| |
ZL3AI > APRDIG 01.04.04 15:53l 265 Lines 10413 Bytes #999 (0) @ WW
BID : 3076-ZL3AI
Read: GUEST
Subj: TAPR Digest, Mar 29, 5/7
Path: DB0FHN<DB0FOR<DB0MRW<OK0PKL<OK0PPL<DB0RES<ON0AR<7M3TJZ<JL1ZND<JK1ZRW<
WB0TAX<GB7ESX<ZL2BAU<ZL3VML
Sent: 040401/1218Z @:ZL3VML.#80.NZL.OC #:21757 [Chch-NZ] FBB7.00i $:3076-ZL3AI
From: ZL3AI@ZL3VML.#80.NZL.OC
To : APRDIG@WW
Subject: Re: New tracker design suggestions
From: "Scott Miller" <scott@opentrac.org>
Date: Mon, 29 Mar 2004 11:26:27 -0800
X-Message-Number: 30
>FYI, off the shelf D cell alkalines are *way* better then D cell NiMH. A D cell
>alkaline has a AMP/Hour rating of 17, the NiMH has a rating of 7 amp hours.
I know this used to be the case with NiCd's, and I think I've seen it in
NiMH as well, but some manufacturers used to package C cells in D sized
cylinders. If they give an amp/hour rating, it's obvious because the C and
D cells are exactly the same.
In any case, I was thinking of a pack of AAs. A few of those ought to give
a week runtime or more.
Scott
N1VG
----------------------------------------------------------------------
Subject: Re: New tracker design suggestions
From: Jeff King <jeff@aerodata.net>
Date: Mon, 29 Mar 2004 13:38:14 -0600 (CST)
X-Message-Number: 31
Quoting Scott Miller <scott@opentrac.org>:
>>switching regulators would be a huge improvement in
>any
>low-power project. A linear reg, taking 12V to 5W wastes more power in heat
>than it delivers to the load. The long term consumption is far more
>important than the short term transmit pulses.
>
>>A switcher is typically 90%+ efficient. Linears win again at extremely low
>currents where the static drain of the switcher becomes significant.
>
>My main concern with a switcher is noise.
If you power the radio, the switcher makes sense. For just the micro, it
doesn't make a lot of sense, since the quiesent current of switchers is
quite a factor, and when you have a micro drawing 4ma, a swither that has
a quiescent current of 5-10ma (LM2574) is a big deal. Not sure what micro
you use, but I power a lot of my commerical circuits >directly< off 4 D
cell's, with NO regulator at all. Using the PIC LF series which can run
from 5.5v to 2.0Volts.
Run the numbers yourself. For low power apps, almost always a linear wins
with battery life, in particular if you put the micro to sleep.
>MOST of the design will run on 3.3 volts.
Take a look at the TPS71533DCKR
http://rocky.digikey.com/WebLib/Texas%20Instruments/Web%20data/TPS715xx.pdf
3.2uA quiescent current, with a typical dropout voltage of 415 mV. Should be
able to take 4 batteries to end of life before you drop out of regulation.
Low power design is a art into itself and a lot of the assumptions we make, in
the big picture, often need to be rethought.
----------------------------------------------------------------------
Subject: Re: New tracker design suggestions
From: David VanHorn <dvanhorn@cedar.net>
Date: Mon, 29 Mar 2004 14:47:20 -0500
X-Message-Number: 32
>Even regular troops need to keep the weight down for those long
>missions. We'd have a revolt if I asked one person from each team
>to carry a tracker using a set of D's. AA's and a tracker I think I
>can get away with.
AAs make a lot of sense. I'm trying to keep all my emergency gear in AAs.
The only exception at the moment is flashlights, which are running 123s and
D cells, which I carry spares of.
----------------------------------------------------------------------
Subject: Re: New tracker design suggestions
From: Jeff King <jeff@aerodata.net>
Date: Mon, 29 Mar 2004 13:47:15 -0600 (CST)
X-Message-Number: 33
Quoting David VanHorn <dvanhorn@cedar.net>:
>Now what's the price of 12V worth of D cells?
The no-name brands at WalMart are under $1 a cell I believe.
Don't forget what was being asked for, a portable digipeater in an ammo
can. Anyway you look at it, Alkaline will give you more then 2x the life of
NiMH. That may make all the difference in a event where you don't have easy
access to the NiMH's to recharge them.
Me? I'd just put a battery holder in it and use whatever the mission was
best suited for. At Dayton, I use alkaline batteries for my HT, even though
I also have a recharable pack.
----------------------------------------------------------------------
Subject: Re: New tracker design suggestions
From: David VanHorn <dvanhorn@cedar.net>
Date: Mon, 29 Mar 2004 14:49:30 -0500
X-Message-Number: 34
At 11:26 AM 3/29/2004 -0800, Scott Miller wrote:
>>FYI, off the shelf D cell alkalines are *way* better then D cell NiMH.
>>A Dcell alkaline has a AMP/Hour rating of 17, the NiMH has a rating
>>of 7 amp hours.
http://www.zbattery.com/mh-2d110.html 11AH nimh
----------------------------------------------------------------------
Subject: Re: New tracker design suggestions
From: "Scott Miller" <scott@opentrac.org>
Date: Mon, 29 Mar 2004 11:57:52 -0800
X-Message-Number: 35
>current of 5-10ma (LM2574) is a big deal. Not sure what micro you use, but I
>power a lot of my commerical circuits >directly< off 4 D cell's, with NO
>regulator at all. Using the PIC LF series which can run from 5.5v to 2.0Volts.
