Node.js Raspberry Pi GPIO - Vloeiende LED's
Gebruik 'n skikking met uitset om vloeiende LED's te skep
In hierdie hoofstuk sal ons verskeie GPIO-penne gebruik om 'n "vloeiende" effek te skep deur hulle in volgorde aan en af te skakel.
Wat het ons nodig?
Hiervoor benodig jy:
- 'n Raspberry Pi met Raspian, internet, SSH, met Node.js geïnstalleer
- Die aanskakelmodule vir Node.js
- 1 x Broodbord
- 8 x 220 Ohm weerstand
- 8 x Deurgat LED
- 9 x vroulike tot manlike jumper drade
Let wel: Die weerstand wat u benodig, kan verskil van wat ons gebruik, afhangende van die tipe LED's wat u gebruik. Die meeste klein LED's benodig net 'n klein weerstand, ongeveer 200-500 ohm. Dit is oor die algemeen nie krities watter presiese waarde jy gebruik nie, maar hoe kleiner die waarde van die weerstand, hoe helderder sal die LED skyn.
Klik op die skakels in die lys hierbo vir beskrywings van die verskillende komponente.
Die bou van die kring
Nou is dit tyd om die kring op ons Broodbord te bou.
As jy nuut is met elektronika, beveel ons aan dat jy die krag vir die Raspberry Pi afskakel. En gebruik 'n anti-statiese mat of 'n grondband om te verhoed dat dit beskadig word.
Skakel die Raspberry Pi behoorlik af met die opdrag:
pi@w3demopi:~ $ sudo shutdown -h now
Nadat die LED's op die Raspberry Pi ophou flikker, trek dan die kragprop uit die Raspberry Pi (of draai die kragstrook waaraan dit gekoppel is) uit.
Deur net die prop te trek sonder om behoorlik af te skakel, kan die geheuekaart beskadig word.
Kyk na die bostaande illustrasie van die stroombaan.
- Op die Raspberry Pi, koppel die vroulike been van 'n jumper-draad aan 'n GND -pen. In ons voorbeeld het ons Fisiese Pen 6 ( GND , ry 3, regterkolom) gebruik
- Op die broodbord, koppel die manlike been van die jumper-draad wat aan die GND -krag gekoppel is, aan die grondbus aan die regterkant. Daardie hele kolom van jou broodbord is verbind, so dit maak nie saak watter ry nie. In ons voorbeeld het ons dit aan ry 1 geheg
- Vir elke LED: Koppel die LED sodat dit aan 2 Tie-Point-rye verbind. In ons voorbeeld het ons verbind:
- LED1 na rye 5 (katode) & 6 (anode) kolom J
- LED2 na rye 8 (katode) & 9 (anode) kolom J
- LED3 to rows 11 (cathode) & 12 (anode) column J
- LED4 to rows 14 (cathode) & 15 (anode) column J
- LED5 to rows 17 (cathode) & 18 (anode) column J
- LED6 to rows 20 (cathode) & 21 (anode) column J
- LED7 to rows 23 (cathode) & 24 (anode) column J
- LED8 to rows 26 (cathode) & 27 (anode) column J
- For each LED: Connect one of the legs of a 220 ohm resistor from the the Ground Bus
column on the right side, and the other leg to the right side Tie-Point row
where it connects to the cathode leg of the LED. In our example we
connected:
- LED1 to row 5 column I
- LED2 to row 8 column I
- LED3 to row 11 column I
- LED4 to row 14 column I
- LED5 to row 17 column I
- LED6 to row 20 column I
- LED7 to row 23 column I
- LED8 to row 26 column I
- For each LED: Connect the female leg of a jumper wire to a
GPIO pin on the Raspberry Pi, and the male leg
of the jumper wire to the right side Tie-Point row
where it connects to the anode leg of the LED. In our example we connected:
- LED1 from Physical Pin 7 (GPIO 4, row 4, left column) to Tie-point row 6 column F
- LED2 from Physical Pin 11 (GPIO 17, row 6, left column) to Tie-point row 9 column F
- LED3 from Physical Pin 13 (GPIO 27, row 7, left column) to Tie-point row 12 column F
- LED4 from Physical Pin 15 (GPIO 22, row 8, left column) to Tie-point row 15 column F
- LED5 from Physical Pin 12 (GPIO 18, row 6, right column) to Tie-point row 18 column F
- LED6 from Physical Pin 16 (GPIO 23, row 8, right column) to Tie-point row 21 column F
- LED7 from Physical Pin 18 (GPIO 24, row 9, right column) to Tie-point row 24 column F
- LED8 from Physical Pin 22 (GPIO 25, row 11, right column) to Tie-point row 27 column F
Your circuit should now be complete, and your connections should look pretty similar to the illustration above.
Now it is time to boot up the Raspberry Pi, and write the Node.js script to interact with it.
Raspberry Pi and Node.js Flowing LEDs Script
Go to the "nodetest" directory, and create a new file called "flowingleds.js":
pi@w3demopi:~ $ nano
flowingleds.js
The file is now open and can be edited with the built in Nano Editor.
Write, or paste the following:
flowingleds.js
var Gpio = require('onoff').Gpio; //include onoff to interact with the GPIO
var LED04 = new Gpio(4, 'out'), //use declare variables for all the GPIO
output pins
LED17 = new Gpio(17, 'out'),
LED27 = new Gpio(27,
'out'),
LED22 = new Gpio(22, 'out'),
LED18 = new Gpio(18,
'out'),
LED23 = new Gpio(23, 'out'),
LED24 = new Gpio(24,
'out'),
LED25 = new Gpio(25, 'out');
//Put all the LED
variables in an array
var leds = [LED04,
LED17, LED27, LED22, LED18, LED23, LED24, LED25];
var indexCount = 0; //a
counter
dir = "up"; //variable for flowing direction
var
flowInterval = setInterval(flowingLeds, 100); //run the flowingLeds function
every 100ms
function flowingLeds() { //function for flowing Leds
leds.forEach(function(currentValue) { //for each item in array
currentValue.writeSync(0); //turn off LED
});
if (indexCount
== 0) dir = "up"; //set flow direction to "up" if the count reaches zero
if (indexCount >= leds.length) dir = "down"; //set flow direction to "down" if
the count reaches 7
if (dir == "down") indexCount--; //count
downwards if direction is down
leds[indexCount].writeSync(1);
//turn on LED that where array index matches count
if (dir ==
"up") indexCount++ //count upwards if direction is up
};
function unexportOnClose() {
//function to run when exiting program
clearInterval(flowInterval);
//stop flow interwal
leds.forEach(function(currentValue) { //for
each LED
currentValue.writeSync(0); //turn off LED
currentValue.unexport(); //unexport GPIO
});
};
process.on('SIGINT', unexportOnClose); //function to
run when user closes using ctrl+cc
Press "Ctrl+x" to save the code. Confirm with "y", and confirm the name with "Enter".
Run the code:
pi@w3demopi:~ $ node flowingleds.js
Now the LEDs should turn on and off in sequence, creating a flowing effect.
End the program with Ctrl+c.