Both Sparkfun and Arduino.cc have great tutorials on this subject (most of these pictures below are taken from these sites). Links are at the bottom.
If you can program an Arduino, you can program a Twitch-n-Howl board. That's because both boards use the same ATmega328 chip to store and execute code. In order to save space, the Twitch-n-Howl board does not have a USB port. In order to upload code, you will need to set up a dedicated Arduino as a "Programmer" and connect that Arduino to the ISP header of the Twitch-n-Howl.
First connect your "Programmer" board to your computer and upload the ArduinoISP.ino file. This is located in the Examples in the File menu. Upload this just like any other sketch.
Now you can connect your programmer board (I'm using a Sparkfun Redboard Arduino Uno clone here) to the Twitch-n-Howl. I like using a clip with pogo pins (like this one), but you could also solder a pin header to the board and just use jumpers.
The pins have to be connected in a very specialized pattern
Uno Pin — Name — ISP Pin — Name — Uno Pin
12 MISO O O 5V 5V
13 SCK O O MOSI 11
10 Reset O O GND GND
Here’s what it looks like when connected with jumpers.
Then you simply put the code for the target board in the Arduino IDE (just like coding a board as usual). You will need to select “Arduino as ISP” as the programmer.
Then you can “Upload Using Programmer”. And, BOOM, your Arduino Uno Programmer board will add the brand new code to your Twitch-n-Howl board.
**On these links you'll see instructions for loading the bootloader onto a new ATmega328 chip. This will be unnecessary for the Twitch-n-Howl board as it has already been done at Jekyll-Labs. **
// Jekyll-Labs Twitchy Attiny85
// Built for Twitchboard v1.7
//
// Pin definitions
int fetpin = 0;
int trigpin = 3;
int potpin = A2;
// global variables
long duration = 200; // duration in miliseconds (200)
long PWM = 255; // Duty cycle 0-255 (255)
long intervallow = 2000; // low end of interval range in sec [2 sec]
long intervalmid = 10000; // middle of interval range in sec [10sec]
long intervalhigh = 90000; // high end of interval range in sec [90sec]
long intervalmax = 36000000; // interval in sec if pot maxed out [10hrs]
// initialize global variables
long timeunit = 0;
unsigned long last = 0;
unsigned long timeinterval = 0;
float exprob=0.50;
void setup() {
randomSeed(A1);
pinMode(fetpin, OUTPUT);
digitalWrite(fetpin, LOW);
pinMode(trigpin, INPUT);
pinMode(potpin, INPUT);
}
void loop() {
// uncomment if pot controls duration
// duration of signal will last from 0.5 - 10 sec
//int durationpot = analogRead(potpin);
//long duration = map(durationpot,100,1023,500,10000);
//if (duration <500) duration = 150;
// uncomment if pot controls PWM
// read middle pot for PWM of fet signal
//int PWMpot = analogRead(potpin);
//int PWM = map(PWMpot,0,1000,0,255);
//if (PWM>255) PWM = 255;
// uncomment if pot controls frequency
// mean frequency of random signals is 1 events per time unit
int freqpot = analogRead(potpin);
long timeunit = map(freqpot,512,1023,intervalmid,intervalhigh); // 2nd half dial range
if (freqpot>1000) timeunit = intervalmax; // far right dial 1hr
if (freqpot<512) timeunit = map(freqpot,0,512,intervallow,intervalmid); // 1st half dial range
if (freqpot<100) timeunit = 0; // bottom of dial continous on
if (timeunit<=0){ // continuous on if left dial all counter clockwise
analogWrite(fetpin,PWM);
}
else {
// Check for trigger (X3 for debounce) and adjust
// timeunit if trigger is positive.
