This project is a PCB soldering kit in the shape of pierced heart. The LEDs on the arrow incrementally illuminates one by one, then incrementally turns off in the same fashion. This kit has a 30x30mm hole in the center of it, which is meant to be used as a picture or engraved-acrylic frame. There are 4 SMD right angle LEDs on the back for the option to light up an acrylic frame than can be placed in the frame hole with the assistance of a custom designed case, which can be found in the Google Drive folder.
Click the Google Drive Logo below to access the project's files, which include the KiCad PCB files, the Gerber files, and the Autodesk Inventor CAD files.
The 555 timer in this circuit is there to generate a square wave that will be fed into 2 shift registers. This is done with the help of a capacitor and a resistor, in which the frequency of the generated sine wave is about 1Hz (This can be changed to your liking). This square wave is fed into 2 74HC595 shift registers cascaded with each other that are setup as a Johnson counter. This is done by tying the last input of the counter back into the input. Assmuming the shift register's output start at 0 (most of the time if the 4.7uF bypass capacitor is placed), Q1 and R19-R20, acting as an inverter, will invert the last output (0 when the device is started) to a 1 and feed that into the data input of the first shift register. Then, on the next clock cycle generated by the 555, that 1 input will be shifted down, turning on the first LED. The input 1 keeps in beign shifted down, eventually turning on all LEDs. When the 1's are shifted to the last input, the inverter then ouputs a 0 to the data input of the shift register. This repeats the same process as shifting down the 1 input, turning off LEDs incrementally. The cycle repeats when the 0 input gets shifted down into the last output, where it gets inverted into a 1 and fed into the input of the first shift register.
D18-21 are independent of this circuit, and are simply constantly on. A SMD-1206 LED can be used if titled 90° while soldered. There are optional, and should be used with a laser engraved 31.5x31.5mm acylic piece or a 30x30 picture.
This kit has some THT and SMD parts to be soldered (THT means through-hole, and SMD means surface-mount).
|PCB Reference||Part Description||Package Size||Quantity per Board|
|U2&U4||74HC595 Shift Register||SOIC-16||1|
|U3||7805 Voltage Regulator||SOT-223||1|
|Q1||2N3904 NPN Transistor||SOT-23||1|
|J1||Micro USB||Molex 47346||1|
|BT1||5-9V Battery Connector||2-pin 0.1" header||1|
|C2||4.7uF Bypass Capacitor||SMD-1206||1|
|D18-D21||Right Angle LED||1206||4|
Here is the PCB's schematic (The first one is for the main tree, the second is for the auxilary tree):
Here is some diagrams relating to the project:
The PCB is designed to be screwed a case at the buttom of the board. I have designed such case, which you can find in the project's Google Drive folder.