Sunday, November 24, 2013

Driving a DC motor using software PWM with AVR ATmega

Update to version 05

This library is an update of the software PWM driver you can find here:
For DC motor information please look at the above link.

This update implements also progressive start / stop features.

So, with this one, you can drive up to 4 motors independently controlling:
  • speed
  • direction
  • slow start / stop


  • 05: renamed timer macros, fixed max speed
  • 04: small fix to rampup
  • 03: small fix to velocity calculation, math.h lib can now be omitted, add a function that returns the current motor speed
  • 02: first version

Setup parameters are contained in dcmotorpwmsoft.h

This library was developed on Eclipse, built with avr-gcc on Atmega8 @ 1MHz.


  • read risk disclaimer
  • excuse my bad english

Tuesday, November 12, 2013

Homemade 2 Guitar Strings Diddley Bow

The diddley bow is a string instrument of African origin made popular in America, probably developed from instruments found on the Ghana coast of west Africa. The diddley bow is typically homemade, consisting usually of a wooden board and a single wire string stretched between two screws, and played by plucking while varying the pitch with a metal or glass slide held in the other hand.

This is my homemade 2 Guitar Strings Diddley Bow.

This diddley bow is built using an "B" (.016), and a "D" (.032) acoustic strings, and a piece of wood.
You can tune this instrument as you want, and use any string you want, in the sample video i've used:
"B" (.016) tuned to F#, "D" (.032) to B.
Wooden board dimension is 82.5cm length, 9.0cm width, 2.2cm height.
The string action is 2.5cm.
Two piece of aluminum L are used as bridge and nut, dimension are: 2.5cm long side (make the diddley action), 1cm short side, 0.2cm thickness.
The tuning peg is a cheap one used for guitar. Two screws are used to direct strings from the nut to the pegs.
The guitar pridge is built using an aluminium cigaret box, it is opened, inside a piezo is glued to act as a pickup, wired to a 500k log pot, and a female 1/4" panel plug. The cigaret box is open and it rely on the bridge aliminium L.
Inside the cigaret box there is a piece of cloth to prevent piezo feedback.
Even it this diddley has no fret reference, the scale is set to 22".
It is painted using wood protective teak.

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  • excuse my bad english

Tuesday, November 5, 2013

A Passive Monitor Controller for Balanced / Unbalanced signals

Monitor Controller 01 is a passive studio monitor controller.

It can control volume for Balanced and Unbalanced signal monitor.
It has an output selector so you can choose between two set of monitor.
Also it has a mute switch to mute the output.

Technically this is a balanced attenuator pad, so it as a minimum reduction gain, which for the proposed schematic is -1.58dB.

A design like this can result in a high frequency loss for long output cables (>15mt).
As you can see, it's just need a logarithmic 10k dual pot, and a 4 1/4w 1k resistors, metal film 1% resistors are better, but you can use even carbon film 5% one without any audible issue.

  • read risk disclaimer
  • excuse my bad english