Step 1: The Circuit
First, a 'Joule Thief' to boost the voltage from a penlight battery to about 4 volts to power red LEDs.
Then, 3 identical circuits to make a 'ring-oscillator' which, when connected as shown, will make strings of the LED chase around in a circle (or a heart-shaped ring).
Step 2: The Parts
The inductance of this coil should be 20uH per side. Make sure you mark the starts and ends - the circuit needs to have them connected a specific way!
Other parts used in the voltage booster are:
1 x 2N4401 or 2N2222 Audio transistor.
1 x 1N4148 or other small signal diode.
1 x 10uF capacitor
1 x .1uF capacitor
The Ring-oscillator has 3 sections, each section is made up of (see 2nd image):
1 x 2N7000 (or BS170) MOSFET
1 x 100K resistor
1 x 2.2M-ohm resistor
1 x 0.1uF (100nF) capacitor
So, you would need 3 times the above parts.
Step 3: Making the Template
Step 4: Begin Assembly
Make sure you note the start and end points of the coil. Remember that only one coil handles the power, which will be our Primary coil. The other is only to provide the timing signal, we will call that the Secondary. If you can, use the thicker wire (AWG# 28 or heavier) for the Primary, while #30 or 32 is enough for the secondary.
In the circuit diagram - terminals 0 and 1 indicate the Primary Start and End, while 2 and 3 are the start and end for the Secondary.
If the boost circuit tests OK, install the LEDs next, They have to be connected in series pairs.
Step 5: Final Assembly
To enhance the effect of the display, I cut out a heart in red paper with the LEDs running around it.