Introduction: How to Make a Bench Power Supply

A bench power supply is an extremely handy bit of kit to have around for electronics hobbyists, but they can be expensive when purchased from the market. In this Instructable, I will show you, how to make a variable lab bench power supply with a limited budget.It is a great DIY project for beginners as well as any one interested in Electronics.

[ Play Video ]

The main objective of the project is to learn how a linear power supply unit works.In the beginning,to explain the working principle of a Linear Power Supply, I have taken an example of LM 317 based power Supply.For making the final Power Supply, I purchased a Power Supply kit from Banggood and assembled it.

This is a high quality stabilized voltage supply with which the voltage can be regulated continuously, and the range in which to regulate the voltage is 0-30V. It even contains a current limit circuit which can effectively control the output current from 2mA to 3A with the ability to regulate the current continuously, and this unique feature makes this device an indispensably powerful tool in the circuit lab.

Feature:

Input voltage: 24V AC

Input current: 3A maximum

Output voltage: 0 to 30V continuous adjustable

Output current: 2mA - 3A continuously adjustable

Output voltage ripple: minimum 0.01%

Step 1: Tools and Parts Required

Parts List :

1. Step Down Transformer - 24V, 3A ( Jaycar )

2. DIY Power Supply Kit ( Banggood / Amazon )

3. Heat Sink and Fan ( Banggood )

4.Volt-Amp Panel Meter ( Amazon )

5. Potentiometer Knob ( Banggood )

6. Buck Converter ( Amazon )

7. USB Port ( Amazon )

8.Binding Post Banana Plug ( Amazon )

9. IEC3 Power Socket ( Banggood )

10.Rocker Switch ( Banggood )

11. Green LED ( Amazon )

12. LED Holder ( Banggod )

13. Heat shrink Tube ( Banggood)

14. Self Adhesive Rubber feet ( Amazon )

15. 3D printing filament-PLA ( GearBest )

Tools/ Machine Used

1. 3D Printer - Creality CR-10 ( GearBest )

2.Soldering Iron ( Amazon )

3. DSO- RIGOL ( Amazon )

4. Glue Gun ( Amazon )

Step 2: Basic Block Diagram

Before heading in to the making process, you should know the basic components of a Linear Power Supply.

The main elements of the linear power supply are:

Transformer: The transformer changes the ac mains voltage to a desired value. It is used to step down the voltage.This also serves to isolate the power supply from the mains input for safety.

Rectifier: The power output of the transformer is in AC, this needs to be converted to a DC.The bridge rectifier converts AC into DC.

Input Smoothing Capacitor / Filter: The rectified voltage from the rectifier is a pulsating DC voltage having very high ripple content. But this is not we want, we want a pure ripple free DC waveform.The filter circuit is used for smoothing out the ac variations( ripple) from the rectified voltage.Large reservoir capacitors are used for this.

Linear regulator: The output voltage or current will fluctuate when there is change in the input from ac mains or due to change in load current at the output of power supply.This problem can be eliminated by using a voltage regulator.It will maintain the output constant even when changes at the input or any other changes occur.

Load : Application Load



Step 3: Transformer

Input high voltage AC going into a transformer which usually steps down the high voltage AC from mains to low voltage AC required for our application.For designing the Power Supply,the transformer secondary voltage is selected by considering the the output voltage of the power supply, losses in the diode bridge and the linear regulator. A typical waveform of 24V transformer is shown above.In general we allow about 2V - 3V drop for the bridge rectifier configuration.So the transformer secondary voltage can be calculated as below

Example :

Suppose we want to make a power supply with output voltage of 30V and 3A.

Before the bridge rectifier the voltage must be = 30 + 3 = 33V ( Peak )

So the RMS voltage = 33 /sq root (2 ) = 23.33 V

The nearest voltage rating transformer available in the market is 24V. So our transformer rating is 230V/24V ,3A .

Note : The above calculation is a rough estimation to buy a transformer.For accurate calculation you have consider voltage drop across diodes,voltage drop of the regulator, ripple voltage and rectifier efficiency also.



Step 4: Bridge Rectifier

The rectifier bridge convert an alternating voltage or current into corresponding direct Current (DC) quantity. The input to a rectifier is ac whereas its output is unidirectional pulsating DC.

The voltage drop across a general purpose diode is around 0.7V and schottky diode is 0.4V. At any instant two of the diodes in the rectifier bridge are in operation.But since the diode conducts heavily, it may effectively be higher. A good safe value is twice the standard or 0.7 x 2 = 1.4V.

The DC output after the bridge rectifier is approximately equal to the secondary voltage multiplied by 1.414 minus the voltage drop across the two conducting diodes.

Vdc = 24 x 1.414 - 2.8 = 31.13 V

Step 5: Smoothing Capacitor / Filter

The rectified voltage from the rectifier is a pulsating DC voltage having very high ripple content. The large ripples that exist in the output makes it almost impossible to be used in any powering application. Hence a filter is used.The most common filter is by using a large capacitor.

The resultant output waveform after the Smoothing Capacitor is shown above.

Step 6: Regulator

The output voltage or current will change or fluctuate when there is change in the input from ac mains or due to change in load current at the output of the regulated power supply or due to other factors like temperature changes. This problem can be eliminated by using a regulator IC or by a suitable circuitry consisting of few components. A regulator will maintain the output constant even when changes at the input or any other changes occur.

IC’s like 78XX and 79XX are used to obtained fixed values of voltages at the output.Where as IC’s like LM 317 we can adjust the output voltage to a required constant value.The LM317T is an adjustable 3-terminal positive voltage regulator capable of supplying different DC voltage outputs other than the fixed voltage power supply.The above example circuit uses a LM3 17 voltage regulator IC. The rectified output from the full wave bridge rectifier is fed to a LM317 regulator IC. By changing the value of potentiometer used in this circuit, the output voltage can be controlled easily.

Till now I have explained how a Linear Power Supply unit work.In the proceeding steps, I will explain the building of Bench Power Supply by assembling a DIY kit.

Step 7: ​How the Power Supply Kit Works

The working of the kit can be understood by following the schematic diagram shown above.

To start with, there is a step-down mains transformer with a secondary winding rated at 24 V/3 A, which is connected across the input points of the circuit at pins 1 & 2. (the quality of the supplies output will be directly proportional to the quality of the transformer). The AC voltage of the transformers secondary winding is rectified by the bridge formed by the four diodes D1-D4. The DC voltage taken across the output of the bridge is smoothed by the filter formed by the reservoir capacitor C1 and the resistor R1. The circuit incorporates some unique features which make it quite different from other power supplies of its class. Instead of using a variable feedback arrangement to control the output voltage, our circuit uses a constant gain amplifier to provide the reference voltage necessary for its stable operation. The reference voltage is generated at the output of U1.

The circuit operates as follows: The diode D8 is a 5.6 V zener, which here operates at its zero temperature coefficient current. The voltage in the output of U1 gradually increases till the diode D8 is turned on. When this happens the circuit stabilises and the Zener reference voltage (5.6 V) appears across the resistor R5. The current which flows through the non inverting input of the op-amp is negligible, therefore the same current flows through R5 and R6, and as the two resistors have the same value the voltage across the two of them in series will be exactly twice the voltage across each one. Thus the voltage present at the output of the op-amp (pin 6 of U1) is 11.2 V, twice the zeners reference voltage. The integrated circuit U2 has a constant amplification factor of approximately 3 X, according to the formula A=(R11+R12)/R11, and raises the 11.2 V reference voltage to approximately 33 V. The trimmer RV1 and the resistor R10 are used for the adjustment of the output voltages limits so that it can be reduced to 0 V, despite any value tolerances of the other components in the circuit.

Another very important feature of the circuit, is the possibility to preset the maximum output current which can be drawn from the p.s.u., effectively converting it from a constant voltage source to a constant current one. To make this possible the circuit detects the voltage drop across a resistor (R7) which is connected in series with the load. The IC responsible for this function of the circuit is U3. The inverting input of U3 is biased at 0 V via R21. At the same time the non inverting input of the same IC can be adjusted to any voltage by means of P2.

