#169Intermediate
Raspberry Pi Pico LED Campfire (8x8 NeoPixel Matrix + Potentiometer + Buzzer)
A campfire that doesn't burn or warm anything, but still crackles! The **Raspberry Pi Pico** draws a realistic flame on an **8x8 NeoPixel matrix**, recalculated every frame: sparks appear at the base, heat cools as it rises and glows from red to white. A **potentiometer** sets the flame height, a **button** switches between Fire, Gas, Magic and Amethyst themes, and a **buzzer** adds the crackle of burning wood. Procedural animation, ADC, PWM and MicroPython in one project.
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A campfire that fits on your desk and never burns anything. On the 8x8 light matrix, flames are born from sparks at the bottom and turn from red to yellow to white as they rise, and you turn a knob to make the fire smaller or bigger. A short press of the button turns the flame blue, green or purple, and a long press switches the crackling-wood sound from the buzzer on or off.
Video
Circuit Diagram
Source Code
MicroPython
1# ─────────────────────────────────────────
2# BlueGrays · bluegrays.com
3# Raspberry Pi Pico LED Campfire (8x8 NeoPixel Matrix + Potentiometer + Buzzer)
4# ─────────────────────────────────────────
5# Realistic fire animation on an 8x8 NeoPixel matrix. The potentiometer
6# sets the flame height, a short button press changes the theme (Fire,
7# Gas, Magic, Amethyst) and a long press toggles the crackle sound.
8#
9# Pins:
10# GP2 -> matrix DIN (VDD -> VBUS, VSS -> GND)
11# GP26 -> Potentiometer wiper (ADC0)
12# GP14 -> Button (other leg to GND)
13# GP17 -> Buzzer (+)
14
15from machine import Pin, PWM, ADC
16from neopixel import NeoPixel
17import time
18import random
19
20# ============ SETTINGS ============
21W = 8 # Columns
22H = 8 # Rows
23SERPENTINE = False # True for zigzag-wired panels
24BRIGHTNESS = 0.4 # Wokwi draws colors as-is, 0.4 shows the flame clearly
25 # 0.15-0.2 recommended on USB 2.0 (500 mA), use external 5V for brighter
26FRAME_MS = 35 # Frame time (~28 FPS)
27LONG_PRESS_MS = 900 # Hold time to toggle sound
28
29# ============ HARDWARE ============
30matrix = NeoPixel(Pin(2), W * H)
31pot = ADC(26) # ADC0
32button = Pin(14, Pin.IN, Pin.PULL_UP)
33buzzer = PWM(Pin(17))
34buzzer.duty_u16(0)
35
36# ============ STATE ============
37# heat[x][y]: column x, y = 0 is the bottom row; 0 = cold, 255 = hottest
38heat = [[0] * H for _ in range(W)]
39theme = 0
40THEME_NAMES = ["Ates / Fire", "Gaz / Gas", "Buyu / Magic", "Ametist / Amethyst"]
41sound_on = True
42
43
44# ============ COLOR PALETTE ============
45def heat_color(t):
46 # Map heat (0-255) to a color by theme: black -> deep -> bright -> white
47 t192 = (t * 191) // 255
48 ramp = (t192 & 0x3F) << 2 # 0-252 ramp per band
49 if t192 & 0x80:
50 r, g, b = 255, 255, ramp # Hottest: yellow -> white
51 elif t192 & 0x40:
52 r, g, b = 255, ramp, 0 # Middle: red -> yellow
53 else:
54 r, g, b = ramp, 0, 0 # Cool: black -> red
55 if theme == 1:
56 r, b = b, r # Gas: blue flame
57 elif theme == 2:
58 r, g = g, r # Magic: green flame
59 elif theme == 3:
60 b = max(b, r * 3 // 4) # Amethyst: purple flame
61 g = g // 2
62 return (int(r * BRIGHTNESS), int(g * BRIGHTNESS), int(b * BRIGHTNESS))
63
64
65def pixel_index(x, row):
66 # row 0 = top row
67 if SERPENTINE and row % 2 == 1:
68 return row * W + (W - 1 - x)
69 return row * W + x
70
71
72# ============ FIRE SIMULATION ============
73def fire_step(intensity):
74 # intensity 0-1: flame height. High = less cooling + more sparks
75 cooling = int(115 - 55 * intensity) # 115 (short) -> 60 (tall)
76 sparking = int(70 + 150 * intensity) # 70 -> 220 (probability)
77 max_cool = (cooling * 10) // H + 2
78
79 for x in range(W):
80 col = heat[x]
81 # Every cell cools a little
82 for y in range(H):
83 c = col[y] - random.getrandbits(8) % max_cool
84 col[y] = c if c > 0 else 0
85 # Heat drifts up and diffuses
86 for y in range(H - 1, 1, -1):
87 col[y] = (col[y - 1] + col[y - 2] + col[y - 2]) // 3
