Impressionist is assembled.
Construction of the LED channels around the
canvas is also non-critical, but selection of the
LEDs themselves is key to getting the painting
effect that you want. While I’ve specified part
numbers for each color of LED in the Parts List, I
found the paintings to be much more interesting
when using scavenged LEDs from my parts
collection that have a variety of brightness, beam
widths, and hues.
Mixing water-clear and diffused LEDs also
adds interest (Figure 4). Experiment with the
placement of each channel around the canvas
and the orientation of each LED within a channel
to change the character of your paintings. Note
that for an all-blue LED channel, only three LEDs
should be used rather than the four in the other
channels in order to get a reasonable brightness (due to
their higher forward voltage drop).
To upgrade your Impressionist’s paintings to “museum
quality,” try some of these modifications:
• Add two more LED channels on the unused pins of
PortC to display other colors.
• Attach one or more of the LED channels to servo
motors and use additional software or hardware PWM
signals to adjust their position between (or during)
paintings. See the Spin Zone article in the September
2011 N&V for a discussion of code to “walk” the servo
outputs so that several servos can be controlled
simultaneously in software without a dedicated servo
• Use a patterned or textured surface instead of a
smooth white canvas.
• With the Impressionist flat on a table, place prisms,
• Add a pause button so that a particularly attractive
painting can be displayed indefinitely.
Then, display your newest Impressionist painting for all
to see! NV
■ FIGURE 4. The Digital Impressionist at work.
ITEM DIGI-KEY PART #
PIC16F887 microcontroller, DIP- 40 PIC16F887-I/P-ND
( 16) 2N3904 transistors, TO-92 package 2N3904FS-ND
TIP120 transistor, TO-220 package TIP120GOS-ND
( 8) Red LEDs, T1 3/4 package C503B-RCN-CW0Z0AA1-ND
( 8) Yellow LEDs, T1 3/4 package C503B-ABN-CW0Z0251-ND
( 8) Green LEDs, T1 3/4 package C503B-GCN-CY0C0791-ND
( 7) Blue LEDs, T1 3/4 package C503B-BCN-CV0Z0461-ND
( 11) 10K ohm resistors, 1/4 watt 10KQBK-ND
( 9) 100K ohm resistors, 1/4 watt 100KQBK-ND
( 8) 270K ohm resistors, 1/4 watt 270KQBK-ND
( 8) 470K ohm resistors, 1/4 watt 470KQBK-ND
( 8) 100 ohm resistors, 1/4 watt 100QBK-ND
CdS photoresistor PDV-P8103-ND
47 μF 16V capacitor 493-5361-1-ND
0.1 μF 50V capacitor 399-4151-ND
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