Suitability of beagle board in a car

GoogleGroups
1

Has anyone tried putting a Beagle Board into a car?

I've been restoring an old car (from the 1960's) so it hasn't any
radio and a modern radio would look out of place. I quite like
tinkering with linux and doing the odd bit of programming (mostly
simply python etc stuff recently but I used to do some C/ASM
programming 5 or so years back).

Having seen a beagle board on display at the LUG radio live (uk) event
I started considering that maybe I could put a beagle board into the
car and a couple of speakers all hidden under the dash board.
Initially probably just playing any music on a usb stick plugged in,
but later on maybe looking into adding a small touch screen on a hinge
to pull down from the dash board and GPS/wifi/usb fm receiver and
possibly (if i can remember my electronics lessons from college)
adding some input from car sensors (battery volts/engine temp etc).

But I'm wondering if anyone has any experience with this and has tried
it before, and would recommend it (or not). Also if theres an easy way
to wire the beagle board up to a cars power supply (which doesn't have
a cigarette lighter). The amount of power the board consumes sounds
like it would be comparable to a normal radio, but correct me if I'm
wrong.

Thanks,
Daniel

2

Yes, look at the Beagles Ride web site

http://www.beaglesride.org/

They are not doing exactly what you want to do, but their work may fit
in with what you want to do.

-Preston

3

> Has anyone tried putting a Beagle Board into a car?

Yes, look at the Beagles Ride web site

http://www.beaglesride.org/

Thanks Preston, I had noticed it earlier but it seems like it had only
recently started and was lacking a little on information, so not sure
if anyone has actually tried this, but i will post a few messages to
there forum in the future.

I've got a couple of questions tho, the Beagle Board requires 5v's
(exactly) but I've not seen anywhere how much current it requires. I
thought initially as it can be powered from the USB socket that it
would need 500ma's, but looking at the details for the mains power
adapter (listed on Google Code Archive - Long-term storage for Google Code Project Hosting.)
the listed power supply outputs 5v's and 2amps. So I'm wondering what
is the recommended current to supply?

Also I've seen mentioned talk of the next revision of the beagle board
and wondering if the changes make it worth holding off on buying the
board till the next revision comes out (as I'm in no hurry, with the
car not yet on the road)

I think I'll start off over Christmas by trying to power a powered USB
hub from the car to get the project started and if that goes well (and
it's a lot less expensive if I make a mistake) I'll move onto buying
and powering the Beagle Board.

Thanks for the help,

Daniel

4

The added power for the adapter is to provide extra power for the USB host, when available on Rev C, and the expansion connector. It will easily run from the USB supply. 500Ma is more than enough depending on what else you decide to add to it. It takes roughly 350mA. Power can be easily red with a voltmeter across J2.

As to waiting, that is your call. All Rev C really provides is a single USB host interface and it won’t be available until late Q1 of next year.

Gerald

5

USB power will work.

Most wall wart power supplies are not regulated, so it could be that
the listed supply is the best fit even though it can supply much more
power than is needed. I run my board off of a bench power supply and
the highest I have seen my board draw (outside of one issue) is 370mA
at 5V. The board is advertised as requiring 2W, which is 400mA at 5V,
and that is close to what I measured. The "outside issue" happened
when I tried to suspend to RAM: the board started drawing over 700mA
after the suspend failed.

The main issue I would worry about for the car is the temperature
extremes. I have not looked at the rated temperature operating range
for the beagle board, but the OMAP3530 comes in a commercial package
that is rated for operating between 0C and 90C, and an industrial
package that is rated for operating between -40C and 105C. Obviously
the industrial part is much better suited for operating in a car.
There are other factors that go into figuring out the true temperature
operating range of a device besides the raw numbers in the datasheets,
and the calculations are not simple.

That said, I actually looked at my board to see if I could tell which
OMAP part (commercial or industrial) is on it, but the OMAP processor
has a Micron logo (ellipse M) with this alphanumeric code: 8DA98 JY192

I cannot speak to whether or not you should hold off on buying a board
until the next rev is released.

-Preston

6

The added power for the adapter is to provide extra power for the USB host,
when available on Rev C, and the expansion connector. It will easily run
from the USB supply. 500Ma is more than enough depending on what else you
decide to add to it. It takes roughly 350mA.

I might run it from the USB supply in the short term, but a dedicated
power regulator for it would free up a socket on the USB hub.

