Increased Current Drive from outputs designed to control LEDs       Code: RK-DRV

This module is designed for use in situations where a LED is normally used, but the user wishes to run say, a higher current lamp, or multiple LEDs, or a relay, up to a current of 1 amp. It assumes the LED is connected in a common cathode configuration.

The common cathode output originally driving the LED is connected to the input marked “From Control output”, and the 12 volt supply to the board that was driving the LED is connected to the DRV board, as well as the original board. The control input must be able to provide 3.5 volts or better, through a source resistance of less than 1K ohm.

The output to be driven is connected between the Load+ and Load- terminals. Load+ supplies positive volatge through various resistence values, and Load- controls the load in synchronism with the Control input. The Load+ resistance may be supplied via an externally connected resistance, allowing the user to choose an appropriate resistance value for the circumstance. The maximum load that can be controlled is 1 amp.

The diagram shows the unit being driven by a lighthouse controller and driving a Star LED so as to light a larger scale lighthouse model. The LED has forward voltage of 3.6V, and we intend to limit the current to 250mA. The ballast resistor required to drop 8.4V at 250mA is 33.6 ohms. We connect a 33ohm resitor to the external terminals and the Star LED load between Load+Ext and Load-.












Kit price for             RK-DRV: $9-50



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Information:         David Crosby         david@railwaykits.net

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Last updated 25th March, 2018.
(C) D. Crosby, August, 2010.