Let us assume that for a given output of several volts, P2 is set so that the input of the IC is kept at 1 V. If the load is increased the output voltage will be kept constant by the voltage amplifier section of the circuit and the presence of R7 in series with the output will have a negligible effect because of its low value and because of its location outside the feedback loop of the voltage control circuit. While the load is kept constant and the output voltage is not changed the circuit is stable. If the load is increased so that the voltage drop across R7 is greater than 1 V, IC3 is forced into action and the circuit is shifted into the constant current mode. The output of U3 is coupled to the non inverting input of U2 by D9. U2 is responsible for the voltage control and as U3 is coupled to its input the latter can effectively override its function. What happens is that the voltage across R7 is monitored and is not allowed to increase above the preset value (1 V in our example) by reducing the output voltage of the circuit.

This is in effect a means of maintaining the output current constant and is so accurate that it is possible to preset the current limit to as low as 2 mA. The capacitor C8 is there to increase the stability of the circuit. Q3 is used to drive the LED whenever the current limiter is activated in order to provide a visual indication of the limiters operation. In order to make it possible for U2 to control the output voltage down to 0 V, it is necessary to provide a negative supply rail and this is done by means of the circuit around C2 & C3. The same negative supply is also used for U3. As U1 is working under fixed conditions it can be run from the unregulated positive supply rail and the earth.

The negative supply rail is produced by a simple voltage pump circuit which is stabilised by means of R3 and D7. In order to avoid uncontrolled situations at shut-down there is a protection circuit built around Q1. As soon as the negative supply rail collapses Q1 removes all drive to the output stage. This in effect brings the output voltage to zero as soon as the AC is removed protecting the circuit and the appliances connected to its output. During normal operation Q1 is kept off by means of R14 but when the negative supply rail collapses the transistor is turned on and brings the output of U2 low. The IC has internal protection and can not be damaged because of this effective short circuiting of its output. It is a great advantage in experimental work to be able to kill the output of a power supply without having to wait for the capacitors to discharge and there is also an added protection because the output of many stabilised power supplies tends to rise instantaneously at switch off with disastrous results.

Credit :This section is not written by me rather it is taken from electronics-lab.com.The full credit goes to the original author.

Step 8: Identify the Components in the Power Supply Kit

Before stating the assembling of the kit read the Instruction manual carefully.

The kit come with all the components mixed together in a single packet.So, it is recommended start working by identifying the components and separating them in groups like : transistors,Opamps,Regulator,Potentiometers and the connectors.This really save a lot of time during the building of the kit.

Step 9: Identify the Resistors

In the power supply kit, the highest number of components used are resistors of different values.In the kit the resistors packed in a bunch and their values are not labeled. So we have to manually measure the resistance value by using a Digital Multi-meter.I measured the values and written on the small strip of paper in the resistor leg.

Step 10: Soldering the Components

The thumb rule for soldering the components on the PCB is " Solder the components according to their height". Always start with smaller height components.First I solder all the resistor,then diodes,then ceramic capacitors,then transistors then Opamps and so on.Use a pliers when bending bridge diodes legs to avoid breaking.In the kit there is no DIP Base for Opamps, so I used the base from my own stock.

Note : Do not solder the 3mm LED, as we are going to connect wires from LED to be mounted on the front panel.

Step 11: Soldering the Power Transistors

The metal part of the high power transistor ( 2SD1047 ) and medium power transistor ( 2SD882 ) is attached to the heat sink, making it suitable for devices dissipating several watts of heat.The heat sink for transistor 2SD882 is included in the kit.So you have to buy a separate heat sink for the other transistor ( 2SD1047 ).But good thing is that the perfect size heat sink matching with the PCB outline and along with a Cooling fan is available from the same manufacturer. You can buy it from Banggood.

Thermal compound is used to improve heat transfer between the device case and the heat sink.

Step 12: Prepare the Potentiometer

The potentiometer could be placed directly onto PCB, and could also be lined onto the board through its socket and wires. Potentiometer tagged with A is the current limit potentiometer and V is the voltage potentiometer. The voltage potentiometer could be substituted by 10K multi turn wire-wound potentiometer at your own will, with which you could adjust in a more accurate way.

