Welcome to this very basic design here we are showing you how you can tell if your power supply has a positive Tip + or Negative tip - with out using a meter.
Now if you would like to see the finished devise working then visit my You Tube video here.
If you have come here from a search engine you can see more of my designs on my electronic page here.
1). I have had a number of requests asking to design a very simple but cheap polarity tester with out using a test meter as most electronic devises need a positive tip this little circuit will let you know if you have a positive tip or a negative Tip on your jack plug.
2). How the devise works is when you connect a + supply to the Diode this is set up to allow a positive + current to flow but block a Negative - flow of current it acts like a valve.
3). The resister is 1K Ohms this limits the current to a safe level for the LED to turn on the LED stands for Light Emitting Diode the LED is facing the same way as the first diode so the positive current being limited by the resister is allowed to flow.
4). Now when you connect your power source to the connecter block or jack socket if you have a positive tip the LED will switch on.
5). Now if you connect your power source to the devise with a negative tip the led will not come on this is down to the way a diode works they can only pass current in one direction only.
6). Now let us look at the set up instructions connect the Black diode with the silver band on it the silver band must be pointing in the same direction of the Resister.
7). Now connect the longest lead of the LED to the end of the R1K Ohms now with the shorter lead of the LED connect this to the Negative - or ground return of your power supply.
8). Now if you want to add a jack plug socket connect the - to the - or ground return on your power supply.
9). Now with the tip of your jack socket connect this to the back of the silver band on the first diode see schematic above.
10). This page was mostly set up for beginners in electronics but may find a number of uses.