if (timeunit>0) {
int trigger = digitalRead(trigpin);
if (trigger == HIGH) {
delay(100);
int trigger = digitalRead(trigpin);
if (trigger == HIGH) {
delay (100);
int trigger = digitalRead(trigpin);
if (trigger == HIGH) {
timeunit = (duration * 2);
}
}
}
}
// Calcuate time interval between events. timeunit depends on:
// Potentiometer value if trig = 0
// Duration multiplier (shorter) if trig = 1
unsigned long timeinterval = exprob * timeunit;
// Check if time interval has passed
if ((millis() - last) > timeinterval) {
last = millis(); // updates timer to last event
analogWrite(fetpin,PWM);
long duration = random(2000)+3000;
delay(duration);
digitalWrite(fetpin,LOW);
// the following equation runs once per event and
// generates a random float (exprob) that falls in an
// exponential distribution. It will be used to
// determine the interval time for the next event.
// Events that occur at exponentially distributed
// intervals form poisson processes.
exprob = (-2)*(log((100-random(100))/100.00));
}
else digitalWrite(fetpin,LOW);
}
delay(20);
}
// Jekyll-Labs Twitch and Sound
// Built for Twitchnhowl v2.2
//
// D2 unused
// D3 Power MOSFET (PWM avail)
// D4 unused
// D5 On Board LED1
// D6 On Board LED2
// D7 SoftSerial Tx
// D8 SoftSerial Rx
// D9 Trigger Input
// D10 unused
// D11 MOSI
// D12 MISO
// D13 SCK
// A0/D14 unused
// A1/D15 unused
// A2/D16 unused
// A3/D17 Potentiometer Top
// A4/D18 Potentiometer Middle
// A5/D19 Potentiometer Bottom
// A6/D20 unused
// A7/D21 unused
//include libraries
#include "Arduino.h"
#include "SoftwareSerial.h"
// set pin identification
int fetpin = 3;
int trigpin = 9;
int led1 = 5;
int led2 = 6;
int potMpin = A4;
int potTpin = A3;
int potBpin = A5;
//set SoftSerial for JQ8900 and basic Hex commands
SoftwareSerial mySoftwareSerial(8, 7); // RX, TX
byte playnext[] = {0xAA, 0x06, 0x00, 0xB0 };
// set global constants
unsigned long durationlow = 200; // low end of duration range in msec [0.2sec]
unsigned long durationhigh = 15000; // high end of duration range in msec [15sec]
long intervallow = 2000; // low end of interval range in sec [2 sec]
long intervalmid = 10000; // middle of interval range in sec [10sec]
long intervalhigh = 90000; // high end of interval range in sec [90sec]
long intervalmax = 36000000; // interval in sec if pot maxed out [10hrs]
unsigned long mosfetdelay = 0; // extra delay to turn mosfet on after audio triggered [0]
// initialize global variables
long timeunit = 12; // mean untriggered time interval (sec)
unsigned long last = 0;
unsigned long timeinterval = 0;
float exprob=0.50;
void setup() {
// setup mosfet pin as output
pinMode(fetpin, OUTPUT);
digitalWrite(fetpin, LOW);
// set up potentiometers and trigger pin
pinMode(trigpin, INPUT);
pinMode(potTpin, INPUT);
pinMode(potMpin, INPUT);
pinMode(potBpin, INPUT);
// Set up and turn off LED
pinMode(led1, OUTPUT);
digitalWrite(led1, LOW);
pinMode(led2, OUTPUT);
digitalWrite(led2, LOW);
// begin softserial for JQ8900
mySoftwareSerial.begin(9600);
last = millis(); // updates timer to start
randomSeed(A0);
}
void loop() {
// duration of signal will last from 0.5 - 10 sec
int durationpot = analogRead(potBpin);
long duration = map(durationpot,100,1023,durationlow,durationhigh);
if (duration <500) duration = 150;
// read middle pot for PWM of fet signal
int PWMpot = analogRead(potMpin);
int PWM = map(PWMpot,0,1000,0,255);
if (PWM>255) PWM = 255;
// mean frequency of random signals is 1 events per timeunit
int intervalpot = analogRead(potTpin);
long timeunit = map(intervalpot,512,1023,intervalmid,intervalhigh); // 2nd half dial range 12-60 sec
if (intervalpot>1000) timeunit = intervalmax; // far right dial 1hr
if (intervalpot<512) timeunit = map(intervalpot,75,512,intervallow,intervalmid); // 1st half dial range 0-12 sec
if (intervalpot<75) timeunit = 0; // bottom of dial continous on
if (timeunit<=0){ // continuous on if left dial all counter clockwise
analogWrite(fetpin,PWM);
digitalWrite(led2,HIGH);
}
else {
// Check for trigger (X3 for debounce) and adjust
// timeunit if trigger is positive.
