DIY projects as gifts?

I did a giant Valentine heart for a shop window last year. A Genie was used as the intelligence, but a shift register was used to drive more effective channels. The lamps were 18V filament ones as they were around. The heart was hot wire cut from polystyrene foam, and the lamps embedded in it. Further layers of foam held and hid the PCBs. The front was covered with red felt which the lamps shone through, even in daylight. The back was covered with card. The whole thing runs from a laptop 19V PSU. I arranged 18 lamps round the outside of the heart, plus 6 in an inner heart shape. The software randomly selects one of three patterns every 10 seconds - pulsing between the inner and outer hearts, a dot chasing round and round, and a third which I can't remember at this moment.

I'd show you a picture but it must be on my other PC.

Here is the unit in close up.

And the insides.

Genie on the right, shift register, driver and power regulation on the left. Rather a lot of wire as my friend Pete was building the electronics (and writing the software) but I was making the heart without any communication with him!

This is the circuit for the shift register part. Please note this design is by Peter, not me, but he has given me permission to publish it. My part was just the overall idea and the hardware (foamware!) of the heart itself. Descriptive text below.

Circuit diagram of interface between Genie (or other controller) and a set of 24 lamps. Used for flashing light display (JG Valentine).
Genie serially loads 8 bits of data into U1's shift register, then stores that data in U1's output register. U2 drives the lamp colums.
Genie separately controls which rows are on and the six transistors drive the lamp rows.

U1: 4094 (CMOS 4000 series) "8-bit shift-register with output latches"

DATA is copied into shift register bit 0 on a Low->High of CLK.

When STR is High the latch contents are the same as the shift register contents. When STR is Low the latch retains the last state of the shift register before STR went Low. In other words, a pulse Low-High-Low on STR will transfer all 8 bits of the shift register to the latch.

When EO is High the outputs Q0 to Q7 (from the latch) are enabled. (When Low the outputs are tri-state - not used here.)
QS and QS' are not important here.

To load a byte: STR is Low. Present bits 7 down to 0 to DATA and pulse CLK Low-High-Low for each data bit. Finally pulse STR Low-High-Low to update the outputs in one go.

Note that sequencing effects do not exploit the shift-register in the 4094 (which can only shift in one direction). All sequencing operations are carried out by the microcontroller and transfered serially to the 4094 one byte at a time.

U2: ULN2803A: "Octal darlington driver"

Eight darlington transistors plus base resistors for 5V operation and back-EMF diodes (CATHODES - not used here).
When input is high, corresponding output is pulled low (about 0.6V).
When input is low, corresponding output is off (open circuit).

Transistors
Three identical stages for three columns.
When an input is High (5V) the NPN transistor with its emitter resistor feed a constant current ((5V-0.6V)/1200ohms=3.7mA) to the PNP base, enough to pull the PNP collector high (VL) for loads up to approx 370mA.
When an input is Low (0V) the NPN and PNP transistors are off.

To turn on the top-left lamp (in the schematic), leaving the others off:
R1=5V, R2=R3=0V, Load byte 00000001 {MSB (0) first}
To turn on all lamps:
R1=R2=R3=5V, Load byte 11111111
To turn on the top 4 lamps of the middle column and the top 4 lamps of the right column:
R1=0V, R2=R3=5V, Load byte 00001111 {MSB (0) first}