Hello,
The output impedance, like a normal potentiometer, goes between 0 (at 0% and 100% attenuation) and nominal_impedance/4 (when the series and shunt parts of the potentiometer are equal).
This unit's nominal impedance can be selected from 5K to 50K, and for the recommended 10K impedance, the maximum output impedance would be 2.5K.
You mean control this unit with a potentiometer instead of the rotary encoder or IR remote? No, not without changing a lot of code.
The volume control follows a logarithmic scale, to fit the human ear response. See the graph below, it's the Excel I used to tweak the LOG law used.
The actual calculation is done by the function float getAttFromStep(byte step), line 908 in the code, which returns the attenuation needed (logarithmic, between 0 and 1) depending of the volume step (linear, between 0 and VOL_MAX_STEP).
I then calculate the LDR series and shunt resistances needed to obtain that attenuation (line 972). Then the calibration routine searches for the current needed to set the LDRs at the resistances calculate at the previous step. Easy.
Attachments
Nice!
A remark - the controller detects when it is being powered down, and it mutes the outputs and saves the current volume into the memory. To do that, it uses the charge stored in the D+ PSU capacitor.
I can't tell what value of capacitor you used, but if it is only 2200µ, it may or it may not work as intended. I'm using 3900µ, the biggest value I could find in E5-13 form factor.
Nice!
A remark - the controller detects when it is being powered down, and it mutes the outputs and saves the current volume into the memory. To do that, it uses the charge stored in the D+ PSU capacitor.
I can't tell what value of capacitor you used, but if it is only 2200µ, it may or it may not work as intended. I'm using 3900µ, the biggest value I could find in E5-13 form factor.
Thanks Vincent. Yes it is 2200uF. But I have tried a few power cycles and it seems to remember the volume setting so far... Only issue so far is the IR remote. It seems prone to getting stuck in the volume up mode regardless of what button I press. But I don't have an apple remote. I am using an Android app to emulate one on my phone.
The pot tracking seems very good. I checked it with a DMM on the bench and both channels seem to track well over the attenuation range. Well done!
The documentation was excellent and it was quite easy to setup. Calibration did seem to take a long time though - maybe 5+ minutes?
I think the BOM is one 5 pin header set short? Also I had to adjust the trimpot on the back of the LCD to get a visible display (took me a while to guess this was reason for a blank display).
Now I have to think if I will order some of your I/O relay boards...
Thank you once again!
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My phone does not have an IR emitter, so I can't test this, but my aluminum Apple remote works well... In fact, many other remotes could work, but you would have to measure and update the specific IR codes in the software.
Indeed, I missed a couple of pin headers: one two-pin and one 5 pin!
I will update the BOM. I should also add a note about adjusting the LCD contrast with the trimpot on the back! Thanks!
Hello Theodosis,
The board is 94x66 mm. You can open the board file with Eagle to see exactly its dimensions and mounting holes.
My phone does not have an IR emitter, so I can't test this, but my aluminum Apple remote works well... In fact, many other remotes could work, but you would have to measure and update the specific IR codes in the software.
Indeed, I missed a couple of pin headers: one two-pin and one 5 pin!
I will update the BOM. I should also add a note about adjusting the LCD contrast with the trimpot on the back! Thanks!
Vincent, I have also tried a genuine apple remote and the symptoms are the same as using my phone to emulate. It can get stuck in either volume up or volume down depending on the preceding keypress. Using debug mode with print statements to the serial monitor, most of the time getIRkey() returns 0 via line 1227 (i.e. a "repeat"). So the last valid ir decode just gets repeated.
Looks a bit like a timing issue? I guess I need to check with HifiDunio? I note your nano is v3 and mine is 3.1. Could that make a difference?
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That's weird. Are you getting IR noise from some external source, like an energy saving lamp?
We'll debug this, but now I'm away from home for a week and I can't really look into it.
The Arduino version should not make a difference.
If you add a PRINTLN(duration); line 1224, what does it say during the spurious repeats?
I quote from an encoder FAQ found online:
So it seems the maximum cable length should be around 10 meters.
Hi Vincent. Its not lighting I think. I have tried it in 2 different locations and even in the dark.
I am typically getting something like this for a "repeat" code on the console for duration :
0
0
2187
This is from a single button press. In this case the volume direction is "stuck" in either up or down mode.
Occasionally the IR code will be detected correctly (and then I can change volume direction). In this case duration will be about 4400.
This is where I put the duration print statement :
while ((duration = pulseIn(PIN_REMOTE, HIGH, 15000)) < 2000 && duration != 0)
{
// Wait for start pulse
}
PRINTLN(duration);
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Vincent, for now I have worked around the issue by substituting pulseIn with newpulseIn in getIRkey.
Code for newpulseIn can be found here :
https://downloadcode.wordpress.com/2011/01/10/code-for-buffalo-ii-dac-vb06e/
However "repeat" no longer works. But the system in now usable and mute key also now works reliably.
Code for newpulseIn can be found here :
https://downloadcode.wordpress.com/2011/01/10/code-for-buffalo-ii-dac-vb06e/
However "repeat" no longer works. But the system in now usable and mute key also now works reliably.
Some USB DACs out there are able to set output volume control according to the volume setting on the computer. It would be super convenient if it was possible to feed the volume setting from an USB audio interface to the Arduino in order to control the LDRs from the voume setting on the audio player of the computer. Is that possible?