if (timeunit>0) {
int trigger = digitalRead(trigpin);
if (trigger == HIGH) {
delay(100);
int trigger = digitalRead(trigpin);
if (trigger == HIGH) {
delay (100);
int trigger = digitalRead(trigpin);
if (trigger == HIGH) {
timeunit = 2000; // minimum mean interval in sec for triggered events
digitalWrite(led1,HIGH);
}
}
}
if (trigger == LOW) digitalWrite(led1,LOW);
}
// Calcuate time interval between events. timeunit depends on:
// Potentiometer value if trig = 0 (not triggered)
// Duration multiplier (shorter) if trig = 1
unsigned long timeinterval = exprob * timeunit;
// Check if time interval has passed and if so trigger event
if ((millis() - last) > timeinterval) {
last = millis(); // updates timer to last event
digitalWrite(led2,HIGH); // indicator LED
mySoftwareSerial.write(playnext, sizeof(playnext)); // play next MP3
delay(10);
if (random(2)<1) mySoftwareSerial.write(playnext, sizeof(playnext)); // 50% of the time skip to next MP3
delay(100 + mosfetdelay);
analogWrite(fetpin,PWM); // turn on mosfet
delay(duration);
digitalWrite(fetpin,LOW);
digitalWrite(led2,LOW);
// the following equation runs once per event and
// generates a random float (exprob) that falls in an
// exponential distribution. It will be used to
// determine the interval time for the next event.
// Events that occur at exponentially distributed
// intervals form poisson processes.
exprob = (-2)*(log((100-random(100))/100.00));
}
else {
digitalWrite(fetpin,LOW);
digitalWrite(led2,LOW);
}
}
delay(20);
}
Most
microprocessors generate pseudorandom numbers that follow a uniform
distribution. This is great for simulating things like rolling dice
where the probability of rolling a 1 is the same as rolling a 4. It
turns out, however, that for most natural processes, the time between
events is more accurately modeled using an exponential distribution of
random numbers. This results in both more clustering of events and
larger gaps in between them. These are called poisson processes because
the distribution of events-per-time-interval follow a Poisson
distribution.
In
both of the two samples below, there are twenty events per time
interval. In the first sample, events are spaced using a uniform
distribution of random numbers. In the second sample, events are spaced
using an approximate exponential distribution (thereby generating a
Poisson process).
It’s
a subtle difference, but the exponentially spaced events seem less
regular—they occur both earlier and later than expected. The Poisson
distribution has been fitted to a wide variety of natural events. Events
as varied as radioactive decay/clicks on a Geiger counter, lightning
strikes, and Prussian soldiers killed by kicking horses have all been
described as Poisson processes.
This default code for the Twitch-n-Howl board uses a mathematical transformation to convert the uniformly distributed pseudorandom numbers into exponentially distributed numbers.
where u is the uniformly distributed random number and lambda is the rate parameter (# of events per unit time)
This same transformation is depicted graphically below. The blue line shows a uniform distribution of random numbers, while the red line shows an exponential distribution of random numbers. Both distributions have the same mean and area under the curve.
