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Why do it for 3 when we can design for 10?! At college we were in charge of designing a 3 Amp power supply, but I was seeking for a challenge, not a grade!

Overcomplicating this kind of “simple” projects can make your life a bit harder but way more exiting, and the rewards just have no price, you will also learn way more than doing a small 3 Amp power supply, fortunately I had a good and experienced mentor to guide me, Lopez Hernandez Jose Antonio from the Investigation and Technologic Innovation Center (CIITEC) in Mexico City.

I completed the project in time thanks to some administrative and economic planning technics , the right tools and a bit of will power

A linear power supply takes the 120vCA 60 Hz mains power, steps the voltage down through a transformer, rectifies, filters, and regulates it. It's simple and robust; the main problem is that it's inefficient. You need a big, heavy transformer to handle the current, high current diodes, huge electrolytic capacitors, and lots of thermal dissipation for your Darlington arrays. It can also become prohibitively expensive to build high power linear supplies, even if they're easy to design. (This one was around $6,500 MXN pesos, around 433 USD considering 1 USD = 15 MXN pesos)

Here you will learn to do what I did right, and how not to not commit the same mistakes I made, mistakes are good because you do learn from them, but on the other hand you can save a lot of time and money by learning from my mistakes instead of doing your own.

Needless to say, this is my first instructable… and this my first project using copper clads… and my first time using Altium CAD PCB software… and my first linear power supply ever… and my first time documenting something in English.... so try to not be so hard on me on the comment section ;), all the feedback is welcome.

The guide is a bit long, as I said please beware, if you find any grammar , calculation or technical mistakes please let me know , and I will review them and see them fixed as soon as possible.

Along the start of each step I will be adding underlined text where I warn about what I did wrong , this bold underlined text can also be an upgrade note to do what I did in a better way, with some other ways I have learned over the time after completing the project

Every single file used to make the power supply is in my GitHub Repository feel free to use it at your discretion, hopefully you can do it better, smaller, cheaper, or why not even bigger!

Step 1: Electronic Component Suppliers

For most of the electronic components i used Newark Element 14, they ship internationally to anywhere in the world in 3 days, with free shipping (its already being charged in the components and yes they also charge the taxes)

For sourcing some other components like the voltmetters and ammeters that are a bit way expensive in Newark, eBay is your friend, however you need to be really patient to get the components since the shipping times can go up to 2 months in the worst case.



Step 2: Enclosure Design

For starters we need to set the objective and decide what we will do, we have many questions;

  • How many outputs will our power supply have?
  • How will I turn it on/off?
  • Where will I get a custom made transformer?
  • How can I measure the voltage from the outputs without using a voltmeter?
  • short circuit protection?
  • How will the chassis look?

Well you can start addressing all this using Corel draw to start drawing your chassis, Corel allows you to input measurements in cm/in so you can print it out and decide where will you put everything in the main panel, to do this you might want to use a Vernier to get the closest real value, and measure the components you have in hand, or you can also use the technical datasheets, in order to have the most accurate visual representation of your final product

As you can see my first draft had an analog ammeter and 2 digital voltmeters, with just 3 voltage outputs, the design was evolving over time as soon as I found a new component I liked, I kept changing the design in order for it to show a preview of how should it look like in the enclosure and even after buying and enclosure, I had to redesign it to fit the size of the front panel of the enclosure

Needless to say I ended up changing the analog ammeter for a digital one, print your design; this will help you keep in mind what or how much space you might need to do your power supply

Step 3: 10Amp Board Calculations

Upgrade Note: I should have asked the technician to make my transformer 10v+0v+10v in the secondary, since 9v is not enough for the 12v Regulators to actually Regulate the 12 volts my OPAMPs power supply can barely get to 11.8 volts, which still can feed OP Amps however I couldn’t have foreseen this since it was my first project of this kind and when I noticed it was too late

Now, we have to define which outputs will be able to provide the 10Amps, i decided to make 2 boards,

  • 10A board, with 5v and the variable 0 to 25v both will be able to output up to 10Amp
  • OPAMPS Board, with fixed -12v, 12v, and a variable negative outputs, the 3 of them limited to 1 Amp

These last 3 will be limited to the maximum output current of the regulator 1 Amp, since these will be used to feed mostly OPAMPs, so it makes little sense to amplify its current , each regulator can provide enough current to feed several OPAMPs,

All the outputs will be feed by a single, custom made transformer that will have 3 outputs in the secondary winding, 9v, 0v and 9v, this will allow us to sum up to 18v from the 9v+9v for out LM317 and 0v+9v for all the other regulators, so we will use this as our starting values for our calculations

