* revised 3/2/15 *
Things I've learned since last post:
- 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.
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!).