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Sly
Premium Member
join:2004-02-20
Tennessee

Sly

Premium Member

Need good 5VDC power supply

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I'm working on a car stereo install as mentioned here: »2015 Subaru WRX stereo install

I'm planning on running a DSP made by MiniDSP. It's an OpenDRC-AN. It needs a constant 5VDC power input and will not work properly with anything over or under this requirement. It's designed to work in a house with a 120VAC to 5VDC transformer. Obviously I can't use this in a car and so I need to take anything from 12VDC to 14.4VDC and regulate it down to 5 volts. I don't have an available USB port as I will be using the receiver's USB to power a thumb drive. So I need an external power supply that is regulated enough and clean enough for audio processing.

Any suggestions? I need it to output 5 volts under all incoming voltage levels and I need it to handle at least a 600 milliamp load. Any noise isolation feature would be nice as well just to eliminate the chances of any alternator whine coming through the system.

SparkChaser
Premium Member
join:2000-06-06
Downingtown, PA

SparkChaser

Premium Member

Most of what I see in a search is a switcher. With your concern for noise and the low current I'd build a something using an LM series regulator and careful wiring.

tschmidt
MVM
join:2000-11-12
Milford, NH
·Consolidated Com..
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tschmidt to Sly

MVM

to Sly
Assuming maximum current draw is 600ma running a linear regulator barefoot from the car electrical system means the regulator has to dissipate 5.64W. Not a huge amount but will need a significant heat sink over the wild temperature extremes of a car.

Since the unit is sensitive to noise the first thing I'd try is running it directly from a switching down converter, set to 5V. If noise is a problem crank the output of the switcher up a few volts and run it through a linear regulator and add some filtering between the switcher and linear regulator.

You are also going to need some noise filter and transient protection on the power supply input regardless of what type of power supply you finally use.

/tom
LittleBill
join:2013-05-24

LittleBill to Sly

Member

to Sly
im confused, 600ma 5v? any usb cell phone charger can do this, the one in my car does 2 amp at 5v

i also highly doubht the voltage needs to be rock solid, nobody has any idea on the voltage at a house, between my house and my neighbor there is a 4 volt difference.. think your making too big of a deal out of this
switchman
join:1999-11-06
ARRIS SB6183
(Software) OPNsense

3 edits

switchman to Sly

Member

to Sly
I would pick up one of these.

»www.amazon.com/KEEDOX%C2 ··· onverter

or these

»www.amazon.com/SMAKN-Con ··· onverter

Probably the same internally.

Add an inline fuse also.

EDIT:
Just noticed the two items above are probably coming from China based on the shipping times.

If you wanted to do ebay, this might work and a shorter time frame as it is already in the states. It is $6 with free shipping.

»www.ebay.com/itm/Waterpr ··· 9c69ffff

or this if you just want screw connections.
»www.ebay.com/itm/SUPERNI ··· 15607cc0

splitt
@comcast.net

splitt to Sly

Anon

to Sly
not mentioned yet:

perhaps you could use a usb splitter,
if the current suppliable by the receiver is sufficient.
for that you need to know the specs of the receiver and the draw of the other usb device.

--
expect car voltages to be a bit higher and lots noisier than you mention. plan for 20 volts and lots of static, thus requiring lots of heat sink and lots of shielding and extra capacitors for anything you build.

you should be able to get a 7805 regulator in to3 metal can that will handle those higher voltages (to 35 V) and currents (to 1.0 A) with ease, and have extra metal heat sinking of its own in the can, more than a plastic regulator. for about $3. for power multiply the volts and current, e.g. 20 volts times 0.6 amp equals 12 watts, so the heat sink should be sized to be able to handle that.

you may also be able to build the regulator circuit into the inside of the case of the mini dsp

Sly
Premium Member
join:2004-02-20
Tennessee

Sly

Premium Member

The DVD receiver will only put out 1amp max. The USB thumb drive pulls about .5 amps and the MiniDSP pulls .6, so I will need a separate power supply. Thanks though.
Sly

