Can I build an AC/DC SMPS in 1 month? - Page 1
Forum section: electronics / beginners

author: KEIN NEIN
author_rank: Contributor
timestamp: May 05, 2019, 12:09:30 am
content: I need to finish to projecs in one month:One that has a transistor in itAnd one that uses arduinoI was planning to build an SMPS + DC load and osciloscope but having seen I don't have a lot of time, should I continue with the SMPS or should I just build the load (which also has a transistor)Can you help me select the right parts?Thanks in advance

author: strawberry
author_rank: Super Contributor
timestamp: May 05, 2019, 01:01:52 am
content: Simplest SMPS with built-in protection ...To build it follow instructions in design sheethttp://www.datasheetcatalog.com/datasheets_pdf/R/D/6/RD6.shtmlDont forget transfomer GAP size or AL(nH/turns2) found in sheetparts available on Mouser, Digikey ...

author: KEIN NEIN
author_rank: Contributor
timestamp: May 05, 2019, 01:20:44 am
content: I see, thanksBut what if I wanted to make a higher power SMPS, could I just use higher rating parts?Or would I have to opt for a difference topology

author: KEIN NEIN
author_rank: Contributor
timestamp: May 05, 2019, 01:22:20 am
content: Is it worth it to do something like a quasi reasonant psu just for efficiency reasons?

author: schmitt trigger
author_rank: Super Contributor
timestamp: May 05, 2019, 01:28:50 am
content: Quote from: windsmurf on May 05, 2019, 12:44:40 amMy exact feelings.What does a SMPS+DC Load has to do with two assignments, one which uses an Arduino, and the other that usesa transistor.?

author: amyk
author_rank: Super Contributor
timestamp: May 05, 2019, 01:31:58 am
content: Quote from: schmitt trigger on May 05, 2019, 01:28:50 amIndeed. I don't know what to be more disappointed with, the OP for not giving us more details, or the institution that's making these vague and not very sensible project demands.To answer the (not that much more, but still) more specific question in the title of the thread: yes.

author: KEIN NEIN
author_rank: Contributor
timestamp: May 05, 2019, 01:44:20 am
content: The specific requirements of the project weren't very clear.There are two different projects for two different subjectsOne is for semiconductors and the requirement is to show a project that makes use of one or more transistors and we need to explain the role of those transistors.And the other project is for visual programming, it consists of pretty much any project that takes advantage of arduino and we are using labview for programmingnow if you want my particular preferences i'd rather the SMPS were efficient and capable of outputting more than 10A through various regulated 5V USB outputs(something like a power strip but with many USB plugs)But I don't know how much price will increase and how viable it isAs for the arduino load if possible it should be able to stress high wattage ATX PSUS (so high current adjustable load) even if I have to tie a huge fan to it

author: Brumby
author_rank: Unknown
timestamp: May 05, 2019, 02:27:15 am
content: Quote from: KEIN NEIN on May 05, 2019, 01:44:20 amWhat level are we talking about here? High school beginner or EE degree?If it's High School level, then I'd probably suggest something like a good, old fashioned two transistor multivibrator or a Colpitts oscillator. A SMPS seems a bit ambitious - and we have no idea of your experience with mains power, so safety is also a question in our minds.If I've taken a "low level" view of the project requirements, then that is based on my assessment on the little information you have presented. For your own sake, you need to be a little more informative for us to be better guided in how to assist - otherwise we are guessing.

author: ejeffrey
author_rank: Super Contributor
timestamp: May 05, 2019, 03:20:06 am
content: No, an AC (mains powered) to DC smps, especially a relatively high current one is not a suitable project for your apparent level of skill and experience. Mains operated gear has significant safety issues and several additional issues with isolation.A simple non isolated DC to DC converter is. A little transistor powered joule thief would be a simple example. A moderate low voltage DC to DC converter of any of the standard types would also be reasonable project as would a discreet class D amplifier which is similar to a modulatable DC-DC converter. It depends on the class level. But my advice is to go on the simple side and make sure you understand it really well. A joule thief presented by someone who understands the operation completely will get higher marks than someone who submits a 100 W D class audio power amplifier based on a design they found on the internet with no detailed analysis. At least they would if it were my class.

author: mariush
author_rank: Super Contributor
timestamp: May 05, 2019, 03:46:51 am
content: I think you're pointlessly complicating your life.If you have to make a project with ONE transistor why make a SMPS? It's like making a plane because you must do something with a wheel.Here's a project idea: use transistor as on/off switch.For example make a device to dry hands that's turned on without touch.Have an arduino, an infrared led and an infrared sensor... when hand goes under fan area, it breaks the invisible infrared and your arduino then turns on a 80/92/120/140mm fan powered from 12v using a transistor.Transistor lets you turn on a 12v device using 5v of arduino.Or instead of fan , think of it as alarm... have hall effect sensor on door edge, magnet on door... if door opens magnet goes away so sensor reports that and arduino reads that and plays alarm on piezo speaker using transistor.could use a 555 to generate sound but arduino and pwm would be easierseehttps://www.murata.com/en-sg/support/faqs/products/sound/sounder/char/sch0001https://electronics.stackexchange.com/questions/15629/driving-piezo-buzzer-from-mcu-pinhttp://hades.mech.northwestern.edu/index.php/Driving_a_piezo_speaker_with_a_PIChttps://www.eevblog.com/forum/projects/how-to-connect-a-piezo-speaker-to-a-microcontroller/Kill two rabbits with one project.

author: KEIN NEIN
author_rank: Contributor
timestamp: May 05, 2019, 06:17:30 pm
content: Electric engineering degree, and yes I'm aware of the risks involved when working with mains voltage

author: KEIN NEIN
author_rank: Contributor
timestamp: May 05, 2019, 06:26:10 pm
content: I guess I'll come back whenever I've made up my mind, I have to read the PSU cookbook but as of right now I believe I'll opt for a flyback PSU bc I believe it can power a few PSU devices and it's not so complex in designCorrect me if I'm wrongThanks anyway

author: KEIN NEIN
author_rank: Contributor
timestamp: May 05, 2019, 06:28:51 pm
content: I am aware I am overcomplicating otherwise I wouldn't plan on building an SMPS don't you think so?

author: TimNJ
author_rank: Super Contributor
timestamp: May 05, 2019, 08:34:28 pm
content: I would notrushworking on a mains switch-mode power supply. Seriously, even though you may have some ideas about the dangers of working with mains, if you have neverreallyworked on something like this before, now is not the time to rush it. There are lots of things to be cognizant of, from both design and test standpoints. Doesn't mean you shouldn't do it in the future, of course.

author: Brumby
author_rank: Unknown
timestamp: May 05, 2019, 11:39:32 pm
content: Just a word about "being aware" of the risks of working with mains voltages.....I've been "working with" mains voltages for more years than I care to admit, but this has been with fairly simple situations - mains wiring, switches, fuses, transformers and such. When there is a problem, these things can often be successfully diagnosed without power applied - and when powerisapplied, the measurements required are often simple and few.Diagnosing an SMPS is more likely to be more involved. You will be making more measurements in a more confined space with more places for probes to slip.I approach SMPS diagnosis with an order of magnitude greater care than "regular" mains circuitry. Not doing much SMPS troubleshooting will influence my caution, but it's still worth being more attentive.

author: KEIN NEIN
author_rank: Contributor
timestamp: May 06, 2019, 02:06:16 am
content: understood, in that case could you tell me how to build an arduino DC load or osciloscope capable of drawing <10A (<50A if possible)I have watched two videos already

author: KEIN NEIN
author_rank: Contributor
timestamp: May 06, 2019, 06:52:49 pm
content: or a buck converter maybe?

author: pigrew
author_rank: Frequent Contributor
timestamp: May 06, 2019, 07:18:22 pm
content: Quote from: KEIN NEIN on May 06, 2019, 06:52:49 pmMy suggestion would be to build a 5V to 3.3V buck converter, using Arduino to implement the PWM & feedback loop. You would need a few capacitors, resistors, an inductor, and diode (maybe a second MOSFET, too). Perhaps use a pMOSFET as the pass transistor (but a BJT could work, too).-Nathan

author: KEIN NEIN
author_rank: Contributor
timestamp: May 06, 2019, 07:37:35 pm
content: Aside from mouser electronics and digikey which other stores do you recommend? (from mexico ofc)

author: KEIN NEIN
author_rank: Contributor
timestamp: May 06, 2019, 07:39:39 pm
content: Quote from: pigrew on May 06, 2019, 07:18:22 pmthank youModern buck converters use two MOSFETs for syncronous rectification right?I didn't know I could do that with arduino, where can I find more info on that?

author: pigrew
author_rank: Frequent Contributor
timestamp: May 06, 2019, 07:45:15 pm
content: Quote from: KEIN NEIN on May 06, 2019, 07:39:39 pmYes, synchronous rectifiers use a second MOSFET to improve efficiency (to avoid diode losses). You can just look at the wiki page for buck converters for help. Building a synchronous rectifier is difficult, and I would suggest making one using a Schottky diode first.I've never used Arduino (except for my 3D printer), so I don't have any good references for you to look at. However, you'll be needing to make 50~200 kHz PWM, which is certainly within the capabilities of most microcontrollers. Getting the feedback loop right may be tricky. I'd suggest starting with doing analog simulations of the inductor+transistor to see how they respond.

author: KEIN NEIN
author_rank: Contributor
timestamp: May 06, 2019, 07:51:39 pm
content: Understood, let me see