Holy Crap! ...a ua723 design, now that goes back a few centuries! I remember some design that used the ua723 in switching supplies (not very reliable). Int the 70-80's the ua723 was the GO-TO chip for PSU design, as was the 2N3055! ...Love It, gonna watch for the nostalgia, thank you! :)
The EasyOne electronic load só,show seems back-to-basics and easy to do anywhere. And if you could do some brainstorming and digressing around, they would be greatly appreciated. Probably because I have some unexplained pleasure to see minimalist circuits working, go figure. Thanks for asking us all!
Surely the DIY’s Bench power supply is the most important hobbyist project - and the most useful one, just not so simple to assemble and follow for a novice, I guess. The good thing is that is a fully ‘analog’ electronics, 0% cpu/MCU.
heya 00:30 yes love to see more DIY bild's for learning ( with a good explanation of the workings ) and maybe some new tools for repairs. oh yeah bilding a dual psu would be great even better wen you can switch between 0-12, 12-24, 24-36 36-48 or something like that, like a mixing console goes up to 90V I don't know I'm learning from you so probeble you know better what are commen used voltagges in differant aplications (sorry for my english) lol
Regarding the boards you showed, all of them seem very interesting projects I would like to see. The soldering iron driver projects are specific to a type of iron, of course, but even those would be interesting to watch. Thanks!
BC547 and BC557 are just standard low power NPN and PNP transistors (50V 100mA). You can replaced them with nearly any other modern low power transistor.
Thanks for the info. I like to keep these things in stock (as you probably noticed) so when I come across things like this that I don't have, and I can buy 25 pairs for a couple of euros, I just go on and hit the button. Probably I just enjoy adding stuff to my component collection 😉
Great vid , so much more than just populating a pcb. Excellent . As you went along you were answering my questions without hearing them .PS even ocd types touch a charged cap now and again😂
That's weird as I had a puzzling moment a couple of days back exactly the same as you with a transistor, mine is 2N5401 has EBC and the 2N5401C has ECB ! the 'C' however isn't always used by sellers so you have to be very careful as Base and Collector can swop, sometimes you have to be aware about letters and numbers after the code ! I wish Digikey did....cheers.
Built something similar 30 years ago! Trouble is, 3055s (often with 3053s) were generic and everywhere in PSUs and other class A amp designs but at times the power dissipation can be horrible. I had a mahoosive passive heatsink (about 0.5C/W) and it still cooked! The switched transformer windings will help the maximum dissipation but it will be interesting to see the switching transient at high currents.
Hi Richard, if you use atx psu as a power source, you can use a duo relay to switch on and off the second PSU if not in duty, just need to switch the ground to PSON pin of the ATX PSU. Regards, Mark
did I put 0h? I suppose it is how you like to call it. Like in a hotel would you be in room one-zero-one or would you be in room one-oh-one? And is James Bond Double-oh-seven or..... I look forward to your reply 🙂
The centre contact on the relay is the "common" terminal - relays don't have wipers :-). I'm not just being pedantic - some people may scratch their heads when looking in vain at datasheets...
To connect 2 ATX (or any PC/server) PSUs in series, go into the high side PSU (the PSU to go from 12V point of the first PS .. the PSU that will measure 24V from the 0V point) and remove the connection to ground from the DC negative. Then, ohms test for no connection/isolation from ground on the high side PSU from ground.
Add a thyristor as a crowbar to protect against over voltage. Need to let the gate follow the adjustable set point. Then you won’t get full DC out if the transistors short circuit. That can ruin your expensive DUT.
