Mirroring the ExpressPCB print out

ExpressPCB is a free and easy to learn PCB drawing cad software for hobbyist, many simple circuit application do not required complicated software such as protel PCB, primarily because numerical control automation make use of gerber file is not required.

But the problem for many user that want to make their own simple PCB is that they need a mirror print out to properly done with iron on transfer or photo resist, the printed side need to be in contact with the circuit board to achieve the best result, especially when using a transparency as photo resist, closer contact possible will make fine line as there are very limited gap for scattered light beam.

The print out can in fact be mirrored by printer setting if you do have one of this option in your printer preference. But if you don't have one, you can make use of the Windows XPS Document Writer, I found out that it was pretty easy to mirror XML drawing script. It describe exactly the pattern of the print out by script not pixel, up to capability of 600dpi.

1. Print the layer you want out by choosing Windows XPS Document Writer as your printer, mind the paper size you choose, A4 is by default, this must be the same as your printer setting for paper size.

2. Rename the print out from .XPS to .zip

3. Extract all file, in the extracted folder look for file 1.fpage in directory drive:\your extracted folder name\Documents\1\Pages\1.fpage

4. Mirror all the value of x coordinate in the file, that will mirror the entire print out. Example:

FixedPage Width="816" Height="1056".....
Path Data="F1 M 302.4,436.8 L 513.6,436.8 513.6,619.2 302.4,619.2 z"  Fill="#ff000000" /

The path data describe a filled rectangle, 302.4, 436.8 is coordinate as (x,y), just modify (can be done with computer program) all x such that:

newX = Width - oldX

The scripts will look like this after modified:
Path Data="F1 M 513.6,436.8 L 302.8,436.8 302.8,619.2 513.6,619.2 z"  Fill="#ff000000" /

Basically XML drawing script use to describe those simple image is just line and rectangle, round pad is describe as a line in revolution, all it need is just coordinate information to describe where to draw the item.

5. Rezip the extracted folder with modified contain back to .zip and rename it back to .xps, I found out that rezip using winzip won't work, right click add a new zip file and drag everything into the zip file do work very well indeed.

6.Open the modified .xps file with xps viewer or internet explorer, at the menu click print and you will have a mirrored image print out.

Alternatively this may also work with Microsoft Word image writer, but the procedure may be different or easier.

4-Pin to 3-Pin CPU Fan V2.0

I have written an blog entry about a heat sink fan unit that come with 3 pin fan where there are 4 pin connector on the motherboard, here.

I have replaced two stop working casing fans to new quality fans, previous casing fans die of lack of grease and rusted. But the new fans is noisy too, so I decided to tie the new casing fans to CPU PWM control.

Picture below show the signal from PWM pin-out of CPU fan socket:

It is ~23.5kHz control signal. Sometime, it take forever to hesitate but it only take one day to complete a not so difficult task.

I know the components used is overkill and not having optimized rating, especially the 100uH 2A inductor, fan won't required 2A, at 23.5kHz 5V output all it need is ~300uH 0.5A, but that is what I have in my hand currently. Without the inductor+capacitor filter, it still work but the rpm signal from fan will be significantly interrupted and there will be some weird reading like 11500 rpm.

Side view of control board showing that it connect to 3 fan. But it only take the rpm signal of CPU fan and feed it back to motherboard.

Integrated graphic

This is some story about integrated graphic processor in north bridge or center processor. Not every day people will think integrated graphic is good and important. Most people will use another PCI-E graphic card to boost 3D graphic performance or video processing, why do we still need to have an integrated graphic?

I once thought that it was a wasteful use of resource to assign more silicon die area for this dumb device, especially when I saw intel integrate those graphic processing unit into their center processor. But I do realize that there is a fact nowadays, graphic card getting more easy to malfunction as the power consumption of it increase over time but their heat sink remain the size of about 2 PCI slot.

I have never seen a CPU malfunction so far, but I do getting few chances to know or witness the malfunctioning of modern graphic card. Therefore I guess modern 3D graphic card required better heat dissipation, such as proper air circulation and more clear space for air, this is what unlikely to occur on most desktop or laptop design.

I experienced a malfunction of a graphic card before, at the moment I really needed the computer to do some important task for me. Thank to the integrated graphic, and fortunately thing was done in time. And I realize, having integrated graphic isn't a bad idea because modern 3D graphic chip just isn't very reliable.