These exponentially distributed random numbers are used to determine spacing between events. One can see that using an exponential distribution of random numbers to determine event spacing would result in some events closer together and some events further apart than would be present using a uniform distribution of random numbers for event spacing. This is one of the properties of a Poisson process and helps explain why natural random events seem so unpredictable.
Flicker LEDs are nifty little components. Give them a tiny bit of current, and they produce a light that bounces up and down in a random-appearing fashion. It can bear a passing resemblance to the flame of a candle. The main problem with these LEDs is that they aren’t very bright. I have my Lightboard with a nice firelight effect, but I still wanted something cheaper and simpler with almost as nice of an effect.
Most of these LEDs have a small integrated circuit embedded in the plastic head that can seen if you look closely.
There’s a great discussion of reverse engineering these flicker LEDs in Tim’s Blog post “Hacking a Candleflicker LED”. He uses a logic analyzer to look at current drawn by the flicker LED. This reveals what appears to be a PWM signal of varying intensity that controls the flicker effect.
He then goes on a really impressive deep dive quantifying the PWM levels and speculating on the pseudorandom sequence generation. —Go read it, seriously. It’s not long and really fascinating.—
Windell Oskay, over at Evil Mad Scientist, put together a great post "Does this LED sound funny to you?" in which he uses a PNP transistor to amplify the signal being drawn by the flicker LED. he then sends this to a LED and then a speaker. Unfortunately the STX790a transistor he selects has been discontinued, and I had some difficulty finding a similar spec’d transistor (ie stopped after 10 minutes of google-ing). I did have some PN2907 PNP transistors lying around. I tried one of those in Oskay’s circuit.
The flicker LED would flicker nicely, but unfortunately just caused the transistor to continuously conduct. The secondary LED would just stay lit, perhaps a bit dimmer than usual. Interestingly enough, when I hooked the transistor up backwards (still in the same place in the circuit, but just swapping the collector and the emitter leads) both the flicker LED and the secondary LED would flicker. The effect seemed stable. The transistor was still working as a PNP transistor, but just with unknown specs. Seemed kind of sketchy and not exactly something I could recommend to others… So back to my parts box…
I have several "logic-level" N-channel mosfets lying around in my parts box, specifically the IRLB8721 and the FQP30N06L. I use both of these frequently for rapid switching (PWM and otherwise) up to a few amps of current at 12V.
I set up my mini digital oscilloscope to query the voltage at a few points along a simple flicker LED circuit and found that I could reliably detect the signal between the LED and the resistor when they were arranged like this.
This meant that I could replace the oscilloscope with my mosfet and use that to turn on and off my secondary LED. In order to protect the LED from the few picoseconds of in rush current to the gate when the fet was switching, I split the resistor before and after the LED like this-
This gave me the following signal
Voltage reliably switches back and forth between 0 and 5v. Perfect for running my mosfet. (Interestingly, it looks like the flicker LED uses an approximately 400Hz PWM signal and varies the duty cycle to change brightness. Most of the time the LED is full on, but will give “flickers” of various lower duty cycles.) This gave me the final circuit diagram.
The circuit is easy to put together on a breadboard, but I wanted a cleaner solution that could run flicker lights for several pumpkins, so I put together a PCB.
Here’s a picture of the board assembled and mounted. It has holes placed such that a zip tie can fasten the board to a 1/2” PVC T fitting. I can then slide a plastic cup over the top. This lets me mount it in the yard, covered from rain, and able to drain well.
And finally, here’s a video of the circuit in action and my assembly of an electronic PVC candle.
So, I’m still rather partial to the firelight effect on my Lightboard, but if you’re looking for something that doesn’t need any coding, this circuit is a great option. You can easily put this together on a breadboard, but if you’d like a more streamlined solution, I’m happy to put a PCB board in the mail. Check out the Jekyll-Labs Store and contact me through the link in the side bar.
