Designing a control panel for the yard

Driving Bi-color LEDs with an ECos Detector Extension.

I needed to use bicolor green/red LEDs on my control panel to indicate which track was selected by a given turnout(switch) to save space and reduce the number of LEDs to 2 per turnout (there will be 43 turnouts on the panel). Unfortunately the ECos Detector Manual is not helpful for this – but the description of the outputs per the ESU website is as follows :”Each one of the 32 outputs provides current up to 100mA max. Since these outputs are conducted as ‘open collectors’, you are able to connect either small light bulbs or LEDs with current limiting resistor directly to it. “

So the logical thing to do was to take off the cover from the detector an get a clue to its architecture. The board is driven by a microprocessor which then leads to 4 shift registers that drive 8 N channel MOSFETS which act as open drain outputs.

Internal architecture of an ECOS Detector Extension

So it is possible to connect two outputs to the U+ terminal via 100K resistors and then bridging a bicolor LED across the two outputs (of course with the appropriate resistor to drop the voltage from 12V to the typical 2.2 Volts tolerated by the LED). I used the bicolor LED L10008-ND for my application. Below is a simulation of the circuit in Proteus VSM. Here there two pairs of bicolor LEDs are connected in revered polarities for use on the control panel. Thus when one route is selected the respective LED turns green and the other red. The switch is mimicking the shift register outputs being reciprocally switched by the detector.

Switching Kato Switches with Panel Push Buttons

As much as I like the ESU Switch Pilot and can drive Kato Switches in combination with the Switch Pilot Extension there is no way to drive these locally except through the use of an ECoS Detector, I found the simpler solution was to use the Digitrax DS64 which not only drives the Kato switches directly but also has a button actuator connection. The only additional requirement is an LNet Converter from ESU to connect the DS64s to the ECoS and then any local switching is also reflected on the ECoS control.