DIY- Continuity Tester Circuit

[Joker94]

Here Is a really, really easy and hand project good for debuging circuits.

[Truckstop]

Awesome. very simple. i like.

Truckstop

[Joker94]

thanks truck stop

[SmAsH]

i have something similar i built for school in electronics.
mine uses a transistor though...

[Finnik]

Looks cool, nice and simple. Just one question though, where is the part that notifies the user about the continuity
There are just batteries, a resistor and a diode, nothing there to signal the user. Or is the diode actually an LED? That would solve the problem, but then you've use the wrong symbol...

[Webbot]

Only comment is that if you are using an LED then you will need to send enough current to light the LED. This current will also pass through the thing you are testing.
If thats just pcb tracks before mounting components, or wire connections,  then ok.  If you are using it on an assembled board then you will need to be careful you dont overcook something.
The benefit of adding a transistor is that you can pass a much lower current and then boost it with the transistor to drive the LED.

[SmAsH]

just if anyone is interested, heres my schematic we used.
this was just what i can remember from class so if you spot anything "out of whack" with it let me know

[Joker94]

yes the diode is ment to be a led. I am haveing a few problems with eagle at the moment and when i printed the screen it must have cut off the top of the symbol. So i did not use the wrong symbol it just got chopped off in the cropping process, sorry about that.

[Soeren]

Hi,

Won't ever light the LED unless you turn the battery around

As Webbot allready stated, it may damage some circuits and it will give false positives on any diode stretch.

A well designed continuity tester should inject less than 100 mV and it should treat anything above something like between 0.1 and 1.0 Ohm as not having continuity.