88 # Random sparks at the base
89 if random.getrandbits(8) < sparking:
90 y = random.getrandbits(1)
91 col[y] = min(255, col[y] + 160 + random.getrandbits(6))
92
93 # 4) Light blending with neighbor columns: the flame waves more naturally
94 for y in range(2, H):
95 row_vals = [heat[x][y] for x in range(W)]
96 for x in range(W):
97 left = row_vals[x - 1] if x > 0 else row_vals[x]
98 right = row_vals[x + 1] if x < W - 1 else row_vals[x]
99 heat[x][y] = (row_vals[x] * 2 + left + right) // 4
100
101
102def render():
103 for x in range(W):
104 for y in range(H):
105 matrix[pixel_index(x, H - 1 - y)] = heat_color(heat[x][y])
106 matrix.write()
107
108
109# ============ CRACKLE SOUND ============
110def crackle(intensity):
111 # Random very short "ticks" = crackling wood
112 if not sound_on:
113 return
114 if random.getrandbits(8) < int(10 + 50 * intensity):
115 buzzer.freq(1500 + random.getrandbits(12)) # 1500-5595 Hz
116 buzzer.duty_u16(6000)
117 time.sleep_ms(2 + random.getrandbits(2))
118 buzzer.duty_u16(0)
119
120
121def beep(freq, ms):
122 buzzer.freq(freq)
123 buzzer.duty_u16(20000)
124 time.sleep_ms(ms)
125 buzzer.duty_u16(0)
126
127
128# ============ BUTTON ============
129btn_state = 1
130btn_raw = 1
131btn_changed = time.ticks_ms()
132press_start = 0
133long_done = False
134
135
136def handle_button():
137 # Short press = theme, long press = sound on/off
138 global btn_state, btn_raw, btn_changed, press_start, long_done, theme, sound_on
139 now = time.ticks_ms()
140 raw = button.value()
141 if raw != btn_raw:
142 btn_raw = raw
143 btn_changed = now
144 if time.ticks_diff(now, btn_changed) > 25 and raw != btn_state:
145 btn_state = raw
146 if raw == 0:
147 press_start = now
148 long_done = False
149 elif not long_done:
150 theme = (theme + 1) % len(THEME_NAMES)
151 print("Tema / Theme:", THEME_NAMES[theme])
152 beep(1200, 30)
153 if btn_state == 0 and not long_done and time.ticks_diff(now, press_start) > LONG_PRESS_MS:
154 long_done = True
155 sound_on = not sound_on
156 print("Ses / Sound:", "ACIK / ON" if sound_on else "KAPALI / OFF")
157 beep(1600 if sound_on else 500, 80)
158
159
160# ============ MAIN LOOP ============
161print("== BlueGrays · bluegrays.com ==")
162print("Pico 8x8 Kamp Atesi / Campfire")
163print("Pot = alev boyu / flame height | Kisa basis = tema / short press = theme | Uzun basis = ses / long press = sound")
164
165smooth = pot.read_u16() / 65535
166while True:
167 start = time.ticks_ms()
168 handle_button()
169
170 # Smooth the pot value (jitter should not make the flame jump)
171 smooth += (pot.read_u16() / 65535 - smooth) * 0.2
172 fire_step(smooth)
173 render()
174 crackle(smooth)
175
176 # Constant frame rate
177 spent = time.ticks_diff(time.ticks_ms(), start)
178 if spent < FRAME_MS:
179 time.sleep_ms(FRAME_MS - spent)
180FAQ
Why should I lower the brightness on a real circuit?▾
The code uses `BRIGHTNESS = 0.4` because Wokwi draws colors exactly as they are sent. A real matrix can draw about 1 A with a big flame, while a USB 2.0 port supplies 500 mA. On USB, set it to 0.15–0.2; for more brightness, power the matrix from a 5V 2A adapter and connect the grounds.
How do I change the flame height and color?▾
Turn the potentiometer left for glowing embers and right for flames that reach the top of the matrix. A short button press cycles through Fire, Gas, Magic and Amethyst. In Wokwi, click the pot and use the arrow keys, and press T to change the theme.
How do I turn off the crackle or make it less frequent?▾
Hold the button for about a second: a high beep means the sound is on, a low beep means it is off. For fewer crackles, lower the 10 and 50 in `10 + 50 * intensity` inside `crackle()`. Use a passive buzzer for the sound.
Do I need to install any libraries?▾
No. The `neopixel`, `machine` and `random` modules ship with MicroPython for the Pico. Flash MicroPython onto the Pico and save the code to it as `main.py` in Thonny; the fire then starts on its own every time the Pico powers up.