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Step 5Construction hints and tips
This project is for experienced people only, the trackwork is very fine and the spacing of the components is very tight.
Because the tracks are very fine, you need to use a temp controlled soldering iron with a fine tip. If you make a mistake, use solder braid and suck up excess solder first, then move the problem component. Be very careful not to lift any tracks, this is a real possibility with tracks this small.
First etch and drill the board using whatever method you are comfortable with. I used the press'n'peel technique successfully. I suggest making multiple copies of the board artwork on your PCB and picking the one that prints the best image before etching.
Use a 0.5mm drill for drilling, the vias are very small and do the vias first. There are no through hole components but there are a few vias. Be careful not to short any tracks.
Note that some vias are inbetween LEDs and one is under a switch. Not a problem if you are using through plated boards, however doing it by hand you may need to trim the result with a scalpel to make the connection between the sides of the boards flat enough. Have a look at the pictures in this section, note the vias in-between the LEDs.
After doing the vias, check with a multimeter that the via is connecting. Use the multimeter on a connecting track, not the via itself.
Now install the LEDs and driver resistors on the top of the board, be careful to note the orientation of the LEDs from the cad files, they are not in any particular order. Check that the LEDs are not butting up too close to a via, and trim the via with a scalpel if you need to get a closer fit.....be very careful to wipe away anything removed with the scalple as it may cause a short later on.
With a voltage around 3.5 volts from a bench supply or a battery test each combination of charlieplex control lines and make sure that each LED lights individually and that there are no missing or multiple LEDs lit up. If you have, then there is a track being shorted or broken.
Now install the SMD switches.
Once you've checked the LED array is correctly you can start on the bottom side. There is much more space on the bottom side and if you can solder in the PIC, nothing else should present any problems except for the crystal. See the sub picture in this section. The crystal overhangs another track by a little bit, when installing the crystal, ensure that it doesn't touch this and is raised a bit. The modified PCB artwork in microdot2.zip should have less of an overhang.
Also note the omitted resistors and wire links in this picture. These are properly layed out in the second revision of the artwork.
Double check no shorts between pins on the PIC or other components.
Connect wires to the power supply pads and check that the PIC gets power. The cct has a diode dropping 6V to 5.4V (approx)....for an initial test, don't crank it up to full power.
Now connect the ICSP wires to whatever ICSP programming adapter you are using.
Because the tracks are very fine, you need to use a temp controlled soldering iron with a fine tip. If you make a mistake, use solder braid and suck up excess solder first, then move the problem component. Be very careful not to lift any tracks, this is a real possibility with tracks this small.
First etch and drill the board using whatever method you are comfortable with. I used the press'n'peel technique successfully. I suggest making multiple copies of the board artwork on your PCB and picking the one that prints the best image before etching.
Use a 0.5mm drill for drilling, the vias are very small and do the vias first. There are no through hole components but there are a few vias. Be careful not to short any tracks.
Note that some vias are inbetween LEDs and one is under a switch. Not a problem if you are using through plated boards, however doing it by hand you may need to trim the result with a scalpel to make the connection between the sides of the boards flat enough. Have a look at the pictures in this section, note the vias in-between the LEDs.
After doing the vias, check with a multimeter that the via is connecting. Use the multimeter on a connecting track, not the via itself.
Now install the LEDs and driver resistors on the top of the board, be careful to note the orientation of the LEDs from the cad files, they are not in any particular order. Check that the LEDs are not butting up too close to a via, and trim the via with a scalpel if you need to get a closer fit.....be very careful to wipe away anything removed with the scalple as it may cause a short later on.
With a voltage around 3.5 volts from a bench supply or a battery test each combination of charlieplex control lines and make sure that each LED lights individually and that there are no missing or multiple LEDs lit up. If you have, then there is a track being shorted or broken.
Now install the SMD switches.
Once you've checked the LED array is correctly you can start on the bottom side. There is much more space on the bottom side and if you can solder in the PIC, nothing else should present any problems except for the crystal. See the sub picture in this section. The crystal overhangs another track by a little bit, when installing the crystal, ensure that it doesn't touch this and is raised a bit. The modified PCB artwork in microdot2.zip should have less of an overhang.
Also note the omitted resistors and wire links in this picture. These are properly layed out in the second revision of the artwork.
Double check no shorts between pins on the PIC or other components.
Connect wires to the power supply pads and check that the PIC gets power. The cct has a diode dropping 6V to 5.4V (approx)....for an initial test, don't crank it up to full power.
Now connect the ICSP wires to whatever ICSP programming adapter you are using.
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