So, I'm really pleased with this new (to me) MP3 player that seems like a nice alternative to the DFPlayer. Its manual is sometimes hard to find so I've hosted a copy of the PFD below. First and foremost, it has onboard storage for audio files. Your computer recognizes it as a USB drive, so it's a simple plug-n-play then drag-n-drop.
To trigger the audio the JQ8900 has a few options:
(1) There is a two-way serial connection using the Rx and Tx pins. This is the most robust way with many options analogous to the DFPlayer serial connection. Unfortunately, the serial commands are different from the DFPlayer, and I'm not aware of an existing Arduino library. Fortunately, the JQ8900 seems to be based on the JQ8400. The JQ8400 does have an Arduino library, but I have not personally used it. Both the JQ8900 and the JQ8400 have manuals that have been translated into English and have good information.
With the JQ8900, I'm partial to using the serial commands directly. "AA 06 00 B0" will play the next file. I've included below some example code that will every 5 seconds play the next file in sequence.
(2) There is a single wire input mode available using the VPP pin. I haven't personally used this, but there are many examples online (unfortunately for me, mostly in Chinese)
(3) The JQ8900 has 7 trigger pins. These are great. When the IO1 pin is connected to ground the JQ8900 will play the file named 00001.mp3 (and so on). This works well for manual buttons as well as microcontrollers. With this board, I used an ATTINY85 sending a signal to an NPN transistor to connect IO1 to ground.
Audio output is either speaker output (appears to be a 3W amplifier) or line level output via DAC and ground. For both outputs, the JQ8900 collapses the right and left channels into a single mono channel. This is a disadvantage as compared to the DFPlayer, which has mono output for the speaker, but stereo ouput for line level. If you need stereo output, the JQ8900 may not be the board for you.
Previously I worked on a motor controller board that would deliver random pulses to a prop. It worked well, but I was not quite happy with the randomization algorithm, and I wanted more titratable control over the pulses. Additionally I wanted something that could be triggered by either a PIR sensor or a button.
I’ve now produced a beta version of this new controller and I’m looking for feedback. Here’s a demo video—
This is the schematic—
And here is the code—
// Jekyll-Labs Twitchy Attiny85// Built for Twitchboard v1.5//int fetpin = 0;
int trigpin = 1;
int potMpin = A1;
int potRpin = A2;
int potLpin = A3;
int lambda = 5; // number of eventint timeunit = 60; // in this time interval (sec)unsignedlong last = 0;
unsignedlong timeinterval = 0;
float exprob=0;
voidsetup() {
randomSeed(A1);
pinMode(fetpin, OUTPUT);
digitalWrite(fetpin, LOW);
pinMode(trigpin, INPUT);
pinMode(potLpin, INPUT);
pinMode(potMpin, INPUT);
pinMode(potRpin, INPUT);
}
voidloop() {
// duration of signal will last from 0.5 - 10 secint durationpot = analogRead(potRpin);
long duration = map(durationpot,100,1023,500,10000);
if (duration <500) duration = 150;
// read middle pot for PWM of fet signalint PWMpot = analogRead(potMpin);
int PWM = map(PWMpot,0,1000,0,255);
if (PWM>255) PWM = 255;
// mean frequency of random signals is 5 events per time unitint freqpot = analogRead(potLpin);
int timeunit = map(freqpot,512,1023,60,300); // 2nd half dial range 1-5 minif (freqpot>1000) timeunit = 3600; // far right dial 1hrif (freqpot<512) timeunit = map(freqpot,0,512,0,60); // 1st half dial range 10-60 secif (freqpot<100) timeunit = 0; // bottom of dial continous on if (timeunit<=0){ // continuous on if left dial all counter clockwise
analogWrite(fetpin,PWM);
}
else {
// Check for trigger (X3 for debounce) and adjust// timeunit if trigger is positive.if (timeunit>0) {
int trigger = digitalRead(trigpin);
if (trigger == HIGH) {
delay(100);
int trigger = digitalRead(trigpin);
if (trigger == HIGH) {
delay (100);
int trigger = digitalRead(trigpin);
if (trigger == HIGH) {
timeunit = (duration * 10)/1000;
}
}
}
}
// Calcuate time interval between events. timeunit depends on:// Potentiometer value if trig = 0 // Duration multiplier (shorter) if trig = 1unsignedlong timeinterval = exprob * timeunit * 1000;
// Check if time interval has passedif ((millis() - last) > timeinterval) {
last = millis(); // updates timer to last event
analogWrite(fetpin,PWM);
delay(duration);
digitalWrite(fetpin,LOW);
// the following equation runs once per event and // generates a random float (exprob) that falls in an // exponential distribution. It will be used to// determine the interval time for the next event.// Events that occur at exponentially distributed // intervals form poisson processes.
