Power the Mindsensors SensorMUX from a 9V Battery

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The SensorMUX is a multiplexer to connect 4x NXT sensors to single NXT port. The multiplexer can connect any sensor designed for Mindstorms NXT, both LEGO and/or third party sensors. The SensorMUX is requires an external battery source supplying a voltage range between 6 and 8.4 volts to operate.

Mindsensors SensorMUX

Mindsensors recommend using LiPO battery or 6-AA battery pack. If the voltage of your battery drops below operating level, the LED on the selected channel of SensorMUX will blink continuously.


Do not exceed 8.4 Volts D.C.


Power Diodes have a voltage drop across them of between 0.6 and 0.7 volts. If we use two 1N4001 Diodes in ‘Series’ the voltage drop is 2 X 0.7, which equates to 1.4 Volts. With a fully charged 9 Volt battery and the diodes attached we drop the batteries output to 9 – (2 x 0.7), or 7.6 Volts. This is well in the ‘ Goldilocks’ zone required for the SensorMUX .

Follow these instructions to build a safe suitable supply for the SensorMUX for under $1.00, using a standard 9 Volt Battery (PP3 battery) as the source. You will need the following parts and equipment:

Begin by trimming the 1N4001 Diodes as per the Diagram below:

1N4001 Diodes
1N4001 Diodes

Next Solder the trimmed 1N4001 Diodes to the Battery Clip’s Fly-leads. Make sure the Diodes are connected ‘EXACTLY‘ the same way as shown below. Take note of the ‘Silver Bands’ on the diode casings.


Remember to place a small diameter piece of heat shrink tubing on the positive lead of the battery clip. The heat shrink should be placed close to the battery clip while soldering.


Once you have the Battery Fly Lead connected to the Diodes, Slide the Heat Shrink on the Red Positive lead over the junction of the Wire and Diode and shrink it. Next slide the larger piece of Heat Shrink over the two Diodes as pictured below. Trim the long Diode Leads back to between 5-10mm.

Final Assembly

The Whole assembly is now ready to connect to the Mindsensors SensorMUX . Be Careful to make sure that the ‘RED‘ Lead connects to the +VE side of the green screw connector on the SensorMUX, and the ‘BLACK‘ Lead to the -VE side of the screw connector.

Connecting to SensorMUX

That’s it, you now have a powers supply for the SensorMUX with an output of 7.6 Volts D.C.

I have used the same approach to power my NXTMMX from a 11.1 Volt Li-Po Battery. For the NXTMMX, I used 3x 1N5400 Rectifier Diodes in series. Unlike the 1N4001 Diodes which have a current rating of 1 Amp, the 1N5400 Diodes have a rating of 3 Amps. These specification is sufficient to power 2x NXT Motors with ease.

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