Passive Monitor Controller- Take 2

Link555

Well-Known Member
Joined
Mar 31, 2007
Location
North Vancouver
Sorry I had issues uploading to youtube yesterday...


On the scope you can see the encoder A output on channel 1(Yellow) and B on channel 2 (Pink) of the scope. The encoder I am using does not have an index pin to count revolutions. But I don't need that for this application, since a single turn is all that is needed. In fact, I put a upper and lower limit on the encoder, if you turn it up past 100% the code keeps it at 100% regardless of how many clockwise turns you make. Alternatively, if you turn the encoder past 0% the codes keeps it at 0%.

The DSPIC30F2010 has a built in encoder module, but I am having trouble with my complier version accessing that module. Right now the logic is done directly be reading the inputs. If A leads B I know your going clockwise, if B leads A then I know your going counter clockwise. Then I just count pulses to determine how far the knob is rotated.
1617110215508.png

On start up I wanted to have the attenuation at -88db, from there I will turn it up as necessary. If this proves annoying I can easily store the last setting the non-volatile memory.

Channel three (Blue) on the scope shows one of the relay outputs from the microcontroller. The relays switch in the and out the ten different shunt resistors in the H attenuator. An low output from the microcontroller board inserts the relays associated resistor, and high output takes the resistor out of circuit.

Last night I started populating the attenuator board now. I am using 1% metal film resistor and am matching the critical values with a meter.
 

Boswell

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Joined
Apr 19, 2006
Location
UK
That all looks good, and pretty much what I would expect from the schematic. How many PPR is the encoder?
 

Boswell

Moderator
Joined
Apr 19, 2006
Location
UK
I've designed with lots of different encoders, but never that one!

I'm surprised that there is no mechanical detent option in the lower PPR counts for use as a panel control. Maybe that miniature packaging simply didn't allow the space.
 

Link555

Well-Known Member
Joined
Mar 31, 2007
Location
North Vancouver
its pretty small for sure, looks like a standard 1/4" pot for four leads. Works great on heavy metal concentrate conveyor belt idlers in pretty horrible operating conditions ;)
 

Boswell

Moderator
Joined
Apr 19, 2006
Location
UK
its pretty small for sure, looks like a standard 1/4" pot for four leads. Works great on heavy metal concentrate conveyor belt idlers in pretty horrible operating conditions ;)
I've not attended any heavy metal gigs recently, so I didn't know they used things like that on stage. I can imagine the operating conditions though.
 

Boswell

Moderator
Joined
Apr 19, 2006
Location
UK
I don't know what you mean - there's plenty of space! I can even see a tiny bit of the floor of the can around the PCBs.
 

kmetal

Kyle P. Gushue
Well-Known Member
Joined
Jul 21, 2009
Location
Boston, Massachusetts
Looks good.

Im curious about the feature where the volume knob is limited to a certain peak % of the signal (excuse the layman terms).

Would this be useful in a case where you had some very high power amps on the speakers for headroom, so that you could never accidentally turn things up to a dangerous volume level?

Ive become paranoid lately thinking about an atmos system id like to have because the wattage is would be really high, and im concerned about a failure or accident letting the thing output 5 or 10 thousand watts.
 

Link555

Well-Known Member
Joined
Mar 31, 2007
Location
North Vancouver
Looks good.

Im curious about the feature where the volume knob is limited to a certain peak % of the signal (excuse the layman terms).

Would this be useful in a case where you had some very high power amps on the speakers for headroom, so that you could never accidentally turn things up to a dangerous volume level?

Ive become paranoid lately thinking about an atmos system id like to have because the wattage is would be really high, and im concerned about a failure or accident letting the thing output 5 or 10 thousand watts.
this Unit does not have a limiter in it, but what I did was set up the unit to have a minimum attenuation of -30db. So when my volume knob is at it’s loudest position I still have a -30db pad in the circuit. I measured my room and speakers and found the pad value to give me 85db out of my speakers from my listening position. That turned out to be a -30db pad. From there I can turn the unit down further by 10 steps of roughly 6 db each. But in practice I think I could get by with 3 or four...
 
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