This is the first time I am writing an Instructable so hopefully I write well enough for you to understand. Today I will be telling you how to make a digital watch from a website that I found. The website is called sainsmart.com. It was really easy except for one time when I put on too much solder, so have fun and don't put on too much solder!
Step 1: Organize the Components of the Watch and the Equipment Needed
Components of the watch:
One Pre-programmed ATMega328 DIP IC
One 28 pin DIP IC base
One 4-digit display
One 32kHz crystal
One 10kOhm resistor
Two 0.1uF capacitors
One right angle tactile button
One 20mm coin cell battery with battery holder
Four screws M2*7mm
Four threaded brass M2*7mm
One nylon watch band
Acrylic enclosure parts
Step 2: Soldering the Resistor
It is always easier to put the smallest parts in first, so start with the resistor. Put the resistor in, so the legs of the resistor are on the side without the numbers and letters. Bend the legs so that it is easier to solder on without having to hold the resistor. Solder it to the board and then use the wire cutters to cut off the bent legs of the resistor. It is ok if some of the solder went to the other side of the board, it helps it to stay together.
Step 3: Soldering the Crystal
When you solder in the crystal it is a bit different. You will want the crystal to be parallel to the board, so bend the legs so that when you fit the legs in, the crystal is parallel to the board. Then solder the crystal on. You want a nice joint to hold it together so be careful that you don't put on too little or too much solder.
Step 4: Soldering the Base of the Chip
You need to be careful when you solder in the base. There is a certain way that you have to solder it in. There is a semicircle on the board that matches a semicircle on the base. Fit the semicircle of the base onto the semicircle of the board. Then you can solder it on. You should start soldering at one end and then you go to the opposite end so that it stays in the board without holding it. Then you work your way in the same way.
Step 5: Soldering the 4 Digit Display
There is a certain way that you have to put in the display. If you look at one of the longer sides there are letters. Make sure the letters are facing where the battery will be, in other words the circle on the board. Solder the display on like how you soldered on the base for the chip. Start soldering on one end and move to the other end and vice versa.
Step 6: Soldering the Capacitors
The capacitors are the next thing you should put in. There is no significant way for the capacitors to go in, so you can just put it in any way. When you put it in, bend the legs of the capacitors so that its easier to solder in. Once soldered, cut off the legs of the capacitors.
Step 7: Soldering the Tactile Button
When you solder on the button, the 2 straight legs go in the little box with a little word outside of it. The crooked legs will go outside of the little box. Then solder on the button. It is advisable to solder the crooked legs in too.
Step 8: Putting the Chip in the Base
There is yet another semicircle on the chip that should match up to the semicircle on the base when you are putting on the chip. However the legs of the chip may not fit right away so you might have to bend the legs a little bit to get the chip to fit.
Step 9: Soldering the Lithium Battery
When you solder in the battery there is a certain way to solder it in. If you look at it there is a metal band with a blunt triangular point. Make sure that is pointing to the button, otherwise it won't work correctly. Then you can solder it on. If there are any more legs, than you cut them off, but be careful because they can fly. If you want to try to turn it on, now would be a good time. If you want to go to a different time then just hold down the button until the numbers start to count up, stop it when it gets to the time.
Step 10: Putting the Watch Together
Remove the protective paper from the acrylic enclosure parts. Then take the watch strap and take one of the parts, it doesn't matter which, and thread it through the longer strap of the watch strap and pull it tight. Then pull the strap through the brass loop. Then put the board on top of the part and put the longer screws through the bottom and twist the threaded brass so that there is very little space between the part and the board. Then put the other part on top of the board and put the shorter screws into the threaded brass. Don't tighten them too much, otherwise you may break the part. Then you're done. You can check to see if it fits and if not then you can fix it.