On 09/30/2014 9:37 AM, dpb wrote: ...
BTW, to get the above I took the easy way out and used the calculator at
Selecting Am-241 Gamma (the alpha as noted above can be discounted entirely as a contributor as long as the source is in the device), and an estimate of 10-ft average distance from a 1-uCi source, the dose rate is ~1.5E-6 mrem/hr. Multiplying by 24*364 and assuming an occupancy of
I think that a unit that used a LSD NiMH 9v battery and integral charger would be a great idea. (such a thing exists, I use them, Tenergy and Maha at least make them...) however the higher price would likely drive off contractors from using them.
I am not certain if that would violate code as currently written, I'd have to research that. Something like that would likely have to go through a NRTL testing/approval process...
nate
Not local; NFPA.
nate
Good to see that apparently someone has a better solution. Curious though, if they are selling them and you are using them, why would you think it wouldn't meet code? IDK what the code says exactly, but I'd expect it to say that you have to have AC+battery, but not be so specific to rule out rechargeable.
r would be a great idea. (such a thing exists, I use them, Tenergy and Mah a at least make them...) however the higher price would likely drive off co ntractors from using them.
ave to research that. Something like that would likely have to go through a NRTL testing/approval process...
I meant that I have used LSD NiMHs, but not in smoke detectors, not that th ere were any detectors on the market that were designed to use them. It wo uld seem to be a nice maintenance-free solution that would last 5-6 years i f a detector were specifically designed to utilize and float charge the NiM Hs. Or why even limit to that? Li-Ions would be a nominal 3.7V so two of those (16340? or even smaller?) would be 7.4V or thereabouts which hopefull y would be enough to run a smoke detector if designed around it.
In the meantime, does Energizer still make a lithium 9V battery? That woul d be my solution for difficult to maintain smoke detectors; those batteries have higher capacity and longer shelf life than alkalines. At a higher co st, of course...
nate
On 10/01/2014 12:28 PM, trader_4 wrote: ...
The answer as outlined above is more than likely "initial cost".
Again, if these bug you so much for that reason, the obvious alternative is to do some research and replace them with ones which do have an extended battery life and/or rechargeables.
Different device/design but the outdoor unit on the local weather station has started indicating "low battery" at night...it's got a solar charger and I replaced the initial battery just a month ago but it showed the missive the other night again already. I suppose the solar cell is now starting to fail/losing its "oomph" after 2-3 yr in the SW KS sun...
The voltage without a diode can drop ..65v further and still power the unit.
Yes, that explains why they didn't use rechargeables. It doesn't explain why they didn't use a 10 cent diode so that the alkaline battery is just there as standby and would last for years.
I agree, that's a possible solution. The comment was directed at why they didn't put in a 10c diode so I would not have to do that.
Does it have AC too?
On 10/01/2014 1:04 PM, trader_4 wrote: ...
I still think it more than likely does... ...
See above... :)
...
Not the external station, no. The base in-house display unit does and it _does_ have pretty good battery life--seems I've changed them out once, maybe. But, this is a much higher-priced device (Davis Instruments VantageVUE) so the few pennies kinds of cost-cutting on mass-produced consumer devices isn't _quite_ so vicious.
On 10/01/2014 1:22 PM, dpb wrote: ...
...
Actually, more precisely, I suspect the cut got made at the earlier "feature selection" level of what were/were not expected capabilities to meet the target market niche/pricing level for the device rather than being pared out on an individual component-level culling (altho that certainly occurs as well as the price/specific component alternative vendors/etc. evaluations that occur).
Please trim text. 328 lines is a bit much for your two line reply.
I can show you plenty of rechargeable, cheap, consumer products that sell for what a smoke detector sells for, or less that have battery "Backup" or rechargeable batteries, that don't draw the battery down along with using AC. Your argument about a 10 cent diode is silly.
Wow, really? How very important. Let's see, we have a smoke detector that's primarily operated by AC. So, it can go forever on AC plus last about as long as a battery operated one if the power goes out. Power almost always goes out for hours or a few days, not a year or two. That voltage drop is important again, why?
I've also cited other common devices where they have battery plus AC and don't draw the battery down unless it's needed because the AC fails.
On 10/01/2014 4:15 PM, trader_4 wrote: ...
That the cost/feature analysis comes out at a different place on other products doesn't negate the general rule. And, in fact, the "feature set" on your device pretty much confirms it for your particular device.
As said, it isn't/wasn't that the particular one selected component got taken back out; the feature of which it might have been a key component wasn't included to begin with. The decision as to whether it was/was not to be included almost certainly included a consideration of the cost for the design/manufacture in comparison to the expected margin and potential increase/decrease in sales and was found lacking...
Pure conjecture on your part. You have no way of knowing what went into the design consideration or why anything was or wasn't done. For all you know it could be just a bad, dumb, design. I've seen battery backup on cheap consumer products where it doesnt' run the battery down in a year. The battery is only used if the AC goes down.
On 10/01/2014 4:42 PM, trader_4 wrote: ...
Surely no more so than conjecture on your part, either,...I pointed that out some time ago upthread, as well, that we're both dealing in nothing but conjecture here (other than the fact that the design did _not_ include the feature I will submit leads to a higher likelihood that was done on purpose than not).
And, again, that other products have a different feature set and cost point has no particular bearing on the given one.
I'm bowing out of a futile and pointless subthread at this point...
On 10/01/2014 4:29 PM, dpb wrote: ...
You never followed up w/ the particular manufacturer/model so can't tell anything about who might have been but if it is a foreign knockoff it may well be that the entire engineering for the specific unit was "copy the model" in which case the feature set simply mimics that of the one chosen to ape.
Which if so simply pushes the original design choice of feature set/cost back to the previous manufacturer...
I wasn't conjecturing on why they did it. Just pointing it out and that it's terribly inconvenient and dumb. Even if I buy your argument that it would make the product cost some tiny amount more, it doesn't make sense. They could charge $2 more, point out that their design, unlike competitors doesn't draw the battery down unless the AC actually goes out and have a marketing advantage. They'd sell more and make more money.
..I pointed that
It does when they are cheap consumer electronics type stuff. And when we know how cheap semiconductors, like a diode are today. That diode could probably be integrated into an IC already in there, in which case it might not actually cost anything.
Kind of like the Muntz TV. Way back when Mad Man Muntz was a car dealer in California. He branched into TV manufacturing by selling an extremely cheap TV set. The way he did it was to have his engineers go through the set and try what would happen if they left that out. One thing they left out was the IF stage. That reduced the sensitivity, but since they were mostly sold in the LA area they were close to the station and would still work, good enough so that people who couldn't afford a good TV would use them.
Bill
nevertheless.
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