What do you think of my PCB design?

[shodan]

shafri, I'm not sure if this is still true but I think the printer head comes with the cartrige in epson printers
if it's still true, then we could try different inks (by drilling the tank, draining it and injecting new ink in it)

even better than whitesilkscreen I was thinking of applying green soldermask and conductive ink (to make conductive through-holes )

also I think I will just mod a HP printer instead because I don't want to be limited to 3.5" wide pcbs

[Mechatrommer]

even better than whitesilkscreen I was thinking of applying green soldermask and conductive ink (to make conductive through-holes )

great idea! if this is achievable, no more messing with toner transfer and etching the copper. and no more need to send to remote pcb maker.

[lamja]

A little update.

- First power on with no load => no smoke...
- Power on with load => shorted out power supply 

I found one MOSFET burnt in the h-bridge, but changed all 4.
Then I tested some more with a lot of 2.2 Ohm resistors on both load and input for the h-bridge.. with lots of smoke 
After a lots of hours testing, I found that I had mounted one diode the wrong way. Even though my silk screen was correct...

But anyhow. its seems to be working good for now, but I had some problems with noise. Then I put 2 capasitors on the supply for the opamp, and the noise almost dissapeared.

What is the best way using capasitors for a double rail opamp? Two from ground, or from + to -?

Should these be as close to the opamp as possible?

[allanw]

But anyhow. its seems to be working good for now, but I had some problems with noise. Then I put 2 capasitors on the supply for the opamp, and the noise almost dissapeared.

What is the best way using capasitors for a double rail opamp? Two from ground, or from + to -?

Should these be as close to the opamp as possible?

One 0.1uF cap on each rail to ground. These should be as close as possible to the op amp. You'll also want a larger capacitor near the op-amp if you need to drive a higher current. If you look up op amp layout, you'll find lots of application notes that discuss this in much detail.