Re: gEDA-user: [OFF] high current amplifier
Levente wrote: Hi, I have to design an audio amplifier that can deliver 100Amps. It should work around 50Hz, and the maximum output power shall be 500W. I am currently reading articles about this topic, but it is very hard to find things like this. If someone has some experience with, or some documentation of high current amplifiers, please share it. If you search the class-D power amp modules available for the audio market I think you may find what you need off the shelf. Steve ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: Surface mounted circuits in hobby projects
Mark Rages wrote: 2) Put a largish solder blob on each end of the part This is the *key* point in desoldering surface mount parts that most beginners mess up on. People have a tendency to try to remove all the solder they can, as they are trying to remove a part. This is the exact opposite of what you should do. Molten solder is the conductor of heat from the iron to the board and components. If you want the heat to be conducted well, and spread around all the pins effectively, you add more and more solder until you achieve your goal. Once all the legs are sitting in molten solder the part will come free, and you can clean up the solder blobs quite easily. Steve ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: Surface mounted circuits in hobby projects
Csanyi Pal wrote: Hello, I find the following on the Internet and want to ask you what do you think about it: Experimentation with Solder Paste and a Toaster Oven http://images.google.com/imgres?imgurl=http://www.curiousinventor.com/images/guides/smt/oven_paste_and_other_equip.jpgimgrefurl=http://www.curiousinventor.com/guides/Surface_Mount_Soldering/Solder_Paste_and_Toaster_Ovenusg=__XIgiZVSYOAq1lUbMhok3ABEhPk8=h=463w=600sz=92hl=hustart=62sig2=_IRzNnfPckWp25fVUftNygum=1tbnid=osu6-oViQITc1M:tbnh=104tbnw=135ei=8I2ySb6MGsec_gbSzrHDBAprev=/images%3Fq%3Dhow%2Bto%2Buse%2Bpaste%2Bflux%26ndsp%3D21%26hl%3Dhu%26client%3Diceweasel-a%26rls%3Dorg.debian:hu-HU:unofficial%26sa%3DN%26start%3D42%26um%3D1 I'd say he's making the job a lot harder than it needs to be. If you want to know what works well, look at what prototyping people do in industry. They use a soldering iron for most things. The use of solder cream is pretty much limited to robot assembly, as you can silk screen it onto the board. Some kind of oven approach might work for BGAs, but on that page doesn't show any of those being used. The high temperature you need right under the package makes temperature control for BGA soldering tough. Steve ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: Surface mounted circuits in hobby projects
Peter TB Brett wrote: On Thursday 02 April 2009 08:32:09 Peter Carlsson wrote: Hello! I have just started my first hobby project with gEDA and noticed that some circuits I need is only available as surface mounted circuits. How do you handle this problem? Or is it a problem? It's not necessarily a problem -- it's actually not particularly hard to hand solder SMT components, with a little practice. When you reach the age where you need reading glasses, the difficulty suddenly increases rather a lot. :-\ The girls (almost always girls) who assemble prototypes by hand for a living will assemble anything other than a BGA very quickly and very cleanly, mostly using a big fat soldering tip. Getting the central pad to solder on a QFN can be a challenge for them, though. Some like to use a huge iron and let a big blob of solder run down each side of a QFP or QFN, soldering the pins as it flows past. With practice they can clear away the surplus solder in seconds. Creating a huge continuous blob of solder around the four side is the strategy for removing a QFP. QFNs tend to be a pain to remove with an iron, because of that big central pad. It all comes down to learning the fine art of using the surface tension of molten solder to your advantage. Use a lot of flux. If you have high impedance circuits, like LCD segment lines, you'll need to clean that flux away really thoroughly as most modern flux is somewhat conductive. Getting it out from under the package can be a pain, though. So, if your sight is good and your hands are steady you can assemble extremely small things very cleanly with some practice. Just don't be discouraged by the mess you'll probably make the first few tries. It doesn't take too long to start getting the hang of it. Steve ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: Surface mounted circuits in hobby projects
Ethan Swint wrote: Steve Underwood wrote: away the surplus solder in seconds. Creating a huge continuous blob of solder around the four side is the strategy for removing a QFP. The way I like to remove QFPs (assuming that they're dead) is with a bit of bare AWG30 behind the pins. Run the wire between pins and package, anchor one end through a via, pull on the free end and the chip will 'unzip' as you move down the edge with a big iron. That way gives you a high risk of pulling pads off the board, and really messes up the pins. You don't want to apply *any* avoidable mechanical load on those pads. Heat the pins until they really come free. If you want to reuse the chip (say for analysis - you'd only really *want* to reuse it in desperate circumstances) you really want to keep its legs as nesr intact as possible. The big solder blob approach is good for that. Stev ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: the joy and sadness of new boards
DJ Delorie wrote: Just got a box of panels from Advanced Circuits. Five panels, ten boards per panel (two each powermeter, usb-gpio pod, and three pod modules - ten sets of boards total). Joy! Unfortunately, I have no way of separating them into individual boards yet. Sadness! But I do have a 60 degree v-scoring bit for my router table. Joy! Last time I used it, the pcbs were too flexible for the big hole the table had around the bit. Sadness! I was thinking of taking an old 7 table saw blade and re-grinding it to a 60 degree point. I can make a zero-clearance insert for it, to ensure correct cuts. Joy! However, I don't have any of the parts for the boards yet. Sadness! But now I get to go through the BOMs, figure out the best parts to use, put together a digikey order, come up with some hobby money, and wait for it all to arrive. Joy! No, wait... sadness? Crap. Don't forget the perforations, or routed grooves next time :-) There should be a DRC check to prevent that kind of slip. Steve ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: the joy and sadness of new boards
DJ Delorie wrote: I think you can score them with a utility knife on both sides and snap them apart. I've tried that before with no luck. The boards are just too thick to be able to score reliably and deeply enough. Yeah, its tough to do yourself. Did you just forget to put the necessary grooving in your drill info, or haven't you crossed that bridge before? Some people still use a row of holes as a snap-off line, but grooving with a router is pretty much the norm now. Steve ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
