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FrozenGate by Avery

Feeler Extremely efficient boost circuits

How well would primaries i think they're called- disposable alkaline AAs, hold up?
 





Alkalines appear to have an internal resistance of 200 mOhms, which means they'd last until around 1.2 V, while NiMH appear to have an internal resistance of 100 mOhms or less, meaning they'd last until about 1.05 V. (source)

Based on the charts on this website, you can expect around 20-30 minutes out of an Alkaline when driving the diode at 200 mA, whereas a (2000mAH) NiMH will last probably 1.25 hours. Maybe it's not a good idea to use disposables.

Due to the size of what most people would be putting these things in, you'd probably only have enough heatsinking capabilities for 100 mA. At that discharge rate, you could probably get 2.5 hours out of an Alkaline, and 3 hours on a NiMH.

All of this is theoretical because I don't have one of these things in hand. I am also allowing the rechargeables to dip below their acceptable low battery threshold. Lithium batteries will be MUCH better than alkaline batteries under either case, but you'll be paying for it.
 
Cool project but I don't really see the benefit right now, you can use rechargeable AAA 10440 size 3.6V and AA 14500 size 3.6V rechargeables with the adjustable Micro FlexDrive right now for about the same price...
 
...says the person who sells FlexDrives :P.  Here's why I want to make them:

1.  Collect underpants
2.  ???
3.  Profit!!!



No, seriously, here's my reasons:

1.  I want to make a few of these for myself.
2.  After the setup costs, the price per board justifies me buying far more boards that I would ever use myself.
3.  These will fit inside an Aixiz module (without trimming), and I think the final design could fit flat in a AA/AAA host.
4.  14500's aren't very common batteries, and neither are their chargers.
5.  NiMH batteries are cheaper...wait...not really.
6.  You could use any single-celled battery with this design, except for Alkaline AAs since you'll probably get only 25 minutes of battery life.

If your design was double sided, you should be able to meet everything outlined in #3, but your costs would probably go up about $5.

If someone used the collimator section of the 12x30mm module, the driver I'm designing laid flat, and a AA, you should be able to get away with some really compact lasers.  One other possibility would be to create a really thin laser due to the driver's small size - I've already found a collimator and a cheap source for AAAAs, I just need to find out how to make/where to get the host.
 
phoenix3200 said:
Alkalines appear to have an internal resistance of 200 mOhms, which means they'd last until around 1.2 V, while NiMH appear to have an internal resistance of 100 mOhms or less, meaning they'd last until about 1.05 V. (source)

Based on the charts on this website, you can expect around 20-30 minutes out of an Alkaline when driving the diode at 200 mA, whereas a (2000mAH) NiMH will last probably 1.25 hours. Maybe it's not a good idea to use disposables.

Due to the size of what most people would be putting these things in, you'd probably only have enough heatsinking capabilities for 100 mA. At that discharge rate, you could probably get 2.5 hours out of an Alkaline, and 3 hours on a NiMH.

All of this is theoretical because I don't have one of these things in hand. I am also allowing the rechargeables to dip below their acceptable low battery threshold. Lithium batteries will be MUCH better than alkaline batteries under either case, but you'll be paying for it.
Click to expand...
You can probably cut these runtimes in half as the capacity of cells usually drops with increased load. Only when discharging at about 0.1C, the full capacity is available.
 
Zom-B said:
You can probably cut these runtimes in half as the capacity of cells usually drops with increased load. Only when discharging at about 0.1C, the full capacity is available.
Click to expand...

That's why the alkalines perform so poorly. You only get to use about 1/4 of the alkaline's stated capacity under these conditions. NiMH batteries, however, perform much better under higher loads.
 
NiMH supply more power under the higher loads, but they still drop in capacity (and not just because they dissipate energy due to the internal resistance). I have no idea what capacities alkaline have and their properties.
 
That's a given, but the capacity drop is probably less than 10% with the NiMH under high loads.

Look at these charts --> http://www.powerstream.com/AA-tests.htm

These charts are rated on the total mAH a cell can put out at a given current drain. If someone wanted to run an 803T at 200 mA (which I think is overkill for several reasons), that would require roughly 1.4 A of current At an internal resistance of 200 mOhms and a discharge rate of 1.4 A, an alkaline should power this unit until it reaches about 1.2 V. Based on the charts at the above website, it will reach 1.2 V before 0.3 AH/1.4 A = about 13 minutes...which is really poor.

A 2000 mAH NiMH, based on a 100 mOhm internal resistance (which is high if you were to look at this 2500 mAH AA) and a 1.4 A discharge rate, should work until about 1.05 V. Based on the charts on the website (and datasheets I have looked at), this occurs at about 1.8 AH/1.4 A = about 1 hour and 15 minutes. To me this looks like a win for NiMH.

Maybe we should save the battery debate until I get one of these guys made.
 
Sure. The chip I'll use will handle up to 6.5 V.

If you're looking for a driver now, I strongly suggest getting a FlexDrive. I'm trying to get this working (will likely order some components/a bunch of boards this weekend to make up some demo drivers), but there's only so much time you can spend on hobbies in grad school.
 
phoenix3200 said:
...says the person who sells FlexDrives :P.  Here's why I want to make them:

1.  Collect underpants
2.  ???
3.  Profit!!!



No, seriously, here's my reasons:

..........
Click to expand...


Another thing:
Wouldn't this driver use 2 AAAs more efficiently in comparison to the flex drive? This is, if you were to use the chip that offered a .3 volt input voltage, then you can drain 3 volts worth of batteries in an efficient manner. I decided to use 4.5 volts worth of AAA batteries for my flex drive. I concluded that the cut of voltage is too high to use with a 3V input. It would not efficiently use a 3V battery source (meaning that the batteries are not completely dead after use).
Does this sound correct?
 
Meh...I have my reasons for not using the 0.3V chip.

Per the relative efficiency, this is probably 80% efficient regardless of the voltage you give it. I haven't the slightest idea on what the efficiency of the FlexDrive is, although I thought I saw someone saying it would work down to 2.4 V.

If you were to use multiple alkaline batteries, you'll get a lot longer life over using the batteries individually since this driver would have a constant power demand which would be distributed across the batteries. An alkaline battery has huge performance losses under high loads.
 
Whoa...I was about to bump this myself and then I saw your post.

Yes, I have the components and boards for a couple of test kits in hand right now, and rkcstr and IgorT also have a couple of kits to help me with testing these. It took close to forever (six weeks) for me to get the circuit boards for these things, and I've got around 140 spare boards beyond the components I ordered. I'll be ordering more components as there is demand - it only takes two days for me to get the parts.

The design is TINY! And by tiny I mean 8mm x 10mm! That's half the area of a FlexDrive!

I'll give an update sometime later this week about how reliable these things are, and I hope to offer these for sale starting sometime next week. They're (tentatively) priced at $25.
 
Wow tiny little suckers :o Hey Jay put one of these in the key chain lights might make the fit a little easier!
 
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