Sly to LittleBill

Premium Member

to LittleBill
said by LittleBill:

im confused, 600ma 5v? any usb cell phone charger can do this, the one in my car does 2 amp at 5v

i also highly doubht the voltage needs to be rock solid, nobody has any idea on the voltage at a house, between my house and my neighbor there is a 4 volt difference.. think your making too big of a deal out of this

The power supply goes to the analog to digital converter built into the MiniDSP. If the voltage rises or falls, it could affect the input gains on the signal processor. The documentation requires a regulated power supply for the ADC/DAC to function properly. Plus in a car's noisy environment, I would like some degree of power isolation.
TheMG
Premium Member
join:2007-09-04
Canada
MikroTik RB450G
Cisco DPC3008
Cisco SPA112

1 recommendation

TheMG

Premium Member

As has already been mentioned, the simplest and cheapest way to approach this is a 7805 linear regulator. Inexpensive, simple circuit to put together, and quite effective. Not very efficient and will dissipate quite a bit of heat but nothing that can't be dealt with with an adequate heatsink and in a car installation I don't think efficiency is too much of a concern unless you plan on running this thing for long periods of time without the engine running.

Heck, if the case of the DSP is aluminum you might even be able to just stick the LM7805 inside it and use the case as the heatsink. It will get a bit warm but nothing too extreme.
lutful
... of ideas
Premium Member
join:2005-06-16
Ottawa, ON

lutful to Sly

Premium Member

to Sly
said by Sly:

I need it to output 5 volts under all incoming voltage levels and I need it to handle at least a 600 milliamp load. Any noise isolation feature would be nice as well just to eliminate the chances of any alternator whine coming through the system.

You can purchase the evaluation board for LT1764A low noise, adjustable, linear regulator IC. It accepts up to 20V input, outputs up to 3A. »www.linear.com/product/LT1764A

Linear tech also has automotive surge protector ICs that isolate any sensitive equipment. If you make a DIY board for the LT1764A, you just add one of them across the input capacitor.

SmokChsr
Who let the magic smoke out?
Premium Member
join:2006-03-17
Saint Augustine, FL

SmokChsr to Sly

Premium Member

to Sly
How about one of these?
»www.prodctodc.com/car-bu ··· ply-c-22
Or even closer..
»www.prodctodc.com/car-bu ··· -c-22_24
lutful
... of ideas
Premium Member
join:2005-06-16
Ottawa, ON

lutful to tschmidt

Premium Member

to tschmidt
said by tschmidt:

Assuming maximum current draw is 600ma running a linear regulator barefoot from the car electrical system means the regulator has to dissipate 5.64W. Not a huge amount but will need a significant heat sink over the wild temperature extremes of a car.

Yes, heat dissipation must be calculated for this application.

Automotive LDOs come in flat packages with a large solder surface, and tolerate 125C junction temp. If PCB has a large copper pour around the LDO, a heat sink may not be needed for 600mA load. But it is always good idea.

*** If a switching regulator is acceptable, TI has a very efficient, low noise module which accept 17V input and provide 650mA: »www.ti.com/lit/ds/symlin ··· 1700.pdf

aurgathor
join:2002-12-01
Lynnwood, WA

aurgathor to Sly

Member

to Sly
No one mentioned it yet, but you could use a capacitance multiplier for additional filtering after a switching power supply.

If you use a linear regulator, you could use a carefully selected light bulb connected in series to drop some of the voltage and dissipate some of the heat that otherwise would be dissipated by the regulator.
b10010011
Whats a Posting tag?
join:2004-09-07
united state

2 edits

b10010011 to Sly

Member

to Sly
How about one of these »www.adafruit.com/products/1065
Even cheaper here »www.newark.com/tracopowe ··· /08R5932

Better yet this one would be easier to install »www.adafruit.com/products/1385

Sly
Premium Member
join:2004-02-20
Tennessee

Sly

Premium Member

Those look pretty cool... I'll look into it. I'm looking for a prepackaged product and those seem to be what I'm looking for.

When it comes to power supplies, I don't have a lot of background knowledge. It's simply something I've never thought about until I found myself in a project that required one. Thanks again.