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Build Instructions, Page 5 / 5

Looking for shorter instructions? Look no further. We’ve prepared a shorter page with the suggested soldering order.

Step 11: Insert Processor Chip

Chips in DIP form usually have legs that are bent out too far to fit easily into sockets. One way to slightly (but uniformly!) bend the legs in is to press the chip against a table as shown in the photo. Insert the chip into the socket, taking care to get all the pins aligned in their holes. Make sure to put the chip in the right way! The notch in the chip lines up with the notch on the board, and the notch in the chip socket (if you aligned the socket properly!).

Carefully bend the chip leadsPIC16F685, 20-DIP Package


Step 12: One Last Test

The most common issue that can affect your Tap-Temp Metronome is bad solder connections. After you solder on the battery holder to the back of the PCB it becomes really difficult to troubleshoot and touch-up all the solder joints on the back of the PCB, so we should test the Metronome before attaching the battery holder. Put the batteries into the battery holder and stick the leads through the holes. Twist the battery holder slightly so the two leads make good, solid contact with the holes. Flip the power switch to ON and you should hear a beep and see “r22” (or some other number) on the seven-segment displays. This confirms that the piezo output and the displays are working correctly. Try tapping the piezo with a pen or pencil a few times. The digits should flash brighter when each tap is detected. After tapping a couple of times, wait two seconds and the metronome should start beeping at the same tempo you used for the input taps. This confirms that the tap detection is working correctly. While the Metronome is playing back your tempo, use the up and down push buttons to adjust the temp. This confirms that the buttons are working correctly. If everything works correctly, continue on to the next step and solder down the battery holders. If things aren’t working try re-melting the solder on the relevant connections. If any of your solder joints are not shiny and clean and smooth, try re-melting them and add just a tiny amount of extra solder to clean it up.


Step 13: Battery Holder

The battery holder is going to attach to the board with sticky foam tape, and also be soldered. In the previous step you should have trimmed off any component leads that were too long, so take a look at your board’s underside to make sure all the leads are trimmed down. Your battery holder may or may not already have the foam tape attached. If the piece of foam tape is not already attached, remove one side of the paper backing and firmly press the sticky side to the back (flat side) of the battery holder.

Foam tape on battery holderCheck for too-long leads

Remove the paper backing from the foam tape on the battery holder, and insert the leads of the battery holder through the back of the holes in the PCB and slowly press the battery holder against the PCB. Be firm, but be careful not to warp the battery holder by pressing unevenly. Solder the leads. These may take a little longer to solder–the thick leads can require a lot of heat. Clip the leads.

Insert leads of battery holder through PCB from the backPeel-off paper backing

Solder leads next to piezoFirmly press battery holder to PCB


Step 14: Completion!

Give the completed board a final look over, checking for loose solder connections or shorted pads. Congratulations! You’re now the proud owner of a Tap-Tempo Metronome. Install some AAA batteries and give it a try!

Step 13: All finished!