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Do you guys think about this PCB design? Answered

Here is revision 1 of my PCB. Also is a link to the schematic that is on the PCB design.


https://easyeda.com/editor#id=BLztPfAkw|vUO60iAua


It is a flyback driver based on the LM339 comparator. What is important is that the MOSFET is switched on and off very hard, very fast. audio is AC coupled into the second comparator which sets the PWM duty cycle. Is there any issue with stray inductance or other parasitic bad stuff in the PCB layout? Or any misteaks in the schematic?

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4 years ago

I decided to try making a custom PCB using this current design. The tricky part seems to be getting the wax paper off the copper substrate without damaging the toner transfer. I will try leaving the paper to soak longer than a few seconds next time :P Any tips?

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Downunder35m
Downunder35m

Answer 4 years ago

I have done some experiments with circuit boards and etching.
There are several ways claiming to work great for etching but so far none of them gave me a 100% clean result, meaning that either manually grinding was required to clear tracks or that the finnish simply looked bad.
I managed to overcome most of these problems by printing directly onto the perf board.
Most older laser printers allow for the removal of the back flap sorting the paper transfer - either go out in the back or move around some roller to come out at the top.
If the printer also allows to feed a single shhet directly it is possible to use the copper plated board like a sheet of paper.
For smaller circuit boards I do a testprint first and cut the area in question out of a thicker sheet of photo paper or thin cardboard, like from a cerial box.
The circuit board is placed in the cut out and fixed in placed with sticky tape on the back.
Works great for single sided boards, double sided ones require near perfect alingment though.

The main difference between the normal transfer method and direct printing on the copper is that you always get more pigment to stick to the surface without any risk of loosing parts of it.
I use an antique HP laserjet for this as all I need to remove is the front and back flaps and they can be put back easy to allow normal printing again.

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Answer 4 years ago

I have an old HP laserjet 1200/1300 series printer. It is a tried and true beast. Toner for it is also really cheap :D It only sucks because it is not duplex and only 600dpi instead of the now common 1200dpi. I just got a successful transfer onto the copper clad PCB, so now I will use the HCL+peroxide solution to etch it!

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Downunder35m
Downunder35m

Answer 4 years ago

See, why do it complicated if a direct print is so much easier ;)

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Answer 4 years ago

I don't know how to do a direct print. will I need to mod the printer?