Micorseven Mic Install
Tested a Micorseven M7WP microphone ($22.00 USD) for use with a Dahua 5242 and 2831 bullet cameras. The mic works well on both and is very sensitive.
Installed on the 2831 using a 9 VDC at 350 mA small transformer (heavy) type of wall wart. The wall wart is of the old design with no regulation but with good filtering. Required a separate pair of wires for the mic DC line which were in place for another application.
At no load, the output voltage is in the 16 to 17 DC volt range. Used 20 feet of shielded wire to connect the mic output audio to the 2831. Works perfectly with no RF interference or hum. The current at 17 VDC is a little over 1 mA (1000 microamps).
The second setup requires that two cameras use one mic as both cameras are within 18 inches of each other. One wide view and one closeup of the same view. The camera inputs (audio) are connected in parallel using one Micorseven mic output.
The overall gain is a bit less, but more than adequate on both cameras. Individual camera gain settings make up for any loss. The gain settings are different on both cameras, but still well within usable ranges. i.e. more audio gain than needed!
To power this second install, used a 12 VDC regulated wall wart (light weight - no transformer) from a Linksys router. It is well regulated with excellent filtering. i.e. the voltage does not change much from fully loaded to uploaded. At 12 VDC the current for the mic is at 760 micoramps. Again, used an existing pair of wires for the mic DC line.
The Micorseven mic will work at 5 VDC but not well. Would recommend starting at 6 VDC as the minimum. At 9 VDC the mike works very well up to 20 VDC.
Listing of mic current requirements at various DC voltages.
5 VDC - 360 microamps
6 VDC - 420 microamps
9 VDC - 600 microamps
12 VDC - 760 microamps
15 VDC - 930 microamps
16.24 VDC - 1000 microamps or (1 mA)
Some have asked if a 9 VDC battery could be used to power the mic. Overall the answer would be yes, but with frequent replacement. If the battery is rated at 450 mAh at .6 mA one could expect 750 hours (about 4 weeks) of 24 x 7 use.
However, if the camera has relay outputs that can be activated when motion occurs, then the mic would be only powered on with motion. Then powered off most of the time depending on motion within the chosen field of view.
Item seems to be discontinued product but can still be found from many places. Yeah that "brick" made me also wonder but no man should never judge by the name:
