Den mandag den 11. november 2013 19.47.01 UTC+1 skrev edward....@gmail.com:
> > > We are using 800mAHr on 3.3V, so around 2.7 WattHour.
>
> >
>
> > > People are leaving essential info on posting, which is really draining my mind reading power, especially over the net.
>
>
>
> > He's stating the size of his load. He hasn't expressed any preference
>
> > for how long the battery needs to last --so, no claims as to how long
>
> > it will take to *charge*, etc. I.e., your (below) battery mmay give him
>
> > an hour or two of runtime. It may give *you* TEN hours, depending on
>
> > *your* load!
>
> >
>
>
>
> Hence, my joke about reading his mind over the net. We need to know the size and type of battery involved, as well as load. For example, you can pull half a watt out of a 3V 200mAHr coin cell at 5mA. But at 50mA (typical 32 bitter), it would not last more than one-tenth of a watt. So, it's better to spec the battery several time more than your load.
>
>
>
> We looked at all kinds of batteries, including LiFePO4, but end up going back
>to NiMH. We can get 800mAHr (3 x AAA) for $2 and 400mAHr (3 x AAAA) for >
>$1.5. Nothing Li* for less than $10.
Reply by Clifford Heath●November 15, 20132013-11-15
On 15/11/13 23:33, mike wrote:
> Now all you need is a radio controlled drone to carry
> the receiver and the camera and some defensive weapons
> to take out the competition.
Hah, good idea. It would need to be quick and have good duration.
Sometimes the fox is 40km away.
Actually one team hunts all bands on equipment that converts first to
21.4MHz. It turns out that's inside a ham band, so we could legally
transmit on their IF and see how good their shielding is :)
We had a balloon hunt at this year's competition, without anyone being
told prior. There's an animation on youtube:
<http://www.youtube.com/watch?v=lJnpUvikUac>
Clifford Heath.
Reply by mike●November 15, 20132013-11-15
On 11/15/2013 4:10 AM, Clifford Heath wrote:
> On 15/11/13 19:30, mike wrote:
>> On 11/14/2013 10:57 PM, Clifford Heath wrote:
>>> Not a concern at this level - it's a ham radio device (fox transmitter
>>> and sniffer receivers).
>
>> I'd be interested in learning more about the device.
>> Back in the early '60's we had transmitter hunts on 6 meters.
>
> Great fun, yeah?
>
Way cool.
Come a long way in 50 years ;-)
Now all you need is a radio controlled drone to carry
the receiver and the camera and some defensive weapons
to take out the competition.
Reply by Clifford Heath●November 15, 20132013-11-15
On 15/11/13 19:30, mike wrote:
> On 11/14/2013 10:57 PM, Clifford Heath wrote:
>> Not a concern at this level - it's a ham radio device (fox transmitter
>> and sniffer receivers).
> I'd be interested in learning more about the device.
> Back in the early '60's we had transmitter hunts on 6 meters.
Great fun, yeah?
I learnt to hunt with the Melbourne crew (VK3's), who have 30+ years
experience and an amazing range of talents. Google for VK3VT (now
VK3FOX), VK3MZ, VK3YNG, for some of the most prolific constructors.
Almost all the gear is home-built, and these days, the most
sophisticated crews have fully integrated in-car systems with motorized
rooftop antenna arrays (including in-car control of polarisation in one
case), 2m dopplers, Watson-Watt receivers, etc, all feeding into
custom-made SDR systems with real-time digital spectrum display
(brick-wall filtering), automated bearing extraction from the returned
antenna lobe display, drawing vectors on a moving map display, etc. The
annual hunt with the VK5's at Mt Gambier in June has a big five-leg
night hunt, usually spread across 3 or 4 bands. Regular hunts are on
80m, 10m, 6m, 2m, 70cm and 22cm. Foot events are on 2m mostly. When we
run ARDF events (see below) they're 80m or 2m.
6m hunts are interesting in the pine plantations around Mt Gambier.
Young pines are planted on a 3m grid, then thinned to a 6m grid. If you
watch the vector display on my team's Watson-Watt as the car creeps
forward, the bearing does a full 360 swing for every 6 metres you drive
forward. Very hard to DF!
