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Comment Joule Thief (Score 4, Interesting) 172

(oops accidentally posted A/C)

I've coincidentally been running a battery experiment using a joule thief on a 1.5v Energizer battery (starting voltage 1.621v)

The LED and resistor I use would normally draw about 20mA from a battery, but run at 3v, requiring 2 AA batteries, and running for around 5 or 6 days in total.

Through the joule thief (similar, I am guessing the to guts of the device), I know that I can run the same LED down to 0.450mV (with a much larger current draw)... but since it basically consists of spikes of power (which can reach 5-12v) with a very short duty cycle, I can run off a single AA battery for some time.

As I use the thief in my own battery experiments (think edison cells), I decided to run an AA down and chart the voltages. I'm currently on day 10, and have made it down to 1.257v I think it will drop off quite quickly around 1.0 or 0.9v, but you can see I've easily doubled the servicable life span. At this point it has only dropped ~20mV per day, so I could possibly get 10 more servicable days out of this battery for the purposes of running an LED... so we're up to around 5X the service life.

I did not major engineering to make my thief, and it isn't particularly well made.. so I think 8X life for an LED is very possible with the data I have.

EXCEPT... I'm just making light, for a human, who can't see that it's not actually "ON" all the time. This is a very simple circuit and can easily handle the duty cycle. I have some concerns about running a microprocessor or similar toy with the device without damage.

ADDITIONALLY.. batteries can swell when they get very low voltage, and all sorts of nastiness can occur. I'd be cautious to drain one to the minimum voltage for my thief... or at least keep it on a glass plate in case of leakage.

Comment I can speak for programming... (Score 2) 280

All of the high-end coders I know, have the following traits:

1. They learned how to teach themselves
2. They learned when it's time to find someone to teach them things
3. They play with the code, they build things, experiment, etc.
4. They aren't afraid to try a new tool, and be a noob ... but they seek out mentors.
5. They understand that the quality of their work is important... and seek out the processes and skills it takes to increase quality

Over my 20 year history, the folks with these traits have always managed to build things that last, and work well, and were easy to maintain.

Very few of them went to school for "Computer Science" degrees, everything from Poly Sci to Construction.

I say:
1. find (or start) an interesting open source project
2. learn how to use git
3. start building tests
4. code.
5. play.

Comment Completely converted house to LED, 3 have died. (Score 5, Insightful) 602

So, the "return" process is iffy. I didn't have my receipt when one died and I took it back to Lowe's for an exchange of the same model (Phillips).. they said they couldn't be sure it was under warranty, I told them it was supposed to last 10 years, and they had only been selling them for a few months. They begrudgingly swapped it out.

Anyway, the other 2 bulbs, I decided to pull them apart. I dug out the silicone potting, and found the failure was in a large capacitor, visibly bulging. I haven't had time to replace the bit - but I'm pretty sure that's all that blew on it. Tested the individual LEDs and they are fine.

So both failures were due to purchasing the cheapest possible components, specifically a "largish" (like 0.3uF 200v) capacitor. My guess is that there was a larger cap that would handle the load, but they needed to reduce the size. Initiating the failure was probably one or more line spikes.

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