I'm planning on using a Motorola MC9S08GT60. For development I'm using a
GB60, but it's mostly a difference in packaging. It'll take anything from
3.6 down to 1.8 volts. 2.08 volts if you want to run at 20 MHz. The CMX860
only operates down to 2.7 though, so it doesn't really matter.
If I do provide an unregulated battery input option, is it likely to cause
any problems if the linear regulator is left in the circuit? Will it care
that it's got a voltage on the output and not on the input?
>3.2uA quiescent current, with a typical dropout voltage of 415 mV. Should be
>able to take 4 batteries to end of life before you drop out of regulation.
>
>Low power design is a art into itself and a lot of the assumptions we make, in
>the big picture, often need to be rethought.
Yeah, I get at least 3 pieces of power related junk mail from TI every week.
I'll check that one out.
The thing that always gets me is dealing with rechargable batteries. NiCd
and NiMH cells only put out 1.2 volts... working with both alkaline and
rechargable is a pain.
Scott
N1VG
----------------------------------------------------------------------
Subject: Re: New tracker design suggestions
From: David VanHorn <dvanhorn@cedar.net>
Date: Mon, 29 Mar 2004 15:00:19 -0500
X-Message-Number: 36
At 01:38 PM 3/29/2004 -0600, Jeff King wrote:
>Quoting Scott Miller <scott@opentrac.org>:
>
>>>switching regulators would be a huge improvement in any
>>low-power project. A linear reg, taking 12V to 5W wastes more power in heat
>>than it delivers to the load. The long term consumption is far more
>>important than the short term transmit pulses.
>>
>>>A switcher is typically 90%+ efficient. Linears win again at extremely low
>>currents where the static drain of the switcher becomes significant.
>>
>>My main concern with a switcher is noise.
>
>If you power the radio, the switcher makes sense. For just the micro, it
>doesn't make a lot of sense, since the quiesent current of switchers is
>quite a factor, and when you have a micro drawing 4ma, a swither that has
>a quiescent current of 5-10ma (LM2574) is a big deal.
Right, you're back in the low current domain where linears win again. In my
system, the "awake" drain can exceed 100mA, so we power the high current
portion with a switcher, and the rest with a linear.
>Not sure what micro you use, but I power a lot of my commerical circuits
>directly< off 4 D cell's, with NO regulator at all. Using the PIC LF
>series which can run from 5.5v to 2.0Volts.
I use AVRS, but in any case, I wouldn't violate the max voltage even a
little..
>Run the numbers yourself. For low power apps, almost always a linear wins
>with battery life, in particular if you put the micro to sleep.
We're saying the same thing here, just differently.
If the drain is in the high, a switcher wins. If low, the linear wins.
The point of transfer is maybe different in different systems.
>>MOST of the design will run on 3.3 volts.
>
>Take a look at the TPS71533DCKR
>http://rocky.digikey.com/WebLib/Texas%20Instruments/Web%20data/TPS715xx.pdf
Nice.
>3.2uA quiescent current, with a typical dropout voltage of 415 mV. Should be
>able to take 4 batteries to end of life before you drop out of regulation.
>
>Low power design is a art into itself and a lot of the assumptions we make,
>in the big picture, often need to be rethought.
Yes.
In my case, printing FAST is significantly less power-expensive than
printing slow, which you wouldn't generally expect to be true.
Beware the Vittoz Oscillator. The avr has one of these, if you set the
CKOPT fuse to "0". It's a very low power, but VERY TOUCHY oscillator
circuit. Even a fingerprint on the PCB can kill it. It is becoming more
popular, due to low power and low EMI. Basically, they replace the upper
mosfet with a constant current source, and the amplitude is around the Vth
of the lower mosfet, typically <1Vpp, instead of nearly rail-rail in a
conventional circuit.
Vittoz is a good approach, but only if it's carefully designed.
----------------------------------------------------------------------
Subject: Re: New tracker design suggestions
From: David VanHorn <dvanhorn@cedar.net>
Date: Mon, 29 Mar 2004 15:04:57 -0500
X-Message-Number: 37
At 01:47 PM 3/29/2004 -0600, Jeff King wrote:
>Quoting David VanHorn <dvanhorn@cedar.net>:
>
>>Now what's the price of 12V worth of D cells?
>
>The no-name brands at WalMart are under $1 a cell I believe.
Yeah, that's what I want strapped to my back.. :)
I have some "no name" nimh's from china I can sell you cheap.
Less than 1% of them spontaneously exceed 120C and vent boiling electrolyte.
>Don't forget what was being asked for, a portable digipeater in an ammo
>can. Anyway you look at it, Alkaline will give you more then 2x the life of
>NiMH. That may make all the difference in a event where you don't have easy
>access to the NiMH's to recharge them.
That's a good point, As the power density goes up, all the chemistries get
more "fussy" about charging, though they are working on that. The early
rechargeable Lithium cells were a real fun thing.
>Me? I'd just put a battery holder in it and use whatever the mission was
>best suited for. At Dayton, I use alkaline batteries for my HT, even though
>I also have a recharable pack.
A good option, provided the voltage difference dosen't become a problem.
There's always going to be the guy who drops 12 alkaline D cells into the
NIMH 14.4 V pack. I hope there aren't any 16V tants in the system! :)
----------------------------------------------------------------------
Read previous mail | Read next mail
| |