Anyhow, I'm in Sydney now, and the barrier to building up such systems
is very high, so I'm going back to basics, building 80m gear for ARDF
and especially sprint ARDF, events held for runners on foot. ARDF events
use five transmitters on the same frequency, transmitting one at a time
in a five minute cycle (or for sprint, a one minute cycle, twelve
seconds each). My new 80m fox is about the size of a cigarette packet,
and pumps out up to a watt. An MSP430 will lock the VCO frequency to its
32KHz clock, while also doing Morse code modulation, managing the ARDF
cycles, keeping real time, and running the iButton scoring that I built
years ago. that's the plan anyhow.
The receiver front end has been designed to feed an Si4735 digital radio
chip, for which we have an SSB software patch. It will use a loop or
loopstick and a sense wire, phase shifted and mixed to produce a
cardioid - hunting on the null. In future I'm keen to try SDR directly
in an ARM7 CortexM4 after down-converting to a 45KHz IF, a broadband DF
antenna for HF to build and try, and maybe a hand-held Watson-Watt with
a colour cell-phone LCD display.
> As for your charger...I'd go to Best Buy.
I'm not concerned with cells, and don't want 3.6 or 3.7 volt Li-ions.
I'm concerned with USB charging for LiFePO4, which charge to 3.4V,
and don't tend to explode at random. They're used in portable drills
etc, which have a higher robustness and safety requirement than your
typical phone or MP3 player.
Nice little device. I might have another use for them.
> If we have the same concept of a transmitter hunt, I think
> the rational choice is 3 AAA alkaline cells or thereabouts.
> Not everything in the world needs to be rechargeable.
Been there, done that. Alkaline is fine for sniffers, but you burn a lot
of cells transmitting one watt or more... and there are six or eleven
transmitters for an event (including the homing beacon). They need to be
rechargable, and if I do it for the foxen, why not the receivers too?
Clifford Heath.
Reply by mike●November 15, 20132013-11-15
On 11/14/2013 10:57 PM, Clifford Heath wrote:
> On 13/11/13 10:34, mike wrote:
>> Is this a REAL USB device that can negotiate power levels
>> with the host? Or are you using the host as a dumb power supply?
>
> Initially, the latter. Using USB connections means chargers are readily
> available.
>
>> Is this a production device that is required to meet, and be tested to
>> international safety standards?
>
> Not a concern at this level - it's a ham radio device (fox transmitter
> and sniffer receivers). The transmitter is programmable (and the RTC is
> settable) but that's through the iButton port which is also used for
> event scoring - not through the USB port.
I'd be interested in learning more about the device.
Back in the early '60's we had transmitter hunts on 6 meters.
I was about 15 years old at the time.
Went to my first hunt and watched guys driving their mobile
rigs around watching the S-meter trying to find the hidden transmitter.
Second hunt, I took a 6-meter converter cobbled onto the front
of a transistor radio and a loop antenna.
Took one direction reading. Drove 90 degrees away from it and took
another reading. Then drove right to the hidden transmitter.
Third hunt, nobody else showed up.
Good times...
As for your charger...I'd go to Best Buy. They've got a recycle bin
for cellphone batteries. Talk the guy into letting you have a pile.
Check out what chips they use.
These guys have some battery protection devices and cells with such
devices already packaged
http://dx.com/p/charge-discharge-protective-circuit-board-for-rechargeable-li-ion-batteries-17-4mm-1-9mm-26112
I bought two, but never used 'em.
There are protected batteries for flashlights in various sizes
with chargers available at the same place.
I don't think your problems are technical. Depending on how
long you plan to sell and support the device, finding something
that will be available in the future (next week) is a big gamble.
If we have the same concept of a transmitter hunt, I think
the rational choice is 3 AAA alkaline cells or thereabouts.
Not everything in the world needs to be rechargeable.
>
> I don't want to roll my own charger, although it's not hard to do a
> basic-level job (current limit into a 3.4V regulator).
>
> The devices have very low quiescent current (uA) so I'm not worried
> about the battery going flat on the shelf.
>
> LiPo cells are much less stable (need temp monitoring and cutout) which
> is why I'm choosing LiFePO4. I should only need low-voltage cutout.
>
> Thanks all for your comments. It appears no-one wants to recommend a
> chip for this, or perhaps has even used one.
