Introduction
Ever wanted to gift something “Electronically Special” to your loved ones? This article will show you how to make such gift in an Engineer’s style. All we need is a 555 Timer IC and a couple of other electronic components to make this LED Heart Flasher.
Components Required
1. 555 Timer IC with IC holder
2. Resistors
3. Capacitors
4. Transistor 2N3019
5. Two 5cm x 5 cm PCBs
6. Tactile switch
7. 4 x AA Battery Holder
8. 4 x AA Batteries
9. A small plastic box
10. Nuts, bolts, spacers, etc.
11. Solid Wires
12. Plastic box
Tools Required
1. Soldering machine, De-Soldering wick, Flux, Soldering wire
2. PCB drilling machine/ Hand Drill
3. Screwdriver, Cutter, Wire stripper
4. Insulation tape
5. Digital Multimeter
Circuit Explanation
Basically, the 555 Timer IC is made to work as an “Astable Multi-vibrator” here. We need at least 12 LEDs to make the shape of a heart and a 555 IC is not capable of directly driving 12 LEDs at a time. So that is why we have used a medium power transistor 2N3019 which can drive loads up to 1 Ampere. The transistor works as a switch here and the output from the 555 IC provides the switching signal to the transistor. We’ll be driving the circuit using 6 volts (4 x 1.5V Battery).
And one more advantage of this circuit is that you can customize the frequency and Pulse width of the signal by changing the value of the resistors and capacitors R1, R2 and C1.
Here is the formula to calculate the parameters of the Timer.
‘ON’ TIME WIDTH= 0.693 X (R1+R2) X C1
‘OFF’ TIME WIDTH=0.693 X R2 X C1
FREQUENCY=1.44 / ((R1 + 2XR2) X C1) [NUMBER OF FLASHES PER SECOND]
I wanted a slowly flashing circuit so I choose the corresponding components for my circuit.
Soldering Process
Before going into the soldering process, make sure that you test the circuit on a Breadboard first and then start soldering. Also don’t forget to drill the necessary holes before your start soldering. It would be difficult to drill holes after all the parts have been soldered and there are chances of the solder joints being damages if holes are drilled after soldering the components.
I will be soldering the circuit onto two PCBs since I felt it was more convenient. You can use a single PCB if you want.
PCB 1
Make sure you arrange the components once on the PCB and see how you are going to solder. See where the power lines should be soldered and if all the components can be connected according to the circuit diagram or not. If you are new to soldering then better use some marker to draw the setup onto the PCB before soldering.
After soldering, the finished product should somewhat look like this
PCB2
Soldering the LEDs in Heart shape arrangement is the most challenging part. You are most likely to make mistakes so do it with extreme focus. I have arranged the LEDs in such a way that the shorter ends of the LEDs, i.e. the cathode terminals are pointed towards the centre and the anode terminals (longer ones) point away from the centre.
First arrange all the LEDs and mark their locations. Then put the LEDs one by one onto the PCB using the marks and solder them.
Once you have soldered all LEDs to the PCB, start bending the anode terminals away from the centre and the cathode terminals toward the centre to make them touch each other and then start melting the soldering wire onto them to form a common joint.
Finished product should look similar to this
HERE IS THE FRONT VIEW
Now cut the excess length anode terminals. Next we need to solder one end of the 330 ohms resistors to each LED’s anode terminals and the other end to the edges of the board where we’ll create our power line.
NOTE: Remember to use the multimeter’s continuity test to check if the joint has been made properly or not after soldering each component. This would avoid a huge trouble at the end.
Once you are done with soldering resistors, you should have something like this
Back View
Join the other ends of the resistor (the one which is NOT connected to the LED) to each other since all of them are going to be connected to the same power line. This is how it would look after the process.
Now the outer line is to be soldered to the VCC LINE of PCB1 and the inner junction is to be connected to the transistor on the 1st PCB.
Now take 4 spacers with 4 nuts and bolts to attach the two PCBs
The PCB containing the LEDs comes on the top and the other PCB on the bottom
Now, tape the GND line of the circuit to the negative terminal of the battery pack. Positive terminal of the battery pack is attached to one end of the tactile switch and other end to the VCC LINE from the PCB.
Next, take a transparent plastic box which is big enough to fit in the battery pack and the circuit setup. Use a double sided tape or some more screws to fix them into the box. Drill a small hole on its lid and pop-out the tactile switch through it.
That’s all! You have made it. Test it by pressing the switch a couple of times and see if it is working.
You can either leave it this way (I prefer not to) or use some of your own creativity and write some special messages on it or paint it. I was presenting it to my sister on her birthday so I choose a corresponding theme for it.
This is how the finished product would look like.
P.S. – I’m very bad in painting and all those stuff so this is what I could actually do.
Here is my YouTube video: I have shown the two phases of testing (test on breadboard and then on PCB) and the finished product’s working (last part taken in dark so that it looks better)
This article was published by me on EngineersGarage