Help to design a PCB for my PI design!

[1843]

Grounds are separated...

[Qiaozhi]

Here's the main changes I'v done on it:


Two opamps are used, so one has a lot of choice... AD797, AD8055, etc etc
As you see the 7660 is synced.

Any comment ?

The power supply looks much improved.

[1843]

The main changes I'v done:



Two opamps are used, so one has a lot of choice... AD797, AD8055, etc etc
As you see the 7660 is synced.

Any comments ?

[1843]

OK - I note that you've already tried that as a solution, but the ATMega8 keeps stopping due to the voltage drop.

I'm modifying the schematic at the moment...
By using a P-MOSFET and changing the 7660 task, all the noise problems will be solved.

Kind regards,
1843

[Qiaozhi]

It doesn't have the noise problem, because it's synced.

OK - I note that you've already tried that as a solution, but the ATMega8 keeps stopping due to the voltage drop.

[1843]

Have a look at the power supply on the Hammerhead II ->

http://www.geotech1.com/forums/showthread.php?t=14940

It is very similar to your previous power supply. Perhaps it will have the same noise problems.

It doesn't have the noise problem, because it's synced.

[Qiaozhi]

Have a look at the power supply on the Hammerhead II ->

http://www.geotech1.com/forums/showthread.php?t=14940

It is very similar to your previous power supply. Perhaps it will have the same noise problems.

[1843]

Here's a programmer you need... including sch, PCB layout, Ponyprog fuses...

AVR-ISP.zip

Sync 7660 ; pin 7 to PB1 through some buffer.

[1843]

Hi all,

After a lot of experiments... the schematic was updated:



Because of using LP filters, the 7660 noise is reduced more than 50%.

Now you only need a PCB to build this PI.

Kind regards,
1843

[Qiaozhi]

When using 78xx or 79xx, i always add 100nF Capacitors at Input and Output.
Without them, i get low Output Voltage or the Thing starts Oscillating.

That's a good point. I always do the same.
In fact the datasheet states that the capacitor on the output improves stability and transient response.

[Götz von Berlichingen]

When using 78xx or 79xx, i always add 100nF Capacitors at Input and Output.
Without them, i get low Output Voltage or the Thing starts Oscillating.

[1843]

I found the problem of the instability.... 79L05...
It's very late here I cannot stay awake anymore...

...

[Qiaozhi]

Yes, I used a bench supply instead of the 7660. The noise faded away.But still the PI is somewhat instable even without coil.

The noise of 7660 doesn't affect the performance much. It's constant and averages out by the software.

The instability at the moment is most likely due to the PCB. I still need some more experiments...like disabling the sound...

Best regards,
1843

Could you try adding a small wire jumper between pins 8 and 22 on the micro to improve the connection between the two ground pins?

[1843]

Yes, I used a bench supply instead of the 7660. The noise faded away.But still the PI is somewhat instable even without coil.

The noise of 7660 doesn't affect the performance much. It's constant and averages out by the software.

The instability at the moment is most likely due to the PCB. I still need some more experiments...like disabling the sound...

Best regards,
1843