Scale model animation: Adding life to a layout
Fig. 2: Sequencer circuit VCC
VCC X1 IC2
1 2
4 3
GND TRIG OUT RST
NE 555
VCC DIS THR CTRL
8 7
5 6
.01uF GND
14 13
GND 15 MR C1
15uF C2
VCC GND IC1
CP1 CP0
Q0 Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9
Q5-9 74HC4017A GND
The NE555 timer is a versatile integrated circuit which can be used along with the 74HC4017A electronic counter to build this sequencer circuit (above). The resulting device (below) can be used to control a number of different effects on a layout. The Arduino Pro (page 77, top) can be programed to control a variety of devices that can be used on a layout.
10 1 5 6 9
3 2 4 7
11 12
Q8 Q9
1N4148 D1
1N4148 D3
2N3904
R13 2.2K
GND
R14 82
for one revolution and stop, generating one complete sequence on all the other wiper circuits. If you replace the push- button with a switch, it will simply turn until the power is turned off and the last cycle completes. You control the timing (duration and frequency) by varying the speed of rotation, the di- ameter of the drum, and the length of the cuts in the masking tape. We can add flexibility by moving to a simple electronic counter (74HC4017A) driven by a slow clock (NE555) ticking off time steps like a metronome (Fig. 2). With each clock “tick” or pulse, the counter advances one step into the se- quence. By changing the “tick” rate, we change the duration of each step. We can combine two or more steps with simple diodes. We can shorten the se- quence by routing a “time step” (Q0-Q9) back into the counter reset (marked MR), instead of connecting it to GND (ground). We can also combine two or more steps with diodes to activate something (like the motor in the dia- gram) for more than one time step. The additional circuitry beyond the diodes is there to control higher currents for the motor. By routing different steps and step combinations to different con- trolled features, we get richer, more var- ied effects. Each of the “Qx” output ter- minals can provide about 20ma, enough for one or two LEDs depending on the current draw.
Programmatic control
Continuing with our building light- ing example,
let’s think about what
happens when one enters a room and turns on a light. The light does not go off haphazardly. One tends to stay in the room for a time before moving on. There is dwell time involved. Building lights don’t turn on and off like a Christmas tree. To handle this more sophisticated sequencing problem, we look to a low-cost, programmable se- quencer (or controller) called an Ar- duino. An Arduino represents a family of micro-controllers based on an Atmel integrated circuit. It is one of the most widely used, low-cost computers that is small enough to fit in an HO scale model.
ists have always asked, “Couldn’t I do that mechanically?” So,
I harkened
back to my high school days of building lighting machines for school dances us- ing electro-mechanical sequencers. A basic mechanical sequencer (Fig.1) can be made with a brass, motor-driven drum that conducts the negative bat- tery (or power supply) lead to LEDs, re- lays, or whatever. Wipers consisting of phosphor bronze wires make contact with the drum as it turns to complete the circuit. The off-on-off sequence is
76
set by wrapping masking tape around the drum and cutting the tape away wherever you want the circuit to turn on. Some may compare this to a player piano roll, but the original player pi- anos were pneumatic, not electro-me- chanical.
The sequence is started when one of the wiper circuits is bridged by a sim- ple contact closure or switch which starts the drum rolling and moves it off the stopping insulation. If the starting switch is released, the drum will turn
Before any of you are put off by the mention of programmable controllers, let me explain how easy it is to set up an Arduino
for animation projects.
There are so many libraries and pro- grams already written and freely avail- able for the Arduino that I often tell modelers, “Don’t bother learning to program; first learn to copy and edit.” This will get most people started quickly. If you have been modeling more than 30 years like me, you might also ask a computer-oriented person to
MAY 2014
100K 100K R11 R12
LED1 R1 2K
LED2 R2 2K
LED3 R3 2K
LED4 R4 2K
LED5 R5 2K
LED6 R6 2K
LED7 R7
LED9 R9 2K
LED8 R8
LED10 R10 2K
2K 2K
MOT1
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100