Resistor Identifier
A handy tool for identifier the resistance of a four band resistor value
Introduction
Resistors typically come with either four or five color bands, and each band represents a specific digit in the resistance value. For color-coded resistors, the first two or three bands indicate the significant digits, while the next band represents the multiplier (i.e., how many zeros to add). The final band typically indicates the tolerance. Refer to KC 12 Electrical Circuits Learning Kit for learn more.
For example, as shown in Figure 0.4, a 4-band resistor with the colors βGreenβ, βBlueβ, βOrangeβ, and βGoldβ (from left to right) represents a nominal resistance of 56,000Ξ© (or 56kΞ©) with a Β±5% tolerance.
In this app, you can easily decode resistor values by selecting colors from the bottom selection bar. Press βForwardβ to move to the next band. Once all colors are selected, the calculated resistance value will automatically appear. Itβs a handy tool when you're unsure about a resistorβs value and donβt have a multimeterβor just donβt feel like using one.
Programming Design
You can go to our Github for complete code block
Source Code
The Whole apps stored here:
This is the code for , you can also find it on our Github Page
Main.py
import uos
import st7789
from UI import Option_Box, Band_Selector
import vga1_16x32 as font
import vga2_8x16 as small_font
import framebuf
from machine import Pin, SPI, ADC,PWM
import time, math,array
from utime import sleep_ms
import test.st7789 as stTest
import struct
pwm = PWM(Pin(19))
pwm.freq(50)
st7789_res = 0
st7789_dc = 1
disp_width = 240
disp_height = 240
CENTER_Y = int(disp_width/2)
CENTER_X = int(disp_height/2)
spi_sck=Pin(2)
spi_tx=Pin(3)
spi0=SPI(0,baudrate=4000000, phase=1, polarity=1, sck=spi_sck, mosi=spi_tx)
#different option box UI elements: parameters(xPos, yPos, color, border_thickness, box_id)
black_box = Option_Box(0,94, st7789.BLACK, 5, 0)
brown_box = Option_Box(60,94, st7789.color565(150, 75, 0),5, 1)
red_box = Option_Box(120,94, st7789.RED, 5, 2)
orange_box = Option_Box(180,94, st7789.color565(255,166,0), 5, 3)
yellow_box = Option_Box(0,130, st7789.color565(255,255,0), 5, 4)
green_box = Option_Box(60,130, st7789.GREEN, 5, 5)
blue_box = Option_Box(120,130, st7789.BLUE, 5, 6)
violet_box = Option_Box(180,130, st7789.color565(127,0,255), 5, 7)
grey_box = Option_Box(0,164, st7789.color565(90,90,90), 5, 8)
white_box = Option_Box(60,164, st7789.color565(230,230,230), 5, 9)
gold_box = Option_Box(120,164, st7789.color565(212,175,55), 5, 10)
silver_box = Option_Box(180,164, st7789.color565(165,169,180), 5, 11)
resistor_color = st7789.color565(255, 188, 107)
band_selector = Band_Selector(0,200, 5)
#coordinate drawing information for each band in resistor UI [xPos, yPos, width, height]
band_pos = [[60,44,9,41],
[85,47,7,35],
[104,47,7,35],
[121,46,7,36],
[166,44,9,41]]
ui_elements = [[black_box, brown_box, red_box, orange_box],
[yellow_box, green_box, blue_box, violet_box],
[grey_box, white_box, gold_box, silver_box],
[band_selector, band_selector, band_selector, band_selector]]
cursor = [0,0] #gives coordinates for the current element selected in ui_elements
prev_cursor = [0,0] #previous position of the cursor
#stores values of for all 5 current bands selected
current_band_values = [None,None,None,None,'']
#stores whether or not the user is selecting a color or not
is_select_mode = True
current_band = 1
#display needs to be initialized with old library in order to turn on
#new library isn't able to turn it on for a mysterious reason
display = stTest.ST7789(spi0, disp_width, disp_width,
reset=machine.Pin(st7789_res, machine.Pin.OUT),
dc=machine.Pin(st7789_dc, machine.Pin.OUT),
xstart=0, ystart=0, rotation=0)
display = st7789.ST7789(spi0, disp_width, disp_width,
reset=machine.Pin(st7789_res, machine.Pin.OUT),
dc=machine.Pin(st7789_dc, machine.Pin.OUT))
display.init()
display.fill(st7789.WHITE)
display.png('Resistor5.png', 5,30)
xAxis = ADC(Pin(28))
yAxis = ADC(Pin(29))
buttonB = Pin(5,Pin.IN, Pin.PULL_UP) #B
buttonA = Pin(6,Pin.IN, Pin.PULL_UP) #A
buttonStart = Pin(7,Pin.IN, Pin.PULL_UP) #A
buttonSelect = Pin(8,Pin.IN, Pin.PULL_UP) #A
#re-draws a ui element
def display_element(element):
#redraw box and box border
display.fill_rect(element.x_pos, element.y_pos, element.width, element.height, element.color)
display.fill_rect(element.border_x, element.border_y, element.border_width, element.border_height, element.fill_color)
if type(element) == Band_Selector:
display.png('arrow_trans.png',155,205, True)
display.png('arrow_left_trans.png',6,205, True)
display.text(font, str(current_band), 110, 204, st7789.BLACK, element.fill_color)
else:
element_value = element.id #by default, the value of an element is equal to its ID
if current_band == 1 or current_band == 2 or current_band == 3:
if element_value > 9:
element_value = '' #element has no value if the current band = 1, 2, or 3 and its ID > 9
elif current_band == 4:
element_value = Option_Box.fourth_band_values[element.id]
elif current_band == 5:
element_value = Option_Box.fifth_band_values[element.id]
display.text(small_font, str(element_value), element.border_x, element.border_y + 5, st7789.BLACK, element.fill_color)
