Hello Guys. Can someone help me with my problem. I am using ARDUINO UNO SMD board. I used MQ sensors to read the data for carbon monoxide readings are good and display in serial monitor. but when I disconnect the cable from arduino and replace it with 9V battery for power supply, the Readings STOPs in Serial monitor. Is it the board problem ?
The problem is the 9V battery. Replace it with 3xAA non-rechargeable or 4xAA rechargeable. Connect to the 5V pin, not Vin.
How much current do the sensors draw? If your batteries are the small rectangular smoke alarm batteries, that is likely your problem. Those batteries will not supply very much current. Get better batteries.
the problem is the battery, you would need a car or truck battery to power the MQ for a couple of days.
that is the wrong sensor for battery power. it has to have power for 24 hours to stabilize before the readings are valid.
5V x 33 ohms - 0.15 amps, 151 mA
24 hours 3,624 mA
A new AA battery will deliver up to 3,000
so to get more than a day, you would need quite a few.
as for the 9V, expect about 400mAh
Use a MEMS sensor.
more expensive, but much less power and does not require continuous heating.
The problem is not comprehending what the "barrel jack", "Vin" or "RAW" terminal is. It is essentially an ornament provided in the very beginning of the Arduino project when "9V" power packs were common and this was a practical way to power a lone Arduino board for initial demonstration purposes. And even then it was limited because an unloaded 9 V transformer-rectifier-capacitor supply would generally provide over 12 V which the regulator could barely handle. Once almost any other device is connected to the "5V" pin (or many outputs are used), it fails.
If powering from batteries, as long as the battery pack cannot exceed 5.5 V, this must be connected to the 5 V pin.
Nowadays, 5 V regulated switchmode packs are arguably the most readily available in the form of "Phone chargers" and switchmode "buck" regulators are cheap on eBay so these can be fed into the USB connector or 5 V pin to provide adequate power for most applications. Unfortunately, many tutorials or "instructables" are seriously outdated or misleading and have not been updated to reflect the contemporary situation.