Most wall wart power supplies are not regulated, so it could be that
the listed supply is the best fit even though it can supply much more
power than is needed. I run my board off of a bench power supply and
the highest I have seen my board draw (outside of one issue) is 370mA
at 5V. The board is advertised as requiring 2W, which is 400mA at 5V,
and that is close to what I measured. The "outside issue" happened
when I tried to suspend to RAM: the board started drawing over 700mA
after the suspend failed.

Thats good, I've seen some power regulators that look like they might
work well that supply 500mA's, but I might look into a 1A power
regulator just in case something causes an above average drain on
power. Those current readings are they with something connected to the
USB socket or just powering the beagle board?

The regulator I was looking at initially (http://www.maplin.co.uk/
Module.aspx?ModuleNo=46473) supplies 5V +/-4% at 500mA's with a peak
output current of 700mA's. I might consider looking at (http://
www.maplin.co.uk/Module.aspx?ModuleNo=46475) a 1A regulator to cover
the eventuality of the beagle board drawing more power.

The main issue I would worry about for the car is the temperature
extremes. I have not looked at the rated temperature operating range
for the beagle board, but the OMAP3530 comes in a commercial package
that is rated for operating between 0C and 90C, and an industrial
package that is rated for operating between -40C and 105C. Obviously
the industrial part is much better suited for operating in a car.
There are other factors that go into figuring out the true temperature
operating range of a device besides the raw numbers in the datasheets,
and the calculations are not simple.

Thats something to think about, I'm hoping it would be ok, it would be
inside the passenger compartment of the car so shouldn't get too hot
or cold. I live in England so the temperature isn't too bad but does
dip a little below freezing in the winter. The temperature here
probably varies anywhere between -5C to 30C, but for most of the year
it's probably more like 15C. But I might be able to attach the beagle
board in such a way I could easily take it out if it's going to be
really cold. I'll give the specifications another look regarding
temperatures later.

Thanks for all the help, this groups been very useful and encouraging.

Daniel

7

i haven't run my beagleboard in the car yet, but i do run a windows P4 and an arm7 board, and the temperatures get quite high out here, 120F+, test a lot in death valley and on the race track, the beagle components are rating similarly to the ones i use now.

when picking a psu make sure it can handle over and undervoltage too, cars tend to throw out all sorts of nasty voltages and try to use signal vs chassis grounds if at all possible (ie if the car has them, not all do), some regulators break down on overvoltage and pass it onto your supply, there are a few off the shelf in car pc's dc to dc convertors that do the job, but they tend to get pricey, mp3car.com has a lot of reviews.

a small fan might help but the airflow in the passenger footwell does tend to be stagnant, so it'll just blow hot air around.

luckily being in blighty you should never see those temps, well maybe not so lucky

cheers

8

Those numbers were with nothing plugged into the USB OTG socket. I
just looked at the power consumption when adding a USB flash drive to
the OTG port, and that caused the current consumption to jump by
70mA. Also, when I run sync(1), the current consumption briefly jumps
by 60 to 70 mA with or without the USB flash drive plugged in.

-Preston

9

when picking a psu make sure it can handle over and undervoltage too, cars
tend to throw out all sorts of nasty voltages and try to use signal vs
chassis grounds if at all possible (ie if the car has them, not all do),
some regulators break down on overvoltage and pass it onto your supply,

All the regulators I've looked at can deal with voltages of 35 to
40v's. But i'm keeping a look out for over voltage protected ones, tho
i expect those will be fine.
How large are the fluctuations you've experienced (if u know)?

Those numbers were with nothing plugged into the USB OTG socket. I
just looked at the power consumption when adding a USB flash drive to
the OTG port, and that caused the current consumption to jump by
70mA. Also, when I run sync(1), the current consumption briefly jumps
by 60 to 70 mA with or without the USB flash drive plugged in.

I think it sounds like a good idea to go for a 1A supply to handle
those possible cases where it just goes over 500mA briefly.
I've got a USB hub and about to order a regulator for that (slightly
larger current supply than needed but choice of slightly under or
over). Hope all the components arrive in the next few weeks to get the
USB hub powered.

Thanks
Daniel

10

All the regulators I've looked at can deal with voltages of 35 to
40v's. But i'm keeping a look out for over voltage protected ones, tho
i expect those will be fine.
How large are the fluctuations you've experienced (if u know)?

Transients obviously can be pretty high, but most regulators will handle those and block them out,

In regular use you'll see around 6V to 15V, lowest at crank and on systems where the alternator or battery isn't able to provide enough current for high load peripherals like power windows, ghetto audio systems etc.

