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I'm looking for a portable power source for an MQ-7 gas sensor. According to my research - it needs 5V D.C power with at least 0.3A of current. I'm not really good with electronics so I need to know if I can use a 9V battery instead which produces 0.5A. Will the cell damage my sensor and if it does may you please recommend me something else.

  • I don't think a 9V battery can supply 0.5A. – Gerben Apr 5 '16 at 15:02
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You can, but you will have to reduce the voltage to the 5V the sensor needs, otherwise you will blow up the sensor.

To that end you require a voltage regulator. You can use a linear regulator like the Arduino has on-board, but they are very wasteful of power and will dissipate the excess 4V of electricity as heat.

Better would be to use a switching regulator (commonly and cheaply available on eBay and other sites) to step the voltage down to 5V more efficiently.

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  • Thanks. I was considering a voltage regulator but I'm not sure If that can be shipped to where I live in a week without extra costs. Can I use 4x AAA cells instead? – ron weasly Apr 5 '16 at 15:05
  • It requires 5V ±100mV, so 4.9V to 5.1V. 4 AAA alkeline is 4x1.5 = 6V (too high). 4 AAA NiMh is 4x1.2 = 4.8 (too low). You might get away with 4x NiMh at a pinch, but as they discharge the voltage will drop and it will fail. – Majenko Apr 5 '16 at 15:08
  • Ok, so do 4 AAA NiMh cells provide 0.3A as well? – ron weasly Apr 5 '16 at 15:22
  • They can provide considerably more than that. They will last much longer than a 9V PP3 which would be lucky to last an hour. – Majenko Apr 5 '16 at 15:23
  • Thanks, so I can safely use 4 AAA NiMh? I don't mind them not lasting over an hour - I just need to make a demonstration then I order a voltage regulator to create a proper circuit! – ron weasly Apr 5 '16 at 15:44

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