sci.electronics.repair@googlegroups.com

Google Groups

Jeff Liebermann <jeffl@cruzio.com>: Apr 15 10:36AM -0700 >Better the devil you know than to take a random shot.   >I've had horrible luck with any 18650's with "ultra" or "fire" in the >name. I'd like not to repeat that with 14500's.   Sorry. I meant the link to show an example of typical LiIon batteries of all sizes, brands, and qualities. I usually avoid making product recommendations unless I've used or tested the product. I can't provide a reliable source of 14500 cells because I have yet to purchase any that I consider to be acceptable.   The problem with buying by brand name is that there are so many counterfeit cells on the market, that chances are good that even an honest vendor might be fooled by a disreputable distributor. "Can you identify the fake LG HG2 18650 Battery?" <https://batterybro.com/blogs/18650-wholesale-battery-reviews/104619270-can-you-identify-the-fake-lg-hg2-18650-battery> Lots of articles on how to spot fake cells. For a while, I was having too success by weighing the cells, but todays fakes are filled with carefully measured amounts of sand making the fakes impossible to spot by the weight. My best source of 18650 cells are used laptop battery packs. The catch is that they don't have a "button top" on the + terminal making them difficult to use in some holders.   In 14500 cells, everything I've purchased on eBay has been lacking. I haven't had time to run any discharge curves on the 14500 cells, such as these for various 18650 cells: <http://www.learnbydestroying.com/jeffl/battery-tests/18650.jpg> I carry around a flashlight with 14500 cells that has a rather short operating time and probably doesn't meet the printed specs.   To: John-Del Before you run out and buy a pile of know to be good 14500 for powering the unspecified device, I suggest you buy some cheap 14500 cells on eBay, which are sure to be inferior and possibly counterfeit. Test the unspecified device and its charging system using cheap cells. Once it's working, then go shopping for good batteries.   So, where to get good 14500 cells? I have no idea. I just checked Digikey and Mouser. Nothing found. I tried NewEgg and found the same bogus brands as on eBay. Nitecore is probably a good (relabeled) brand, but the price is too high: <https://www.amazon.com/TETC-1200mah-Rechargeable-Battery-charger/dp/B017IGL5HA> I found an article recommending brands: <http://www.25tobuy.com/electronics/top-9-best-14500-rechargeable-lithium-ion-batteries> but no sources. There's also the risk of buying counterfeits.   Bottom line... Sorry, I can't answer your question at this time.   -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann <jeffl@cruzio.com>: Apr 15 02:18PM -0700 >If there are 14 cells in series, there's a lot of opportunity >to have at least one cell reversed by the time you sense >any symptoms. Keep doing that and you'll kill 'em all eventually.   If that were true, then all the 19.2v laptop batteries, which consist of 6 lithium ion cells in series, would also be dying from cell reversal. I've seen dead cells in such battery packs, but usually when the other cells are near death. It's just a question of which cell blows up first.   You can kill series batteries several ways with cell reversal. The most common is during discharge and charge. The problems can happen with any chemistry if a cell is discharged to zero. Lithium Ion batteries have battery protection circuitry (usually called a BMS or battery management system) to prevent individual cells from dropping below 2.7 to 3.0V which might kill the cell. Something like these: <https://www.ebay.com/itm/162735609854> <https://www.ebay.com/itm/191978019369> A BMS will also protect against over voltage and over charging and might include a charger and balancing circuit.   Keeping all the cells at the same voltage is also a problem. For that, there is the "balanced charger" such as the Imax B6 V2 I previously mentioned. <https://en.wikipedia.org/wiki/Battery_balancing> The battery pack has an extra connector with wired going to the junction between adjacent cells. There are various schemes for balancing. Most common is if the voltage across a cell is too high, the balance charger adds some resistance across the cell to draw away some of the charging current, so that the other cells can catch up.   Balance chargers are very common in the RC (radio control) and power tool areas, where running unprotected LiPo batteries without BMS boards is common.   >The best strategy is to charge the cells externally in a proper >charger and put 'em >back in when you're ready to use it.   I agree, with one possible exception. The battery holders found in consumer devices are not known for being rugged and reliable. The springs make lousy connections, they become intermittent when banged around, or they contacts go high resistance when an alkaline cell leaks. This is not the best environment for precision LiIon charging. I'm beginning to think that my suggestion of using 14500 cells in series might be susceptible to these mechanical problems and that 5S battery pack of 18650 cells, with welded nickel strips, and proper XT60 connectors, might be a better choice.   >There are many charging strategies, but depend heavily on >the usage patterns and actual cell configurations.   Yep. I don't know what's appropriate for a metal detector. If it's lightly used, a single battery pack, as I mentioned above, would be easy to remove when the device is not in use. (Anything is better than fumbling with 14 cells, as I do with my MFJ-269 antenna analyzer. The pack could also be charged externally. Hmmm... yet another project.   -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558

