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Wiring LEDs to Hare Accessory Decoder

Posted by on Apr 24, 2017 in Tips DCC Components, Tony's Tips |

I have just installed the Hare 1 (Rev K) and it works well. I have added a toggle switch that is installed on a control panel and I have added a dwarf signal (two 2-wire bipolar LEDs stacked one on top of the other with a common wire connecting the two, one wire for the top LED and one wire for the bottom LED then wired according to the top illustration on page 4 of the manual included with the product) to the Hare connections and they also work well. I now want to add 2 3-wire bipolar LEDs to the circuit that will go with the toggle switch on the control panel. The illustration in the manual is not clear how to wire this type of LED … they need to be in series but I don’t know how to do this. Can you suggest a wiring solution or provide a wiring diagram? Thank you Kindly, Marvin P.

CAM output

Marvin, the problem is that the Hare cannot drive all of the LEDs that you want. I have attached a schematic showing how to build a current multiplier so you can run any number of LEDs that you want. For your dwarf signal, you connect one LED to the Clear group and one to the Throw group as shown in the schematic. For the bi-color LEDs, you need a common anode style (available from Tony’s Trains). The common anode lead is connected to the +5V. One cathode goes through a 390 ohm resistor (as shown) to Q1-3. The other cathode goes through a 390 ohm resistor to Q2-3. This design will run each LED at about 10mA, so make sure the 5V can supply enough current for all of the LEDs you are using. If the LEDs are too bright, you can change the 390 ohms to 750. This will give you about 5 mA of LED current. These parts are generally available, but Digikey stocks all of them in addition to Vector boards that you can use to make the circuit (Digikey part V1044-ND). You will need one circuit for each Hare.