As we want to install the potentiometer in our enclosure, we have to solder the the PCB board through the JST connectors in the kit.

First insert the heat shrink tubes in to the 3 wires of the JST connector and then solder the wires to the legs of the potentiometer. Then cover the soldering joint by heat shrink tube and apply heat all around to give the final touch.For better understanding you can see the above picture.

Step 13: Wiring Diagram for Input Power Socket

I used a IEC 3 Pin 320 C14 Socket for power input.It has inbuilt power socket,fuse for protection and a switch.The connection diagram is shown in the above image.The red and blue wire in the diagram is connected to the primary side of the transformer.I have left the ground connection ( green wire ), if you have a metal enclosure, you can connect it.

Step 14: Volt-Amp Dual Display Meter Wiring

My Volt-Amp meter display had thick black, red and blue wires. Thin ones are red and black for power supply for chip itself.The wiring diagram is as follows :

● Black line (thin): vacant or module negative

● Red line (thin): power supply positive

● Black line (thick): Common measuring (GND )

● Red line (thick): Measuring terminal voltage input positive

● Blue line (thick): Current input+

Please refer to the wiring diagrams for more details

Step 15: Make the USB Circuit

Another optional connector that you can add is a USB outlet. This will let you run any device that is powered by a USB port.USB output voltage is 5V which can be get by step down the 24V DC.First adjust the trimpot in the buck converter to set the output voltage to 5V.Then soldered the buck converter input terminal to the 24V linear regulator output or the terminal provided for the fan connection.The output of the buck converter module is connected to the USB port.

Step 16: Complete Wiring Diagram

The wiring is pretty straight forward.I added an extra Volt-Amp meter and an USB circuit in the circuit.

1. Inlet Power Socket : Connect wires as explained in the earlier step.

2. The output wires from the Inlet Power Socket is connected to transformer primary (220V ) side.

3.The secondary (24V ) side is connected to input terminal of the Power Supply kit.

4. Volt-Amp Meter : The wires from output screw terminal is connected to Volt-Amp meter as explained earlier .

5.The post terminal is connected to the Power Supply PCB output through a rocker switch as shown in the above wiring diagram.

6. USB Connection : The DC power after the diode bridge is tapped off to provide supply to the USB through a buck converter module.

Step 17: Making the Enclosure

The enclosure is designed based on the Thingiverse design "The Ultimate box maker".I used Customizer to get the exact size of the enclosure according to my requirement. First I measure the PCB and transformer size and then finalized the enclosure size ( 200 x 140 x 80 ).

I have designed the front and back panel separately in Autodesk Fusion 360.After design, I printed all the components ( Top Shell , Bottom Shell, Front Panel and Back Panel ) separately.

I used my Creality CR-10 3D printer to print all the parts.I have printed with 0.3mm layer height and 50 mm/s speed.The print quality is really excellent.

The .stl files for the enclosure is attached below.

Step 18: Install the All Components

Insert the components on the front and back panel slots as shown in the picture.

Mount the PCB board by screwing at the four corners.

Place the transformer on the base provided on the enclosure and then mount it.

Mount the buck converter module on the lower shell of the enclosure by applying hot glue.

Route all the wires properly.

Then place the top shell and secure the nuts on the two sides.

Step 19: Warning

When all the external connections have been finished make a very careful inspection of the board and clean it to remove soldering flux residues. Make sure that there are no bridges that may short circuit adjacent tracks and if everything seems to be all right connect the input of the circuit with the secondary of a suitable mains transformer. Connect a voltmeter across the output of the circuit and the primary of the transformer to the mains.

Note :Do not touch any part of the circuit while it is under power.

Step 20: Testing

I will recommend to test the power supply before closing the enclosure.If anything went wrong you can rectify it easily.Once finished,plug in the power cable, power up the power supply using switch in the back of the supply and LED should turn on along with fan.Now turn the voltage knob clockwise, you will notice the gradual increase of the voltage reading on the display unit.To see the current reading you have to connect a load at the post terminals.If everything goes perfect,then congratulations !!! You have done your bench power supply.

You can add more features as well as modify the kit to get desired output according to your requirement.Have a look to the following link where lots of discussions is going on regarding the modifications of this power supply kit.

Modification : https://www.eevblog.com/forum/beginners/bangood-ps...


I hope you have enjoyed and learned how to make a linear power supply. Thanks !

Comments

author
WannaDuino made it!(author)2017-07-11

or use mine, it`s portable. 6400mAh

5V USB Output\ and Input for charging.

4.5V to 30Volts regular output

2x ON OFF switches

Sorry to CRASH your IBLE like this, found it funny in my eye`s.

WannaDuino STYLE.

F74FIL1IV0AA3K3.jpegIMG_3070 (1).JPGIMG_3072.JPGIMG_20161103_061105.jpgIMG_20160926_000127.jpgIMG_20160926_000412.jpg
author
deba168 made it!(author)2017-07-12

Nice build.

Thanks for sharing the pictures here.

author
dbess made it!(author)2017-07-10

Awesome!

author
deba168 made it!(author)2017-07-12

Thank You..

author
procter made it!(author)2017-07-11

The portions that you have authored yourself are very good and I give you credit for them.

BUT, this instructable is clearly made up of much material that has been copied from other websites AND you have NOT GIVEN SUFFICIENT CREDIT (that I can see) to the original authors who are the copyright holders!

In my opinion this article should be temporarily withdrawn as it is plagiarism. When you have amended it and properly acknowledged EVERY copied paragraph, photograph and diagram, you might be ethically permitted to resubmit it, although copyright material, and whole sections copied, require explicit permission from copyright holders. Acknowledgement includes a caption for every item, something like "The above paragraph copied from...", or "The above image published with the permission of...".

Examples:

(1) Circuit Diagram: Under section "Step 7: How the Power Supply Kit Works", you have used a circuit diagram that is identical to, and presumably lifted from webpage [http://www.electronics-lab.com/project/0-30-vdc-stabilized-power-supply-with-current-control-0-002-3-a/] (Electronics Lab). That webpage has the words "Copyright of this circuit belongs to smart kit electronics" so you should not be using it! You have not given them credit in your article for the copyright diagram and there is no disclaimer saying "published with the permission of...".

(2) Your third paragraph: "This is a high quality stabilised voltage supply..." is identical to the opening paragraph of Electronics Lab.

(3) The text: Following the diagram (#2 above) you have cut and pasted the entire section of six paragraphs from Electronics Lab material.

(4) The acknowledgement "credit : electronics-lab.com" is NOT SUFFICIENT. You may not copy entire sections of copyright work without permission. You may quote from it to a 'reasonable' extent, but not copy it and claim it as your own article.

(5) You also seem to have lifted a lot of material, text and graphics, from [http://img.banggood.com/file/products/201505080459530-30Vinstall.pdf], or elsewhere. You have provided a link to them but have also cut/pasted lot of their material without acknowledgement/permission.

(6) You also seem to have lifted a lot of material, text and graphics, from the kitset site [https://www.banggood.com/0-30V-2mA-3A-Adjustable-DC-Regulated-Power-Supply-DIY-Kit-p-958308.html], or elsewhere. You have provided a link to them but have also cut/pasted lot of their material without acknowledgement/permission.

And there is a more...

If you take the care to 'honestly' produce excellent Instructables, I will have no hesitation in giving you the credit - I look forward to that.

author
deba168 made it!(author)2017-07-11

Dear Sir,

Most of the images and the schematic are taken from Banggood.com and their instruction manual given in the kit.I should clear here that, the kit itself provided by Banggood without any charge for reviewing purpose to me.That is the reason why I used their resources.

The circuit diagram in the step-7 is also a part of the instruction pdf provided by Banggood.com. Here is the link.

For explanation part, I have now given full credit to the original author, because I have not written it.I just put it here for easy understanding of the subject of matter.Anyway I have given credit t earlier also.

Thank you.

author
procter made it!(author)2017-07-11

I see you have added

"Credit :This section is not written by me rather it is taken from electronics-lab.com.The full credit goes to the original author."

That is excellent and acceptable.

Unfortunately the fact that Banggood (may) have illegally used copyright material does not excuse you from doing the same. Banggod may also have got written permission to use it.

When I read an instructable, I expect it to (mostly) be created by the writer. That includes schematics, photos, videos, etc. There would never be a complaint like this if you inserted a link to other material and said something like "See here for details on how to...". But if you did that, your article may be a little smaller... Or you only copied small pieces and put an acknowledgement caption under each piece. Bear in mind that someone else has invested a lot of time and money putting together that material.

Keep up the good work, and I'll look forward to your next article.

author
CPUDOCTHE1. made it!(author)2017-07-11

Cool build. It is always fun to build things. I bought a 0-30V, 0-10A power supply off of Amazon. Much quicker and about the same cost as building one. We used it to anodize aluminum and to charge a kids 24v riding toy. We tend to build the bigger stuff and buy the smaller cheap stuff. We built pallet forks and a grapple for our tractor with front end loader. My son has started drawing/engineering a tree shear for it. We also built a 4'x9' CNC plasma table that will convert to oxy/acetylene for about 1/2 the price of a $20,000 one.

author
davide.bisio made it!(author)2017-07-09

Hi! I found that the schematic you have proposed is very popular on the web, many people have discussed about that. But I have not found on the web the answer to a simple question I posed myself. You seem to be very qualified, so probably you can clarify my doubt.

What about the introduced filters? I can see filters around C6, C8 and C9 that seems to limit the bandwidth of the feedback loops. But I briefly analized the circuit and it seems to be naturally stable. I'm wrong? Is there something I miss? Otherwise I think is plausible to remove those filters, to get a faster response of the power supply.

Thank you in advance!

author
Phantom+OfT made it!(author)2017-07-11

He has no idea

The power supply is a DYI off of amazon or eBay. You can purchase it for as little as $8.00

https://www.amazon.com/dp/B01NBE97WH/_encoding=UTF...

It's
the enclosure that bugs me why would you go thru all that to make one
on a 3D printer. When you can buy one for $12.00 at Amazon.

https://www.amazon.com/XCSOURCE-200x175x70mm-Elect...

author
deba168 made it!(author)2017-07-10

Sorry I am not that much expert to answer your question.I hope someone in this community may answer your question.

author
ahmets12 made it!(author)2017-07-11

Temin edeceğimiz sitenin adını yazarmısın

author
Veli+Can+Ayd%C4%B1n made it!(author)2017-07-11

Temin edilecek parçaların çoğu Türkiye'de yok. Zaten yazar yabancı olduğu için parantez içinde ürünleri temin edebileceğiniz yabancı siteleri belirtmiş, tabi kaçı Türkiye'ye geliyor ... parçaların isimlerini sitelerden kopyalayıp webde araştırırsanız Türkiye'ye yollayan bir çin sitesi bulabilirsiniz (Aliexpress, Banggood gibi). Birde ekleme yapayım bu sitede çok az Türk var yorumlarınızı Türkçe belirtirseniz büyük ihtimalle yanıt alammazsınız. Umarım yardımcı olmuşumdur iyi günler.

author
throbscottle made it!(author)2017-07-11

They are there so the negative feedback increases at higher frequencies, to prevent the supply from oscillating.

author
Phantom+OfT made it!(author)2017-07-11

If your interested A enclosure can be bought for $12.00 at Amazon.

https://www.amazon.com/XCSOURCE-200x175x70mm-Electronics-Components-TE554/dp/B01K4HYGV2/ref=sr_1_fkmr1_2?ie=UTF8&qid=1499824102&sr=8-2-fkmr1&keywords=Instrument+case+DIY+200x175x70mm

author
marcm95 made it!(author)2017-07-11

Hi ! Nice work !