mike <ham789@netzero.net>: Apr 15 02:18PM -0700 On 4/15/2018 10:36 AM, Jeff Liebermann wrote: > by the weight. My best source of 18650 cells are used laptop battery > packs. The catch is that they don't have a "button top" on the + > terminal making them difficult to use in some holders.   Lotsa people recommending tiny magnets to replace the button top. I asked about the series resistance and was assured it wasn't a problem. I spot-weld a tab on top and fold it over until it's tall enough.   Best source for 18650 cells I've found is this: https://www.lowes.com/pd/Kobalt-24-Volt-Max-1-5-Amp-Hours-Lithium-Power-Tool-Battery/1000090833   Has six 18650 cells. Only 1.5 Amp-Hours, but they're rated for 30A peak discharge. Six for $10 is tough to beat.   If you saw the tabs in half, you can solder to the tab...if you're quick about it.   The pack works great as a replacement for two series lead acids in my weed whacker, but the voltage is too high for most things. If my analysis is correct, there's no protection disconnect. The reason the pack is cheap is that, it looks like, they monitor the cells and send a bit stream to the tool. The tool makes the decision about discharge protection. The charger makes the decisions about charge protection...so it seems. Good news is that there's a battery gauge. If you can use all 24V and watch the gauge, you can keep from over-discharging the cells...YMMV. > Once it's working, then go shopping for good batteries.   > So, where to get good 14500 cells? I have no idea. I just checked > Digikey and Mouser. Nothing found.   AS I recall, there was a ban on individual cells in the US. Don't know if it's true, but it's still a BIG liability issue for sellers. People seem to throw in any battery that fits and make smoke. You can't rely on anything you read on EBAY. You can't even buy one and test it. The next purchase of the same part from the same vendor may be completely different.   I tried NewEgg and found the same

mike <ham789@netzero.net>: Apr 15 02:50PM -0700 On 4/15/2018 2:18 PM, Jeff Liebermann wrote:   > If that were true, then all the 19.2v laptop batteries, which consist > of 6 lithium ion cells in series, would also be dying from cell > reversal.   Yet, you describe why that doesn't happen, for a protected battery pack, in the next paragraphs.   For unmonitored series connections, the shape of the discharge curve matters. Lithium voltage decreases gradually. By the time you trigger shutdown, the cells may be unbalanced, but likely not damaged. NiMH has a flatter voltage that drops suddenly at the end. Minor imbalance can cause one cell to drop by more than a volt before any symptoms are visible. For 14 in series, one cell can go from 1V to 0V with only about 7% change in voltage.   For unmonitored devices like NiCd or NiMH cordless drills... The speed drops, but you've got only one more hole to drill. That last hole damages a cell. That weakened cell is the first to go next time. Increase in self-discharge also means that if it sits on the shelf for a month before you need it again, it runs out of charge far faster than the other cells, compounding the problem. Eventually it shorts. Now, all the rest get overcharged. I suggest that practice is why most unmonitored drill batteries fail.   I've seen dead cells in such battery packs, but usually > when the other cells are near death. It's just a question of which > cell blows up first. Yep.