exprob = (-1)*(log((100-random(100))/100.00)/lambda);
}
else digitalWrite(fetpin,LOW);
}
delay(20);
}
So I’m, really happy about this new board I had made.
It uses a Arduino Nano to control PWM signals for six different channels of lights. There are two potentiometers, one to select the effect, and a second to change the speed of that effect. The board uses IRLB8721 mosfets to control current to the lights. According to Adafruit these mosfets are capable of switching 15A of current so each channel could run several lights in parallel.
These are the lights I use. They were suggested by another haunter, because they are waterproof, they fit inside a PVC fitting, and draw only 60mA at 12V DC. To find them you can search Eagle Eye LED 18mm on Amazon/EBay/AliExpress.
Here’s a 4 minute demo of the board in the lab:
There are 4 different effects:
1. Solid - all lights are on and dimmable by the speed potentiometer
2. Firelight - a low flicker meant to evoke the light of a fire. Works well with several amber on the same channel and 1 dim red on another channel
3. Wavey - All channels slowly pulse on and off at slightly different wavelengths so they don’t synchronize. Speed potentiometer controls how fast they pulse
4. Lightning - Each channel strobes on with a random delay and a random number of flashes. Speed potentiometer controls how frequent the flashes are.
**I'm not in the business of selling Halloween circuit boards, but I usually have to order more than I need for any given project. If you're into DIY electronics (and let's face it, you wouldn't be reading this otherwise), and want one of my boards, send me a PM.**
Here's the Fritzing:
The schematic:
Here's the code for the nano: (updated 9-27-22 to fix millis() rollover.)
// Jekyll-Labs Lightboard v1.0
// D2 sensor
// D3 Power MOSFET (PWM avail)
// D4 sensor
// D5 Power MOSFET (PWM avail)
// D6 Power MOSFET (PWM avail)
// D7 Unused
// D8 Unused
// D9 Power MOSFET (PWM avail)
// D10 Power MOSFET (PWM avail)
// D11 Power MOSFET (PWM avail)
// D12 unused
// D13 unused
// A0/D14 Unused
// A1/D15 10k potentiometer
// A2/D16 10k potentiometer
// A3/D17 Unused
// A4/D18 Unused
// A5/D19 Unused
// A6/D20 Unused
// A7/D21 Unused
int ledpin[] = {3, 5, 6, 9, 10, 11};
int effectpin = A1;
int freqpin = A2;
int effect = 0;
int freq = 0;
int brightness[6];
int oldbrightness[6];
int fldelay = 75; // fire light flicker delay
int flalpha = 20; // fire light alpha 0-100 (low values less dynamic changes)
unsigned long lastupdate[6];
int between=500;
int randwavel[6];
int wavelength[6];
void setup() {
Serial.begin(9600);
randomSeed(A0);
for (int i =0; i<=5; i++) {
pinMode(ledpin[i],OUTPUT);
digitalWrite(ledpin[i],LOW);
}
for (int i =0; i<=5; i++) { //setting variables for flicker
brightness[i]= random(256);
oldbrightness[i] = brightness[i];
randwavel[i] = random(500);
}
}
void firelight(){
for (int i =0; i<=5; i++) {
if ((millis()-lastupdate[i])>fldelay) {
lastupdate[i] = millis();
brightness[i] = random(255);
brightness[i] = (flalpha * brightness[i] + (100 - flalpha)*oldbrightness[i])/100;
oldbrightness[i] = brightness[i];
analogWrite(ledpin[i],brightness[i]);
}
}
}
void wavey(){
for (int i =0; i<=5; i++) {
wavelength[i] = (freq/100)*1500 +1000 + randwavel[i];
