The DIY'rs Cookbook

[Clemmaster]

Aren't the Rednets earthed because of the potential lethal voltages it operates at (phantom bias at 48V)?

Running at 5V only could alleviate the need to running earth to the wall socket?

 

[Superdad]

Hi Gents:
 
Quick question for those who had modded their RN3 or D16.  From skimming this thread I got the impression that your Focusrite units just need a bipolar 5 volts (that is + and - 5V)--is that correct?  Have any of you measured that 5V DC current draw?  Is it less than about 1.1A on each polarity?
 
If the current draw is modest--which I expect it is--then I might consider offering a DIY wiring kit for folks to use with a pair of our isolated UltraCap LPS-1 supplies.  It is easy to wire them in series and center-tap to create a proper bi-polar supply.
 
I'm not trying to plug anything here, just looking for some facts about the PS requirements of the Focusrite units.
 
Thanks and regards,
 
--Alex C.

 

[mourip]

  Hi Gents:
 
Quick question for those who had modded their RN3 or D16.  From skimming this thread I got the impression that your Focusrite units just need a bipolar 5 volts (that is + and - 5V)--is that correct?  Have any of you measured that 5V DC current draw?  Is it less than about 1.1A on each polarity?
 
If the current draw is modest--which I expect it is--then I might consider offering a DIY wiring kit for folks to use with a pair of our isolated UltraCap LPS-1 supplies.  It is easy to wire them in series and center-tap to create a proper bi-polar supply.
 
I'm not trying to plug anything here, just looking for some facts about the PS requirements of the Focusrite units.
 
Thanks and regards,
 
--Alex C.

I have not made the mod yet but just got the parts for connecting my external LPS which has a simple +5v output.
 
My understanding is that the RN3(D16) board just needs +5v and gnd connections to the multi-pin board connector. I do not believe that a bipolar +5/-5v supply is required even though I keep reading about -5v which is a bit confusing to me. 
 
The supplies I see images of here all look like simple single voltage supplies with some folks advocating grounding the chassis with the (-) leg which I believe is basically a safety technique.

 

[Superdad]

  I have not made the mod yet but just got the parts for connecting my external LPS which has a simple +5v output.
 
My understanding is that the RN3(D16) board just needs +5v and gnd connections to the multi-pin board connector. I do not believe that a bipolar +5/-5v supply is required even though I keep reading about -5v which is a bit confusing to me. 
 
The supplies I see images of here all look like simple single voltage supplies with some folks advocating grounding the chassis with the (-) leg which I believe is basically a safety technique.

 
 
Thanks for the quick reply.  Well that certainly makes it easier.  Really, as an all-digital device (i.e. no analog stages), I was surprised by the posts that made it seem like it needs a bi-polar supply.  Folks need to be careful not to bandy about the term -5VDC unless they really mean it.  

 
Now we just need to get an ammeter in line with the +5VDC to see how much current the unit actually draws.

 

[mourip]

   
 
Thanks for the quick reply.  Well that certainly makes it easier.  Really, as an all-digital device (i.e. no analog stages), I was surprised by the posts that made it seem like it needs a bi-polar supply.  Folks need to be careful not to bandy about the term -5VDC unless they really mean it.  

 
Now we just need to get an ammeter in line with the +5VDC to see how much current the unit actually draws.

 
I have a Kill-a-Watt. If I measure the wattage and the line voltage can we extrapolate roughly for the single voltage supply?

 

[Superdad]

   
I have a Kill-a-Watt. If I measure the wattage and the line voltage can we extrapolate roughly for the single voltage supply?

Not really.  Especially if the supply being used is an SMPS.  And if a linear, then I'd still need to know the raw voltage going into the regulators to include/exclude the drop.
 
Really best to just put a meter in line with the +5V and measure the current directly.

 

[Clemmaster]

It's been measured few months ago already.
The lps-1 is sufficient.

 

[johnjen]

Aren't the Rednets earthed because of the potential lethal voltages it operates at (phantom bias at 48V)?

Running at 5V only could alleviate the need to running earth to the wall socket?

