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Author Topic: DNA 30 passthru project...  (Read 6688 times)

Offline mamu

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DNA 30 passthru project...
« on: April 05, 2014, 12:33:28 PM »
I found a few AC to DC power supplies that are suitable for use with a DNA passthru mod I'm working on.

RS-75-3.3 is 0-15A, 3.3v (adjustable from 3.0v - 3.6v mine adjusted up to 3.7v).



Input voltage drop 0.23v running the DNA at 30W:


HSP-150-3.8 is 0-30A, 3.8v (adjustable from 3.4v - 4.2v mine adjusted up to 4.34 but turned it down to 4.2v).



Input voltage drop 0.13v running the DNA at 30W:


These power supplies will need to be enclosed in a protective case, so the search is on for one. 

But now I have the decision what case I want to use for this project.  No need to have space for batts woot!   :cheesy:


Offline Blewt

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Re: DNA 30 passthru project...
« Reply #1 on: April 05, 2014, 02:36:58 PM »
Ok.  That's seriously bad ass!  I want one of these for my office in the worst way.  :fuckrocks:
No oral or dirty trombone and I am in.
I will give you a taint massage though.

Offline jkmtwo

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Re: DNA 30 passthru project...
« Reply #2 on: April 05, 2014, 04:50:49 PM »
Ho Lee Sheet

ImagineMax preorder coming soon.


Offline Cappadoc

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Re: DNA 30 passthru project...
« Reply #3 on: April 05, 2014, 05:03:18 PM »
Very cool.
Want.
Nah, I live under a rock.  Doc lives in a cave way below the surface, under my rock.

Offline warbdan

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Re: DNA 30 passthru project...
« Reply #4 on: April 06, 2014, 09:14:38 AM »
Bow down, boys. We are in the presence of greatness! That's some cool shit, Mamu.

Offline mamu

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Re: DNA 30 passthru project...
« Reply #5 on: April 27, 2014, 08:02:20 AM »
ok... finally got my ducks in a row and got er done.

I spent a huge amount of time searching for high amp DC connectors and finally found Switchcraft's 11A jacks and plugs.  They aint cheap either.  :cheesy: http://www.switchcraft.com/productsummary.aspx?Parent=1074

I had to nix the RS-75-3.3 MeanWell power supply - wasn't enough of a voltage cushion to account for the voltage drop under load with using a 3' DC power cord and DC connectors.

I found a looper case that fit the HSP-150-3.8 MeanWell power supply perfect.  Total cost of assembly for this power supply (power supply, AC power cord, 3' 16AWG DC power cord, Switchcraft 11A DC connector, 10A on/off switch, looper case) ~95.00.



So, while I was waiting for parts to come in, I decided to play with a 5V 10A power brick.


The power brick I got metered at 5.6V.  I pried it open and added 2x 16A diodes (FES16DT-E3/45) in series to drop the source voltage by at least 1V (metered at 4.5V - 4.6V).  I mounted the diodes to the power brick's heat shield to use as a heat sink - works great and the diodes stay cool to the touch under load.


I was getting a voltage drop under load at the watts I vape (15W) that brought the source voltage down to under 4.5V, so I removed 1 diode.  If you vape lower watts, you'll need the 2 diodes to bring that source voltage down to less than 4.5V under load.

I replaced the power brick's DC connector with a Switchcraft connector.  Total cost of assembly for the power brick (power brick, 2x diodes, Switchcraft 11A DC connector) ~45.

HSP-150-3.8 with 3' 16AWG DC cord and set of Switchcraft's 11A DC connectors...
Source voltage...


Voltage drop @ 15W...


Voltage drop @ 30W...


5V 10A power brick with 3' 16AWG DC cord and set of Switchcraft's 11A DC connectors...
Source voltage with 1 diode...


Voltage drop @ 15W...


Voltage drop @ 30W...


Now that the power supply was settled, I went on a search for a case and chose Hammond's 1455D601BU case (60mm x 45mm x 25mm).

All done...







Offline Evelyn

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Re: DNA 30 passthru project...
« Reply #6 on: April 27, 2014, 08:20:09 AM »
Okay - was this posted BEFORE or AFTER the 'when is Mamu gonna quit quitting - again' pool?
Tactical Garanimals will be used again.  Oh yes it will.




Offline mamu

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Re: DNA 30 passthru project...
« Reply #7 on: April 27, 2014, 08:28:44 AM »
The only thing I quit was making mods for sale, Ev.  I didn't quit making mods for me and family.  :cheesy:

Offline junquedujour

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Re: DNA 30 passthru project...
« Reply #8 on: April 27, 2014, 12:10:46 PM »
another puzzle solved and more mamu artwork!
'tis a beauty.

Offline Vicks

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Re: DNA 30 passthru project...
« Reply #9 on: April 28, 2014, 01:53:37 PM »
The only thing I quit was making mods for sale, Ev.  I didn't quit making mods for me and family.  :cheesy:

Have you adopted Whtt yet?