int remainder = millis() % wavelength[i];
if (remainder <wavelength[i]/2){
brightness[i] = map(remainder, 0, wavelength[i]/2,-128,384);
if (brightness[i]<0) brightness[i]=0;
if (brightness[i]>255) brightness[i]=255;
}
if (remainder >=wavelength[i]/2) {
brightness[i] = map(remainder,wavelength[i]/2,wavelength[i],384,-128);
if (brightness[i]<0) brightness[i]=0;
if (brightness[i]>255) brightness[i]=255;
}
analogWrite(ledpin[i],brightness[i]);
}
}
void solid(){
freq = map(freq,100,923,0,255);
if (freq<0) freq=0;
if (freq>255) freq=255;
for (int i =0; i<=5; i++) {
analogWrite(ledpin[i],freq);
}
}
void lightning(){
for (int i =0; i<=5; i++) {
if ((millis() - lastupdate[i])> between) {
for (int c=0; c< random(7); c++){
digitalWrite(ledpin[i], HIGH);
delay(40);
digitalWrite(ledpin[i], LOW);
delay(10);
}
int lidelay = map(freq,0,1023,3000,20000);
between = 500+ random(lidelay);
lastupdate[i] = millis();
}
}
}
void loop() {
freq = analogRead(freqpin);
effect = analogRead(effectpin);
if (effect<100) solid();
if ((effect>=100)&(effect<512)) firelight();
if ((effect>=512)&(effect<923)) wavey();
if (effect>=923) lightning();
delay(10);
}
Parts List and links
Where convenient, I’m including links to parts on Digi-Key. I do not receive any commission from Digi-Key (or the parts fabricators), and I can’t vouch for the specific parts I link to. But I generally find Digi-Key to be very reliable with a good library of parts. You may find cheaper prices elsewhere.
Another Haunter on Facebook asked about making a barb wire fence that would make an "electric shock" noise when you touched it. That inspired me to put together a quick prop based on capacitive touch.
It’s pretty simple to put together. No Arduino involved. The sound comes from an Adafruit Sound FX board. They aren’t the cheapest option, but really easy to work with. I've saved a sound clip of electric shock to the board's memory as T01HOLDL.wav. This way it will play the sound whenever pin #1 is connected to ground. WAV files require less decoding so play faster. Pin #1 is hooked to the output from a capacitive touch sensor. The sensor is set to give a ground signal when you touch it, 5v when you don’t touch it. For this particular sensor, you need to add a glob of solder to connect the "A" pads. I then scratched off some of the plastic covering the sensor and soldered a long wire to the sensor. That’s then connected to the outlet (which is of course NOT connected to household power or anything else.) 5V DC power from a wall wart transformer (or even 3 AA batteries) run to the power pins for both the sound board and touch sensor.
I highly recommend the Adafruit tutorial on their SoundFX boards. There are cheaper options for audio (DFPlayer mini is one of my favorites) but Adafruit is a great place to start. Adafruit also sells a great Capacitive Touch sensor board, but this one is cheaper and has the option to output ground signal with touch.
I wanted to show off a twitching victim I made for a friend's spider themed haunt. Here's a video of the prop in action.
The mechanism is based on an automatic car door lock motor like this:
It's available on Amazon for about $6 and runs on 12v DC. Here are a couple close up pictures of the mechanics.
