APPLICATION NOTE 010

ILLUMINATION AND SECURITY

Benjamin Bacon, Owner, Plane Space Design

The POWIM-PD and MISO are both ideally suited for applications that involve illumination and the security scenarios in which light is used. Two properties of these products make this the case. One is that the pulsed driver can power LEDs that are powerful enough to illuminate an area. The other is that there is a backup power port on these products that defeat the attempts made by intruders to cut the electricity that powers security devices.   Tampering and other haphazard power loss events are prevented from causing a security hole when the POWIM-PD and MISO are applied.

Illumination is possible through the Pulsed Driver front end of the POWIM-PD. The current capability at the pulsed driver is defined by the equation

I_out = V_in / (R_L + 0.80)                                               (1)

where R_L is the load resistance. It is a good idea to consider the inductance and capacitance of the load also. The lower the inductance of the load the more suitable it is for use with the pulsed driver.  That is because reactive loads are sensitive to the pulse frequency which is about 3.57 kHz typically. The frequency is 3.5 times the usual frequency encountered in this type of pulsed driver. The higher frequency enables higher illumination from light emitting devices, but the inductive reactance is the trade-off.

The input voltage, V_in, can always be two independent sources. One source is the backup of the main source. If the you connect two sources of the same voltage to the two input ports of the POWIM-PD or MISO they will share the current drive to the front end at a ratio of roughly 50-to-50. If one of the sources should cut out, then the remaining source will take 100% of the current drive responsibility of the load.

All of the MISO units can be operated with source voltages of different magnitudes. The switching behavior of the particular model that you have will determine how each unit will behave. The three possibilities are

• MISO 13.5-12 :a unit that switches MAIN on when the MAIN voltage is above 13.5 V and MAIN off when its voltage falls below 12.5 V. When MAIN switches off the SECOND voltage switches on.

• MISO 12-10 :a unit that switches MAIN on when the MAIN voltage is 12 V and MAIN off when its voltage falls below 10 V. When MAIN switches off SECOND switches on.

• MISO 100MV :a unit that switches MAIN on when the MAIN voltage is 100 mV above SECOND and MAIN off when its voltage falls 100 mV below SECOND. When MAIN switches off SECOND switches on.

All of the above units are dependable security power sources and have equivalent capabilities.

The reasons to choose a MISO over a POWIM-PD are

• The enclosure of the MISO, which is a durable easily mountable cylinder.

• You do not need the pulsed driver to illuminate an area; the MISO uses the pulsed driver to operate a power level indicator LED.

In the case where you want to use the pulsed driver for illumination and you want the enclosure also, the MISO can be easily modified to accommodate your light emitting devices.

In these turbulent times, the possibility that security systems will be tampered with by nefarious forces is real. Especially in the places where subversion and sabotage is the primary means of preparation for an act of felony under the cover of darkness. Imagine the surprise that the wrongdoer will suffer when they get illuminated by the security lights that they thought they had cut the power to.