Project - Continuity tester

This is a continuity tester to check conductors or wiring with a resistance lesser than 1 Ohm (maximum imprecision is 50%). This continutity tester is intended to be minimalist and uses cheap components (for example 5% tolerance resistors) to perform this simple task where acuracy is not a requesit.
The LED should light if the resistance between the probes is lesser than 1 Ohm (will light for sure if the resistance is lesser than 0.5 Ohm).
To feed the tester you will need two 3V lithium batteries (prefered type for its size). You can use other types as well.

P.S.: Once more, the project is in portuguese. Sorry! (I make these projects for my own use, so I use my home language. What can I say!?)

View attachment VerContin.pdf
List of components (version 1):
B1/2 - 3V lithium battery;
D - Red LED (GaAsP/GaP dice);
IC - LM358 double operational amplifier;
R1 - 3.3M carbon resistor (1/8W, tolerance 5%);
R2 - 15K carbon resistor (1/8W, tolerance 5%);
R3 - 220 Ohm carbon resistor (1/2W, tolerance 5%);
R4 - 180 Ohm carbon resistor (1/8W, tolerance 5%);
S - SPST switch.

Technical data (version 1):
Limits:
- V d. max. = 7.10V
- V d. min. = 3.20V
Electrical characteristics:
- I d. (V d. = 6.00V) = 42mA *1
- P (V d. = 6.00V) = 252mW *1

View attachment VerContin(2).pdf
List of components (version 2):
B - 3V lithium battery;
D - Red LED (GaAsP/GaP dice);
IC - LM393 comparator;
Q - 2N3906 PNP transistor;
R1 - 100R carbon resistor (1/4W, tolerance 5%);
R2 - 470K carbon resistor (1/8W, tolerance 5%);
R3 - 4.7K carbon resistor (1/8W, tolerance 5%);
R4 - 2.7K carbon resistor (1/8W, tolerance 5%);
R5 - 82R carbon resistor (1/8W, tolerance 5%);
S - SPST switch.

Technical data (version 2):
Limits:
- V d. max. = 3.52V
- V d. min. = 2.00V
Electrical characteristics:
- I d. (V d. = 3.00V) = 42.59mA *1
- P (V d. = 3.00V) = 127.8mW *1

*1 - This value refers to a situation when the circuit to be tested has zero resistance.
d. - Denotes direct current. Inverse current will not be tolerated.

cumesoftware said:

P.S.: Once more, the project is in portuguese. Sorry! (I make these projects for my own use, so I use my home language. What can I say!?)

Click to expand...

Could you possibly use one of the on-line translators to translate it into English? Given that you are the project author and from your previous posts you have a decent grasp of English, would this be a big problem?

Dave

Dave said:

Could you possibly use one of the on-line translators to translate it into English? Given that you are the project author and from your previous posts you have a decent grasp of English, would this be a big problem?

Dave

Click to expand...

I understand your position, but the original projects were made using Visio, which at the moment I don't have installed. However, I can post the component list in English. Also, using translators to translate from Portuguese would give an erroneous translation, since Portuguese is a complex language.

cumesoftware said:

I understand your position, but the original projects were made using Visio, which at the moment I don't have installed. However, I can post the component list in English. Also, using translators to translate from Portuguese would give an erroneous translation, since Portuguese is a complex language.

Click to expand...

Ok, thanks for the additional information. I appreciate your concern regarding the errors that may propagate into the project as a result of an automated translator.

Dave