The PVC and motor were then covered with plastic bags for bulk and then a couple layers of plastic treated with a heat gun to give the right corpsed/spun web appearance.
This electronics for this project are an extension of a lighting simulator I made previously. For this project, the frequency of the random twitches are controlled by the potentiometer. The arduino sends 5 volt signals to the mosfet which in turn controls the 12 volt motor.
To keep things small and cheap, I built the circuit based around an ATTINY85. These processors are great because they are very cheap (usually <$2) and programmable using the Arduino IDE. Here's a picture of the board.
Alternatively this could be built with an arduino uno and mosfet as a simple first arduino project.
Here's the schematic for the circuit:
And here's the code: [code updated 8/29/22 to account for millis() rollover]
// Jekyll-Labs Twitchy Att
iny85
// Built for Randflash board v1.1
//
int fet = 0;
int pulses = 1;
int pot = A1;
unsigned long start = 0;
void setup() {
// initialize digital pin LED_BUILTIN as an output.
pinMode(fet, OUTPUT);
randomSeed(A0);
}
// the loop function runs over and over again forever
void loop() {
int potsens = analogRead(pot);
if (potsens < 120) potsens = 0;
unsigned long delaybonus = map(potsens,0,1023,0,600000);
if ((millis() - start)>(3000 + delaybonus)){
start = millis();
pulses = random(3)+1;
for (int i = 0; i < pulses; i++) {
digitalWrite(fet, HIGH); // turn the LED on (HIGH is the voltage level)
delay(150); // wait for a second
digitalWrite(fet, LOW); // turn the LED off by making the voltage LOW
delay(600); // wait for a second
}
}
else {
digitalWrite(fet,LOW);
}
delay(10);
}
I decided to start playing with the Attiny85 processors because they are small, cute, and cheap. I love the arduino nano, but even the knockoff clones shipped from China are costing more than $5. I decided a great first project would be the lightning simulator. Here's a video of the final project:
Here is the Fritzing layout: (with 12v's worth of AA batteries and a single LED for the 12v light)
and the schematic:
After making it on a breadboard, I had a PCB printed to make the process more compact:
The code is Rob Tillaart's lightning code. Simple and effective.
//
// FILE: lightning.pde
// AUTHOR: Rob Tillaart
// DATE: 2012-05-08
//
// PUPROSE: simulate lighning POC
//
//
#define BETWEEN 2579
#define DURATION 43
#define TIMES 7
#define LEDPIN 0
unsigned long lastTime = 0;
int waitTime = 0;
void setup()
{
randomSeed(analogRead(2));
pinMode(LEDPIN, OUTPUT);
}
void loop()
{
if (millis() - waitTime > lastTime) // time for a new flash
{
// adjust timing params
lastTime += waitTime;
waitTime = random(BETWEEN);
for (int i=0; i< random(TIMES); i++)
{
digitalWrite(LEDPIN, HIGH);
delay(20 + random(DURATION));
digitalWrite(LEDPIN, LOW);
delay(10);
}
}
// do other stuff here
}
I wanted to share a new method I’m using for making electrical connections in my yard holiday setup. I’ve been looking for something safe, waterproof and ideally modifiable/reusable for when I change my mind/layout.
I’m sure that others have discovered these previously, but I am loving the WAGO 221 lever nuts. Works for AWG 12-24, rated for mains mower amps/volts. Apparently more common in Europe for household wiring, but also certified by UL for household wiring in the US. I’m only using them for 12V 5A DC circuits, but it’s nice to know they’ve been well tested.
I’m using 18g landscaping “lamp” wire and 35mm film canisters for my junction boxes. Here are a few pictures of my set up.
*I have no financial connection with any of this. Just sharing something that works well for me. ** I’ve also tried a similar product that I found on Ali-express. It is much cheaper. But also much lower quality. Perfectly fine for throwing something together, but the wires fit in less well. I’d also never use it with mains power.
