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Connecting the N8012 Signal Flasher

 

This flasher is part of a series that incorporates a state-of-the-art component which provides a constant 20 ma current source for LEDs connected to the flasher. This means any color 20 ma LED can be connected without the need of external current limiting resistors, multiple LEDs can be connected in series* and different colors of LEDs can be combined in the same series. All will operate at 20 ma and full brightness.

* A power supply of sufficient regulated DC voltage (not exceeding 16VDC) is required to support multiple LED in series. To determine power supply requirements, add all device voltages of the desired LED series together plus another 5 volts for the current source. This total is the minimum supply requirement and it must not exceed 16 VDC.

Connecting the N8012 Flasher:

Included with the flasher are two 6” lengths of #24 wire (red & black). If necessary, these can be used for connection to a regulated DC power source. The black wire should be soldered to the – DC connection (upper right corner of the flasher board—see Fig 1 below). The red is soldered to the +DC (upper left corner of the board) . If desired, the red can be wired through a switch to turn the flasher on and off.

An LED is connected to the flasher with the anode or + side of the LED wired to the A solder point on the flasher and the cathode or - side of the LED connected to the C solder point. If multiple LEDs are wired in series, the anode of the first LED in the string connects to “A” and the cathode of the last LED connects to C.

 

                            Figure 1

LEDs wired in series are always to be connected anode to cathode.

Do not connect anything to solder point B. This is used for a different version of the flasher circuit and is not functional with this N8012 Signal Flasher.

Adjusting LED brightness

For certain applications it may be desirable to have the LED or LEDs connected to this flasher operate at less than full brightness (less than 20 ma current). If this is desired, solder a short piece of wire as a jumper (shown in red) between the two holes as indicated in Fig. 2 below.

                            Figure 2

Next, solder pads are included on the back of the flasher board (on the backside of the C solder point) for placement of a resistor to compensate current source output down from 20 ma. Fig. 3 below shows a resistor placed on the C solder pads).

 

                            Figure 3

To calculate the resistor value, divide the LED device voltage by the milliamps (ma) you wish to reduce. This will give the value in ohms of the resistor (we recommend using a 1/4 watt resistor).

Example: Reduce the current output from 20 ma to 10 ma with a red LED having a device voltage of 1.7. Divide 1.7 by 0.010 (10 ma). The result equals 170. Use a 170 ohm resistor. To reduce current through a series of LEDs, add the device voltages in the series together then divide by the amount of ma current reduction.

A mounting hole is provided for a #4 or 4-40 screw for mounting the flasher. A small spacer or non-conducting washer should be placed on the underside so the back of the board is not in contact with a surface or object which might short-circuit the board.

 

Using the Flasher and bypassing the on-board current source

 

There may be applications where power supply limitations, and device voltage requirements (of series connected LEDs), call for bypassing the Flasher's on-board 20ma current source. Remember, as noted above this current source takes 5-volts from the connected power source for proper operation.

An example would be our little N-scale intersection diorama as seen in the Video of effect for this Flasher. In this case we powered our portable display with a 9-volt battery. The signal head consists of 4 LEDs (2 red Micros and 2 yellow Micros) wired in series. Remember, a variation of Ohm's Law (details here) states that when LEDs are connected in series, the current drawn doesn't change, but the required voltage for operation is the sum of all LED device voltages added together. So... in our example, the 4 LEDs add up to 7.7-volts. Using a 9-volt battery for power, we only have 1.3 volts left over, certainly not enough for the current source to operate correctly. In this case, we use the wiring method shown in Figure 4 below.

                                                    Figure 4 

 

Here, we connect the series wired LEDs (with a current limiting resistor) to the + power connection for the Flasher (where the + of our 9-volt battery will be connected), instead of the A solder point on the board. The last LED cathode in the series gets connected to the C solder point as normal. By doing this we have bypassed the on-board current source and are able to operate the circuit using the 9-volt battery. The down-side is that we must use a current limiting resistor in series with the LEDs because we have eliminated the current source. In this case, a 65-ohm resistor would be required for full brightness of the LEDs. We used one of our N80R6 (81-ohm) resistors which was close enough for full intensity.

 

Using DCC Track Power

 

While it is always preferable to use track power exclusively for things running on the track, there may be situations where it is necessary to tap into track power to drive various stationary devices. Should this be the case in a DCC environment, our Super Flashers can be powered from the track with the addition of two readily available components: a bridge rectifier (our N301S would work just fine), and a polarized (electrolytic) capacitor. Figure 5 below is schematic diagram of the connections required.

                                                    Figure 5

DCC track power is such that to devices requiring plain DC voltage, it looks like AC power. That is because voltage levels on each track go both + and –. The DCC decoders in locomotives “descramble” the track signals and provide correct polarity so their motors can function normally. What this small circuit is doing is running the DCC voltages through a bridge rectifier to “filter” the track voltages so that + DC is output on the bridge’s + terminal and –DC is output on the bridge’s – terminal. This DC signal is still a bit “bumpy” (not a smooth DC signal) so we add the capacitor to smooth it out. As a result, the voltage going into our flasher is smooth DC and the flasher works normally.

One caution: Make sure the DC voltage level at the output of the bridge rectifier does not exceed 16-volts or the Super Flasher will be damaged. Some DCC systems (typically larger scales) can produce voltage levels higher than 16-volts.

 

This completes connection of the N8012 flasher. We recommend a thorough re-inspection of all connections and placement of the flasher be performed prior to applying power .We hope you enjoy the added realism our flasher provides.

 

© 2008 Ngineering