Jeff Liebermann <jeffl@cruzio.com>: Apr 15 08:05PM -0700 >Lotsa people recommending tiny magnets to replace the button top. >I asked about the series resistance and was assured it wasn't a problem. >I spot-weld a tab on top and fold it over until it's tall enough.   I bought an assortment of magnets to replace the button top on an 18650 cell. They're not quite the right size, but work well enough in my various flashlights. My spot welder died and I haven't bothered to work on its replacement. When I get something working, I'll go back to spot welding fake button tops (made by pounding a home made die set with a big hammer). I measured the resistance of the magnet with a ESR meter and found the resistance to be negligible. I forgot the exact value. Bug me if you want the numbers.   >Don't know if it's true, but it's still a BIG liability issue >for sellers. People seem to throw in any battery that fits >and make smoke.   I hadn't heard of any such ban and couldn't find anything searching with Google. There are various limits to how many cells can be shipped and how they should be packages, but no ban that I could find. <https://about.usps.com/postal-bulletin/2012/pb22336/html/updt_004.htm> <https://www.ups.com/assets/resources/media/us_lithium_battery_regulations.pdf> <http://images.fedex.com/us/services/pdf/LithiumBattery_Overview_2018.pdf> <http://www.dhl.com/en/express/shipping/shipping_advice/lithium_batteries.html> <http://www.iata.org/whatwedo/cargo/dgr/Pages/lithium-batteries.aspx> <http://www.batteryspace.com/Lithium-Battery-Shipping-Regulations.aspx>   >You can't rely on anything you read on EBAY.   I prefer "Trust, but verify".   >You can't even buy one and test it. The next purchase of the same >part from the same vendor may be completely different.   Well, I bought 10 cells on eBay twice from the same vendor and received the same junk cells twice. Like these but from a different vendor: <https://www.ebay.com/itm/202070101554>   I just realized that I don't have any 14500 data, so I dug out the West Mountain Radio CBA-II discharge tester and ran a graph: <http://www.learnbydestroying.com/jeffl/battery-tests/14500%20SkyWolfsEye%201200.jpg> The cell is labeled 1200 ma-hr. Nominal, normal, or typical for a 14500 LiIon cell is 750 ma-hr. My test produced about 225 ma-hr capacity, which is well below 750 ma-hr nominal. The cell is junk.   Also, there's a problem. Capacity is measured at 0.2C. For a nominal 750 ma-hr rated capacity, 0.2C would be 150 ma test current. That would require 5 hrs to run the test. It's also well below where I normally run these batteries in my various flashlights. Testing the battery at operating conditions makes more sense, so I measured the current of my cheap junk Chinese flashlight at 850 ma and ran the test at 850 ma which would only require 1.1 hrs. If I had run it at 150 ma, it capacity would have been somewhat higher, but nowhere near the nominal 750 ma-hr.       -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558

Mike S <mscir@yahoo.com>: Apr 15 08:31PM -0700 On 4/15/2018 8:05 PM, Jeff Liebermann wrote: > at 850 ma which would only require 1.1 hrs. If I had run it at 150 > ma, it capacity would have been somewhat higher, but nowhere near the > nominal 750 ma-hr.   If you use magnets you might consider grabbing the magnets out of a dead hard drive, neodymium is IIRC the strongest fixed magnet made, and it has very low resistance. https://e-magnetsuk.com/neodymium_magnets/characteristics.aspx   What do you like for a small spot welder? I've been thinking of getting one.