Offline Evelyn

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Re: DNA 30 passthru project...
« Reply #10 on: April 28, 2014, 01:55:57 PM »
I was gonna mention the A word myself - but i figured there were way to many ahead of me in line.
Tactical Garanimals will be used again.  Oh yes it will.




Offline mamu

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Re: DNA 30 passthru project...
« Reply #11 on: April 29, 2014, 04:14:08 PM »
Thanks guys!

ecat from ECF shared a quick and easy way to drop the source voltage from a power supply.  Many many thanks to ecat!!

Quote from: ecat;12988811
My pleasure Mamu.

There's a lot of words in this post as I've tried to dot the i's and cross the t's but really there is not much to it. Feel free to ask if anything is not clear.

This is the schematic of a typical switch mode power supply (smps). Yours may not be exactly like this and certainly the names and values of the components will be different but the basic principle is most likely the same.




Firstly, beware of everything to the left of T1, the voltages there are dangerous. Even when power is removed that pesky capacitor C103 may be holding a nasty surprise.

On to the good bit:

The output of this supply is 5V, we can ignore the upper 12V part because it doesn't exist on your supply, the low voltage cable would connect to 5V and ground (0V).

As you look down the right hand side of the schematic you can see +5V line connects to resistor R204 and then through R205 to ground, we'll call these resistors Rt for R204 the top one and Rb for R205 the bottom one. Two resistors in series like this are known as a 'voltage divider', the voltage that appears where Rt and Rb connect to each other, marked with 'fb' above, is 5V divided by the ratio of the two.

The voltage at Vfb = (Vout / (Rt + Rb)) * Rb = (5V / (4k + 4k)) * 4k = 2.5V

What we need to do is change either or both Rt and Rb such that whatever voltage we want out appears as 2.5V were the two resistors join.

For your smps you need to locate this voltage divider, two resister near the output cable that join to each other and connect to the output +ve and 0v. There is not usually very much going on at the output of a simple smps so I think your chances are good.

Measure the output voltage.
Measure the voltage where the two resistors join.
Unsolder one end of each of the two resistors you have identified, we need to unsolder at least one end so we can...
Measure the resistance of the two resistors.

Remembering the voltage divider equation above, do the maths and double check that the calculated Vfb voltage is the same as the measured Vfb voltage (it will probably be around 1V to 2.5V). If you are within about 0.2V you probably have the correct resistors.

if Vfb = (( Vout / (Rt + Rb)) * Rb an you now know the value of Vfb you can calculate a new value of, say, Rt to give you the output voltage you require.

Rt = ((Vout - Vfb) * Rb) / Vfb

In this example, we want 4V out and changing 5V to 4V is not a big enough change to cause concern. Both Rt and Rb measure as 4k ohms and our measured and double checked Vfb = 2.5V

Rt = ((4V - 2.5V) * 4k) / 2.5V
Rt = 2.4k ohms

2.4k is quite a large change from the existing 4k but this shouldn't cause any problems. You would pick a standard resistor with a value as close to the calculated value as possible. Higher values of Rt increase the output voltage, lower values of Rt decrease the output voltage.

Now, if you are very unlucky and your smps does not use a voltage divider, looking something like this perhaps...



then, unless you can hand draw a schematic for me, it's back to the diodes I'm afraid :(

Following ecat's guide, I calculated I needed a 4K resistor for R18 in my power supply.  I only had a 3.9K on hand so used that.  I was shooting for 4.5V and got 4.4V.   woohoo I'll take it!!  :cheesy:

original source voltage 5.6V...


R18 (6.2K) and R19 (5K)... voltage where the resistors join = 2.5V


replaced R18 with a 3.9K resistor... voltage where the resistors join = 2.49V


source voltage 4.4V...


Thanks again for sharing ecat!! 

ETA: ecat's warning about tinkering with power supplies... please heed this warning if attempting this modification to a power supply...

Quote from: ecat;12999693
Switch mode power supplies are very dangerous things to play with.
High voltage in parts, the capacitors hold this voltage even when disconnected from the mains, the heatsinks are sometimes live etc. If anyone else tries this then please be aware of the risks, accept the dangers and do not blame anyone else if something, or someone, goes up in smoke.

Offline Vatic vapor

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Re: DNA 30 passthru project...
« Reply #12 on: April 30, 2014, 02:27:30 AM »
That was pretty genius. Awesome result, Mamu!
Considering a "Vatic" is named after Vatic, I'd say Vatic.

Offline junquedujour

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Re: DNA 30 passthru project...
« Reply #13 on: April 30, 2014, 06:51:50 AM »
i have no idea what this all means, but if it makes mamu happy and works for her, i'm content with that. 

plus, i'm downloading the pics in case i meet someone in real life that has a *need to know*, soooooooooooo thanks much mamu! you da bestest! :hug:



Offline mamu

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Re: DNA 30 passthru project...
« Reply #14 on: April 30, 2014, 07:07:09 AM »
I hope I can meet you some day, junque.   :love:

TY

SpaceCiggysForum

Re: DNA 30 passthru project...
« Reply #14 on: April 30, 2014, 07:07:09 AM »

 



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