One possible issue with such schematic is , in case of failure of the voltage potentiomer, a serious lack of output control. Amazingly some of the Banggood products are fitted with a safer arrangement , adding a transistor leading the control voltage to zero in case of pot failure, PLS have a look at added document.

alim compar.jpg
author
RockeyDA made it!(author)2017-07-11

thing 1... WHY DOSE IT HAVE A USB PORT? so you can see what happens if you overvolt your webcam or flashdrive?

thing 2, and i cant stress this enough, this is not making a powersupply, its assembling a kit. if it was making i could go to my scrap circuit bord boxes and recreated without to much effort.

looks like im just gonna keep rectifiing power out of my variac, i just hate that limits me at 5 amps.

author
Blackanga made it!(author)2017-07-11

The USB part is simple - to use this output for charging various devices, instead of connecting them to the computer - for example. Not a bad idea.

As to this being a real instructable? Yes, it still is, IMHO. Going your way, you should build from scratch your own capacitors, resistors, transistors, and so on. Gee, you should really start from digging up some copper ore and turning it into a copper wire first.

What difference does it make if he purchases the brand new components, rather than scrapping them from some old boards (apart from the environmental, of course)? If anything, their quality should be better than the old ones. And not everybody has an access (for various reasons) to surplus old devices to take the components from.

Yes, he used the ready-made PCB, transformer, Volt Amp Meter Display and a bunch of pre-selected components. This is not the point. Not everybody is savvy enough to come up with their own design of every step of the way, create a schematic and then make a PCB.

At least he shows here (and in a very neat way) how to utilise and put together these components readily obtainable from various sources, so everybody wanting to build something similar can do it too.

I thik it is a good instructable.

author
askvictor made it!(author)2017-07-11

I don't know if the power supply kit isolates gnd between input and output, but if it doesn't then the current display will be incorrect; the volt/current meter needs a completely isolated supply to what it is measuring. But you can get a DC/DC converter that will do this for a couple of dollars.

Also, it's probably a _lot_ safer just to use an old laptop Power supply to handle the high voltage/ac stage, then handle the low voltage side with your own stuff.

author
Polymorph made it!(author)2017-07-10

1000uF is way too low for a power supply that may easily draw 1A. The approximate value of ripple current is Vpp = I/(2fC) where I is the max continuous current, f is the line frequency, and C is the smoothing capacitor. With 1000uF at 60Hz and 1A current, the ripple is a bit over 8V!

The voltage out of the bridge rectifier, with 24Vac input, is about 32V after diode drops. So to go up to 30V output, you're circuit will require a LOT more smoothing capacitance.

http://www.zen22142.zen.co.uk/Design/dcpsu.htm

author
PickyBiker made it!(author)2017-07-11

I am getting a much lower value than 8v.

I am using

Vpp is in ma, I is in ma, f is in Hz and C is in uf

What am I doing wrong?

author
Polymorph made it!(author)2017-07-11

Vpp should be in Volts, I in Amps, f in Hz, and C in Farads.

1A / (2 x 60Hz x 0.001F)
1/(0.120)
About 8V

author
deba168 made it!(author)2017-07-10

Thanks for sharing your experience.

author
Polymorph made it!(author)2017-07-10

I'm always happy to help. The amount of smoothing capacitance often is way too low on these kits, and widely misunderstood.

author
jerry.ericsson2 made it!(author)2017-07-10

A few years ago, I built one nearly like that, only I powered it with 6 18650 batteries, she does a great job when building, and can easily power most of my projects. I have another in straight 12 volts with a volt/amp meter like that but with cables so I can use it to test projects I am powering with it. The batteries all came from torn down laptop batteries. I find when tearing them down, there is uaually only one or two bad cells the rest seem to be in great shape. Shame how most folks throw away their spent lipo batteries from laptops.

author
WannaDuino made it!(author)2017-07-11

yeah i would buy all them batterys in a hartbead

author
ElizabethGreene made it!(author)2017-07-11

A lm317 is a linear power supply chip, so it converts the waste power to heat. If you are building a battery powered bench power supply you might take a look at a switching power supply instead. Switching power supplies aren't as smooth as linears, but are significantly more efficient.

It is possible, if more expensive, to have the best of both worlds. Use a buck-boost switching power supply to create the input voltage 1-2v higher than your desired output and feed that into a linear. That gives you nice smooth linear power without burning a bunch of extra power just to make waste heat.

author
Kevanf1 made it!(author)2017-07-11

Agreed about people throwing out seemingly useless old laptop batteries :( I've harvested 18650's myself in the past :) A little tip here. buy a cheap replacement laptop battery (doesn't really matter what model laptop it's for) from somewhere like Amazon. I can get them here in the UK for anything from from around £10 up to £40 or so. You pays your money and you takes your choice. Strip the new battery down and harvest those 18650's. Much cheaper than the rubbish cells off eBay mainly because they are inevitably far better quality even though they may not be OEM. They are indeed a good way to power a PSU or a power bank.

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BSJensen made it!(author)2017-07-11

Very nice guide :)

I've assembled this kit a long time ago and it works like a charm.
I did a rewinding of a transformer from a microwave to hit about 24VAC for the input, it ended up at 23,7 VAC which is perfectly fine for this board.
I also replaced the 24V regulator with a 12V one. It's just there to provide voltage for a fan, so might aswell just use another since 24V fans are quite expensive compared to 12V ones.

By the way (for those of you who doesn't like reading manuals like the one linked to in this instructable), when first testing, always use the onboard trimpot (100K) to set the output to 0V (all external pots turned to their minimum, the 10K ones). Adjust the onboard trimpot to hit 0V on the output.

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jtechian made it!(author)2017-07-11

I would include an added load resistor on the output of around 20k to improve regulation. These kits never seem to include that.

Nice work to inspire others to do their own kits. Give some hands on experience.

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JoeyyBoyy made it!(author)2017-07-11

Nice instructable, very through and neat. How much time (hours) did it

take to build and what was the total cost in US dollars?

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RobBest made it!(author)2017-07-11
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schmitta made it!(author)2017-07-11

Should not R1 go to VI and not VO? If it goes to VO it the regulator may oscillate.

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John+T+MacF+Mood made it!(author)2017-07-11

Thanks for the link to the MODS. I'm looking for a beefier supply, with output up to about 25 amps continuous. I figure the transformer and ALL downstream components will have to be beefed up to make that high an amperage.

And good warning about the "don't handle the components while under power". Some parts of the circuit may contain some voltage due to the capacitors so, letting it sit, or shorting the leads while it is off may help. Best not to fiddle in any case. Excellent bit of kit, as you say really good work. and you must be a very patient person, ordering from Banggood, shipping times are like they use a slow boat from china. (Maybe literally!) It seems unless you ask for express, which is still a bit slow, it took one kit I bought from them 16 weeks to arrive with standard shipping... And he rates shipping back to China are exorbitant. Glad your kit worked out well. I may look for someone who stocks in North America to order from.

Great work!

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PaulH391 made it!(author)2017-07-11

LTC 3780 Buck Boost converters are extremely cheap on ebay now, all you need to do with them is remove the preinstalled cc &cv pots and wire the others up.

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drj-research made it!(author)2017-07-10

Made my version with lm317 and the lm337 - found the transformer - looked to be part of tv - it worked . As ebay paypal international shipping not then - used some analoge meters . Dig metering not then available - all such equiopment expensive . After 30 years it still works . Repurposed bits - brings cost down if appearance sacrificed

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TryxCorp made it!(author)2017-07-10

Great work! :-D

Were the holes on the enclosure box drilled manually or were the too 3D printed?

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deba168 made it!(author)2017-07-10

All are 3D printed.I have not drilled anything manually.

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tutdude98 made it!(author)2017-07-07

Nice explanation on how suppy works, also really nice enclosure

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deba168 made it!(author)2017-07-07

Glad you like my work.

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kavish+laxkar made it!(author)2017-07-07

Nice built:D

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deba168 made it!(author)2017-07-07

Thanks dear !

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Surajit+Majumdar made it!(author)2017-07-06

Awesome power supply. Voted for u

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deba168 made it!(author)2017-07-06

Thank you so much.

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Bio: I am an Electrical Engineer.I love to harvest Solar Energy and make things by recycling old stuffs. I believe ""IF YOU TRY YOU MIGHT ... More »
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