Jeff Liebermann <jeffl@cruzio.com>: Apr 16 12:54AM -0700 >hard drive, neodymium is IIRC the strongest fixed magnet made, and it >has very low resistance. >https://e-magnetsuk.com/neodymium_magnets/characteristics.aspx   Those magnets are much too big I have a fairly large pile of such hard disk magnets that I bought at a local flea market. Very handy, but not for making button tabs.   The magnets I bought were some of these: <https://www.ebay.com/itm/282388785539> in 6mm x 1mm and 6mm x 2mm. 1mm is a bit thin but works for most battery holders. 2mm is a bit too thick but works ok in a few holders. The magnets stick fairly well to the stainless battery case. I had to punch out a few sticky back vinyl "washers" to keep the magnets centered.   >What do you like for a small spot welder? I've been thinking of getting >one.   I looked at what was available and decided that I didn't like anything that was also affordable. So, I'm building my own. Nothing fancy. The biggest automotive starting battery I can find (I want cold cranking amps), a large high current relay, a less than 1 second timer board to drive the relay, a foot switch to start the timer, some heavy gauge wire, and some machined parts for the copper electrodes. It didn't take much testing to determine that if I wanted to weld something, I want DC, and to use AC if I wanted to blow a hole in something. There are several YouTube videos describing how to throw something together. For example: "Simple and dirt cheap Spot Welder for lithium cells" <https://www.youtube.com/watch?v=UU7QC5Uby6M> It needs 2 electrodes, no ground clamp, and heavier gauge wire.   -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558

mike <ham789@netzero.net>: Apr 16 03:01AM -0700 On 4/16/2018 12:54 AM, Jeff Liebermann wrote: > "Simple and dirt cheap Spot Welder for lithium cells" > <https://www.youtube.com/watch?v=UU7QC5Uby6M> > It needs 2 electrodes, no ground clamp, and heavier gauge wire.   Stable/controlled pressure is very important. You can make a serviceable electrode pair from a small arbor press and some hobby store brass. I use #6 solid copper wire for the electrode and a file to shape the end. The trick is to make sure that the current doesn't go thru any part of the probe actuation assembly. I could put up some pix if anybody cares.   You need a lot of energy in a short time to melt the nickel without overheating the bottom of the cell. At the risk of repeating myself, the secret is to use an energy pulse, not a current or voltage pulse.   I started with a microwave transformer and some logic to count full cycles of 60 Hz. to keep the transformer from saturating arbitrarily. I used 4-6 cycles for a weld. If you try to do it without the full cycle counter, the transformer ends up at some arbitrary point on the B-H curve and saturation effects can raise havoc with your welds. Repeatability was horrible. I could make some very nice welds, but not enough in a row to make a battery pack. Starting the pulse at a zero crossing and counting cycles improved repeatability dramatically, but it was still crap. Problem is the low voltage is very intolerant of contact resistance variation.   I tried discharging a cap, but at the time, I didn't have anything that would switch the required current. And I didn't have a storage scope so I could see what I was doing. Turns out that it's harder than I thought to instrument a welder. When the pulse fires, everything on the bench jumps. Getting a scope to trigger on a specific part of the waveform was just wishful thinking.   I tripped over a Unitek CD welder for $17 shipped on EBAY and snapped it up. It can put 7V across a milliohm. Welds got instantly very much more repeatable. Since it's an energy pulse rather than a current pulse, it's much more tolerant of resistance variations. It's only 125 Watt-Seconds, so it works great on thin nickel for low current stuff. It won't weld the thick links for high current stuff.   Turns out that hobby store brass sheet can be cut into battery tabs. It welds very easily. I wouldn't use it for anything high current tho.

