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Circuit building: stop using antique parts (2014)
- joezydeco 10y agoMOSFETs driving motors or large coils without spike protection? Good luck with that. Have a fire extinguisher handy.
- jamesmp98 10y agoI'll keep on using 6502's for fun
- el_isma 10y agoThe page colors are terrible, but he does make a good point. Bipolars out, FETs in!
- jhpankow 10y agoYou can have my 2N2222's when you pry them from my cold dead hands.
- platz 10y agoAlthough I am on board with OP's reccomendation, I think many folks using arduino are in the milliamp range; they are not driving amps of current. So the 'constant factor' of obtaining less well known parts from digikey is significant. Do you really want to provide any more disincentive for budding hobbyists?
- Severian 10y agoThe irony is that the MOSFET he suggests to use, the NTD4906N, is listed as obsolete on Digikey. Which is why I pointed out. A lot of reasons people use antiquated components is probably because documentation and reference schematics are easy to find and have probably been refined to be very reliable.
- HeyLaughingBoy 10y agoAlso what you have on hand. 20 years ago I bought about 100 LM324's for a dirt cheap price. I drag one out whenever I need a non-precision amp or comparator.
- happycube 10y agoThe irony here is that the NTD4096N is discontinued/NLA. (There are other suitable parts in the price range, though.)
- blackguardx 10y agoThere is nothing wrong with bipolar transistors. They aren't antiquated. FETs have definitely overtaken them in power applications (for good reason) but it seems hard to displace them for small signal applications. Small signal FETs just aren't that plentiful or cheap. There are many instances where a small signal FET makes sense (level translators, etc) but the cost doesn't justify its use. Using a 2n2222 and the like is appropriate. On top of that, BJTs excel in many analog applications. There is a good reason why many analog IC companies make parts using a BiCMOS process. If you are doing a discrete analog design (generally for performance reasons) you often need the performance of BJTs or JFETs.
- spott 10y ago2n7000, BS270 are both pretty cheap for small signal FET applications. For analog applications, BJTs are still very much important, but for digital stuff (and especially power stuff), it is usually easier to grab a cheap FET than use a BJT.
- Florin_Andrei 10y agoThe article seems mostly right when it's about interfacing logic circuits with loads that require even moderate currents. FET is king in this field. I've a little aquarium and I've noticed how fish always get scared when lights turn suddenly on or off. So I took an Arduino and wrote a timer app for it, using PWM to slowly drive the output up over 60 minutes (sunrise), keep it at max for a few hours, then drive it down slowly over 60 minutes (sunset). I used a MOS-FET to drive the power LEDs directly from the Arduino. Works fantastic, and the FET is cold at all times. A 2N3055 would have been pretty hot most of the time. I've been playing with electronics for a few decades now, so I can't be accused of change for the sake of change. The old stuff still works, sure, but there are new toys which are better in some cases.
- mrob 10y agoWhat frequency are you PWMing at, and are you applying any analog filtering? I frequently get annoyed by slow PWMed lighting, and I wonder how other animals with possibly faster vision perceive it.
- spott 10y agoThe response referenced by Hackaday: http://hackaday.com/2015/08/17/you-can-have-my-tips-when-you-pry-them-from-my-cold-dead-hands/ http://hackaday.com/2015/08/17/you-can-have-my-tips-when-you...
- ChuckMcM 10y agoSigh. I like FETs as much as the next engineer but if you're going to write about them, try to not make things worse. In particular, this made me sad: the 10K resistor to ground isn't strictly necessary, but it ensures that the MOSFET remains OFF if the arduino is disconnected or it's pin is not an OUTPUT. I was helping a high school student with a transistor project and he was complaining that "half the FETs he bought were 'bad'". And they weren't really bad, but they were destroyed. They were destroyed because, like our author, the student had no understanding of how the FET worked and so didn't realize that when you exceed the maximum Gate voltage on a FET it generally causes a current to "jump the gap" to the source and that permanently breaks it. What is even more, since the gate is essentially a capacitor, you can just touch the gate with your finger and pass enough charge (without feeling a shock or anything) to greatly exceed the gate voltage. Pick up the FET without being grounded and "boom!" dead FET. Now there is almost no way to generate enough current by touching a Bipolar transistor to kill it, and so they continue to work for a long time while plugging them in and out of breadboards. Do they dissipate more power? Absolutely. Are they difficult to run in parallel? Sure. But they are pretty robust parts. Sort of like the difference between alkaline batteries and LiON rechargeable batteries. Sure the latter are a "better" choice, you can recharge them after all, but if you use them wrong they catch on fire, if you short an alkaline battery it gets hot but doesn't go ballistic on you. So those "antique" parts are generally very cost effective, very robust, and easy to get. So they make excellent tools to teach you the basics. Do you want to stay with them as you get more advanced? Probably not, but you're probably not skiing on the same skis you learned on either. /endrant
- aexaey 10y agoYep. It is indeed easy to ruin a FET with minuscule amount of static charge. That is, unless there is a zener (or two, back-to-back) connecting gate to source. Many modern FETs have this built right in. E.g. ATP214 [1]. [1] http://www.onsemi.com/pub/Collateral/ENA1712-D.PDF http://www.onsemi.com/pub/Collateral/ENA1712-D.PDF
- Obi_Juan_Kenobi 10y agoThat does sound like a very useful part for learning purposes, as well as general robustness, but they don't appear to be particularly common. I get no results on eBay, nor can I find through-hole packages. Do you know of anything available like that?
- PeanutNore 10y agoI build a lot of guitar effects, and that community is even worse when it comes to attachement to obsolete components. The discontinuation of J201 JFETs (in TO-92 through hole package at least) by Fairchild has caused a lot of upset. My perspective, not widely shared, is that JFETs in general have been made obsolete by depletion-mode MOSFETs, at least in audio circuits. Part of the reason, I think, is that a lot of "designers" of guitar pedals don't understand the math that determines component values for a particular transistor in a particular circuit so they don't know how to either select a modern transistor to replace an obsolete one based on datasheet parameters or to change the collector / emitter / source / drain / etc resistor values to work right with a new part.
- blackguardx 10y agoJFETs main application these days is for when you need very low noise, usually for precise measurements. A depletion mode MOSFET has similar behavior, but not specs.
- PeanutNore 10y agoYeah, I see them used for that purpose and for VHF / UHF applications. A lot of precision op-amps also have JFET inputs. In guitar effects land JFETs are popular because as a class-a amplifier in common source configuration they bias the same way that a triode does. Ironically when people try to replicate tube preamp circuits by cascading JFET stages the result is anything but "very low noise". Depletion-mode MOSFETs can be cascaded like triodes without creating unacceptable (for a guitar pedal) noise levels.
- bsder 10y ago> My perspective, not widely shared, is that JFETs in general have been made obsolete by depletion-mode MOSFETs, at least in audio circuits. A guitarist friend decided to "test" me once and put this in front of me and ask what it would sound like: http://el34world.com/charts/Schematics/files/randall/Randall%20RG100.PNG http://el34world.com/charts/Schematics/files/randall/Randall... My immediate response was: "That looks like a really great amp from the mid 1980's--looks like it was designed by someone who actually understands electrical engineering. It should have a pretty clean. But if you overdrive it, the clipping on those JFET's is gonna sound like fscking buzzsaw trash." He, of course, laughed knowing that Dimebag Darrell used the amp for precisely that buzzsaw sound. You would have to add lots of "clipping" components to get the same sound out of depletion mode MOSFET's. Now, whether that's a good sound is open to debate. :)
- mrob 10y agoMechanical relays are not obsolete. They can have lower resistance and capacitance than solid state equivalents. A good relay is a very close approximation to a plain wire when closed. Relays are still commonly used for RF switching.
- jacquesm 10y agoRF grade relays will cost you an arm and a leg though.
- makomk 10y agoI think a lot of ham radio gear just uses standard relays for switching RF signals. Apparently they work well enough in many applications.
- jacquesm 10y agoAs long as you are loading with a resonant load then yes, it can work. But as soon as you are in any way reflecting power back on the line or have an impedance mismatch (which will result in reflected power) you're in big trouble. Another problem is if you use one to switch from say an antenna to a dummy load, you might find that you are leaking quite a bit of power onto the supposedly disconnected antenna link. RF is tricky, especially at higher power levels. One trick you can use is to use only single contact relays and to bend open the contacts as far as they will go as long as they reliably close again when the relay is energized. That way you minimize capacitive coupling between the contacts. DC relays are your best bet for a starting point because they already have larger gaps than most AC relays (to inhibit arcing).
- CamperBob2 10y agoTo that point, another mistake a lot of amateurs make is that they buy expensive things on DigiKey without looking on eBay first.
- jacquesm 10y ago
- coreyp_1 10y agoDon't tell me that a LM386 is bad without telling me why and what to replace it with. If you don't, then you're not actually helping me at all, but rather it just sounds like you're spreading FUD.
- cr0sh 10y agoAbout the only thing "bad" with the LM386 is how finicky it is with component selection and layout. It's a great little amp when it works well, but sometimes it will go dopey on you just looking at it sideways. It actually works better in a PCB situation (breadboarding is where it can be wonky in operation - ymmv). As far as a replacement part? I don't think there are many alternatives there (at least with the same size, and easy to configure - there are a few stereo ICs I've seen used for class-D amps, but they weren't as simple to use or as small).
- cylinder714 10y agoThe very first article of the book More QRP Power discusses surface-mount tech and why amateur radio people should embrace it, and the author specifically mentions an SMD chip with better specs than the LM386...but I don't have the book handy. I'll search for it later.
- Animats 10y agoIf you want to switch power, MOSFETs are the way to go today. Voltage drop is near zero. Digi-Key has over a thousand MOSFETs in TO-220 packages. Here's one of the cheapest with a low gate threshold.[1] Probably good enough for most Arduino on/off applications. MOSFETs do have some problems. They can draw large gate currents for the first few nanoseconds of turn-on, which can overload whatever is driving them. The gate input is very vulnerable to electrostatic discharge during handling. Device failure tends to be into the ON state. I just went through a big struggle with MOSFET selection for a special purpose switching power supply. The big through-hole parts have too much gate capacitance and need too much drive at turn-on. Only in surface-mount could I get something that would work. That's the real problem with antique parts. The new stuff is surface-mount only. [1] https://www.fairchildsemi.com/datasheets/FQ/FQP4N20L.pdf https://www.fairchildsemi.com/datasheets/FQ/FQP4N20L.pdf
- PeanutNore 10y agoThere are definitely still new through-hole parts, but the selection is limited. It seems like maybe 20% of new transistors get a TO-92 or TO-220 version.
- sounds 10y agoI would love to see something on digikey or mouser that allowed me to search for MOSFETs in a way that was less painful. Let's say you wanted to do a special purpose switching power supply. Digikey doesn't have a column for gate capacitance (for the mosfet), or Q (for the inductor). All that manual work to read datasheets is terrible, especially if your design takes a little while to perfect and some of the components go end-of-life, so you have to replace them. I personally like to graph the cost-efficiency curve so I actually have to tabulate lots of mosfets, inductors, and caps, then simulate them in a spreadsheet. I know about the specialized design tools done by each manufacturer that will recommend parts and do a design for you based on your criteria. I want something that does a much broader search for parts though. Maybe I should write one. :)
- PeanutNore 10y agoMouser does have a column for gate charge that you can sort by.
- dyselon 10y agoIs there a good reference for potential upgrades to old, obsolete-ish parts? I definitely understand that many of the old logic ICs, transistors, and op-amps have been displaced by better parts, but I don't always know how to identify them short of a parametric search on digikey and hoping there's not some sharp corner I missed. I'd find a lot of value in a page that had some recommendations for "Are you using <OLD PART> for <PURPOSE>? Consider <NEW PART>!"
- CamperBob2 10y agoNot really, because as so many commenters have pointed out, the choice to use "antique" parts is more of a value judgement than a violation of natural law. When in doubt, your best move is probably to see what Horowitz and Hill have to say. AoE3 has a lot of specific component recommendations.
- lpmay 10y agoThere's not much of substance to this article. The world of electronics is a bigger place than turning a load full on or full off with a Mosfet. A couple exercises if you want to see why having some BJT's around is handy: Try to find a Mosfet that turns on at 0.6 Vgs. Compare the leakage Ids leakage of a Mosfet to the Ice leakage of a comparable BJT. I also take issue with the idea that "all that extra stuff" is drawn in the Mosfet symbol for "no reason". The body diode alone is an important factor to consider EVERY time you use a Mosfet. When you read schematics every day, you're trained to recognize when diodes will forward conduct in your circuit and having that drawn in the Mosfet symbol helps you immediately see problems that would otherwise make it into your final circuit.
- nom 10y agoAlso: the LM317! Case in point: https://encrypted.google.com/search?q=lm317+hot https://encrypted.google.com/search?q=lm317+hot
- zw123456 10y agoWhile we are on the topic of using more modern parts, if you are controlling a motor as shown in the example, why not use an H-Bridge chip ?
- TD-Linux 10y agoYou might only need to spin the motor in one direction.
- zw123456 10y agoYes, but even so, they also have half bridge chips, all the biasing and compensation, the correct diodes etc. The point is, a motor controller chip is more modern way that the old transistor or MOSFET way. unless you are designing some cheapo thing that will be produced in the millions and have to scrape every penny out of the design, it is better and easier to simply use a motor controller chip in my view.
- clarry 10y agoMaybe you have a box full of transistors and diodes in the closet, because they're kinda needed for everything or at least very useful to have around. You can start building yesterday. If you want that special bridge chip, you start looking through online stores and datasheets (what a chore, why do they have to suck so hard?), trying to find the chip that has the availability, a reasonable price, the right specs and appropriate package for your use. Then you pay the shipping cost on top of the component, which might be more than the component itself. Then you wait a week or two for the thing to arrive. Then you pray it is intact and you can maybe start building. Hope you ordered the right part and didn't make a mistake in reading the specs.
- bschwindHN 10y agoI'm an electronics amateur, got a question here: I use a PN2222 [1] transistor to switch a 5V supply through an infrared LED from a microcontroller. It works, but should I be using something better/smaller/more cost effective/more appropriate for the circuit [2]? [1] https://blog.bschwind.com/2016/05/29/sending-infrared-commands-from-a-raspberry-pi-without-lirc/images/transistorPackCloseup.jpg https://blog.bschwind.com/2016/05/29/sending-infrared-comman... [2] https://blog.bschwind.com/2016/05/29/sending-infrared-commands-from-a-raspberry-pi-without-lirc/images/breadboardCircuit.jpg https://blog.bschwind.com/2016/05/29/sending-infrared-comman... (the resistor in the photo is 680 ohms)
- Itsdijital 10y agoFor something like that? If it works, it's good. If you are trying to optimize for whatever parameters, then maybe there are better parts. But for something simple and basic like that, its fine.
- TD-Linux 10y agoNo, in fact in that circuit the PN2222 is the only thing limiting current to your LED. If you switch that to a MOSFET you'll blow up your LED unless you add a series resistor. (are you sure you aren't already giving too much current to your LED?)
- deepnet 10y agoPage author is Tom Jennings, the creator of FIDONet, the BBS network that pre-saged the internet. https://youtu.be/_Cm6EFYktRQ?t=2m32s https://youtu.be/_Cm6EFYktRQ?t=2m32s
- basicplus2 10y agothat's funny really, because MOSFETs were around in the 70's
- smileysteve 10y agoThe author addressed exactly this fact. They were rarer and pricier (they're still pricier)
- noonespecial 10y agoWhy use a 120 in todays modern age? Because that thing you're repairing was Woz'd to the point that that VCE plays an important part in the circuit's operation. Keep your TIPS, you might not necessarily use them for that brand new design of yours, but you'll probably use them for something.
- lightedman 10y agoGood luck building a BFO metal detector using MOSFETs without a ton of additional useless circuitry.
- AceJohnny2 10y agoI've recently gotten back into hobby electronics, trying to revive all that EE knowledge I haven't used in 15 years, and one thing I sorely lack is knowledge of common components to use. Online electronics stores are no help because of the overload of possible components. Is there some sort of Cookbook out there I could refer to for up-to-date examples of common circuits and electronic tasks? I mean, I otherwise totally would've used a 2N2222 transistor for some tasks, because I wouldn't know better.
- chuckdries 10y agoI've been looking for the same thing for weeks, I ended up just texting my electrical engineer friend
- wbl 10y agoHorowitz and Hill third edition.
- markrages 10y agoAlso, searhc digikey and sort by quantity in stock, descending. The popular parts are the ones to use (if you don't have special requirements of course).
- TD-Linux 10y agoA lot of manufacturers have parts designed as drop in replacements for older parts, sometimes even with similar looking part numbers. Another thing that I often do is use Digikey's search and check their stock quantity to find out what's "popular". For example, if I want an op amp, I'll go to that category on Digikey and then first enter a quantity and sort by price. Then I'll start adding constraints - for example, for a 324 replacement, I might want it to be through hole (I nearly always do SMD designs though). From that, I unsurprisingly find the LM324 (it's still one of the cheapest!). But I also find the MCP6002, which is lower voltage but has rail to rail inputs and is designed for a capacitive load - perfect for driving a microcontroller ADC. The truth though is that it's not like the old parts got any worse, and are still often the cheapest choice. You have to add additional constraints (I want lower loss, better performance etc) for something else to be "better".
- amelius 10y agoFor anyone interested, I can highly recommend the course "Structured Electronic Design", [1]. [1] https://ocw.tudelft.nl/courses/structured-electronic-design/ https://ocw.tudelft.nl/courses/structured-electronic-design/
- duskwuff 10y agoThe obsolete part I'd really like to see everyone get away from is the 741 operational amplifier. The 741 was introduced in the late 1960s. It's completely outclassed by modern general-purpose op-amps; there is absolutely no reason to still be using it today.
- GregBuchholz 10y agoNow if only we can get people to stop antique computer languages from 1972. (yeah, yeah, I know, special cases. In fact I'm current working on a project using C on three different microcontrollers).
- deleted 10y ago[deleted]
- kazinator 10y ago> 40% of the power is pissed away as heat in the stupid TIP120!!! wtf! You can find a BJT about just as antiquated with a lower VCE(sat). Also, maybe don't run a motor off 5V and then complain that the transistor is eating too much of that voltage.
- kevin_thibedeau 10y ago> relays Can't be taken seriously if he's going to malign the utility of an entire class of components.
- wyc 10y agoI think the author describes my point of view and defuses many of his own points at the very bottom of the page: also, you are likely making one circuit, not planning on mass-producing 1,000,000,000 of whatever it is; who cares if you spend a buck where a dime might do? you want it to work first time every time, right? this is art not technology (eg. industrial capitalism); we have different design criteria here. That's exactly right. I'm usually making one circuit, and not mass-producing them. My inefficiencies will likely be limited in scale to no more than cents per month on the electricity bill. If I were mass-producing, then of course I'll reach for the low-power switching FETs.
- monochromatic 10y agoDark green text on a light green background??
- anneBarcelona 10y agonah, why wasting all this parts? just the production created a huge pollution and then it was all for nothing,..no no.
- anneBarcelona 10y agonah, why wasting all this parts? jsut the production created a huge pollution and then it was all for nothing,..no no.
- retrogradeorbit 10y agoThere's still plenty of reason to use discontinued components in DIY. And that reason is the form of the component's package. This is a problem for me when building high end audio circuits. A lot of the modern components are only available in surface mount forms. I find this with matched transistor packages. Like a matched quad. There are modern components, like AD's MAT14 [1], but if you are building your own circuits and using through hole components your ONLY choice is discontinued components. They simply are not made in a through hole package anymore. At some point I'll be forced to move to surface mount, but at the moment getting old components is a lot easier. And those old components are as good as the new ones. Just different packages. If anyone knows of a modern precision matched quad like the MAT14, but in a traditional package, please reply with the component! [1] http://www.analog.com/media/en/technical-documentation/data-sheets/MAT14.pdf http://www.analog.com/media/en/technical-documentation/data-...
- pmorici 10y agoI disagree. Using a stencil and paste with a cheap toaster oven is easier to make high quality boards than with PTH and an iron. It's fast and almost always comes out great.
- retrogradeorbit 10y ago"easier". Just pull apart a toaster oven. Reconfigure it. Rewire it. Get some paste. Make a stencil. You know. Easy peasy. Get the software. Learn how to use it. Get the stencils printing. Easy. Oh, you've got registration problems. Come on! Its easy! So much easier than spending one minute ordering a through hole component. You see, its not actually "easier". Its "easier" to you because you already have the equipment and are already doing it. Hey! I already know this! This is easy!
- pmorici 10y agoDon't knock it till you try it. You don't need to modify your toaster oven or any of that non-sense. I got a cheap $25 of Amazon and just use a stop watch and the toaster dial to set the temp by hand. There is really nothing to learn. Also ordering a stencil is just as simple as ordering PCBs now with the OSHStencil service.
- burntrelish1273 10y agoIGBTs, although very expensive, are also interesting alternatives to MOSFETs and relays where large voltages need to be switched where speed isn't critical.
- burntrelish1273 10y agoHere's an example of a very large module for 4.5kV and 1.2kA https://www.infineon.com/cms/en/product/power/igbt/igbt-module/igbt-module-4500v-6500v/channel.html?channel=ff80808112ab681d0112ab69f8450396 https://www.infineon.com/cms/en/product/power/igbt/igbt-modu...
- HowardSamantha 10y agoTime simulator to virtualize your system clock and manipulate time. This tool is used for time zone correction, to time travel servers & software testing. Click here: https://www.timesimulator.com/ https://www.timesimulator.com/
- shove 10y agoAny similar thoughts on the 2N390X series? (Datasheets are a PITA)
- sunstone 10y agoVce Sat is closer to .2V (rather than 2v) as I recall.