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MM100s - Increased Amp Turn-On Capacity

The Amp Turn-On output (blue wire) of the MediaMaster® MM100s is used to remotely activate (or turn-on) external amplifiers. Its maximum output capacity is 40mA, which should be more than adequate to turn on a few amplifiers without issue.

In some situations, such as systems with many amplifiers or amplifiers equipped with less efficient turn-on circuits, it may be necessary to increase the output capacity of the Amp Turn-On wire. This can be accomplished with a few electronic components and a standard, SPDT automotive relay with a built-in diode.

We recommend using a SparkFun MOSFET Power Control Kit, which includes two screw terminals (one 2-pin and one 3-pin), a single RFP30N06LE MOSFET, a 10k resistor, and a PCB (printed circuit board), as shown in Figure 1. This prepackaged kit has a labeled PCB and is designed for easy assembly, with only ten pins to solder and easy-to-use screw terminals for wire connections.

SparkFun MOSFET Power Control Kit
Figure 1

Once assembled, the Power Control Kit’s output is used to trigger a relay, which may be wired in a variety of ways to accomplish your needs. For this application, we’ll use the relay to deliver a higher capacity output that can be used for turning on amplifiers or activating other +12VDC circuits.

Arrange the components on the PCB as illustrated in Figure 2. Note, the text printed on the PCB indicates the top. Be sure to position the terminals with the openings facing outward, so that wires can be easily inserted. Trim the pins as needed and solder all connections from the underside of the PCB. The assembled Power Control Kit should look like Figure 3.

MOSFET Power Control Kit Assembly
Figure 2
MOSFET Power Control Kit Assembled
Figure 3

Make connections to the Power Control Kit and relay as illustrated in Figure 4. For most “amp turn-on” applications, you may use 18 AWG size wire and the relay’s +12VDC input may be fused with a 3-amp fuse. For circuit applications requiring more current capacity, we recommend increasing the fuse value and wire size, as appropriate.

MOSFET Power Control Kit Diagram
Figure 4

Once completed, make sure to insulate the entire Power Control Kit with heat shrink tubing to prevent possible short circuits. For marine applications, we recommend applying silicone or other moisture barrier to inhibit corrosion.

* Use a SPDT, non-latching relay that is equipped with an internal diode. If your relay is not equipped with an internal diode, you must add a 1-amp diode across the relay’s coils (terminal 85 and 86). Make sure to position the diode’s cathode (stripe) towards terminal 86 as pictured above in Figure 4.


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