MCP4261 as logarithmic potentiometer

   In previous article, I tested my MCP4261-502E/P dual digital potentiometer, now I show you how can use this dual potentiometer for audio (volume control), for that must change liniar characteristic to logarithmic characteristic (or like this).
   So, I use info from article Controlling Volume - log pots publish on TEXAS INSTRUMENS's site.
   

   For simple sketch and for not use more resource, I use log aproxximation, so I calculate the equations for each straights:

- for first, from 0 to 63%: y = x/5 (I know x=0 -> y=0 & x=50 -> y=10)

- for second, from 63 to 100%: y = 7/3 * x - 400/3 (I know x=70 y=30 & x=100 -> y=100)

  I use same schematic like in previous article:

and I write a sketch for test more cases, this sketch is MCP4261_lin_to_log_1.ino .

  I made 2 movies:

- MCP4261 as logarithmic pot using Arduino

- MCP4261 as logarithmic pot using Arduino (2)

  For digital potentiometer with 16 steps + mute, I have next cases:

   Centralizing, we see some errors but for me there are acceptable:

and I cat continue experiments for implements this digital potentiometer in future audio project..

MCP4261 dual digital potentiometer

   I have an MCP4261-503E/P dual digital potentiometer hwo can control via SPI interface in 256 steps (0 to 255 - 8 bits).

   I use info find in article Arduino - Using digital potentiometers part 2 (MCP4251) from Matthew McMillan's blog.
   My digital potentiometer is in THT/PDIP capsule:

   After info from Mattew's sketch I made my test schematic:

and after made some changes, I upload MCP4261_mega_lcd1602_i2c_test.ino sketch.

   For tests, I have some particular cases:

- both on minimum 

- first potentiomer at minimum and second at maximum:

- first potentimeter at maximum and second at minumum value:

- both at maximum:

and after that I put to change steps from 0 to 255 to see the difference between potentiometers:

   I put on net 2 movies:

-  MCP4261 digital dual potentiometer with Arduino Mega:

- MCP4261 digital dual potentiometer with Arduino Mega (2)

FM radio with TEA5767 and Arduino

   A 3 years ago I tested a radio with TEA5767 module controlled by Arduino and use 1602 alphanumerical display (see article named Radio FM cu TEA5767 si... Arduino)

or Nokia 5110 display (see article Radio FM cu TEA5767 si... Arduino (II)

  Now, I use a 1602 alphanumerical display with i2c interface and Arduino Leonardo board:

   Schematic is very simple:

   Using TEA5767_eeprom_i2c_lcd1602_1m1a.ino sketch I can search forward or backward and after I decided what radiostation I listen, frequency value is sotred in internal EEPROM memory of microcontroller from Arduino board.
   In TEA5767 FM radio and Arduino movie you cand see all feature of this radio with Arduino...

MCP41xxx digital potentiometer

   I have one MCP41010 digital potentiometer with 10kohms value in 256 steps (0 to 255 steps = 8 bits) who can controllled by a microcontroler or development board thru SPI conenctor.

   I search info about this digital potentiometer and I noted 2 usefull articles:

- Single/Dual digital Potentiometer (MCP41xxx, MCP42xxx) from www.arduino-projekte.de

- MCP41010 Digital Potentiometer Arduino User Manual from Henry's bench

   I use Arduino Mega board in this schematic:

am I use MCP41xxx_lcd1602_i2c_test.ino sketch.

   After I read the datasheet I realised this digital potetiometer has a "wiper ressitance". Tipical value for 5V is 52 ohms (maximum 100 ohms).

   In tests, I can see:

- minimum value (step no. 0):

- maximum value (step no. 255):

If I change potentiometer at 3.3V, I can see:

- minimum value (step no. 0):

- maximum value (step no. 255):

   You can see test with MCP41010 digital potentiometer and Arduino Mega (2) movie for understund more clear what i write: