Resettable fuses are a very useful complement significantly increasing a safety of devices.
Polyswitch-es provide a big service at protection of devices, where they behave like „resettable“ fuses. How many times it is suitable or necessary to use a fuse in a device, but a relatively bulky fuse socket simply doesn´t have a space in our device (or it would spoil a device design) and we also don´t want to use a PCB fuse holder, because a device would have to be constructed as user accessible… Then and not only then, is the ideal solution to use a Polyswitch. Such „fuses“ are available from various producers (for example also under names Polyfuse, Multifuse), Polyswitch is a trade name of company TE Connectivity/ Raychem, representing a top level in this segment. In a principle, a Polyswitch is a PTC resistor with a Polymeric structure designed for a big change of resistance in a narrow temperature range. Conductive particles are dissipated in an amorphous polumer, which changes its structure at a higher temperature (melts), increases its volume resulting in a rapid increasing of a component resistance. In this point (tripping point) a very rapid increasing of resistance appears, which is high enough, so that a leakage current is practically negligible and won´t cause a damage to a protected circuit. Each Polyswitch has a defined holding current (I hold), nominal resistance at a given temperature and tripping (switch off) current (I trip). By a current flowing through a Polyswitch, it gets calorified (I2R), until a certain current it will reach a level, where a rapid increasing of its resistance appears. An exact current at which this change arises naturally depends also on an ambient temperature (at higher temperature a lower current is sufficient). This behavior is digestedly illustrated on an enclosed graph (Fig.4). In the A region, a Polyswitch is switched off (tripped) and a device is disconnected. In the region B the Polyswitch allows for normal operation (on) at any combination of a current and ambient temperature. In the region C can the component go tripped (off) so to say “anytime” depending on a concrete resistance value of a given piece. Read the rest of this entry »
alexglow @ instructables.com writes:
Note: By “beginner’s guide”, I mean a guide written by a beginner. (I made it at TechShop SF, during my first weeks!) I have some technique tips to share, but for more in-depth questions, Google is your friend.
Solder paste allows you to populate a board with many tiny components, without straining your eyes and fingers. Using minuscule components saves space, and you can dramatically cut down the space between them when you don’t have to solder every connection by hand.
Beginner’s Guide to Solder Paste - [Link]
Testing probes, clips, cables and other products of company SKS enable simpler and more effective testing and development.
Probably, you´ve already faced the situation, when it was necessary to measure several signals at once, or for example to have a voltmeter connected in some point of a device and to control another equipment at the same time. In such cases, it would be great to have another pair of hands. The solution not only for these cases are the well proven SKS-Hirschmann measuring and testing accessories of German company SKS.
Who´ve ever worked with test probes or various other testing clamps, for example of the KLEPS series knows, how significantly these components can simplify and speed-up development or testing. The KLEPS 2700 test probe is extraordinary by a fact, that it comprises a stainless steel piercing tip, able to penetrate insulation of common leads (without damage), thus enabling to measure a voltage in a given lead without its stripping. Similarly for example PRUF series testing probes are able to reliably penetrate a PCB protective lacquer or through an oxidized layer and enable a precise measurement even in relatively dense PCBs without risk of tracks short-circuit.
With the Micro-SMD Clip it is possible to measure signals on all common 2-pole SMT components. Various crocodile probes enable a reliable connection with wires or PCB terminals. A big benefit of SKS-Hirschmann crocodile probes is the fact, that their jaws enable a reliable grip even of very thin wires.
A common feature of all SKS-Hirschmann components is a high quality being reflected even in such common products like banana plugs and sockets (2mm and 4mm, including reductions). A useful accessory for every workplace can also be measuring leads and cost-effective sets.
In case of interest in any SKS-Hirschmann product, please contact us at firstname.lastname@example.org.
SKS – measuring and testing with pleasure - [Link]
Company YAGEO announced its intention to remove marking of RC/AC 0603,0805,1206 SMD chip resistors from July, 1-st, 2013.
Everything implies, that the situation with marking of chip resistors (0603/0805/1206) will soon be similar to chip capacitors – i.e. no marking on the top of the component. The reason for this step is to reduce unnecessary chemical usages for environmental protections.