Um, Rednet boxes are earthed because of code and UL etc rating requirements, not because of the 51Vdc the SMPS generates (with very low current), and the 2 we use (D16 and RN3) don't actually use this voltage, at all.
 
As for the polarity confusion, let me try and make it simple.
These LPS's I have used and described, are like a car battery.
They have a + connection and a - connection, with 12Vdc (5Vdc for our LPS's) between these 2 connection points.
 
And you don't want to connect batteries (nor LPS's) backwards, because that lets all the magic smoke out of the unit and turns it into a  'brick'.
 
Does this help?
 
JJ

 

[johnjen]

  Hi Gents:
 
Quick question for those who had modded their RN3 or D16.  From skimming this thread I got the impression that your Focusrite units just need a bipolar 5 volts (that is + and - 5V)--is that correct?  Have any of you measured that 5V DC current draw?  Is it less than about 1.1A on each polarity?
 
If the current draw is modest--which I expect it is--then I might consider offering a DIY wiring kit for folks to use with a pair of our isolated UltraCap LPS-1 supplies.  It is easy to wire them in series and center-tap to create a proper bi-polar supply.
 
I'm not trying to plug anything here, just looking for some facts about the PS requirements of the Focusrite units.
 
Thanks and regards,
 
--Alex C.

Say there.
I measured my RN3 and posted the results previously in this thread.
 
My RN3 draws 0.9Amps at 5Vdc when operating just a stereo pair of channels.
 
JJ

 

[mourip]

  Um, Rednet boxes are earthed because of code and UL etc rating requirements, not because of the 51Vdc the SMPS generates (with very low current), and the 2 we use (D16 and RN3) don't actually use this voltage, at all.
 
As for the polarity confusion, let me try and make it simple.
These LPS's I have used and described, are like a car battery.
They have a + connection and a - connection, with 12Vdc (5Vdc for our LPS's) between these 2 connection points.
 
And you don't want to connect batteries (nor LPS's) backwards, because that lets all the magic smoke out of the unit and turns it into a  'brick'.
 
Does this help?
 
JJ

 
Thanks for confirming that the RN3 uses a simple +5v supply. This makes it very easy for those of us who want to use an external LPS.
 
I think that someone previously confirmed that the Focusrite SMPS was somewhat generic and is probably also used in other REDnet products that require the standard 48v phantom microphone power source which as you mention is not being used in our RN3 or D16 devices.
 
Keep up the good work and going boldly....

 

[mourip]

 
Not really.  Especially if the supply being used is an SMPS.  And if a linear, then I'd still need to know the raw voltage going into the regulators to include/exclude the drop.
 
Really best to just put a meter in line with the +5V and measure the current directly.

 
My RN3 draws 0.9Amps at 5Vdc when operating just a stereo pair of channels.
 

 
Thanks.

 

[Superdad]

  Say there.
I measured my RN3 and posted the results previously in this thread.
 
My RN3 draws 0.9Amps at 5Vdc when operating just a stereo pair of channels.
 
JJ

Excellent.  Thank you!  Now maybe I can look at offering a kit so that novices can mod their units to use an external supply (ideally our UltraCap LPS-1 

).

 

[Clemmaster]

It'd be great to build a dummy IEC panel connector with a DC jack in it (instead of the 3 pongs).
I've been looking for such an adapter, to make things simpler and prevent chassis work to install the DC jack.

 

[Golfnutz]

  It'd be great to build a dummy IEC panel connector with a DC jack in it (instead of the 3 pongs).
I've been looking for such an adapter, to make things simpler and prevent chassis work to install the DC jack.

You don't have to use 3-prong, you can switch it out with 2-prong (c18/c19). Just cut the C19 power cord and put the appropriate end that would connect to your LPS.
 

 
 
 

 

[Clemmaster]

 
You don't have to use 3-prong, you can switch it out with 2-prong (c18/c19). Just cut the C19 power cord and put the appropriate end that would connect to your LPS.
 

 
 
 

 
There's still the potential for plugging in an AC cord and fry the board.
The DC barrel jack in IEC socket prevents that. It doesn't prevent the use of the wrong PSU voltage, though.