10: Spark Core Battery Drain

I don't have a meter on input but the 12,000mAh battery shown in the post 9 image is only down 25% after about 30 hours. The same battery will only run a Raspberry Pi model B (and similar devices) for about 24 hours.

9: Spark Core/Imitation Arduino

I've managed to build a sketch for the Core that lights an LED, switches relays, reads a photo sensor and reads temperature from a TMP36. These activities are controlled from a Raspberry Pi and the results are posted on the Web. Here's a messy pic of the Spark setup powered by a battery.

(the cludged-up 9V flashlight (lower-left) is to prove the switch is working)

Here's the sketch:
int led = D0;
int relay1 = D7;
int relay2 = D6;
int photo = A0;
int tmp36 = A1;
int rval;
int r1state = 0;
int r2state = 0;

void setup()
{
    Spark.function("spark", getSpark);
    pinMode(led,OUTPUT);
    pinMode(photo, INPUT);
    pinMode(relay1, OUTPUT);
    digitalWrite(relay1, HIGH); // backwards for "normally closed" relay
    pinMode(relay2, OUTPUT);
    digitalWrite(relay2, HIGH);
    pinMode(tmp36pin, INPUT);
}

void loop() {
    // not used
}

int getSpark(String command)
{
    int raw, f;
    float v, c;
    
    int cmd = command.toInt();
   
    blink(cmd); // for my visible feedback
    switch(cmd) {
    case 1: // return photo sensor analog reading
        rval = analogRead(photo);
        return rval;
    case 2: // switch relay 1
        if(r1state == 0) {
            digitalWrite(relay1, LOW);
            r1state = 1;
        } else {
            digitalWrite(relay1, HIGH);
            r1state = 0;
        }
        return r1state;
    case 3: // switch relay 2
        if(r2state == 0) {
            digitalWrite(relay2, LOW);
            r2state = 1;
        } else {
            digitalWrite(relay2, HIGH);
            r2state = 0;
        }
        return r2state;
    case 4: // return TMP36 temperature in F
        raw = analogRead(tmp36);
        v = (raw * 3.3) / 4095;
        c = (v - 0.5) *100;
        f = (c * 9.0/5.0 + 32.0);
        return f;
    default:
        break;
    }
    return cmd;
}

void blink(int n)
{
    int i;
    
    for(i = 0; i < n; ++i) {
        digitalWrite(led, HIGH);
        delay(500);
        digitalWrite(led, LOW);
        delay(500);
    }
}

8: My Spark Core

This wasn't too painful. The $40 Core came in a cute box complete with cable and half-size breadboard (neither of which I needed).

Spark's web info is nicely finished and things work almost as smoothly. However, the idea that the Core is "Arduino compatible" is a stretch. First off, the processor is different; it's 4 times faster and has 4 times the memory, but fewer ports. The C Language programming syntax is the same but not the libraries. Also, a C "int" variable is 32 bits, not 16. Non-trivial Arduino sketches will not just plug-and-play. There's no Arduino-like app for my Mac. One programs from their www.spark.io/build web-based interface. Once you get the Core set up with your wifi & Internet (both required) the USB cable is mostly just for power. When you are ready to test a program you click the "flash" button and the source gets uploaded, compiled and downloaded. This takes longer than from the Arduino.app but for the smallish programs one usually writes for a "programmable controller" it's not a big deal.

7: A Compact, Secure Way to Mount a Nano
(modified 9/22/15)

I got a couple of these through Aliexpress. Without wires coming out the edges this thing is less than 1.5" wide.

Each Arduino pin is brought out to a screw-down connector. Screw the patch wires down and the whole thing is much more rugged than using a no-solder breadboard. The unit came in pieces -- 60 solder joints to complete it. Yuck. Testing them all was a trial.

Another mounting trick I'm interested in: use a 40-pin ZIF (zero insertion force) connector.

I'm not sure if this will work -- is it wide enough? But if the Nano fits with width to spare then you could put the Nano at one end and also clamp jumper wires out to sensors, etc. NOTE: Doesn't work!

6: Question about RFID-522 Reader

I wanted to do the "unlock the door using an RFID chip" trick. So I got a device from Sainsmart.

http://www.sainsmart.com/arduino/arduino-components/sainsmart-mifare-rc522-card-read-antenna-rf-rfid-reader-ic-card-proximity-module.html

Besides the sensor the package handily included one-each RFID keyfob- and credit card-type test devices.  I downloaded a library and sample sketch from the Internet, wired up the device and -- it didn't work. I downloaded a different library and sketch -- also didn't work. I was trying to test using the keyfob. Then I accidentally tested using the card. Worked! It had always worked.

I complained to Sainsmart and they eventually sent me a whole 2nd setup (new device, new fob, new card). Both cards work, neither of the fobs are recognized.

Anyone understand this problem?

Here's my sketch:

/*  Nano pins:
  RST: Pin 9
  SS: Pin 10
  MOSI: Pin 11 
  MISO: Pin 12 
  SCK: Pin 13  
*/  
#include <SPI.h>  
#include <RFID.h>  
#define SS_PIN 10  
#define RST_PIN 9 

RFID rfid(SS_PIN,RST_PIN);  
int serNum[5];

void setup(){  
  Serial.begin(9600);  
  SPI.begin();  
  rfid.init();  
}  

void loop(){
  int i;
  
  if(rfid.isCard()) {  
    if(rfid.readCardSerial()) { 
      for(i = 0; i <= 4; ++i) {
        Serial.print(rfid.serNum[i]); Serial.print(" ");
      }
      Serial.println("");  
    } else {
      Serial.println("nr");
    }
  } else {
   Serial.println("-");
  } 
  rfid.halt();
  delay(1000);  
}   

5: Have You Heard of the Spark Core?

Where have I been? Sounds like what I've been looking for. See--

https://store.spark.io/?product=spark-core

4: More on Gas Sensors
* revised 3/2/15 *

Things I've learned since last post:

1. The timing for letting the sensor heat up in my last post is wrong. I did 50 tries waiting 4 seconds between each. 50 is ok but 5 second wait is better.
2. The usual web examples suggest that the 5v to heat up the sensor needs too much current for it to come from the Arduino 5v pin. So I tested both my MQ-4 and MQ-7 both ways -- with external source and from the 5v pin. Both ways worked with the following caveat: the base (heated up) values were higher (both MQs) with Arduino juice (30%-ish). So why bother with external? Wrong again! Seemingly any change on the current load on the Arduino's pins changes the warm-up and base readings from the MQs. Back to external 5v (Drat!).

I want to mount my project as a hand-held portable unit like the diagram below. But I'll need to do 2 things to make this work: a) put a switch on the 5v lines to the MQs (so as not draw both currents at once) and b) de-solder the actual sensors from their circuit boards so I can mount them as shown.

the size of a flashlight

Comments?