MK133 - Question about external LED indicators


I just finished assembling the MK133, and everything is working perfectly. I am planning to enclose the project, and would like to add some external LEDs. I will solder the wires to the appropriate location on the board where it indicates “9V 50mA”.

Here is my question: Does each external LED need to have its own resistor? Or do the existing resistors already provide the appropriate voltage for the external LEDs? If the former, then what would be the appropriate amount of resistance to use with a standard 3mm LED?


Yes, each external LED need to have its own resistor. You can’t put them simply in parrallel.

If you don’t need the led’s that go directly on the board, you can connect your external led’s to these sites on the board with wires that can (within reason) as long as you like and you won’t need any extra resistors.

I do this to have the led’s mounted on a case, away from the board.

If you need both the local and external led’s, put a 1K resistor in series with the led and connect them to the external light connectors

Hello! :smiley:

I’ve electronic horns (3V) for bicycles. I want to use these like external indicator for the mk133 kit. I tried to connect them (via the cnnectors) , nothing… :frowning:

Can you help me please? :slight_smile:

Please note that the outputs are 9V and current is limited to 50mA max.

OK, what can I do?

Adding a resistor? What value?


Check the consumption of the horns. Most likely, they consume more than 50mA, so they are not suited.
If they consume less, add a series resistor. Sorry, no values. Please experiment. Add resistor to achieve identical current consumption.