Circuit Skills: Power Supply

Find more at the Maker Shed: makershed.com
The requisite starting point for anything electronic - you won't get much blinking, buzzing, or processing done without a power supply!
Learn more here:
makezine.com/vi...

[@Alex-ck4in]

Ive been coming back to Colin's videos since I was a 15 year-old when these videos were first released... Thank you Colin for helping me realise my love of engineering!

[@youfrancis]

Collin Cunningham's videos never cease to impress, entertain or enlighten. He speaks with a cadence that is both patient and lucid. Frankly: I could only wish everyone was as good a teacher as he is.

[@dancoulson6579]

I love it when I click on one of these videos. As soon as I hear the familiar background music, I immediately pause it, turn the TV to mute, and get comfortable. You always know you're going to learn something interesting!

[@madhatter2k]

Colin, you have style. Loving your work. Half the time I don't even care about what you're building, I just like your presenting. OK, so I do care about what you're building...

[@rexjuggler19]

This is how to make KZbin videos. If your KZbin is over 10 minutes, you need to re-think it. I stumbled on these just last week. These are probably the best on electronics out there. I have viewed other popular ones, but who has time for 30-60 minutes on a topic that can be effectively covered in the time Collin does these? This one is 7 years old. It is still relevant. I hope he still makes videos. They are engaging, provide the information I am looking for, and don't consume extraordinary amounts of time like others. Thanks Collin - 7 years after you made this.

[@iLoveEatingPie]

Awesome as ever, probably the only reason why I'm still subscribed to this channel.

[@yoanmilenkov]

I know nothing about circuits, but I still watch those videos!

[@salihtaysi]

You and your videos are awesome man! Also, watching you talk about something you're passionate about is so attractive

[@holdmybeer]

he has the most relaxed way of teaching i have ever seen, and i love it!

[@geofreyr]

Collin, your videos are excellent. Your presentation style is very clear and easy to understand, thanks!

[@mikado387]

i miss Collin please come back you're amazing

[@RickTrajan]

He's still around somewhere just look for him

[@mikado387]

Actually , i want to meet him, since im almost as crazy interested in electronics as Collin himself XD

[@RetroGameTech]

Collin's electronic vids are excellent! They're really interesting and I always end up learning something new. More like these please, Make!

[@Hatimoooo]

I wanted the PWM "Circuit skills" because I love your videos !!! Thanks Mr Collin

[@eelcogg]

He didn't say he is usign those, he just wanted an example of a circuit that needs both positive and negative rails. You are right about the 'newer' rail-to-rail devices, they make life easier :) Another example would be high-end transistor audio amplifiers I guess, but they seem to favor much higher voltages, both positive and negative.

[@WaterRabbit]

Great video, Thanks MakeMagazine and Mr. Cunningham. Multi Multimeters, Mega Multi Multimeters

[@MrLespaul1963]

Thanks Colin...I'm a musician (not my day job) that got bit by the DIY bug. On top of that, I found out how much the bits of gear cost to build as compared to the butt raping retail that places like Guitar Center charge and looking inside at the circuitry, I realized that this stuff isn't that complex. You, and a few other KZbinrs are my bridge to realizing my dream of building my own preamps, power amps, stompboxes, pedal board switching loops ...you get the idea. Have you published any books or manuals with basic projects that will let me build, for example a push pull, Class AB 20 watt amp using all solid state with a preamp that allows for adjustment of the bass, mid and treble bands. I'd be happy with a passive three band Eq that simply rolls off the treble, mids and bass in their respective ranges...sort of a mixer, but for frequencies or a low, high and all pass kind of tone control circuit?

[@blva888]

Again the only reason I'm still subscribed.

[@yoy58913]

this guy is amazing! !

[@rodolfomaduro8157]

redcinos Yeah! He is so ugly yet so cool! How that is possible?

[@supernewuser]

You need to realise that he's aiming these tutorials at people who do not already have these kinds of skills. His cadence and facial expressions are so the viewer feels like they are learning along with him.

[@DantalionNl]

Dont forget that the switching frequency of your switching power supply can create noise on the power line which is detrimental to an analog synthesizer!

[@ecv03]

And my Ham Radio.

[@fomalhaut9]

And my effects pedals

[@0h2ezy]

Colin! Where did you go? Your videos have alway been my favorite to learn or develop electronics from. "Make" some more please :)

[@Atwenty3]

The only reason I'm subscribed to make magazine

[@HazeAnderson]

i put mine in a large plastic case I bought from Radio Shack (yes we still got one!). I cut out a square on the front that extends across the front of the top and covered the top with some protective mesh. This allows access to the PCB mounted binding posts and prevents hands from touching further back than the PCB mounted potentiometers. I finally added two digital voltmeters to the front sides. 👍

[@LReBe7]

About the linear vs. switchmode issue: you must always be aware of the ripple on the output of a switchmode psu!

[@D4no00]

the biggest advantage of transformer is that you can bash it in the head of the guy complaining about switchmode converters.

[@latzobear]

your videos are wonderful

[@Bravo1989Tango]

I almost forgot why am I subscribed here, then I saw a new Collin video is up.

[@gelfling6]

@LightSwitchr The supply Colin assembled, is fixed to 115V input, so you would need a 230V primary, 12.6V 2-amp Split secondary (3-wire, 12.6-GND-12.6) transformer, and at that level of voltage, a enclosure,nevermind electrical tape over the primary wiring. Also a 230V primary transformer might not mount on the board as the 115V one does, though you could still run the wiring to the secondary points on the board.

[@321reh]

Always Interesting and NEVER BORING,,,Another Great Video From MAKE,,,Thanks Collin,,,,,,Best Regards from MR.OHM!!!

[@di4352]

Every time he builds a circuit he has the most awesome geeky background music!

[@chuckaedw]

Awesome video as usual. I just wish you would of put it in an enclosure at the end.. Still a great one, keep 'em comin. I always look forward to the circuit skills videos.

[@danielfrei6213]

we've been watching you with great interest, Mr anderson.

[@w0mblemania]

@3:10 Super graphic explanation of the transformation and rectification process. Thank you!

[@James_Haskin]

I feel like I've learned more from this video than any other circuit video. Keep em coming Collin :D

[@CampKohler]

@StoreFood In a pinch, you can always use two wall warts and swap the wires of one to get the two different polarities needed by a ckt. You wouldn't want to do that if something bad would happen if only one voltage was present (one of the wall warts might get unplugged accidentally). If you are using two metal-cased supplies where the negative is attached to the case (meaning the supply is not "floating"), then you would have to make sure the cases never touch each other or ground, else sparks.

[@MatthiasDeSater]

Finally! Another Collin video!

[@CampKohler]

@BunnySk8rProductions Two designs: Charger feeds batt which feeds ckts (complicated) or when the batt dies, remove it and charge separately. Use a DC power supply ("wall wart") of a few volts more than the batt volt, thru a resistor, to charge the batt, then put it back in the ckt. The resistor is sized (in ohms) to limit the charging current to that which won't overheat the batt (it absorbs the diff between PS and batt volts. Start large and reduce ohms until max charging current is reached.

[@megaman1025]

I didn't remember that "Circuit Skills" was Collin's show, so I didn't know what to expect when I clicked on the video, then I heard Collin's theme song and I thought, "YES! Collin's Lab, haven't seen one of those in a while!"

[@CampKohler]

@LightSwitchr The number of turns of wire in the transformer primary is designed to limit the amount of current that flows in the primary (even without using the secondary winding). Putting a 120V unit across 240V will burn up the primary, because there won't be enough inductance to keep the current in check. Using a 240V on 120V won't burn up, but it may have weak output under full load. Just look for a kit manufacturer in your own country, so that it is compatible without worrying.

[@nahueljo]

Finally, a Collin video!

[@CampKohler]

@ZboneWalker There are lots of videos on PCB making on KZbin. Some are for fairly complicated designs. For simple stuff, you can cut strips from electrical tape, stick them on the copper where you want the traces to be, and drop it in etching solution until the unwanted copper is eaten up. Do it all on paper first, marking where you will drill the holes for the parts, etc.

[@jamj30]

Collin for President!!! As usual good episode.

[@sooth15]

Pretty cool. It would look great in a clear acrylic case!

[@kolby4078]

It is only using half the sine wave pear output. That is why it only uses two. what you are thinking of is a bridge rectifier witch would flip all the waves positive. What this does is take one side of the original sine wave and just smooth that and then do the same with the other side, thus making it supply positive and negative voltage.

[@CampKohler]

@jakuba8 Negative voltages are not really a separate thing anymore than "water going into a hose" is different from "water going out of a hose." Pressure and flow are the same, just in a different direction. We usually use positive as the "hot" side of a supply merely out of tradition. Benjamin Franklin thought positive flowed out and negative flowed in (like air or water), but he had them backwards, so now the arrows in diode and transistor symbols are reversed and always will be.

[@supernewuser]

Whoa I hadn't noticed that until now. I couldn't put my finger on who he sounded like until I saw your comment.

[@Arazand]

Since this is posted last year you have probably already read this, but switching PSU's are in general more noisy, as in PWM instability have some procent less clean power, the best way to describe this is with a battery that give a constant volt-value when filled up. A linear supply give a very close constant volt-value, while switching supplies although more effective give the least constant volt-value of the three. That makes a switching supply bad for sensitive equipment, such as audio.

[@rikzel]

kipkay, collin, and tiny yellow house are the best of all!

[@monstergarage2]

@davidenelson It's because the capacitor store some more power upping it up to around 17 volts because voltage regulators need a little more power then they output.

[@bretdavis8097]

So if you have a +15V terminal than if you were to connect a load between that terminal and the ground terminal, you would have a 15V drop across the load. If you were to connect a load between the -15V terminal and the GND terminal you would have a 15V drop across the load (with current flowing in the opposite direction. You could connect a load between -15V and 15V and get a voltage of 30V dropped across the load.

[@chems]

single diode rectification? pretty cheap and crap

[@ankdoeslego9731]

You wouldn't get -15v with full wave rectification.

[@AbsoluteTrash_]

the problem is linear regulators are very inefficient

[@laszu7137]

Making switch mode power supply that is good enough for audio application is very hard. The problem with this is the transformer doesn't have connection in the middle of secondary winding. With transformer that does have that you can make symetric voltage much better.

[@GeoN0JRJ]

And...Switching supplies are a lot more noisy in the RF domain which can sometimes be a real problem. Nice video. Thanks!

[@orbit639]

this should be re-titled building shit on acid.

[@Orcinus24x5]

The transformer is rated at 12.6v AC, not DC. When you rectify and filter an AC source, multiply by 1.414 (or rather, the square root of 2) to get the approximate DC voltage. This transformer, when rectified, will produce ~17.8 VDC, which is enough to allow for the voltage dropout of the LM317/LM337 at 15 volts. However, the heatsinks included in the kit are grossly inadequate, and will not allow 750mA to be drawn from the regulators (which are actually 1.5A rated) for more than a min. or two.

[@alphabeets]

Fantastic job! Thanks again for these wonderful videos.

[@CampKohler]

@j7512 Plastic enclosures reduce the design precautions required to keep line voltage away from the user. However, metal is more rugged (doesn't crack when impacted or melt from component heat) and provides shielding, i.e. keeps signals in and noise out. Plastic is quicker and cheaper to build with. "You pays your money and you takes your choice."

[@jj74qformerlyjailbreak3]

Great stuff Collin

[@BlackJavaBean]

With great power comes... great current squared times resistance. I thought you were going there. Interesting video none the less.

[@lenzkessler9969]

Great video as always, but the actual product isn't much so. I bought the kit from Jameco after watching this, just out of curiosity. Well... There is no input protection at all, no full bridge rectifier and the PCB itself has no silkscreen and no solder mask - just like the ones you get from Bare Bones PCB. Some caps appear to be of questionable brands and quality. If that would have been a hobbyist DIY LED Blinking project, it would be okay, but for a power supply - it's too expensive to use such cheap design and components and without any kind of protection this is just outrageously dangerous. Be very careful if you buy this kit.

[@fegolem]

Yea! Collin! Good to see you again. Thanks for the vid.

[@CampKohler]

@thewii552 The tip is likely bent to get into tight spaces. In this case, it allows the tip to be placed flat against the work (as opposed to just touching it with the tiny point). The more intimate contact allows better heat transfer (lower thermal resistance), so the joint heats to soldering temp. quicker. Quicker is better, because the glue that holds the traces to the board doesn't cook as long; ditto the components. That is better than using a big blob of solder to improve the heat flow.

[@gillean2]

Bravo!!! Excellent explanation!

[@Jonnysea1986]

It really depends on how much current your project is going to be drawing. The larger the load the larger your transformer and the larger the filter cap needs to be (since the filtering affect with fixed capacitance will decrease with an increasing load). Since he is using both negative and positive voltages he has to use larger caps to smooth the gaps between the half waves. Your idea would only provide positive voltages. Soooo there's that.

[@CampKohler]

@uut0 Many power supplies are built like you suggest, with a mains/line cord, especially for expensive portable use devices such as laptops, etc. However, it costs extra, and when the device is likely to stay plugged in and is being built to a price, they elect the cheaper two prongs. The Bell System, recoginizing the "easiness" of which you speak, supplied 2-ft-long 3-conductor extension cords to allow no-cord wall warts to be plugged into tight places.

[@fairyheli2]

@logos2600 we use 240 as you only need a quarter of the copper, but we are smart enough not to electrocute ourselves with 240, we use 415v for big appliances

[@poruatokin]

No, it is not illegal in Europe as it is sold as a kit and under EU laws, that makes the builder take the responsibility for safety. That is why some nixie clock kits that use high voltage are only sold pre-built as an option for countries outside the EU. For shipment inside the EU, only kits are supplied.

[@nahueljo]

Collin! your videos are by far the best on this channel. Switching power supplies are indeed very interesting. However, given that the input and the output circuits are not isolated from eachother (not sure isolated is the right word), this change of frequence that it creates generates harmonics which increase the current in the power lines. I don't know how it is in the U.S. but in Argentina this reactive power is CHARGED if not corrected. Of course, if you use a lot of these power supplies :P

[@XIAOTIANism]

usually you can have isolated outputs by using isolation transformers, which gives you floating voltages on terminals.

[@KristoZ]

Thanks a lot! Now i know how to get a "negative voltage" - which I didn't know before this video. Thank you! :)

[@Dth091]

@TheSupertecnology Actually, only a few milliamps can kill. Depends entirely on where it is applied. Larger voltages means more of those amps can pass through you, causing more damage.

[@CampKohler]

@ZboneWalker Oh. What can I say? You lay out the parts on the board so that they fit nicely (don't physically interfere, heat from one part doesn't cook another, noisy ckts are separated from sensitive ones, air flow isn't blocked and so forth). Then you draw traces with a pencil (or two colors if it is double sided) until you have you connect everything with the least number of feed-throughs and the most direct runs. It's almost art. Beyond that, do you have any specific questions?

[@bretdavis8097]

When people say something is 5V or 15V or -15V, these numbers are only meaningful with a ground reference. I can have 1000V at one terminal and 1015V at another terminal and the voltage between them would be the difference, 15V (Of course those two voltages are also in reference to ground). In a circuit, ground is the point to which you compare voltages in the circuit.

[@Pygar2]

@mewmaster151 I know that old picture-tube type TVs made a high pitched sound like that. The "flyback transformer" that controlled the beam, made an audible high whistle or whine that you just had to ignore. And the older electronic flash units for cameras did too... may still, for all I know. So it is more than likely the items are actually making a noise you can hear.

[@thewii552]

@CampKohler or you could use a chisel tip. Or hold the iron sideways

[@lovelysilenthills]

I love this guy!

[@CampKohler]

@nahjos Yes, modern commercial building wiring must have beefed up neutral wires to handle the harmonics from all the PCs plugged in if more that one or two. Lot of people ignore this. In U.S. most residential power meters don't register reactive power that motors, etc. draw AND GIVE BACK TO THE LINE, just the actual power used up. Pwr companies will use correcting caps to lower reactive pwr so pwr isn't wasted running back and forth from this. Read the Wiki article on Electricity Meter.

[@DSteyn86]

No from -15V to +15V you have a potential difference of 30V which he uses to drive the synthesizer (box he holds up at the start). If you want a 15V output you must use the ground (0V) and +15V only output. You must look at the potential difference; from +15V to -15V it is 15 - (-15) which gives you a potential difference of 30V and if your only using ground and the +15V then the potential difference is the 15 - 0 = 15V. Hope this helps you out

[@nakalokofilms]

Finally a collin video!

[@CampKohler]

Wall warts and similar simple linear supplies usually have only crude circuitry, with poor voltage regulation, no overcurrent protection, high noise and hum, etc. The user must ensure that this is OK for the circuit in mind or else build in additional power processing circuitry in the load. High-end electronics will require high-quality power supplies for the best results. Don't hitch a pig to Cinderella's coach and expect "happily ever after." It doesn't hurt to try, though.

[@jvcrules]

To create a full bridge, yes, you would need four. But this PSU uses 2 half bridges (1 diode each) to get both positive and negative voltages.

[@xasdrubalex]

@FrancekPirosrancek it depends on ic's, i think in the kit there's a lm7818 and a 7918 and they provide 1Amp with heatsink.

[@NiMareQ]

This guy is awesome!

[@MrROTD]

I realy don't tinker with electronics much except for rc planes and thats all plug and play components so no skill required. I like these videos a lot anyway I'm learning a lot.

[@whiskeyify]

I used to work in a TV repair shop, tv's have 25,000 volts inside, however Colin is right...it's the AC line voltage that is dangerous.

[@mariushmedias]

Yeah, just checked the manual on site. The transformer is rated for 12.6v DC in the manual - I don't see how the kit will do 15v @0.75A as advertised, especially considering it's not doing full rectification of the AC voltage, but rather uses only two diodes to chop one side of the AC voltage.

[@AlexBolm]

Cool, as always !

[@ZboneWalker]

@CampKohler i know all of that stuff, but i mean the desingn of the board, i mean copper traces to be placed smartly so the board is as small as possible

[@Orcinus24x5]

Nope, you don't need a special type of pot. Just use the same value as the ones in the kit, 2.5 Kohms. You can even use a dual-tracking pot for greater convenience (two pots affixed to one shaft), or a pair of multi-turn pots for greater accuracy.

[@eelcogg]

That is true, but amps are hard to measure through a human body. That's why we used ohm's law to calculate the maximum voltage you safely touch. It of course depends on the resistance of your skin. For dry skin, the legal maximum is 50V. Damp/wet skin will lower that to 25V. If you are submerged or soaking wet the maximum is 12V. But you are absolutely right that it is the current that kills you. That's why the RCD in your house trips on differential current, not voltage.

[@BunnySk8rProductions]

@matthewtchernev123 4 leds and 3 fans the lights are powered by 2 AAs and the fans are also powered by 2 AAs, the radio is 3 AAAs

[@CampKohler]

@KaciFoxProductions Since there are two outputs, your question should really be "...over one diode per output." The answer is yes, because the BR would output twice as many power pulses/sec. than the half-wave rectifier, making regulation and smoothing hum easier for the regulators. But it would require two secondary windings instead of one and more expensive rectifiers, which would run up the cost. You get what you... um, you don't get what you don't pay for.

[@slap_my_hand]

120 volts? Come on! Get some 240!

[@thenrmguy06]

+StarTrek123456 fuck your shitty europe, europeice of shit

[@gustavferdman214]

+StarTrek123456 Go easy on the americans, 120 volts is more than enough to make bacon!

[@thethirdventure]

+Gustav Ferdman mmmm bacon....

[@gustavferdman214]

Edward Deaney They don't even have their own money, fucking borrowers.

[@638hds669900]

In Sweden we switched from left to right in 1969 and it's actually bin less accidents per year since then, and if you still think it's safer to drive on the left side then why does almost every country switch to the right side?

[@fairyheli2]

@mtj770 our 3 phase is 415v, I was talking about household electricity from a socket

[@jakuba8]

Can you make a video explaining the use of negative voltages in the world of electronics?

[@lucasmontec]

COllin collin collin! I missed you man! Make moar vids bro, you are my inspiration!

[@CioranClaudiu]

i subscribed to makemagazin just for Collin's videos

[@blva888]

@CampKohler a high intensity LED and a battery or dc power supply. Oh the flash should be variable and no multivibrater or 555 timers involved.

[@souravchakraborty4571]

7:26 With great power comes great responsibility. 😲

[@TheIronSavior]

There are two problems with that position. It is true that voltage is only the potential for current and it is the current that damages your body. However, current can't exist without a voltage potential and resistance is variable in the human body. Less resistance means more current and if I'm not mistaken, given the water content of the human body (among other factors), a person will have less resistance to higher voltages. TL;DR: Don't discount the voltage factor.

[@ElectricSparq]

More circuit skills videos,please.

[@atcaleb]

Wall worts, killed me with that one Collin!