Ragnusen Ultred <rragnusen@ultred.com>: Apr 16 01:38AM This is just one easy way to use Windows, Linux, and iOS together, to quickly and easily watch a YouTube DIY at a location that has no Internet.   1. On Windows, I downloaded the desired YouTube DIY: youtubedl https://youtu.be/Ve-kcKxbXx4   2. It's easy to transfer files into VLC over USB on dual-boot Linux: http://i.cubeupload.com/360Laq.jpg   That's it. Now the video was on iOS playable where there is no Internet. http://i.cubeupload.com/CuxNtP.jpg   A. I bought the tools at Harbor Freight & the speakers at Fryes: http://i.cubeupload.com/GtSVFI.jpg   B. I followed the YouTube DIY in VLC, step by step: http://i.cubeupload.com/IDheqM.jpg   C. I removed the decrepit Toyota OEM 20W $300 Panasonic speakers: http://i.cubeupload.com/CweFrP.jpg   D. I had to drill holes to fit the 450W Blaupunkt 3-way speakers: http://i.cubeupload.com/6ugHnx.jpg   E. Everything else but the holes fit perfectly back into place: http://i.cubeupload.com/rczDpa.jpg   The only catch is that it's amazing that something as common as a 6x9" oval speaker requires holes to be drilled in the rear deck given that these things should simply be standard.

Fox's Mercantile <jdangus@att.net>: Apr 15 08:51PM -0500 On 4/15/18 8:38 PM, Ragnusen Ultred wrote: > This is just one easy way to use Windows, Linux, and iOS > together, to quickly and easily watch a YouTube DIY at a > location that has no Internet.   Go peddle your shit somewhere else.     -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com

Ragnusen Ultred <rragnusen@ultred.com>: Apr 16 04:12AM Am Sun, 15 Apr 2018 20:51:24 -0500, schrieb Fox's Mercantile:   > Go peddle your shit somewhere else.   Hi Snit (aka Fox's Mercantile),   What's your mental age? About fifth grade, right?   The proof is your answer to the following adult question...   *Have you ever added technical value to _any_ thread in your life?*

tabbypurr@gmail.com: Apr 16 02:22AM -0700 On Monday, 16 April 2018 02:38:14 UTC+1, Ragnusen Ultred wrote:   > The only catch is that it's amazing that something as common as a 6x9" oval > speaker requires holes to be drilled in the rear deck given that these > things should simply be standard.   I'm pretty sure if you put 450W through one of those speaker's it'd glow dull red.     NT

Mike S <mscir@yahoo.com>: Apr 15 04:39PM -0700 I was given a broken LED light (on a headband) that takes 3 AA batteries, can't find the lumen spec as there is no company name or part number on the ct. board. If I just run the 3 batteries directly to the LED will the batteries drain too fast or will I damage the LED? I don't know if I have to limit the current for either case.

mike <ham789@netzero.net>: Apr 15 05:01PM -0700 On 4/15/2018 4:39 PM, Mike S wrote: > number on the ct. board. If I just run the 3 batteries directly to the > LED will the batteries drain too fast or will I damage the LED? I don't > know if I have to limit the current for either case.   It depends... What components are on the circuit board? Does it look like a voltage or current regulator?   A typical cheapo light might use crap "Heavy Duty" batteries and expect the series resistance of the battery to limit the current. Putting Alkaline cells, which have lower voltage, can overheat the cheapest ones.   Others have sophisticated control circuitry.   There's a lot you can do to figger it out, but the nature of your question suggests that you don't have the tools to do that...or you'd have done it already.   I put an 18650 lithium battery into a 9-LED Harborfreight 3X-AA cell light. 4.2V is less than 4.5, right? Well, it was bright...but the LED's burned out in short order. I put 1.5 ohms in series in the next one because that's what I had. Has been working fine.   You can actually calculate the best resistor, but since you don't know the specs of the led, there's nothing to put into the equation. And the range of voltage over the life of the battery can exceed the drop across the resistor at full charge.   Safest thing is to put something like 10 ohms in series with a full battery and drop the value until it gets as bright as you dare.   Sometimes, you can use google images to find lights that look like yours and go searching down those paths for representative specs.

