enthusiast

Sun Jan 11 2009, 12:29PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

You have to rework the ground plane. The worst thing you can is break-up the ground plane. Try desiging your board so the ground plane is pretty even across the entire board. Also, the ground plane gets really necked down between the big caps on left and your components on the right.

Also, for optimum performance, as i said before, you don't want to break-up the ground plane which you are doing with all those long traces in the middle of the board. Your better off making the board mostly ground plane and using wires to make those long trace connections as opposed to actual traces. This would be optimal for a single-layer board.

cjk2

Sun Jan 11 2009, 03:57PM

Registered Member #51 Joined: Thu Feb 09 2006, 04:17AM
Location:
Posts: 263

You need thermals.
Don't leave the unused inverter gates floating.
The top of your board is at a funky angle.
Most if not all of your traces are way oversized.

coillah

Sun Jan 11 2009, 05:58PM

Registered Member #1517 Joined: Wed Jun 04 2008, 06:55AM
Location: Chico CA
Posts: 304

OK whew that's a lot of stuff guys! I am actually signed up for a digital systems design course this next semester, so this is all very new to me.

You should have seen the first mock up I did, my signal traces were running all over the place. XD

As far as components go, do I have the right idea?

- I am going to put a heat sink on the back of the regulator.
- all I have are 2 sided PCB's should I make the top side the ground plane and run the traces for everything else on the bottom? I am having trouble visualizing how I am going to solder some of the components without bottom traces.
- vias, I take it you need to fill these with solder when the board is complete, otherwise how do you get a connection?
- are the power traces thick enough? I am going to downsize the signal traces and try to run them in one direction.
- i read up a bit on tying down the unused inverter gates, I will add 1k resistors to the inputs and tie them to the Vcc outputs I will leave alone

thanks guys!

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