Light Magic Wiring

We have been playing with new graphics software, and I thought that it might provide clear illustrations of how to wire your Light Magic. Light Magic has five connectors, three are outputs to the three light circuits, and two are inputs for power and signal.

Light Magic Overview

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leds

Long lead gets the (+) wire

First, lets examine the LED circuits. You can use any LED that will operate on less than 70 milliamps (mA) of current, but the leds that we recommend are either 5mm or 3mm superbrights that require about 25mA to achieve full brightness. These LEDs are made of a round small glass bulb containing semiconducting materials that produce light of a particular frequency when a voltage larger than the forward voltage is applied to the leads. If you take a careful look at the device, you will see that one of the leads is longer than the other. This longer lead is the anode or the (+) terminal that is connected to the (+) side of the battery.

You will also observe that the glass is clear regardless of the color of the LED.

 

Nav circuit

LED’s are wired in series

The Navigation light circuit shown consists of three LEDs. All three are different colors. Each color has a different forward voltage, ranging from 1.7v for the red led to 3.5v for the white led. The different forward voltages require that the lights be wired in series, as shown. If you wire these lights in parallel, you will find that only the red light works. This is because the electric current takes the easiest path through the circuit, which is through the lowest forward voltage. We recommend that you wire the circuit as shown using a specific color (red shown) for the positive wire of the circuit. Attach this wire to the (+) side of the connector on the Light Magic board.

 

output connections

Output connections

In a series circuit, the first two LEDs have red wires on both sides because each is connected to a long lead. This will make it easier for you to identify particular wires in the airplane. The other two LED circuits are wired in exactly the same way.  If you measure the voltage between the positive side of each LED and ground, you will find that at the first led the voltage will be equal to your battery voltage. The voltage will drop an amount equal to the forward voltage for each successive LED in the circuit. This means that the battery voltage must be greater that the sum of all of the forward voltages in the circuit, or none of the lights will turn on. (One caution on voltage measurements: the pin marked (-) on the output connections is not a ground. Use the battery negative as a ground.) On a typical NAV light circuit, the sum of the three voltage drops will be about 8.7v. A 2S li-po battery that produces 7.4v will not light up this circuit. You will never have to scratch your head over this one if you use a minimum of a 3S (11.1v) battery to power your lights.

For the same reason, your receiver battery will not power your Light Magic. Look at the following illustration:

inputs

Input connections

Note that the red (middle wire) from the receiver is marked “Not required”. While it is perfectly OK to hook up the unit as shown, realize that the middle terminal on the Light Magic is not connected to anything. Your receiver battery will not power Light Magic and Light Magic will not deplete your receiver battery. Light Magic is intended to be powered through the battconnection marked “BATT” for two reasons; (1) it is not a good idea to use the limited capacity of the receiver battery for lights, and (2)  the voltage of a typical receiver battery to far too low for LEDs in series. Therefore, a separate 3S battery or the plane’s 3S (or larger) propulsion battery should be used to power Light Magic. The maximum voltage that you can place on the battery terminal is 30v. If you use greater than 30v (10S battery or larger), you will destroy the Light Magic unit.

output connections2Connect the Light Magic to your receiver via the SIGNAL connection on the unit using the three wire connector that came with the unit. Make sure that the ground connection and the signal connection are not reversed. inputsUse a spare channel on the receiver and the transmitter that you can assign to a two position switch on the transmitter.

Plug one end of the 3 wire connector into the channel that you have assigned the two positions switch, and the other end on to the connector marked SIGNAL (pin marked S). Connect the battery you have chosen to power your lights to the BATT connection on the Light Magic.Light Magic power connection

 

There is something else to be aware of. You probably have heard that it is necessary to limit the current flowing through an LED. This is often done with a current limiting resistor in series with the battery. Note that there are no resistors in the Light Magic led circuits. In Light Magic, the function of the resistors is handled output current controllers on the Light Magic board. The current controllers automatically limit the current to the 25mA needed by the superbright LEDs.

I hope these illustrations have been helpful in understanding how to wire up Light Magic. Although Light Magic is shown here, the same process is used to wire the LEDs on both Flash Magic and Jet Magic. Have fun flying.

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