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Arduino Ohm Meter

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ResistorMeter.sch53.29 KB
ResistorMeter.pde version: 2011-05-042.07 KB
ResistorMeter.png18.18 KB

After my old trusty analog multimeter's 0Ω adjust pot stopped working I had no reliable way to measure my resistors.
I thought I could built one with my just-bought arduino and learn some arduinish along the way.
Unfortunately in the cost is not included the lcd display (it was purchased something like ~10 years ago with the Basic Stamp II) and the 7404 (it was included in the "kit" that DeAgostini made available ~5 years ago as a magazine series).
The only problem I encountered was that my serial lcd display (seetron bpi-216) uses inverted TTL signals for its serial communications. So here comes the 74HC04N to the rescue.


 

19th April 2011

I was looking for a way to auto-zero the device, but nothing came to mind.
I even thought of using a Wheatstone Bridge, but that needs 3 known resistor values to do the calculations.


 

19th April 2011 - Update 2

By mistake the wrong version of the software got uploaded.


 

4th May 2011 - Update

Software update to final version.
Removed debuggin Serial communication and added "normal" Serial communication for future Processing usage (maybe).


 

24th January 2014 - Update

Uploaded schematic in image format (.pdf) upon request.

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Hi Basile. Am interested in this project but can't seem to open your schematicspdf file. Is it ok to request for it through my email? Would like to use it as a reference for my university project. Thanks!! 

email: ahbirdbernie@hotmail.com

The schematic I had uploaded was in EAGLE file format (.sch)
I have uploaded the schematic in image format (.png).
The R2 is the known resistor (1K) and the R1 is the resistor you want to measure.
The 74HC04 is used because my LCD used inverted signals.
The Arduino code (.pde file) was written using Arduino IDE v0022, but I don't think you will have any trouble converting it to v1 or newer.

basile

Hi Basile. Thank u for the efficient reply last week. 

Anyways, do u have any tips on converting the codes? it suggests me convert the "BYTES" to serial.write() instead and I only have basic knowledge on C++ and JAVA.

I am using the Arduino Uno btw.  

Hi Bernie,

just delete the "BYTE" from all the print commands.
eg: line 42 right now is "myLCD.print(254, BYTE); myLCD.print(1, BYTE);"
has to be converted to "myLCD.print(254); myLCD.print(1);"

This should fix your problem.
On my v1.0.5 it compiles. Haven't tested that it actually works though.

basile

P.S.: Looking forward to seeing what you will built.

the byte issues is solved now. but what does it mean on the line " Serial << Runknown << endl; " that it has an error? 

 error: no match for 'operator<<' in 'Serial << Runknown'

I will be building a sensor related to yours and then transmit the readings to a receiver. My main focus is actually building an antenna which is going to be a major headache haha!

Hi Bernie,
I was using the Streaming v4 library that can be found here ( http://arduiniana.org/libraries/streaming/ )
It's not really needed and can be replaced by simple .print commands.

This line "Serial << Runknown << endl;" can be written as "Serial.print(Runknown);"

I wanted to use the Streaming library for the LCD, but it wasn't working ok and I used it only for the Serial prints instead.

basile

Hi again Basile.

Thank u so much for the infos. Was reading your description and saw u mentioning about the 7404IC. 

Do I still need it if I am using a (model no.: 1602GD1622Y) 16x2 LCD display? Because I don't quite get what u meant by J1 in the schematic. Assuming the general LCDs have 16pins. Which pin is that?

Hi Bernie,

as I mention in the description I am using a seetron BPI-216 LCD display.
This particular display has a serial interface, but uses inverted TTL signals so I used the 7404.
The J1 in my schematic is the 5-pin connector of the LCD.

Unfortunately I haven't worked with a parallel LCD display so far and I can't help you with that.
But I think I have seen several posts using one.

basile

Hi Basile. Am interested in this project but can't seem to open your schematicspdf file. Is it ok to request for it through my email? Would like to use it as a reference for my university project. Thanks!! 

email: ahbirdbernie@hotmail.com

Hi Basile. Am interested in this project but can't seem to open your schematicspdf file. Is it ok to request for it through my email? Would like to use it as a reference for my university project. Thanks!! 

email: ahbirdbernie@hotmail.com