>
> I'll be off USENET for a couple of weeks now. Any further comments would
> be appreciated, even if I don't respond quickly.
>
> Clifford Heath.
Reply by Clifford Heath●November 15, 20132013-11-15
On 13/11/13 10:34, mike wrote:
> Is this a REAL USB device that can negotiate power levels
> with the host? Or are you using the host as a dumb power supply?
Initially, the latter. Using USB connections means chargers are readily
available.
> Is this a production device that is required to meet, and be tested to
> international safety standards?
Not a concern at this level - it's a ham radio device (fox transmitter
and sniffer receivers). The transmitter is programmable (and the RTC is
settable) but that's through the iButton port which is also used for
event scoring - not through the USB port.
I don't want to roll my own charger, although it's not hard to do a
basic-level job (current limit into a 3.4V regulator).
The devices have very low quiescent current (uA) so I'm not worried
about the battery going flat on the shelf.
LiPo cells are much less stable (need temp monitoring and cutout) which
is why I'm choosing LiFePO4. I should only need low-voltage cutout.
Thanks all for your comments. It appears no-one wants to recommend a
chip for this, or perhaps has even used one.
I'll be off USENET for a couple of weeks now. Any further comments would
be appreciated, even if I don't respond quickly.
Clifford Heath.
Reply by Don Y●November 14, 20132013-11-14
Hi Dimiter,
On 11/13/2013 8:52 PM, dp wrote:
>>> Both, generally I needed many hours (was it 6 or 8...) autonomous
>>> operation (here it is: http://tgi-sci.com/tgi/pntb.htm ) .
>>> I had two groups of 9 batteries in series each tied in parallel.
>>> I was wise enough to have them discharged before making the parallel
>>> connection, obviously, and was careful enough to measure the voltage
>>> before that, but generally things worked quite OK.
>>
>> Hmmm... I guess I would have tried to treat them as separate packs
>> charged independently with their outputs merged through sharing
>> "diodes" (or actively)
>
> These were (well, must have been) my initial thoughts back then (20
> years ago when I first did it this way). But things are not that bad,
Ah, OK.
> really. Given that I sell a battery pack (cells soldered to a PCB) and
> I buy cells of the same batch, have parallel cells stuck to each other,
> it makes little difference to whatever they have wound inside
> the batteries whether it is in one or in two packages. Once you charge
> the whole pack and keep for a day or two on trickle charge things
> level out quite OK.
I suspect for an instrument with the level of "investment" as
yours, you probably don't encounter folks trying to replace
batteries "on the cheap".
>> I guess I'm hoping for a "breakthrough" before I *need* it! :>
>
> Hah, aren't we all (for this or some other breakthrough) :D .
Sometimes we get lucky! :>
>> My current strategy is to make devices inexpensive enough that you can
>> buy several and just swap them out as their batteries need recharging.
>> Even if that means carrying a "spare" with you...
>
> That's of course a good strategy but not applicable to my low volume
> (sometimes one-off) designs, hence the different approach. I have yet
> to make a Li-ion charger though, hopefully my bold approaches don't
> put me in the news :D :D :D . (I think I am wise enough not to be
> too bold with these things but then who knows.... :D ).
Some of my devices are in the "coin cell" ballpark. If you're
already that small, adding another cell is a big increase in
volume, etc. (One I am targeting as a "large wristwatch")
Of course, the advantage of that small size is that it is not
unreasonable to stuff a spare in your pocket in case the battery
in the first is exhausted and needs to sit on a charger for
some time...
Reply by dp●November 13, 20132013-11-13
On Thursday, November 14, 2013 4:38:17 AM UTC+2, Don Y wrote:
> Hi Dimiter,
>
> [still 30C, here! Ice on your trees, yet? :> ]
>
No, summer was half as long as it should have been but I guess
that paid for a delayed cold. Still around +15C max/5C min, fairly
merciful for mid November.
>
> On 11/13/2013 5:50 PM, dp wrote:
> >> Yikes! Because you needed ampacity (wide) or potential (stacked)?
> >> (as well as CAPACITY)
> >
> > Both, generally I needed many hours (was it 6 or 8...) autonomous
> > operation (here it is: http://tgi-sci.com/tgi/pntb.htm ) .