Mike S <mscir@yahoo.com>: Apr 15 05:25PM -0700 On 4/15/2018 5:01 PM, mike wrote:   > Sometimes, you can use google images to find lights that look > like yours and go searching down those paths for representative > specs.   Thanks, I looked through a lot of google images and ebay head lights and couldn't find this model. There was a component of some sort on the ct. board that had a large dollop of very tough epoxy completely covering it, I would have destroyed it getting the cement off, after about 10 minutes of trying to carefully shave/chip it away I gave up. There were 3 resistors and a transistor on the m/b in addition to the mystery component, and since something was malfunctioning and reflowing the solder joints didn't help I couldn't measure the voltage at the LED. There were 4 smaller LEDs on the board as well, complicating the ct. enough that without knowing the mystery component I didn't know how to sort it out. I like your approach, starting high, try decreasing values of series R until I have decent brightness, then see how the batteries and LED hold up. Thanks for your thoughts.

Clifford Heath <no.spam@please.net>: Apr 16 10:40AM +1000 On 16/04/18 10:25, Mike S wrote: > board that had a large dollop of very tough epoxy completely covering > it, I would have destroyed it getting the cement off, after about 10 > minutes of trying to carefully shave/chip it away I gave up.   You wouldn't have learned anything even if you'd successfully decapped the chip. It's what they call COB (Chip On Board) technology; you would have seen a bare silicon wafer with bonds to the PCB.   These chips usually provide dimming and flashing function. If there's no external inductor - and I'm betting there's not - then the device is relying on bang-bang control for dimming. Peak current is limited by the battery's internal resistance, average current by the on/off duty cycle.   The best way to estimate the power capability is to look at how much heat can be removed from the LED. If it's not got much metal attached, keep the current below 100mA and you'll be safe and still get very good brightness.   Bear in mind, that ten times the current only doubles the perceived brightness. I have an 8W headlamp for night hiking, but I usually use it on the low setting; under 1W. So if you run it below its limit, it'll still be useful.   Clifford Heath

tabbypurr@gmail.com: Apr 15 06:26PM -0700 On Monday, 16 April 2018 01:25:26 UTC+1, Mike S wrote: > sort it out. I like your approach, starting high, try decreasing values > of series R until I have decent brightness, then see how the batteries > and LED hold up. Thanks for your thoughts.   If you had uncovered the chip your light would be dead for sure. 4.5v is far too high to run an LED direct - at least with most LEDs. If it's a 20mA LED, which I can't assume, a new battery of 4.65v would need the R to drop about 1.15v at 20mA = 57 ohms. A near flat battery at 3.5v would want a resistor of 0 ohms. And there's the problem with running an LED off a battery & resistor. What's really wanted is a constant current circuit. There are simple ways to do nearly that, but it's not as simple as a resistor.     NT

Jeff Liebermann <jeffl@cruzio.com>: Apr 15 06:28PM -0700 >I was given a broken LED light (on a headband) that takes 3 AA >batteries, can't find the lumen spec as there is no company name or part >number on the ct. board.   I'll assume that there was only one LED in the headlight. Lumens are fairly easy to guess. The commodity LED du jure is the Cree T6 series. It produces about 100 lumens/watt of power consumed (minus whatever the optics attenuates). There are LED's with higher efficacy available, but you won't find them in commodity lights. The LED will be mounted on a COB (chip on board) which also acts as heat sink. Somewhere in the package, either on the COB or on the on/off/dim switch, will be some electronics to control the light. These also include a current source to regulate the current drawn by the LED. You should not need any additional current limiting resistors. On the really cheap junk LED lights, there might be one or two tiny chip resistors on the COB to provide some current limiting. Three AA alkaline cells in series is about typical for powering a low end, single LED light.   >If I just run the 3 batteries directly to the >LED will the batteries drain too fast or will I damage the LED? I don't >know if I have to limit the current for either case.   I don't know. Take it apart and see what's inside. Most battery compartments include a label or molded description of the type of battery to install. Look for it. Unless you were given a bag of parts, it's unlikely that you'll need to add anything to make the light work. Start with three alkaline cells and measure the current. If the LED burns about 1 watt or less as in: voltage_across_LED * current through LED = watts it should work.   Also, while it might be possible that your headlight runs on LiIon cells, I doubt it. The lights that use AA size cells (14500) tend to use alkaline or NiMH, while the one's I like use one (or two in parallel) 18650 LiIon cells. I haven't seen any 14500 LiIon cells used in headlights yet, although such a light might be possible.   -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558