HID's tend to cause very nasty spikes too, especially the aftermarket ones they're extremely noisy, same goes for the AC compressors and so on, you'll want to add something to smooth it all out, thats why i'd look at one of the fancier dc-dc convertors specifically for in car use, unfortunately they cost almost as much as a beagleboard.

11

i haven't run my beagleboard in the car yet, but i do run a windows P4 and
an arm7 board, and the temperatures get quite high out here, 120F+, test a
lot in death valley and on the race track, the beagle components are rating
similarly to the ones i use now.

...

a small fan might help but the airflow in the passenger footwell does tend
to be stagnant, so it'll just blow hot air around.

I'm also planning on running by beagleboard in my car, actually bought
it specifically for that purpose. I was already wondering about safe
operating temperature limits, not so much at the high end but mainly
at the low end. Where I live 90F+ (30C) is rare but around 0F (-15C)
is pretty common. Do you have any experience with that kind of
operating temperatures?

Wouter

12

The OMAP and Memory device is in the commercial range of operation as are the rest of the components on the board. I cannot guarantee how the board will behave in the environments being discussed.

Gerald

13

I found this which lists where the beagle is probably operating
( Commercial range ):
TEMPERATURE RANGE C = Commercial (0°C to +70°C) I = Industrial (–40°C
to +85°C) E = Extended (–55°C to +125°C)

if that is the case and you need to operate with temps of -15C, you
probably need a microcontroller which can operate in that range and
use it to drive a heating system(maybe PID based), and a circulation
fan in the box with the Beagle. Have the uCPU drive the Beagle power
so after a short warm-up to take the beagleboard to the required
operating temp and then powering it up. After that, the running beagle
might keep the ambient temp in the box high enough for the uCPU to no
longer run the heating element though a PID system on the uCPU would
handle this anyways. The Arduino has example PID code and it comes in
the require operating range( -40°C to +85°C ) for the ATMEGA168-20PU
part .

14

In regular use you'll see around 6V to 15V, lowest at crank and on systems
where the alternator or battery isn't able to provide enough current for
high load peripherals like power windows, ghetto audio systems etc.

Yes I've noticed on my other car that the radio turns off when
starting the engine, but if I bare this in mind it might work.

HID's tend to cause very nasty spikes too, especially the aftermarket ones
they're extremely noisy, same goes for the AC compressors and so on, you'll
want to add something to smooth it all out, thats why i'd look at one of the
fancier dc-dc convertors specifically for in car use, unfortunately they
cost almost as much as a beagleboard.

I've looked around and the ones that could power the USB hub at full
load start at £20. So I'm tempted to initially stick to a cheap
voltage regulator based circuit, which would probably cost nearer £5.
I'm hoping if it does die it'll not damage anything connected to it,
just trip the internal thermal cutoff.

But the beagleboard itself I might connect to a dc-dc (pcb mounted,
Recom R-78B5.0-1.0) converter as that is nearer £7, and wouldn't want
to damage the beagleboard in any way. Would there be any risk if there
was a fault with the USB hub power supply it causing damage to the
beagleboard's USB port? (If so any reasonable precautions that could
be taken?)

Thanks
Daniel

15

Hi daniel,

keep in Mind that the 12V supply of the car is loaded with ignition noise, or generator commutation noise.
These are spikes on the supply that probably will not kill your supply (12V - 5V regulator)…

BUT you will find that if the regulator is not isolating input from output then the following
is likely to happen:

  1. Spikes are creating inrush currents in your input capacitor for the input regulation
  2. return current (when it went through input capacitor) is adding its voltage drop to the ground level the BB is connected to…
  3. thus ground level of BB audio is floating (due to spike currents) against vehicle ground
  4. connecting BB audio out to the cars audio unit will introduce noise to audio because ground is floating on voltage drop of spike currents (this is when you can hear noise that is related to engine rpm)

So you will have to decide on where to connect BBs ground.

  1. If you connect BBs ground to the input ground of your regulator you are at risk to introduce spikes on the 5V supply which may be risky.
  2. If you connect BBs ground to the output of your regulator,- then you are at risk to audio noise…

Filtering is not a very good option,- the noise is rather low frequency so you will need large and heavy inductors to prevent from spike currents…

Connecting the regulators input GND shortly to the audio device GND may be an option, but still is 2nd best solution.

regards,
A.d.T

schrieb:

16

Here is a power supply for powering a regular PC motherboard from a
car battery. Overkill for the beagle, but the features should give you
an idea of things that should be considered powering electronics from
a car battery:

http://www.mini-box.com/M1-ATX-90w-Intelligent-Automotive-DC-DC-Power-Supply?sc=8&category=101

Philip