The EC1515B digital clock is a popular building kit for both beginners and advanced hobbyists. For a few euros you not only have a whole afternoon or evening of soldering pleasure but when the project is finished you also have a nice and usable clock.
Just like in the previous soldering project “Solder fun: Geekcreit Christmas Music Box kit“, the main ingredients are a microcontroller, LEDs and a buzzer. The time is kept by the DS1302 IC, which uses a CR 2032 button cell battery as a backup power supply. A light-dependent resistor (LDR) controls the intensity of the display. There is also a thermistor for displaying the temperature. Finally, everything is neatly packaged in a beautiful transparent case.
The kit comes complete with coin-cell battery, USB cable and laser-cut housing. I received it as a birthday present and it came from VNGSystems in Gouda. There they have many more fun and geeky tech stuff, so if you are looking for a gift again: look no further 😉
The DS1302 IC
The DS1302 is a Real Time Clock (RTC) chip with a built-in trickle charger. If the power fails, the IC automatically switches to a coin-cell battery as a backup power supply. The chip manages all time functions. It counts seconds, minutes, hours, date of the month, month, day of the week and year, with compensation for leap years up to the year 2100. The chip communicates with the microcontroller via a simple 3-pin serial interface
The quick guide to the kit does not describe a sequence for assembly, which is why I will describe a possible method here. Move from the low components (LEDs, resistors) to the higher (battery holder, buzzer) as usual. But of course you can decide in which order you want to solder everything, this is just a suggestion.
First, it is the turn of the LEDs. They must be placed with the short pin (cathode, negative) on the inside of the printed circuit board and the long pin (anode, positive) along the edge. The easiest way is to solder them in stages. First solder only the outer pin of each LED, then you can check them one by one and see if they are straight. If not, you can easily reheat the first soldering point to correct. If the LED is straight then you can solder the second pin. For example, start with the 12 blue LEDs. Cut them short after soldering.
Then solder the red LEDs in 4 stages. Do not try to heat the LEDs for too long, they cannot handle that very well.
Then the following parts will be soldered on the back of the board:
Resistors: the orientation of the resistors is not important. I prefer to solder them all in the same direction with the color code, that looks nicer.
IC sockets: note the orientation. The location of the recess must correspond to the printing on the printed circuit board.
Capacitors: There are 5 capacitors: two yellow, two orange and one black. The orientation of the electrolytic capacitor (black) is important. The minus sign must match the print on the PCB. With the remaining 4, the orientation is not important.
Buzzer, battery holder and USB connector: pay attention to the correct orientation for these components as well, this is clearly indicated on the printed circuit board.
Crystal: orientation is not important in this section. The intention is that the crystal will lie flat on the circuit board and that you solder not only the legs but also the other end.
Buttons: before we continue on the other side, we finally solder the two push buttons on this side. Carefully put the ICs in the sockets, then we continue at the front of the PCB.
LED display on the EC1515B
The 4-digit LED display appears on the front. Note the orientation: the decimal points belong at the bottom. Then the trick is to neatly solder this component. This is easiest by first soldering two opposite corners. Then you can see if everything is straight and correct if necessary. When everything is in place you can solder the rest of the pins. Don’t forget to remove the protection sticker.
Thermistor and LDR
The thermistor and light-dependent resistor (LDR) must protrude through the openings in the front plate for them to function optimally. Temporarily attach the front plate (on the 4 spacers) as in the pictures below. This way you can get an idea of how long you have to leave the wires of the sensors. The front plate still has the protective film in the photo.
The thermistor and light-sensitive resistor protrude beyond the LCD display. The LDR is approximately flush with the outside of the front plate, the thermistor preferably protrudes slightly further.
The housing of the EC1515B
Then it’s time to assemble the housing. The tall buses come at the rear, the short ones at the front. Note the recess for the LDR and thermistor.
In the back, there are holes for the two terminals, buzzer and USB connection. And of course do not forget to install the battery :p
Connect it to a hub, power bank or telephone charger with the supplied USB cable. The end result: a handy clock that also looks interesting.