need help double checking schemetic/pcb before build.

Dgswaner

I've been away from propellerism for a while besides that, I have never made a custom board like this before, I'd love a review from someone to make sure I'm not going to smoke my parts.

If your kids watch iCarly you may know what this is... it's a 1x1x6 in. box that has 5 buttons Each button plays a different sound, read from an SDcard. I'm going to test and see if I need an audio amp but for now it's not included.

I would also appreciate a recommendation for a small speaker. Some where in the 1W range, the amp I'll be using (if needed) will be a LM386.

I do realize there is no Propplug connection on the PCB, I'm going to program the IC on a different board.

Thanks for the help

Dave

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DGSwaner

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"When in doubt, use C4" - Jamie Hyneman, Myth Buster

Clock Loop

Having a blinking LED that you can see, to indicate the prop is running, is something more valuable than gold. Also having a fuse in there will potentially save any liquid from frying it all, and perhaps for saftey. (kids)

Just make the pcb, populate it all, and measure the current thru the + battery wire, but measure it with peak mode on, to capture the initial peak turn on spike that your circuit draws. Then do the same when you run your device thru all its possible modes, you will most likely see the peak when you playback some loud, full wave sound. Set your fuse just above your peak!

Rayman

Personally, I always try to use a ground plane... You show pins 9 and 29 connected to Vss, but they don't appear to be connected to each other...

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My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm

Clock Loop

Rayman said...
Personally, I always try to use a ground plane... You show pins 9 and 29 connected to Vss, but they don't appear to be connected to each other...

Hes talking about your pcb file. You have two grounds that are disconnected to eachother.

What are you using to create your pcb?

you should check out www.4pcb.com and download the pcbartist program, its free and will warn you when your doing something like not connecting all 5v / GND traces to eachother.

Phil Pilgrim (PhiPi)

I don't see any bypass caps. You've got a 100nF cap next to the regulator, but it's not doing any good there. You need to put one next to the EEPROM and at least one — preferably two — near the Prop, one at each Vdd pin. This is not optional! PLL failures have been known to occur with inadequate bypassing.

Also, where you have "T" junctions, it's a good idea to add some diagonal copper to "fair" the traces better. In general, inside right-angle corners are bad; not fatal, though. Try to avoid right-angle turns. 45-degree turns are much better.

Once you've corrected the electrical errors, here's how to proof a PCB:

1. Print out both the layout and the schematic.

2. With a yellow overliner, trace the same circuit on both printouts, one at a time.

3. Any errors will become readily apparent, either in the course of doing this, or at the end if you have traces/circuits left over.

-Phil

Leon

The software I use checks the PCB against the schematic, automatically. It also checks the schematic and reports unconnected pins, and so on.

The supply tracks should be a lot wider.

Leon

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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle

Tubular

re the small 1 watt speaker:-

I quite like the ones from CUI, available from digikey. Laptop style.
www.cui.com/catfeatures.asp?catky=638744

tubular

Dgswaner

thanks for all the help, I'm using express PCB, I'll check out the site you recommended. the PCB part doesn't let you check for errors.

the caps by the regulator are there based on a schematic I found. Should I keep C2 and C3?, it's my understanding that they help compensate for power fluctuation on either side of the regulator.

I usually use a ground plane but for some reason I chose not to..... I think I will add it.

I got my schematic from the proto board pdf, I missed the bypass cap, I'll add them in.

thanks again

Dave

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DGSwaner

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"When in doubt, use C4" - Jamie Hyneman, Myth Buster

Phil Pilgrim (PhiPi)

Yes, keep C2 and C3, and leave them where they are, next to the regulator. But move C1 close to the Vdd line on the EEPROM; then add two more 100nF caps near the Prop's Vdd pins.

-Phil

Rayman

Check out this page for some ExpressPCB Prop examples:

http://www.rayslogic.com/propeller/PropPCB/PCB_Boards.htm

PS:· There is a little bit of manual error checking using the route tool...

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My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm

Toby Seckshund

I saw somewhere that the track width to pass 1 Amp for only 10 deg C rise, with the usual 1oz copper, is about 12 mils. I use toner tranfer so that thin isn't really an option. 15 mils for signals and 50+ mils for power rails.

The more decoupling caps scattered, about the better. Definately connect all VDDs and VSSs. The power to the audio amp doesn't have to be regulated and if you did try to use the 3.3v rail then there wouldn't be any drive for a LS without a bridge output stage, and the current would be high.

Leon

I use 25 mil or 50 mil supply tracks for most of my MCU designs with plenty of decoupling and careful layout, and don't have any problems.

Leon

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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle

ElectricAye

Maybe I'm just too tired to think straight, but is your battery hooked up backwards?

Dgswaner

I've made the changes suggested, and I think I'm good to go, I also added the audio amp.

Thanks for any help.

Dg

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DGSwaner

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"When in doubt, use C4" - Jamie Hyneman, Myth Buster

Sapieha

Hi Dgswaner.

First. You have one XTal on SCH but I cant see it on PCB.
Second. Never end traces in any other with angles only in 90 Degres.
Third. Voltage regulator is any IC and all IC's will have in standard one 100nF Decoplings Cap. Old school on Regs is that them will have 100nF on both sides of Regulator for Bypas Transcient/Parasitic high frequencies and on both sides Electrolityc/Tantalum Caps.

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Nothing is impossible, there are only different degrees of difficulty.
For every stupid question there is at least one intelligent answer.
Don't guess - ask instead.
If you don't ask you won't know.
If your gonna construct something, make it·as simple as·possible yet as versatile as posible.


Sapieha

Nick Mueller

There's a pulldown missing for /RES

Nick

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Never use force, just go for a bigger hammer!

The DIY Digital-Readout for mills, lathes etc.:
YADRO

Dgswaner

1st....My bad I decided to just use the internal Xtal. and for got to take it off the schematic.
2nd from my original design I did away with all 90deg corners. are you talking about. when it goes into a component. keep it at 90deg to the part...
3rd are you saying I should have a 100nf Cap on both sides of the regulator?

thanks

Dave

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DGSwaner

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"When in doubt, use C4" - Jamie Hyneman, Myth Buster

Sapieha

Hi Dgswaner.

On 2.
Read atached PDF document on trace building.

On 3.
Yes. Have both Types of Caps. one 100nF on both sides of Reg. and them You have in Yours schematics

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Nothing is impossible, there are only different degrees of difficulty.
For every stupid question there is at least one intelligent answer.
Don't guess - ask instead.
If you don't ask you won't know.
If your gonna construct something, make it·as simple as·possible yet as versatile as posible.


Sapieha

mctrivia

Trace size rule of thumb:

For a 1oz copper board low current(<500mA) signal traces can be 8mil-12mil.

Power traces for 1oz copper:
0-2A - 40mil/A
2-6A - 60mil/A
6-12 - 80mil/A
12-22 - 100mil/A

For 2oz copper divide by 2
For 3oz copper divide by 3
...

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