hey. can somebody help me with the power thingy
i hav 3 sensor modules (fire,vibration,gas)
i want to power them externally. what is the best way?
P.S : recently i build a 5v regulator circuit using 7805
when i use 9v battery in input ..
the sensors reading are varying/chaotic/noisy 
please help :))
7805 needs correct decoupling capacitors mounted close-by to work properly - did you
use them?
By 9V battery do you mean those small PP3-size ones? They cannot produce much current,
gas sensors normally have a heater element that takes quite large currents, you need
to ensure the supply can power the load...
Sir , can you tell me what is the best way to power them externally.?
following are the sensors i need to power them ..
http://dx.com/en/p/mq3-high-sensitivity-alcohol-detector-sensor-module-red-165242#.UvjG6_mrSLV
all requires 5v !
i made this voltage regulator before
http://competefornothing.com/l7805-voltage-regulator-for-arduino-5v-1amp/