Author Topic: New "Next Generation Speech Synthesizer" for the CPC 464  (Read 18401 times)

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Offline LambdaMikel

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Re: New "Next Generation Speech Synthesizer" for the CPC 464
« Reply #375 on: 06:33, 16 March 19 »
One thing I could try is fill also the front with copper - for VCC.Two negative things I read related to that are:
  • increases the chances of unintended shorts
  • makes soldering hard, because the copper absorbs a lot of heat
Well I ordered 3 of them by now and I believe if they should not work, then this is probably caused by issues unrelated to VCC, GND, or capacitors (after all, the breadboard prototype had MUCH WORSE electrical properties, and was working fine). We will see.

Sure thing, I can add the VCC copper pour. Or make the traces even wider by hand, even if that should not really be necessary. For the next batch.

But then, I also don't know how much I can trust these websites (see above) that do the trace / track width calculation for you.
So, what is wrong with the decoupling capacitors? Not close enough to the chips in your opinion?
« Last Edit: 06:41, 16 March 19 by LambdaMikel »

Offline Bryce

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Re: New "Next Generation Speech Synthesizer" for the CPC 464
« Reply #376 on: 16:51, 16 March 19 »
I used this one to calculate VCC width - I am not drawing more than 600 mA  ;)

http://circuitcalculator.com/wordpress/?p=25/

What tool are you using?


So, just for the record - with the Oshpark 1 oz/ft^2 copper weight for the 2 layer prototype board, I can draw 850 mA of current and still be under the VCC width of the 9.84 mils... (this would be for 0,25 mm - I even used 0,30 mm). I appreciate your concern though.

In general, I must say that I trust the autorouting of a tool that is aware of the design rules (rather than guessing constraints) more than the hand layout of a hobbyist. Sure, Bryce's team is a different story (those are professionals, I am not).



IPC-2152 (the industry standard guidelines) says that a 0,3mm trace can carry 630mA with a trace length up to 250mm, so you should be fine.

Bryce.

Offline Bryce

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Re: New "Next Generation Speech Synthesizer" for the CPC 464
« Reply #377 on: 17:00, 16 March 19 »
Use this for your calculations: http://www.saturnpcb.com/pcb_toolkit/

Bryce.

Offline LambdaMikel

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Re: New "Next Generation Speech Synthesizer" for the CPC 464
« Reply #378 on: 17:32, 16 March 19 »
Use this for your calculations: http://www.saturnpcb.com/pcb_toolkit/

Bryce.
Thanks for the link! Will check it out.

One more question - do you recommend VCC copper fill, or not worth the hassle?
(Heat absorb -> difficult soldering, chances of incidental shorts increased)
« Last Edit: 17:34, 16 March 19 by LambdaMikel »

Offline Bryce

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Re: New "Next Generation Speech Synthesizer" for the CPC 464
« Reply #379 on: 18:32, 16 March 19 »
No, a VCC plane is pointless on a device this small and with only two layers. VCC planes only make sense on devices that have regular big and sudden current changes and a free layer for VCC alone.

Bryce.