Ohmmeter 2.0

Miguel Alejandro Ramírez Anaya and José Miguel Galeas Merchán, students of 'Electrónica Creativa' (Creative Electronics), a Beng Electronics Engineering module at the University of Málaga, School of Telecommunications. We decide to make as final project a Ohmmeter using Arduino Mega development board.

Git repository

Supplies:

- Arduino Mega

- 4 RGB Leds

- 3 Red Leds

- 3 White Leds

- 4 x 4 Membrane Switch Keypad

- OLED Display I2C 128 x 64 pixels and 0.96 Inch

- 2 connection terminals for resistors

- Potentiometer 50kΩ

- Resistors

• 1kΩ x1
• 220Ω x3
• 22kΩ x1
• 68Ω x1

- Pre-drilled plate

- 4 screws

Step 1: 3D RGB Resistor

First the cables are soldered to the LEDs and the LED is glued on the piece inside the band. Each of the bands are mounted and glued together to build the resistance.

In the space between the bands, the white reference LEDs are soldered in parallel.

All cables are passed from one to another so that they all exit through the last.

Finally the two ends are glued and the resistance is finished.

Step 2: Assembling the Box

After printing all the pieces, we passed the resistance wires through the hole and soldered the terminations and the wires of the LEDs and the potentiometer.

The pcb is soldered according to the diagram and we connect all the wires.

Step 3: Programming

A state machine has been implemented to differentiate the modes.

'A' mode - Value to color

A value is entered by keyboard, it goes through an algorithm that returns its commercial value and displays it in the 3D resistor.

The program remains on active standby until a keyboard event arrives and if it is different from 'D' it shows the value on the screen and saves it in an array.
When pressing 'D', the array with the resistor value is passed to the "valor_a_comercial" function that converts the value into a commercial value and then, this array is passed to the "mostrar_resistencia" function that turns on the RGB LEDs of the 3D resistor with the right colors.

'B' mode - Color to value

The colors are entered and the value is displayed on the screen and the colors in the 3D resistor.

A legend is shown on the screen with the values and the corresponding number. The program saves the colors coded with numbers in an array and when pressing 'D' it shows the resistor value. While the colors are being entered, the RGB led of the corresponding band lights up.

'C' mode - Ohmmeter

This mode reads through the terminals and shows the value on the screen and the colors in the 3D resistor.

In order to measure various ranges, a potentiometer has been used. In a loop, the value of the potentiometer is read and this value is used as a reference to measure the connected resistor.
This process is repeated every programmable time (600 ms).

Comments

[raul7321]

Great! You have my vote! have you considered making a version using NeoPixels?

[ohmetrojym]

Thanks!!
It could be a good a idea!

[itscolin46]

I just don't get it - why does everything require a microprocessor?
1) OK it gives you the closest "Preferred Value" but you quickly learn that,
2) You can buy a cheap multi-meter for under £5.00 GB,
3) You can very easily learn the colour code and how to apply it,
there are many rhymes to help yo remember the colours using the first letter of each word. Black Brown Red Orange Green Blue Violet Grey White
Billy Blogs Ran Out Yelling Gawd Blimy Violet Get Weaving. I worked in East-End of London

[raphan]

I made a similar device (without the Neopixels) a few years ago to read resistors values, I know the colour code and how to read it, but my eyes are getting older, with this apparel I can read the exact value, or the most approaching in the chosen serie (E12, E24, etc.), on a large display. No need for a magnifier !

[pmcclay]

Um, I think this was more 'Electrónica Creativa' than 'T&M práctica'.

[raphan]

There are many similarities with edited code, including mine. My code deals with two series of resistors E12 and E24, not only 14 values which is not even an existing serie.

[mridgley]

English code for ohmmeter please?

[tagarrojl]

Original y buena idea, muy bien pensado. Por favor, el esquema siempre es esencial para redondearlo. ¿Podéis incluirlo?
Y el vídeo es bastante mejorable, mas estabilidad en la cámara y control del diafragma para evitar desenfoques y escenas muy oscuras y/o las luces tan brillantes que no se sabe de qué color son.
Original and good idea, very well thought out. Please, the schematic is always essential to round it off. Can you include it?
And the video is quite improvable, more stability in the camera and diaphragm control would be desirable for technicians as capable as you to avoid blurring and very dark scenes and / or lights so bright that it is not known what color they are.

[ohmetrojym]

Ya hemos incluido un esquemático del circuito.
El video se grabó con un móvil y debido a eso la calidad no es muy buena.
Gracias por el comentario, saludos.

[JhonDee]

Buen trabajo, aunque talvez con LEDs multicolor hubiera quedado más guay
y además se suele incluir el esquemático del circuito que si, es muy sencillo
pero hay gente que esta aprendiendo.
Bueno, sólo es un toke para que el próximo tuto lo peteis, vale.
Saludos y cuidaros, esto no ha terminado.

[ohmetrojym]

Gracias por el comentario, ya hemos añadido un esquemático del circuito de la PCB.
Los LEDs que se han usado para la resistencia 3D son multicolor, los puedes ver en la segunda foto del paso 1.
Saludos.

[Kulotan]

Original design - great job!

[ohmetrojym]

Thanks mate !

[alberfuentes99]

¡Gran aportación! Gracias por compartir, enhorabuena a los creadores de este proyecto.

[ohmetrojym]

¡Muchas gracias!

[hugheswho]

What a cool project!
This should be integrated into every multimeter!
Also - you should enter into First Time Author contest.
(with the prize money maybe get a tripod...)

[ohmetrojym]

Thank you very much for the comment!
Have no doubt that if we win we will buy a tripod.

[samuelpetrich]

lol