#refreshes all UI elements
def refresh_box_ui():
for rows in ui_elements:
for box in rows:
display_element(box)
#calculates resistance based on current bands selected (current_band_values list)
def calculate_resistance():
#if a multiplier value (4th band) hasn't been selected, don't calculate
if current_band_values[3] == None:
return
#stores all 3 digit for first 3 bands of ressistor
digits = ''
#combine all digits to form 1 value, ignore digits that have no value (band isn't selected for that digit)
for i in range(3):
if current_band_values[i] != None:
digits = digits + str(current_band_values[i])
digits = int(digits)
resistance = digits * current_band_values[3]
prefix = ''
#handles what prefix to give based on "raw" value of resistance
if resistance > 999999999:
#give prefix G for giga
prefix = 'G'
resistance /= 1000000000
elif resistance > 999999:
#give prefix M for mega
prefix = 'M'
resistance /= 1000000
elif resistance > 999:
#give prefix K for kilo
prefix = 'K'
resistance /= 1000
else:
prefix = ''
if(current_band_values[4] != ''):
percentage_text = ' +-' + str(current_band_values[4])
else:
percentage_text = ''
#clear previous resistance text and drew updated one
display.fill_rect(2,0,225,32,st7789.WHITE)
display.text(font, str(resistance) + prefix + percentage_text , 2,0, st7789.BLACK, st7789.WHITE)
#draw all 5 bands to be empty
for i in range(5):
display.fill_rect(band_pos[i][0], band_pos[i][1], band_pos[i][2], band_pos[i][3], resistor_color)
ui_elements[cursor[0]][cursor[1]].is_highlighted(True)
refresh_box_ui()
while True:
if is_select_mode:
#update previous cursor values to current
prev_cursor[0] = cursor[0]
prev_cursor[1] = cursor[1]
#move cursor according to joystick movement (bounds detection included)
if xAxis.read_u16() < 500: #if joystick is pressed up, move cursor up
cursor[0] -= 1
if(cursor[0] < 0):
cursor[0] = 0
elif xAxis.read_u16() > 55500: #if joystick is pressed down, move cursor down
cursor[0] += 1
if(cursor[0] > 3):
cursor[0] = 3
elif yAxis.read_u16() < 500 and cursor[0] != 3: #if joystick is pressed left, move cursor left
cursor[1] -= 1
if(cursor[1] < 0):
cursor[1] = 0
elif yAxis.read_u16() > 55500 and cursor[0] != 3: #if joystick is pressed right, move cursor right
cursor[1] += 1
if(cursor[1] > 3):
cursor[1] = 3
#if the cursor has moved, update which UI element is highlighted by cursor
if prev_cursor[0] != cursor[0] or prev_cursor[1] != cursor[1]:
#revert previously highlighted element
ui_elements[prev_cursor[0]][prev_cursor[1]].is_highlighted(False)
display_element(ui_elements[prev_cursor[0]][prev_cursor[1]])
#highlight element cursor is on
ui_elements[cursor[0]][cursor[1]].is_highlighted(True)
display_element(ui_elements[cursor[0]][cursor[1]])
time.sleep(0.25)
#if the confirm selection button is pressed, move out of select mode
if buttonStart.value() == 0:
is_select_mode = False
time.sleep(0.3)
else:
#if the element that was selected is the band selector...
if type(ui_elements[cursor[0]][cursor[1]]) == Band_Selector:
#handle current band we're on based on joystick movement (bounds detection included)
if yAxis.read_u16() < 500: #if joystick is pressed left, current band we are on decreases
current_band -= 1
if(current_band < 1):
current_band = 1
display.text(font, str(current_band), 110, 204, st7789.BLACK, ui_elements[cursor[0]][cursor[1]].fill_color) #draw new number based on current_band
time.sleep(0.25)
elif yAxis.read_u16() > 55500: #if joystick is pressed right, current band we are on increases
current_band += 1
if(current_band > 5):
current_band = 5
display.text(font, str(current_band), 110, 204, st7789.BLACK, ui_elements[cursor[0]][cursor[1]].fill_color) #draw new number based on current_band
time.sleep(0.25)
if buttonStart.value() == 0:
is_select_mode = True
refresh_box_ui()
time.sleep(0.3)
else:
selected_option = ui_elements[cursor[0]][cursor[1]]
#assign 4th band value based on list of multiplier values and selected box
if current_band == 4:
current_band_values[current_band - 1] = Option_Box.multiplier_values[selected_option.id]
#assign 5th band value based on list of fifth band values and selected box
elif current_band == 5:
#if the selected box has a value, assign band value, else set is_select_mode to True
if Option_Box.fifth_band_values[selected_option.id] != '':
current_band_values[current_band - 1] = Option_Box.fifth_band_values[selected_option.id]
else:
is_select_mode = True
else:
#if the selected box has a value (not box with ids 11 or 10), assign band value, else set is_select_mode to True
if selected_option.id != 11 and selected_option.id != 10:
current_band_values[current_band - 1] = selected_option.id
else:
is_select_mode = True
#if is_select_mode is False, the selected box has a value, calculate resistance and update current band UI
if is_select_mode == False:
calculate_resistance()
display.fill_rect(band_pos[current_band - 1][0],
band_pos[current_band - 1][1],
band_pos[current_band - 1][2],
band_pos[current_band - 1][3],
ui_elements[cursor[0]][cursor[1]].color)
#go back to the selection mode
is_select_mode = True
This is the code for , you can also find it on our Github Page
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