Naturally, to identify the product resistance value, each single reel will be labeled with all relevant data as so far. Performance, features, specifications and manufacturing process of these resistors remain the same. So, the elimination of the marking on top of the product itself has no impact on the product functionality and reliability. There will be a short period of time that both types of the products, with marking and without marking, co exist while changing the production lines one by one.
Detailed information: Yageo – Remove marking of RC/AC 0603/0805/1206.
Will the SMD resistors marking become a history? - [Link]
If you´re facing a decision which diode to use in your device or searching for a replacement, then this article is dedicated right for you.
Reliable diodes are often one of the fundamental pillars of a proper operation of devices. Many designers choose a suitable type so to say “by an eye” , by experience. So it can easily happen, that there will be used a uselessly overrated diode (occupying more PCB space) or in a worse case – an insufficiently rated diode, which will work in a given device on the border of its possibilities.
Diodes in general feature one good property – they´re relatively easily replaceable by a similar type from another producer. KAs SOS electronic is the authorized distributor of company Diotec, we´re able to offer you a suitable type for virtually any device, or a replacement for almost any diode from other producers. Diotec as a producer specialized mainly on diodes, offers a wide portfolio of diodes with axial leads, in SMT packages, including power types like power sod-123, Power-SMD, D-PAK (TO252AA) and D2PAK (TO263AB), super-fast with low losses but even rectifying bridges and many other types.
Schottky diodes naturally provide lower losses thanks to a lower forward voltage, that´s why their usage is mainly in place in applications with relatively higher currents. In general it´s also valid, that a small SMT package can significantly eliminate the radiation of EMI in switch-mode power supplies (thanks to a minimal parasitic inductance), what can be one of factors, whether a given device will meet EMI regulations or not.
On the internet, it´s possible to find various „cross-reference-lists“, but for a given application, usually only some selected parameters are important. That´s why we better recommend to choose according to concrete parameters. A help at selection will provide you the case cross reference and the list of most commonly used 1A diodes. For a practical usage, it´s good to be familiar with hints for soldering and assembly, minimum solder pads sizes as well as basic facts about basic facts about thermal stresses of diodes.
Also available to download is the example of usage of Diotec diodes in Set Top Boxes and in LED driving. It is worth to mention, that also several fakes of Diotec diodes appeared on the market.
Do you need diodes? – Diotec has them - [Link]
SMD solder paste stencils are used to accurately “print” a thin layer of solder paste onto a PCB on which the components are placed before reflow soldering. The “printing” is done in a method similar to screen printing, where the solder paste is squeegeed through a 4 mil thick, stainless steel stencil onto the PCB.
This is all well and good, but commercial stencils are expensive, and are massive overkill for prototype boards. Here is a method for producing a “good-enough” stencil using aluminium sheet via a method similar to PCB production via the UV photosensitive film method.
Home-made solder paste stencil - [Link]
This project is “NanoUtils Xtal” – a crystal oscillator breakout board. The board is designed to be interfaced with microcontrollers that have their oscillator pins next to a ground pin. [via]
This board is a breakout containing a SMD crystal, two caps and a resistor meant to be used in breadboards when building something with an Atmel ATmega or a Microchip PIC that have the two crystal pins next to a GND pin. For instance the atmega328 or pic18f2550.
Crystal oscillator breakout - [Link]
Our friend Vasilis posted a video story of a successful SMD reflow process… at his home, amazing!
Powered by the Low Budget Manual Pick and Place : http://vpapanik.blogspot.gr/2012/11/low-budget-manual-pick-place.html
SMD reflow at home - [Link]
Action video of the Low Budget Manual Pick and Place Originally posted in : http://vpapanik.blogspot.gr/2012/11/low-budget-manual-pick-place.html
Low Budget Manual Pick and Place (HD) - [Link]
Our friend Vassilis decided to build his own manual Pick & Place machine to facilitate his work with 0402 SMD and other fine pitch parts. He used plywood, a pen microscope and a vacuum pump to build this dirty cheap Pick and Place manual machine:
If you are dealing with tiny SMD parts (e.g. 0402 resistors and capacitors), a manual pick and place machine is a helpful piece of equipment for prototyping and small-batch manufacturing. On the other side, traditional SMD placement using precision tweezers not only requires an ultra-steady hand but also becomes a tiresome drill, especially when working long hours upon fine-pitch PCB footprints.
Low Budget Manual Pick & Place - [Link]