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Old 3rd January 2012, 03:15 PM   #831
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Quote:
Originally Posted by borges View Post
Oneoclock,

While you're at it, could you als check if exposing the front/back panel metal to the four screws improves on things?

(If you ruin your panels, I'll send you replacements!)

BÝrge
Front and rear panels make contact with the rest of the box without having to do anything.

The important thing is the miniUSB conector not touch the box. And how to attach the box to the circuit ground so the noise not go up over time. I guess with a Varistor or resistor and a capacitor in series or in parallel, but do not know how, and typical values.
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Old 3rd January 2012, 04:48 PM   #832
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Hi all:

The AW box must be a Faraday cage:

Put your cell phone inside and close the box. If it doesn't ring when you call it, the AW box works!

(Citation from a Faraday box Wiki on the web)

Regards

Juan
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Old 3rd January 2012, 05:42 PM   #833
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Quote:
Originally Posted by 1audio View Post
.......I have attached a quick LTSpice schematic. They did not have a TL431 or equivalent so I used another device to show the connections.
1audio from your proposal I am simulated three circuit to compare, your supply, one variation from yours, and Salas supply .

I have change the model components of your circuit and the salas supply. I hope not bother you. You can put yours in the comparisons.

I have searched for low-cost components that allow power to 3.3 V 100 mA The idea is to design a mini circuit board.

Here I leave the scheme and the models used so they can compare. I would appreciate comments.
Click the image to open in full size.
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Old 3rd January 2012, 06:18 PM   #834
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oneoclock:
Take an look at TeddyPardo.
The allow positive and negative versions using the same PCB and can delivery
5 and 3.3V as an alternative.

Regards Juan
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Old 3rd January 2012, 06:59 PM   #835
MrSlim is offline MrSlim  Canada
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Quote:
Originally Posted by realmadrid View Post
oneoclock:
Take an look at TeddyPardo.
The allow positive and negative versions using the same PCB and can delivery
5 and 3.3V as an alternative.

Regards Juan
If the "open-source" spirit of the project is to be continued, personally copywrited designs like the TeddyPardo must be avoided.

Besides, I this line from the website:
"The SuperTeddyReg is extremely sensitive to component choice, I therefore strongly recommend buying the built-and-tested version."
does not inspire confidence in repeatability..
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Old 3rd January 2012, 07:09 PM   #836
borges is offline borges  Norway
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I still have a lot to learn about PSU design. Just one question: why do the LEDs set up a voltage below filtered Vin, not above GND?

BÝrge

Quote:
Originally Posted by oneoclock View Post
1audio from your proposal I am simulated three circuit to compare, your supply, one variation from yours, and Salas supply .

I have change the model components of your circuit and the salas supply. I hope not bother you. You can put yours in the comparisons.

I have searched for low-cost components that allow power to 3.3 V 100 mA The idea is to design a mini circuit board.

Here I leave the scheme and the models used so they can compare. I would appreciate comments.
Click the image to open in full size.
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Old 3rd January 2012, 08:53 PM   #837
1audio is offline 1audio  United States
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The simulation model looks like a good effort. However this is also an object lesson in understanding the importance of understanding the application's requirements.

The series regulator I came up with was intended for ultra low phase noise oscillators. The load changes essentially never with a stable oscillator. The key issue is low noise and high line isolation. A driver for a headphone has much different issues. the peak current needs to be accomodated, the load can change as much as 100%, transient response is important and noise is less of an issue. providing power for a digital circuit is still somewhat different with very high peak currents usually at the clock edges.

Add an ac source at the input to simulate line isolation. And then you could add resistors to simulate the effects of drops across the grounds.

Shunt regulators make things easier since you know where the regulator is referencing to. But they are not right for a headphone load since they need to dissipate a lot of power when idle. The thermals will also cause modulation in the voltages. Remote sensing for a series regulator is more complex and prone to instability.

Lots to think about.
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Old 3rd January 2012, 09:45 PM   #838
UnixMan is offline UnixMan  Europe
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Quote:
Originally Posted by 1audio View Post
However this is also an object lesson in understanding the importance of understanding the application's requirements.
second!

Quote:
Originally Posted by 1audio View Post
The series regulator I came up with was intended for ultra low phase noise oscillators.
where can I see that design?
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Old 3rd January 2012, 10:21 PM   #839
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Quote:
Originally Posted by borges View Post
I still have a lot to learn about PSU design. Just one question: why do the LEDs set up a voltage below filtered Vin, not above GND?

BÝrge
Because you want a constant bias voltage for M1, which has the source at input voltage level :-)

The more I studied Demian's PSU I more I like it :-). Especially after reading his "object lesson" :-)

Alex
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Old 3rd January 2012, 10:36 PM   #840
1audio is offline 1audio  United States
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The series regulator is on the lower right of the simulation schematic.

I have serious mixed feelings about using LED's as references. They will have the following issues; temperature sensitivity with a significant tempco, noise and optical sensitivity. I got burned in the past with LED's being the source of hum in a circuit. Others disagree. I need to get some representative LED's and test them to see if they have changed. However getting a stabilized bandgap with a suitable amp in a TL431 for less than $1.00 it a great deal.
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