EMI FilterFN284-6-06

We need a passive electronic device to suppress conducted interferenCe present on the mains, for this we will use an EMI filter rated at 6Amps since our primary current wont surpass 3Amps plus this provides dual fuse holder for live and neutral connections and the case of the filter its connected to mains earth which will allow us to ground our enclosure with little effort

Peak Voltage


18V is the RMS value, to obtain our Peak value we have to multiply it by sqrt(2) so:

Vp= 18v * (1.414) = 25.45 Vp

We will be using this value as our Vmax value from now on

Diode Bridge GSIB2560

To select a diode bridge, we need the maximum power that will flow through the entry of the circuit this is estimated by the maximum current plus a surplus of 30%

Pmax = 10+0.3(10) = 13A

Filtering ECO-S1JA472CA and ECO-S1JA682EA

The filtering capacitor to lower the rise is given by the maximum current, period of the signal after the diode bridge divided by the peak voltage minus the Regulator Dropout Voltage of 2.5v

C1= (Imax(T))/(Vmax-Vmin)

C1= (13A-(1/120Hz))/(25.45-(5 - 2.5)) = 4700uF at 63v

We could also choose a lower value 43v no problem, but since the cost the same we will go with the bigger ones this time

Choke Inductor 7448262510

To protect our circuit against transients, we need inductors at the entry and the output, there is little math involved in the selection of this component so we will just pick up a 25Amp one

Darlington Array MJ11015

To calculate the transistors Base current we need to select a Darlington array transistor first, and then do the calculations for it using its hfe so we will go with MJ11015, since its supposed to be able to hold 30 Amperes of current and work up to 200 degrees C (it doesn’t I actually killed one by getting to 90C), according to its datasheet it has a hfe of 1000, then

Ic= Ib (hfe)

Ib= 10/1000

Ib= 10mA

Ir= Ib+Ireg = 10mA + 100mA = 110mA
R1= Vbe/Ir = 3.5/40mA = 33 Ohm at 10watts

Protection Diode RURG5060

D2 is an ultra-fast recovery diode, to protect the regulator from inverse polarity and short circuits at the output

Output Filtering ECO-S1JA472CA and ECO-S1JA682EA

Same value as input filtering to assure a clean DC signal

Voltage Regulators LM7805 and LM317

For this board we will be using the classic LM7805 for 5v Output, and LM317 for our variable positive output the first is cap capped at 1 Amp max Current and the LM317 can output up to 1.5Amps, however since we are using a resistor to limit the current they will handle very low currents while the Darlington makes the hard job in order for our outputs to output 10Amps, while the voltage regulators, are actually handling 10mA currents

Step 4: OPAMP Board Power Supply Calculations

Most of the entry circuit up to the Diode bridge can be reused for our second low power board, this means we will plug a connector in parallel to the output of the diode bridge, very few values will change, the main difference will be the size of the components, and current capabilities

However you need to be careful with the pins of each regulators, they keep changing from model to model, so make sure you check the datasheets every time, also another thing worth noticing is that you need to turn around the electrolytic caps for all the negative value regulators otherwise they will just blow up

Filtering ECO-S1JA472CA and ECO-S1JA682EA

Peak Voltage

9v is our half secondary RMS value, to obtain our Peak value we have to multiply it by 1.414 or sqrt(2) so:

Vp= 9v (sqrt(2)*2) = 25.45 Vp

We will be using this value as our Vmax value from now on

C2= (Imax(T))/(Vmax-Vmin)

C2= (1A-(1/120Hz))/(12.72-(5 - 2.5)) = 4700uF at 63v

We could also choose a lower value 43v no problem , but since the cost the same we will go with the bigger ones this time Choke Inductor 7448262510

Step 5: Heat Dissipation

The Power Formula P = IV

If a current I flows through through a given element in your circuit, losing voltage V in the process, then the power dissipated becomes heat product of that current and voltage to make sure the regulatoers and darlingtonscan handle the power. we need to undestrand a bit about heat dissipation

TO-220 package is rated can usually dissipate up to 1 W by itself for 1.5 A output current and up to 35 V input voltage. Naively, you might guess that you can hook this right up to 35 V input, and expect to get 1.5 A of output, meaning that the regulator would be radiating 30 V * 1.5 A = 45 W of power.

But the short answer is no, TO220 can’t handle that much power. If you look in the datasheet under the “Absolute maximum ratings” section, to try and find how much power it can handle, all that it says is “Internally limited”, which isnt very clear on its own.

It does turn out that there is an actual power rating, but it’s usually somewhat “hidden” within the datasheet. You can figure it out by looking at the following

  • TOP, Operating junction temperature range: -40 to 125 °C
  • RthJA, Thermal resistance junction-ambient: 50 °C/W
  • RthJC, Thermal resistance junction-case: 5 °C/W

The Operating junction temperature range, TOP, specifies how hot the “junction”, the active part of the regulator integrated circuit, can be allowed to get before it goes into thermal shutdown. (The thermal shutdown is the internal limit that makes the regulator power “Internally limited”.) For us, that’s a maximum of 125 °C.

The thermal resistance junction-ambient RthJA (Often written as ΘJA), tells us how hot the junction gets when

  • The regulator is dissipating a given amount of power
  • The regulator is sitting in open air, at a given ambient temperature.

Suppose that we need to design our regulator to only work under modest commercial conditions, that will not exceed 60 °C. If we need to keep the junction temperature under 125 °C, then the maximum temperature rise that we can allow is 65°C. If we have RthJA of 50 °C/W, then the maximum power dissipation that we can allow is 65/50 = 1.3 W, if we are to prevent the regulator from going into thermal shutdown. That’s well below the 4 W that we would expect with a 1 A load current. In fact, we can only tolerate 1.3 W / 4 V = 325 mA of average output current without sending the regulator into thermal shutdown. This, however, is for the case of the TO-220 radiating to ambient air– almost a worst-case situation. If we can add a heat sink or otherwise cool the regulator, we can do much better.

The thermal resistance junction-case, RthJC. This specifies how much temperature difference you can expect between the junction and the outside of the TO-220 package: only 5 °C/W. This is the relevant number if you can quickly remove heat from the package, for example if you have a very good heat sink hooked up to the outside of the TO-220 package. With a big heat sink and perfect coupling to that heat sink, at 4 W, the junction temperature would rise only 20 °C above the temperature of your heat sink.

You can then verify the couplings and relative temperatures of each component with a spot-reading non-contact infrared thermometer ot ar a thermocouple.

Step 6: TO-3 Darlington Heat Disippation

We need heat dissipation for our Darlington’s, since the currents above 500mA will be flowing through them, a dargliton array has a base, emitter and collector, in the TO-3 package the case itself it’s the collector, meaning the case its part of the circuit

We will need to buy some specific, items in order to insulate them from the heat sink itself, the chassis from the pins and, to be very careful of not short circuiting anything around them, this is probably the most complicated part, in the entire design, since not only we have to solder AWG 14 wiring to each pin of our Darlington’s, we also need to be able to insulate the pins that go through the enclosure box itself, and we also need to add an insulator to the TO 3 case, here’s how to do it.

The metal package can be attached to a heat sink, making it suitable for devices dissipating several watts of heat. Thermal compound is used to improve heat transfer between the device case and the heat sink.

Since the device case is one of the electrical connections, an insulator is required to electrically isolate the component from the heat sink.

TO 3 insulating mica

Allows us to insulate the Darlington from the case itself, it may be made of mica or other materials with good thermal conductivity in order to dissipate the heat

Insulating washers

These allow us to insulate the screws that hold the TO3 in place to theheat sink and to the chassis by using metal screws they become part of the collector, by touching the case, an alternative is to use nylon screws, that wont be conductive, however they are not as strong as metal screws

Thermal Compound

We can’t actually see it, but there is air and lots of holes between the mica and the chassis, we need to fill that air gap between the mica, and the case with thermal compound this will allow the system to have a better thermal conductivity and the heat sink will take most of the heat

Heat Shrink

We will have to solder the emitter and base pins together along a AWG 14 cable, there is a lot of stuff going on inside the case, so to be sure we don’t get any kind of shot circuit problems with the pins we might as well insulate them using heatsrhink

Step 7: Prototyping and Testing

Now that you have gathered all your components you might want to spend some time in the breadboard sadly the size of the components can actually damage and deform the internal pins and the plastic holes, this might be a problem but nothing we can’t deal with a bit of creativity, remember that the maximum current that the breadboard can handle goes around 3A, after that it just starts melting

To test the Darlington’s you might want to buy the following resistors

  • 2Ω 25W
  • 1Ω 25W
  • .5Ω 50W

The higher the wattage the higher it can hold together at higher currents

Let’s have an example using the LM7805 that can output 5v

Using Ohms law we know that

V = IR

or

I=V/R

We can calculate the theorical output current using every resistor

I = 5v/2Ω = 2.5A

I = 5v/1Ω = 5A

I = 5v/.5Ω = 10A

To do this test you might want to use a good quality silicon Banana-Alligator cables thick enough to handle the current that will flow through the resistor and an ammeter in series with fuses big enough to handle the maximum output current, if you don’t have this kind of ammeter, then you can just avoid testing the .5Ω resistor.

Just make sure you do the math before doing this , and be careful with the time you leave them plugged since the breadboard can start melting and the resistor can start getting to way hot to touch up to 150C

Eventually something will start burning, the current its way to much for the little AWG 20 wires i used and for the breadboard, so you will barely have time to see if the circuit is actually working as intended, you can start by testing the Vreg only to make sure you have all your connections fine, and then you add the Darlington to test it using your resistors individuality, but remember you need to be fast and always ready to deactivate the input power to your breadboard

Step 8: PCB Design

Now for the design I used Altium Designer, you can use your preferred PCB Design software, however no matter what software you use, there are few “rules” to might want stick to for this 10A design

  • Fiber Glass 1oz copper clad (Can handle more heat)
  • 40Mils per Amp
  • 10mils between tracks
  • Ground Plane
  • One side PCB

From the 1st PCB you can see that the tracks are huge, it mostly depends of the thickness of your pcb but if you don’t know what thickness does your copper clad have then its most likely a 1oz copper clad (the thinnest) , you can’t trust the auto-router to do this job, you will literally have to route every single line manually, in order for it to stay 1 side PCB, this will take a considerable amount of time in order to get it right, you might want to start by drawing your ground line around the area of your PCB this will allow you to quickly get to the ground no matter where your components are, but still try to remember that PCB design is 90% placement and 10% routing

I did my print my circuit board using a single face PCB, since as I said at the start of this guide this was my 1st PCB I had ever done, and I had the theory and information to do a double side board but I decided not to in an attempt to keep it as simple as possible and lower the chances of error

As you can see from the pictures I had to bridge using an AWG 12 wire, it took me around 2 days to come to the conclusion that it can’t be done, completely in one face and so I decided to “cheat” and bride it,

Another thing you need to take into consideration is that you might want do measurements one by one your components using either a Vernier or the manufacturers datasheet , this will allow you to draw the footprints of your components, after you think you have it as it should be, you can print it out use this foam rubber and star plugging your components there, this way you can decide if you have enough space to solder, or just verify if you have enough flexibility, this is quite useful, to have a “physical preview” of your PCB

Step 9: Testing Phase

This is the time of truth, all the theory finally has become a physical project, in order for you to test the circuits you will end un using the high power resistors and your ammeter

To test your circuits might want to use a good quality silicon Banana-Alligator cables thick enough to handle the current that will flow through the resistor and a multimeter in series with fuses big enough to handle the maximum output current , if you don’t have this kind of ammeter, then you can just avoid testing the .5Ω resistor.

Just make sure you do the math before doing this , and be careful with the time you leave them plugged since the breadboard can start melting and the resistor can start getting to way hot to touch up to 100C

Eventually something will start burning, the current its way to much for the little AWG 20 wires i used and for the breadboard, so you will barely have time to see if the circuit is actually working as intended, you can start by testing the Vreg only to make sure you have all your connections fine, and then you add the darlignton to test it individuality

Step 10: Preparing the Enclosure

We need to drill the enclosure, in my case this was probably the hardest step since I was using a really big, and thick metal enclosure

To start the drilling phase I used tape to stick the printed predesigned panel made in Corel to the chassis, I had to drill first using 1/32 Drill bits, to “draw” the contour of the components, slowly and every 2 millimeters, and then I used a ¼ drill bit in order to take the metal piece completely off, if you follow my steps you really need to have a lot of patience if you use a metal enclosure like mine, in my case it took me 2 entire days to complete drilling the entire panel, and my arms were ended up in pain since im not used to do this kind of work,

It might be easier if you use an acrylic enclosure or any other kind of material, is up to you to this point, after ending the drilling and sanding the sharp things, in order to take off all the residues of the drilled edges, this will is probably the most dangerous part, you might want to use protection glasses, a mask and gloves to do this, I ended up using a sandpaper and sometimes a dremel however the dremel has problems with its own disposable metal sanding bits, they run out really fast, so I ended up using a sandpaper for most of the edges, if you have any magnets around you can use them to pick up the metal residue from your work area, just make sure you don’t have any kind of electronics or fans while you work with metal since it can cause havoc around your work area

Step 11: Panel Devices

Panel Led Indicator 127vAC

How to make sure that the EMI filter fuses are actually ok? Well you do it by adding a Panel LED indicator light to the main panel, this green led will turn on as soon as the EMI filter gets AC power this allows you to tell that the rear fuses are ok and that you can turn on the power supply, right below it, it’s the turn on sptd switch, this one also has a back light in order to tell if it’s on or off,

SPDT Switch 120v 15A

Right below the Led indicator, in series we can find an rocker switch, this one will help us to turn on or off as fast as possible the supply in case of an emergency (mostly electronics getting burned), this one also has its own back light, you need to make sure the rocker switch can handle the 120vAC in order for it to work, (I plugged a 12v one at my 1st attempt)

Digital voltmeter Four Digit 0.36" Red and Blue LED digital voltmeters

We have 5 voltage outputs, but we only need to have displays for 2, the variable positive and negative ones, these 2 we will use red voltmeter for the positive voltages and a blue for the negative ones, as you well now voltages are measured in parallel, however these voltmeters also need to be powered up, how do you power up meters? Well... for once you can use the inputs of your +-12v power supplies,

Digital ammeter Three Digit 0.56" Green digital voltmeter

Current is measured in series, we only have 1 ammeter and we will use it for the biggest output power supply (the positive variable one LM317)

Temperature meter Yellow 3 Digit

In order to make sure the darlingon transistors that already have a heat sink do not die (I blew one by reaching the maximum temperature) we need some kind of meter hanging around back there with our heasink, this will work as a warning when the temperature goes to high, and we can either shut down the supply or let it go on, the probe needs to be between the heat sink and the Darlington, to have the best possible measurement of temperature, but keep it safe and use a 10% tolerance in the measurement you see, it will update in real time but the Darlington array I killed died when the meter had a 79 in it, (so it probably got to 100C)

Most of the meters are being feed by the 5v power supply, since it can also handle 10amps, some other need more voltage so they are being feed by the 12v power supply

Multiturn potentiometers Bourns 15 Turns

This one is a must for any kind of variable power supply, the multiturn potentiometers will allow us to set any voltage to both variable voltage regulators in 15 turns, and this means we can have exactly the value we want with minimum effort saving time and energy,

Multiturn potentiometers knobs H-22-6a Bourns 0-15

If we have spent all that money in the circuit, we better get fancy with the potentiometers, these caps also allow the user to set the presition of the turn by making them easier or harder to turn, you can also set them to a locked position, and they have a tiny little indicator for the turn number

Step 12: Fuse Blown Indicator Circuit

We need protections for our outputs, as well as indicators to tell us when such protections have been activated typically a short circuit will destroy our fuses, in order for it to protect our load and our power supply, and prevent it to get damaged (or burned)

You might be thinking about using a polyfuse which is a resettable fuse (I did) however the response in time of the resettable fuses is not as good as a simple fast acting glass fuse, and they also decay over time

In short, stick to the fuse holder and our trusty glass fuse, it might be annoying to change them constantly if required but it’s probably the best protection to stop something as catastrophic as a short circuit,

You have 2 options here, Simple indicator and MOSFET indicator, whatever you chose will have its fuse holder in the chasis anyway

  1. Simple indicator.- the easiest of the fuse blown indicator circuits, in this circuit, when the fuse blows the current needed to turn on the circuit flows through the load, meaning that if you unplug the load from your power supply it will turn off, it will also be as bright depending on the impedance of the load
  2. Mosfet Indicator In the mosfet circuit you don’t need an actual LOAD for the led to turn on, as soon as your fuse blows, you will see the led on with or without load at maximum brightness assuming you calculate the resistor right using ohms law, about the mosfet basically gets activated by a voltage above 2.5v between Source and gate, this allows the current to flow from Source to Drain in the circuit, using the PMOS for positive voltage and NMOS for negative voltage, the zener diodes are there to protect the gate from any kind of transient that can kill the gate, in the NMOS the led goes fliped since im using negative voltages from the source

Step 13: Tunning It Up

Our circuit works, its protected, however its missing a bit of art, I was getting all kind of jokes about burning the building down with the power supply so i decided to make it symbolical and add flames to the enclosure, using adobe illustrator i designed a couple vectors, printed the outlines and just used scissors to carefully cut them as intended and finally paste them to the enclosure along with my college logotype at the top of it

Step 14: Conclusion

If you got to this step congratulations, you have a lot of patience and a lot of stamina to keep reading up to this point, hopefully you might learn something from this guide and do an even bigger amperage power supply, maybe a 25Amp, it will be a lot of work and sacrifice but the reward is just as big if not even bigger, a power supply is one of the projects that you have to do, because it will teach you the basis of electronic design and if you keep going in the electronics way it will be useful, i will keep up reading the comments and updating this guide going into deep detail of everything that i havent explained yet slowly every weekend new content should arrive, until every single thing in this guide can be replicated or upgraded

Step 15: Costs, Mistakes and Something More

Lucky few mistakes were made, many had something to do with fans, be sure to add a protection to the fans so no one can put a finger in there and break a wing!

<p>Awesome job. Beautifully built! Well done and bravo!</p><p> Comments (constructive criticism from my own mistakes):</p><p>When I build power supplies, I always design for 100% overkill. This means if I want 200W output, I design for 400W.</p><p>Also if our supplied voltage sags 3-4 volts and we end up with only 3 volts Vce on pass transistors, regulated voltage suffers.</p><p>Use much larger heat sinks on pass transistors, too. Each 10 degrees Centigrade collector junction increase cuts the life expectancy of the transistor by 50%.</p><p>Outputs should always be minimally loaded (around .5 Watt) and around .1 Mfd. disc ceramics.</p><p>ALL grounds should be connected to ONE POINT with shortest possible wires to prevent parasitic oscillation.</p>
<p>Thanks for sharing your experience, i was kind of using that overkill rule probably not 100% but yes I was handling a 50 to 80% tolerance, you can notice in the component selection that whatever value I calculated was used as a reference to get the NEXT high common commercial value, (sometimes the double) the custom made transformer it&rsquo;s actually a 15Amper one, however the design was made considering it can hold 10Amps, </p><p>The heat sink for the Darlington&rsquo;s was the biggest I could find at the moment ,I also had to remove the black painting from the case to use the entire rear of the enclosure as heat sink, I added some thermal paste to join the enclosure with the heat sink</p><p>Another thing worth mentioning is that I added that huge fan to blow to the 2 cards inside the enclosure when I should have had setup a fan for the Darlington transistors instead along the heat sink, I didn&rsquo;t think about it then, but I will make sure to add a section about this in the next days</p><p>The grounding was done at the entry of the circuits (right before the diode bridge), also worth mentioning, the EMI filter case has a ground earth connection, this means the entire enclosure has been grounded trough the screws that hold the EMI filter in place, providing ground fault protection in the entire enclosure, this can also be dangerous since a bad connection can short out the entire device and blow your home fuse or trip the thermomagnetic switch, but it&rsquo;s a protection worth having</p><p>Thank you sir for your comment and interest in sharing it</p>
<p>Hi Vazerik, I am also graduated from the ESIME, I just have a question based on the squematic: Looks that the lowest voltage this power supply con go is actually 1.25V, and not 0 V, do I am correct?</p>
<p>hola... veo que eres de ESIME .. yo soy de ESIME Culhuacan ... una pregunta.. donde compraste ese modelo de borneras banana de colores.. por que no las eh conseguido?.</p>
<p>Felicidades! Tu proyecto est&aacute; muuuy bien hecho, ando ahorita haciendo una fuente (Tambi&eacute;n para electr&oacute;nica lineal de la ESIME) y estoy d&aacute;ndome de topes con un par de cuestiones de p&eacute;rdidas de voltaje. Leer&eacute; a fondo todo lo que escribiste y estoy seguro de que me ayudar&aacute; mucho. Saludos y gracias!</p>
<p>P.S. You may find much less expensive components at mcmelectronics.com.</p><p>This is where I purchase most of my components.</p>
<p>You can also use octopart.com it indexes most of the electronic components suppliers aviable (including MCM Electronics) and shows you the same component in all the sites giving priority to the lowest price first</p>
<p>Thank you for that tip, sir.</p>
<p>That is incredible work! I am new to instructables and was looking for a way to make a bench supply from a pc power supply when I stumbled upon you build. This is WAY beyond me (at least for now). I'm a software guy whose trying to teach himself a bit of the electronics side. Just getting started and amazed that you did that in college.</p><p>Great work!</p>
<p>Congratulations, great job.</p>
<p>Awesome job, thanks for the built.</p>
<p>Very nicely done, and it is clear that you put a lot of thought into the design. The only thing that I fail to understand is why you would choose to use a linear regulator for a high current supply. Switch mode supplies are not hard to design and the difference in efficiency is enormous.</p><p>Wasted energy is important even in our hobbies.</p>
<p>As I said in step one, this was my first time doing something like this (a PCB), this was a project for 1 of the courses at my college, called &quot;Linear Electronics&quot;, I just wanted to do it as big as possible, I am currently designing a 45 Amper switching power supply, and yes, they are more efficient but they have problems with, Harmonics and power factor, which it&rsquo;s not present in linear regulators, my guess is that there still have to be a method to create power supplies without wasting energy and without having electrical harmonics, I wonder if we will ever get to see that day</p>
<p>Awesome instructible! Thanks a lot for sharing! From my point of view it is very detailed and complete, yet not too much. I have the feeling u have a profound understanding of the topic, but don't loose yourself in gimics! <br>Refreshing to read and thanks for the insights of how u work! I love it!</p>
Top job, well done! I suspect you're pleased and the other students are jealous!
<p>Hello. Where you able to source the metal enclosure in Mexico? Any leads you can give me? Thanks!</p>
<p>There&rsquo;s a business called named CASA TORT here at Mexico&rsquo;s city down town, https://goo.gl/maps/aE0cJ they are specialized in making all kinds of enclosures, they even make steel ones, I went there in picked up a smaller version of this one, I noticed it wasn&rsquo;t big enough, sold it to a classmate and then went to buy another one of the same model but bigger</p>
<p>Thank you! Their web page is down but I'll try calling them.</p>
<p>I absolutely love this project. It is arguably one of my favorite instructables I have seen. I can barely believe english is not your first language!</p><p>I was curious as to where you got that enclosure. I like it a lot. Do you know what type it is, or where I could find it?</p>
<p>Thanks for your support, im still updating the chapters and i plan to add at least 3 more, so be sure to check them out in the near future, about the enclosure, there&rsquo;s a business called named CASA TORT here at Mexico&rsquo;s city down town, https://goo.gl/maps/aE0cJ they are specialized in making all kinds of enclosures, they even make steel ones.</p>
<p>The inductors L1, L2 and L3 are of common mode chokes, these inductors work with a flux practically zero in their core. If you use them as a single inductor (the two windings are in parallel) in DC, the core of these inductors saturates and the inductance falls down. It's like having an inductor of a few coils wrapped in air. If you want to have an DC inductor you should use cores with air gap or iron powder cores like KoolMu manufactured by Magnetics.</p><p>I appreciate your commitment to make the circuit.</p><p>Stefano</p>
<p>thanks a lot, to be honest at the time i had to design the PCB, when i got these inductors i had no idea how to use them this actually i was really confused and only until your comment, as you can see in the following link, http://electronics.stackexchange.com/questions/170156/how-to-use-common-mode-choke-inductors-differential-vs-common-mode , today im still trying to figure out the exact difference betwen common mode and differential mode,i will really dig into your comment in order for a future revision 2 of the circuit </p>
<p>vaserick: Step 4, several lines down, sqrt(2) = 1.414 not 0.707 which is the inverse!</p>
<p>Got it, , you are right, just edited that part</p>
<p>It's a work of art.... Well done.</p><p>Now you'll need to build a good, robust dummy load to test it, instead of using resistors.... :)</p>
<p>Now this is interesting I never heard about this dummy load, I will get into it asap, at first glance it looks like it&rsquo;s just a bunch of power resistors in parallel I have successfully tested the power supply up to 9.9Amps with a single resistor, but I have yet to test it using a bunch of resistors in parallel, the effect should be the same due to resistors in parallel having an equivalent impedance, with the main differience of the darlingtons heating up way more quickly than the entire resitors array... i might need a bigger heatsink for this, but still I will read more about this topic in the weekend, and might attempt to do it just to verify, if I end up doing it, I will add a chapter about testing, and how did it work out, thanks for the comment lee</p>
<p>Hi vazerick, congratulations on your project and it looks really cool. I am also building a power supply mine being a mix of switching and linear type. Am still working on it and will post it here when i finish it. I uploaded an electronic dc load capable of 10 amps here on Instuctables if interests you.<strong> </strong><strong>https://www.instructables.com/id/A-200-watt-Electronic-DC-Load/</strong> You can also use used car headlamps as load, i get mine from the local car electrician for free as i tell him to save them for me instead of trowing them away. I am referring for the ones with one broken filament but the other will still be of some use. hook them in parallel series etc.</p>
<p>Nice Project</p><p>I did something similar during my education. (We also had to build the transformer and the case from scratch...)</p><p>What i miss in this project, the variable voltage doesn't go down to zero and there is no variable current limit (also down to zero). This would require a negative voltage of course, making the design a bit more complicated. But for a Lab/Bench supply, i'd do it.</p><p>When i remember correctly, we used a LM723 and 2 or 3 parallel power transistors in the output stage, with a darlington stage to drive them. (33 years ago ;-)</p>
<p>During development (around step 3) it was contemplated to have a potentiometer to limit the current output however due to time constraints (it had to be done in 2-3 months max) , the lack of space in the front panel for another potentiometer, and the amount of components inside of the enclosure (I will add pictures and a chapter about this on the weekend), I ended up not implementing it, I do have a schematic around about how to limit the current, If ever do a second revision of this power supply I will make sure to fix all the mistakes made in this one and I will make sure to add the current limiting feature along with many other features that I keep up pilling on my list, and why not?, I might even start working from the schematic you just posted seems like fun, thanks for sharing</p>
<p>Circuit diagram of a easy way, to generate a negative voltage for such a application.</p><p>The part under the ground line could be used for a LM317 circuit as well.</p>
<p>Felicidades en tu manejo del ingl&eacute;s!. El proyecto es interesante</p>
<p>Muchas gracias estoy al pendiente de lo que se tenga que corregir y maejorar, si encuentra algun detalle que corregir no dude en hacermelo llegar por este medio, lo atendere a la brevedad posible</p>
<p>Hi, where you say &quot;lime&quot; the word in English is file. </p>
<p>Thank you, Apparently I wrote that word without thinking, I fixed the entire paragraph, the word I was looking for was actually &quot;sanding sheet&quot; not lime, BTW I love lemons, I was probably thinking about them</p>
Ok ? I know &quot;lima&quot; means file (the metal rasp kind) in Spanish and also lime, the fruit. The common word for &quot;sanding sheet&quot; (papel de lija) is sandpaper. Your English is really terrific!
<p>double edit, thanks a lot </p>
welldone.. and keep it up.. if you need any kind of help .. I will be with you..
<p>WOW, so awesome. Very nicely done and written up. Not only is the project interesting you gave details, information and learnings that is great for people like to me better understand instead of just following a recipe. I want one of these but I think it is out of my realm of skills at this point.</p>
<p>That&rsquo;s exactly what i thought when I started working on it, that this was out of my realm of skills, I assure you that if I could make this, you can do it too, and you can probably do it even better than me, like most of the things in this world, you just need to want to do it!</p>
<p>What was your true cost to build this on your own?</p>
<p>Around 430 USD + another 50 USD to mend up mistakes, 3 months of daily work, I had to ask my mentor how to do some stuff using WhatsApp and physically show him some other stuff, then he would give me advice about how to do it, I also used online a lot, google and electronics.stackexchange.com/ for more electrical/electronic related questions, sometimes I would replicate the question in the EEVBLOG, the idea was that if one I couldn&rsquo;t do something because I didn&rsquo;t know how to do it, I would just ask how was it done online and almost always in the next morning I already had an answer from someone in the internet, something else to note about the costs is that Newark, charges around 20% more in every component to make up for the shipping and taxes to my country so in theory if you live in the United States you should cut around 20% to each component from Newark element14, I mainly used newark because, they ship internationally in 3 days, and they have no minimum amount of order, you can buy 1 resistor that costs .05 cents and they will ship it to you in 3 days, however I do know there are others sites that are less expensive, like mouser, digikey, mcmelectronics, i know some of them have a minimum order of 50 USD to ship it for &ldquo;free&rdquo; while newark already charges the shipping and taxes in the price of the products, you can also use octopart to look for better prices in the same components, I just used newark for the convenience and the shipping times</p>
<p>Really nice build. Well done :)</p>
<p>Nice job, I like your blown fuse indicator discussion and enjoyed reading about your project. The completed case looks fantastic. Thanks Vazerick.</p>
<p>:A good practical circuit..The following line may please be corrected.</p><p>18V is the RMS value, to obtain our Peak value we have to<em><strong> multiply it by 0.707 or sqrt(2) so:</strong></em><em><strong>......</strong></em></p><p><em><strong>(X 1.414)</strong></em></p>
Im on it, thanks for your time to read it and verify
<p>I have to say, your English is better than most web blogs. Great work. Thanks.</p>
Hey, great project! I think there might be a mistake in step 3, when calculating peak voltage. You need to multiply by sqrt(2) or divide by 0.707, not multiply!
<p>ill check it out and get it fixed, thanks </p>
<p>&quot;The guide is a bit long, as i said please beware, English is my 2nd <br>lenguage, if you find any grammar , calculation or technical mistakes <br>please let me know , and I will review it and see them fixed ass soon as <br> possible.&quot;</p><p>Ironicly there's a mistake in this paragraph. It should be &quot;as soon as possible&quot; ;)</p>
<p>Damn that one its quite embarrassing :)</p>

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