Polarity Reversing Switch Experiment




About: Texas Instruments; Launchpads; Arduino; Electronics; Climbing
I want to make a simple polarity reversing switch but I hadn't a switch with 6 legs like this one at Instructables. I had a lot of resistors and a small DC motor. Finally I used 2 pieces of 62R resistors and a switch. This is how it works


Step 1: How Does It Work?

I used two resistors with 62R. I connect each pole of the motor to +5V through a resistor. My first experiment with GND on right side of the circuit results the motor turns right.
During the second step the motor turns left.
So if I insert a switch I can turn the motor to rotate right or left.

Step 2: Some Calculations ...

I want to understand what happens so I started to calculate the paralell resistors value. You may find here a paralell resistor value calculator.

I tried with resistors 3R - 10R - 33R - 62R. They all worked but resistors lower than < 62R were warmed.
With 100R resistor it doesn't work.

The R3  resistance of the motor is 12R. So total I had 12R (motor) + 62R resistor = 74R.
Rtotal = (R2 + R3) * R1 / (R2 + R3) + R1 = (62 + 12)*62 / (62 + 12)+62 = 33.7

Step 3: The Polarity Switch

I measured the total resistance and there is some difference between theoretical and practical result (33R and 37R). But all in all the switch works and I made my XANAX.

Don't you know what xanax is?
It is a sleeping pill "developed" by the old man from Emir Kusturica's movie Promise Me This. Here is a sample on youtube.



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    9 Discussions


    5 years ago on Introduction

    You referenced one of my Ibles :) I'm kinda flattered!

    I have to hand it to you that I have never seen this done, and I am impressed with it, even if there IS power loss to the motor and power drain straight to ground, but you ALSO get something else, automatically, that could be useful and in the right application, possibly a pro to outweigh other cons: Resistive Braking. With the series of resistors from pole to pole on the motor, your motor stops very quickly, as shown in the vids. This is the same braking technology as is used on virtually all modern locomotives.

    Ikssk asked about using diodes, and Lemonie gave a clear and concise answer .. No. But ..... why not? Oh ... wait ... I just answered my own question while typing it . There would be no way to orient them for both states without switching their orientation when the state changes ....



    Reply 5 years ago on Introduction

    Hi dac_cast !
    I used 5V and a cheap DC motor disassembled from a toy or a CD drive or printer. :-)
    A photo from my motors used in this experiment.


    7 years ago on Introduction

    I would suggest a double through double pull switch.


    Reply 7 years ago on Introduction

    But you can use transistors !

    I used this concept for DC motors on a three rail model railroad for many years.

    Halfbridge Switch.png

    7 years ago on Introduction

    I'd rather use 4 transistors or mosfets to avoid limiting current going through motor, and overheating resistors. And in your method power splits to the motor and some of it goes straight from + to minus through seconr resistor. But if you don't care about it, it's very good idea because it's a lot cheaper than transistors :)


    7 years ago on Introduction

    For a way of avoiding the better solution of a switch, this is interesting.