> > I had two groups of 9 batteries in series each tied in parallel.
> > I was wise enough to have them discharged before making the parallel
> > connection, obviously, and was careful enough to measure the voltage
> > before that, but generally things worked quite OK.
>
> Hmmm... I guess I would have tried to treat them as separate packs
> charged independently with their outputs merged through sharing
> "diodes" (or actively)
These were (well, must have been) my initial thoughts back then (20
years ago when I first did it this way). But things are not that bad,
really. Given that I sell a battery pack (cells soldered to a PCB) and
I buy cells of the same batch, have parallel cells stuck to each other,
it makes little difference to whatever they have wound inside
the batteries whether it is in one or in two packages. Once you charge
the whole pack and keep for a day or two on trickle charge things
level out quite OK.
> I guess I'm hoping for a "breakthrough" before I *need* it! :>
Hah, aren't we all (for this or some other breakthrough) :D .
> My current strategy is to make devices inexpensive enough that you can
> buy several and just swap them out as their batteries need recharging.
> Even if that means carrying a "spare" with you...
That's of course a good strategy but not applicable to my low volume
(sometimes one-off) designs, hence the different approach. I have yet
to make a Li-ion charger though, hopefully my bold approaches don't
put me in the news :D :D :D . (I think I am wise enough not to be
too bold with these things but then who knows.... :D ).
Dimiter
------------------------------------------------------
Dimiter Popoff Transgalactic Instruments
http://www.tgi-sci.com
------------------------------------------------------
http://www.flickr.com/photos/didi_tgi/sets/72157600228621276/
Reply by Don Y●November 13, 20132013-11-13
Hi Dimiter,
[still 30C, here! Ice on your trees, yet? :> ]
On 11/13/2013 5:50 PM, dp wrote:
>> Yikes! Because you needed ampacity (wide) or potential (stacked)?
>> (as well as CAPACITY)
>
> Both, generally I needed many hours (was it 6 or 8...) autonomous
> operation (here it is: http://tgi-sci.com/tgi/pntb.htm ) .
> I had two groups of 9 batteries in series each tied in parallel.
> I was wise enough to have them discharged before making the parallel
> connection, obviously, and was careful enough to measure the voltage
> before that, but generally things worked quite OK.
Hmmm... I guess I would have tried to treat them as separate packs
charged independently with their outputs merged through sharing
"diodes" (or actively)
> I had mounted
> each cell to be pressed against its parallel counterpart and
> that was all, the battery lasted for years. Used those 76mm long 17mm
> diameter cells, the whole pack was 75Wh. Not that much more compared
> to what todays laptops have, nor was it much larger. Somewhat heavier
> than equivalent Li-ion of course.
I'm treading carefully on my battery requirements. Trying hard to
find ways to "eliminate load" so I can reduce the size and
complexity of the "battery". But, I'm more constrained on
space/volume than you are so I don't have much choice to
"add capacity".
I guess I'm hoping for a "breakthrough" before I *need* it! :>
My current strategy is to make devices inexpensive enough that you can
buy several and just swap them out as their batteries need recharging.
Even if that means carrying a "spare" with you...
Reply by dp●November 13, 20132013-11-13
Hi Don,
On Thursday, November 14, 2013 12:36:33 AM UTC+2, Don Y wrote:
> ...
>
> Yikes! Because you needed ampacity (wide) or potential (stacked)?
> (as well as CAPACITY)
Both, generally I needed many hours (was it 6 or 8...) autonomous
operation (here it is: http://tgi-sci.com/tgi/pntb.htm ) .
I had two groups of 9 batteries in series each tied in parallel.
I was wise enough to have them discharged before making the parallel
connection, obviously, and was careful enough to measure the voltage
before that, but generally things worked quite OK. I had mounted
each cell to be pressed against its parallel counterpart and
that was all, the battery lasted for years. Used those 76mm long 17mm
diameter cells, the whole pack was 75Wh. Not that much more compared
to what todays laptops have, nor was it much larger. Somewhat heavier
than equivalent Li-ion of course.
Dimiter
------------------------------------------------------
Dimiter Popoff, TGI http://www.tgi-sci.com
------------------------------------------------------
http://www.flickr.com/photos/didi_tgi/sets/72157600228621276/