2- IR version PCB Assembly - Bag2

[Tony]

Fit the first plastic IR LED in the space marked D1 as shown. NOTE this is polarised and must be fitted the right way round. There is a flat mark on the side of the LED body,

If you received one BLACK and one CLEAR LED use the BLACK one for D1. The flat side faces to the RIGHT of the PCB when viewed as shown in the photograph.

If you received two CLEAR LEDs (3mm or 5mm) you can use either for D1 but the flat side faces to the LEFT of the PCB when viewed as shown in the photograph.





Take the clear plastic IR LED and bend the leads as shown - the flat mark on the LED body must face away from you when bending them and to the top/rear of the PCB when it's fitted:



Solder it in the place marked for D17. The leads need to be flexible enough to allow it to be pointed out of the case when it's assembled.

[Tony]

Fit the IC sockets SK3 and 4 as shown, making sure BOTH the notches face D8 as marked on the PCB:

[Tony]

Fit IC3 and 4 as shown (the domed black plastic 3 legged block). IC3 is flat against the PCB and IC4 is vertical and faces to the left.

If you received one black plastic and one silver metal sensor, use the metal-cased one for IC4 (the sensor on the left edge of the PCB) and the black plastic one as shown for IC3 (middle front of the PCB). If you received 2 black plastic sensors, IC3 is the one with a cross on the lens.

[Tony]

Fit T12 (the square black plastic 3 legged part), bending the end 3mm of its legs down 90 degrees to fit in the holes. Make sure it lies flat on the PCB and solder the tab on the top first, then the three legs. Some kits may be supplied with a version only having 2 full length legs - don't worry as the tab provides the third connection.

DON'T FORGET TO SOLDER THE TAB! it acts as a heatsink connection to the PCB.

[Tony]

Now fit T13 (2N7000) - it looks the same as T1-11 so was packed in the second bag to avoid it being mixed up. The flat edge faces RIGHT.

[Tony]

V1 ONLY: Now a small modification to the PCB is required. The original plan was to use TCXO modules but the largest SMD devices we could find were still tricky to solder without bridges so the decision was made to revert to a standard crystal. These are 20ppm not 50ppm parts though. Solder X1 (the crystal) into the 2 pads marked above the text 'IC6 TCXO'



V2:



V1 ONLY: Now underneath the PCB solder the 2 ceramic capacitors Cx,y between the crystal pins and the large ground pad:






V1 ONLY: Solder a short piece of wire from the rightmost crystal pin and pin 15 of IC1 (the pad is about halfway between the unused R30 pads)



V2: Fit Cx,y in places C20,21 (marked 22 or 220):

[Tony]

Now that is out of the way it's time to try power for the first time. Connect a multimeter on a current range (about 0-500mA) between the pads where R13 will be - this is just to the right of C8. Connect the + red lead to the topmost pad and the - black lead to the lower pad. Plug in the USB power supply and switch on.



You should have a reading of a few mA which rapidly drops to almost nothing as C8 charges. Switch off and disconnect everything. If the test was OK move onto the next stage, if not check for solder bridges. If there was no reading at all make sure your meter is working and connected correctly. If you PCB bag had a green dot sticker, skip the next part as it won't apply to your PCB.

V2 ONLY: There's an option to allow either IN-14 or Z570 nixies to be used on these PCBs, for this clock you need to make the following mod to select IN-14 nixes. Consider these 4 holes to be in the pattern

1 2
3 4

Using a small screwdriver or drill bit, carefully remove the through hole plating from holes 2 and 3 by 'drilling' through them, breaking the connection between the top and bottom tracks. If it's not done correctly the decimal point and '8' will both light up together.

[Tony]

Fit IC1 (PIC 16F1827) and IC2 (KM155ID1) into their sockets (you'll probably need to trim about 1/8" off the leads of IC2) and reconnect the multimeter and USB supply. Make sure both notches point towards D8, IC1 is 'upside down' relative to IC2.



This time the current reading should be about 20-25mA and the 5 blue LEDs will light up, flickering slightly.



I cheated a little, it's being powered from a bench supply.

If it's reached this stage you now know the CPU is running and the crystal mod worked.

Now test the IR detector is working - hold your hand about 6" above the clock for a few seconds - there should be a beep and LED D3 will go out. If not try using a phone camera to view D1 to make sure it's lighting up. If it's not, check you have it fitted the right way round. You may need to temporarily fit the piece of heatshrink sleeving over LED D1 for it to work.