Mike S <mscir@yahoo.com>: Apr 15 06:30PM -0700 On 4/15/2018 5:40 PM, Clifford Heath wrote: >> I didn't know how to sort it out. I like your approach, starting high, >> try decreasing values of series R until I have decent brightness, then >> see how the batteries and LED hold up. Thanks for your thoughts.   Thanks Clifford, I get good brightness using 35 ohms, I'll measure the current to see where that is. There's no heat sink on the LED. This doesn't have to be super-bright, it's in addition to a handlebar mounted light so it's basically to increase visibility to cars, being higher and moving out of sync with the handlebar light. Once I make sure the current is < 100mA and install a small toggle switch and I'm good. Thanks again.

mike <ham789@netzero.net>: Apr 15 08:30PM -0700 On 4/15/2018 6:30 PM, Mike S wrote: > moving out of sync with the handlebar light. Once I make sure the > current is < 100mA and install a small toggle switch and I'm good. > Thanks again.   What you really want is a resistor that automagically drops the series resistance as the battery discharges. Lucky for you, they exist.   They're called incandescent light bulbs. Try a lamp from a single-cell incandescent pen light. I just tried one. Looks like the sweet spot is around 150ma. But the lamp was unmarked, so I can't be sure what I had. Gotta test 'em.   Also might try a lamp from a string of tiny incandescent Christmas tree lights. I can't find one, but, as I recall, those were about 3V nominal. Might be too high.   Not enough current, parallel some. Too much current, series some. Could even switch to change brightness of the LED.   Are we having fun yet?

Mike S <mscir@yahoo.com>: Apr 15 09:30PM -0700 On 4/15/2018 8:30 PM, mike wrote:   > Not enough current, parallel some.  Too much current, > series some.  Could even switch to change brightness of the LED.   > Are we having fun yet?   I was thinking of building a simple voltage/current regulator, and wondering how much current would be spent in the ct. This is another idea I never thought of. I found a small pot in an old blown up computer pwr supply I had saved, was thinking of using it to vary the brightness as the batteries were drained. It's funny how complicated a simple head lamp can become.

Fox's Mercantile <jdangus@att.net>: Apr 15 11:55AM -0500 > Kroil is wonderful stuff.   Which I keep telling folks. "It just fucking works."     -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com

Ralph Mowery <rmowery28146@earthlink.net>: Apr 15 02:00PM -0400 In article <C-GdnWR41aFsHk7HnZ2dnUU7-cudnZ2d@giganews.com>, jdangus@att.net says...   > Which I keep telling folks. "It just fucking works."   I have used several cases of it at work and the others have also. If you spray the bolts/nuts the day before and let it soak over night and then again shortly before they almost unscrew theirselves in many cases.   Found that some 200 watt or so MV light bulbs would screw out very easy if you give them a shot of Kroil before unscrewing them.

Fox's Mercantile <jdangus@att.net>: Apr 15 01:30PM -0500 On 4/15/18 1:00 PM, Ralph Mowery wrote: > I have used several cases of it at work and the others have also.   And it certainly beats pissing around with all those alleged home brew recipes.   -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com

N_Cook <diverse@tcp.co.uk>: Apr 15 06:34PM +0100 On 15/04/2018 16:31, John-Del wrote: > I've never seen an egg with streaks on it, so >> difficult to believe that mechanism.   > That's because Epson doesn't print eggs...   Another thing Epson failed to deal with - generating the substrate at the same time as the image. You have to supply your own paper, how stupid in comparison to nature.

You received this digest because you're subscribed to updates for this group. You can change your settings on the group membership page. To unsubscribe from this group and stop receiving emails from it send an email to sci.electronics.repair+unsubscribe@googlegroups.com.