sci.electronics.repair@googlegroups.com

Google Groups

micky <NONONOmisc07@fmguy.com>: Nov 08 09:24PM -0500 In alt.home.repair, on Fri, 6 Nov 2020 09:12:43 -0800, Bob F >for $10 or so. They are fully programmable from an online data base, so >most components can be found. They can also learn.   >Most of the previous learning remotes I had had limited learning capacity.   Good to know.   I started to recall that I once had a learning remote, but I'd never used it. I remember 4 colored buttons that can accept any command. I think it's on the other half of my bed, but I'll need a crew to move all the junk that is there. I'll know in a few weeks. ;-)

Al5 <al5@anywhere.net>: Nov 08 04:23PM -0500 I have a question about a typical PC power supply. Let's say that they are marked 12V 14A, 5V 20A, and 3V 27A. I know these voltages and currents may not be right (just using as an example), but can the amount of current indicated per voltage be used simultaneously (in other words, can I use say 12V @ 13A & 5V @ 19A at the same time) or are the maximum (or near max) currents available for one voltage only at a time?

ehsjr <ehsjr@verizon.net>: Nov 08 05:29PM -0500 On 11/8/2020 4:23 PM, Al5 wrote: > of current indicated per voltage be used simultaneously (in other words, > can I use say 12V @ 13A & 5V @ 19A at the same time) or are the maximum > (or near max) currents available for one voltage only at a time?   They are not rated to draw maximum rated current from all the voltage outputs at the same time. And ... who knows how accurate the ratings are in the first place?   Ed

Jeff Liebermann <jeffl@cruzio.com>: Nov 08 03:52PM -0800 >of current indicated per voltage be used simultaneously (in other words, >can I use say 12V @ 13A & 5V @ 19A at the same time) or are the maximum >(or near max) currents available for one voltage only at a time?   If the power supply "brick" is fixed voltage (non-adjustable), then the maximum current specification is at that voltage. A 12V 10A power supply will deliver 12V at 10A. However, you'll need to read the fine print for how long the power supply can deliver that 120 watts. It may have a 20% duty cycle, or perhaps 10 minutes on, 50 minutes off, or som similar spec. Unless the power supply has plenty of heat sinking and a big fan, it's not likely to run continuously at the maximum rated output.   If there is more than one fixed output (not variable), the power supply should deliver power on both outputs simultaneously at the rated load (and duty cycle). Often, the maximum power output and duty cycle are rated by the total output, where you can trade power between outputs, as long as the total output is within the maximum rated output power. The limitation is usually not the circuitry, but rather the cooling system.   Power supplies with adjustable outputs usually include a graph showing how much output current is considered safe at various voltage output setting. Of course, nobody looks at the graph until after they blow up the power supply.   Good luck and try not to get too close to the maximum ratings. -- 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>: Nov 08 10:27AM -0800 On Sun, 8 Nov 2020 08:12:19 -0800 (PST), "Peter W." >Should do the trick.   >Peter Wieck >Melrose Park, PA   Ham radio has the same problem and has mostly standardized on Anderson Power Pole type connectors for 12V power: <https://www.google.com/search?q=anderson+power+pole&tbm=isch> Personally, I hate these, but I must admit that they do work well for high current applications.   What I prefer are XT60 60 amp connectors used by RC enthusiasts for LiPo cells: <https://www.google.com/search?q=xt60+connector&tbm=isch> <https://www.ebay.com/itm/132200748004> They are also available in 30 amp (XT30) and 90 amp (XT90). Note that these are intended to be soldered, not crimped.   Back to the original problem. The cigarette lighter connector was never intended to power anything continuously. It wasn't even designed to maintain a reliable connection. It's the only connector which has a spring that pushes the plug *OUT* of the receptacle instead of pushing it in or locking it in place. To make matters worse, there is usually a fuse behind the tip, with a marginal spring connection and insufficient fuse connection clips. Just count the number of crimps, connections, rivets, and dissimilar metals that the current has to go through and you'll see why it might be getting hot. At 5V 7.5A, it doesn't take much resistance to create an unacceptably high voltage drop. Try measuring the voltage drop under load across the entire connector sandwich. I don't think you'll be too happy with your measurement.   There have been attempts to standardize the cigarette lighter connector as ANSI/SAE J563: <https://en.wikipedia.org/wiki/Automobile_auxiliary_power_outlet> The problem is that most commodity connectors don't even come close to meeting the specifications. I think that's the cause of the heating problem that you're experiencing.   Good luck.   -- 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

OJ Oxford <bestnet@none.com>: Nov 08 03:02PM -0500 On 11/8/20 1:27 PM, Jeff Liebermann wrote: > high voltage drop. Try measuring the voltage drop under load across > the entire connector sandwich. I don't think you'll be too happy with > your measurement.   Yeah, this one was pulled off of an unused auto inverter. On the plug is says to not draw more than 100 W through it and it has either 12 or 14 gauge pigtails with a 10 amp fuse inside the plug. I know it must be pretty lossy since it is heating up more than anything else in the circuit.   I like the XT60 connector you mentioned after checking out its specs. I think that's the one I'll go with when I order tomorrow. And I do like the fact that it is solder and not crimped. I don't always trust crimped connections. I know it's probably my fault since I don't often have the correct crimping tool so when the wire works out, that's why, but soldering with circumvent that issue. Thank you.

Jeff Liebermann <jeffl@cruzio.com>: Nov 08 03:41PM -0800 >crimped connections. I know it's probably my fault since I don't often >have the correct crimping tool so when the wire works out, that's why, >but soldering with circumvent that issue. Thank you.   Well, if you're going to use XT60 connectors, here are some hints and hazards:   1. The connectors are NOT standardized. That means that connectors from different vendors might not fit together. There are also poor quality copies. I tend to buy my connectors from Hobby King because I can be sure that they're made from nylon and not some plastic that melts as soon as I apply the soldering iron. Note the "genuine" in the description: <https://hobbyking.com/en_us/workbench/accessories/connectors.html#q=xt60> <https://hobbyking.com/en_us/genuine-xt60-nylon-connectors-male-female-5-pairs.html> I've bought some on eBay with mixed results. Some were really good, while others required a heat gun to form them into a usable shape.   2. When soldering the connectors, it's really easy to get them too hot and melt the plastic. Nylon is better, but plastic is cheaper and more common. To keep the pins aligned, push a mating connector together with the one you're soldering to help reduce the tendency to melt the insulation. The mating connectors do not have any way for solder to ruin your day by soldering both connectors together.   3. Use shrink tube on the wires and a big shrink tube over the connector. Follow the color code and polarity defacto standards. Pointed end of the connector is negative and black wire.   4. Gold plating is very thin but gives a good low resistance connection. However, it's easily pitted by arcing. Therefore, don't connect or disconnect the XT60 connectors with power applied.   5. Panel mounting is a bit tricky. Fortunately, there are panel mount adapters: <https://hobbyking.com/en_us/xt60-panel-mounting-kit.html>   6. Think about high current inline blade type fuse holders: <https://www.google.com/search?tbm=isch&q=inline+blade+fuse+holders> There should be at least one fuse in the circuit.   Good luck...   -- 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

"Peter W." <peterwieck33@gmail.com>: Nov 08 10:00AM -0800 At this point, and given a very successful track-record with smaller pieces, I will focus on making larger resin-castings rather than a 3D printer with perhaps-marginal resolution. The nice thing about silicon molds is that they may be used over and over after a little bit of care in the making. I will let 3D printer technology evolve for a bit before investing at what I see is the level necessary to be useful for my intentions.   Thank you for all your input.   Peter Wieck Melrose Park, PA

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.