Translation of original text of builder The adjustable power supply has a power output of 10A, but the number of output transistors and the value of the series resistors can be configured for power levels such as 3A, 5A. Based on my experience, higher currents can also be obtained, and the output voltage can even be modified for 0-50V, but this requires effort and tests. For now, 0-30V is sufficient. I applied the "0-30V 10A Power Supply (LM723 TIP3055)" circuit that was previously shared. The PCB design is regular and small (91.6 X 72.2mm) and is single-layer. I had the PCB board made and printed a double-layer PCB for hole filling and jumps. The circuit works really well with precise voltage adjustment. I used 2SC5200 transistors instead of TIP3055 for the power transistors. If you can find it, use TIP3055 in a TO218 case. Also, calibrate the potentiometers well, meaning rotate them thoroughly left and right before operating the circuit. I had a problem in a few circuits because of the potentiometers, but I solved it with this method. 1. 0-30V 10A K7200 Power Supply Circuit Diagram 2. Power Supply Test Video 3. 0-30V 10A Power Supply Installation Details 4. Power Supply Connection Diagram 5. Current Adjustments of the Power Supply I actually implemented the power supply circuit with limited resources, but it is sufficient for me. The initial tests were successful. I have a toroidal transformer with an estimated voltage of 250W...300W 2X15VAC, so I tested it with that. A normal transformer can also be used as long as its power is at least 300W or more. I directly wired the DC rectifier, filter, and solid state relay (I made a PCB for these parts of the circuit). 0-30V 10A K7200 Power Supply Circuit Diagram Adjustable power supply based on 2 LM723 (UC723) ICs. Normally, LM723 can control voltage and current on its own, but in this design, separate LM723s are used for voltage and current control. LM741 opamp is used for AC voltage stabilizationization. Power Supply Technical Specs: Adjustable output voltage range: 0V to 30V Adjustable output current range: 0V to 10A Fine adjustment over 1V LED-indicated current limiting indicator Output current: 8A continuous / 10A max Maximum ripple of 0.5mV RMS All connections for 2SC5200 output transistors are made with separate cables, which is not necessary, but was done this way for the lack of proper cooling during testing (a PCB layout for the output transistors has been prepared). The transistors can be mounted on a single row cooler, and the collector and base terminals can be connected with thick single cables or wires. The output of the 0.22 OHM 5W balancing resistors can be combined with a thick single cable or wire. I used a radial resistor, and did not make any additions, using cables salvaged from a PC power supply. Power Supply Test Video The assembled power supply, including short-circuit tests, load tests, and notes, is quickly shown in the video below. The video is short but fairly detailed. Setup Details for 0-30V 10A Power Supply If I had them, I would use low-power metal film resistors with a 1% tolerance, but since not all values are available, some of them are using metal film. The metal film resistors you see in the finished product are not specific to the circuit. If possible, let the resistors be metal film and the potentiometers be high-quality Alps brand. I recommend cleaning the power supply control board with soldering tin after material assembly and checking the solders. I don't use an integrated socket in circuits I'm confident in, but I used an integrated socket for this one because I'm testing it for the first time and there's a chance of problems. In the material list for the control board, 33nF, 68nF, and 1uF capacitors are listed as MKM type, but I used standard polyester type. Voltage values are 63V. In the power supply circuit, the voltage sensing resistor in the bypass circuit used to reduce the power consumed by the transistors is fixed at 8.2K, but I used a 10K multi-turn trimpot instead. With an 8.2K resistor, the output is approximately 11V and the relay pulls in when the input is 42V, but I set it to activate when the output is between 12V and 13V. For example, if we set the output to 13V, 42V DC will be applied to the DC input of the circuit and the dual winding of the transformer will be used (15VAC + 15VAC = 30V, 30 x 1.41 = 42). When the output is below 13V, 21V DC is applied and only one winding of the transformer is used and the bypass circuit automatically adjusts this. As I said, I built this part directly, but those who don't want to work can use the PCB design I made. Capacitors can be 4700uf 50v or 6800uf, bridge diode 35-50 amp metal type, relay 12V 16 amp. In the original document, only the measurement information for the current sensing shunt resistors is given, and no value is given. In a shared document, 4 pieces of 1ohm 11w are noted, but this value is incorrect. With 4 pieces of 1ohm, only about 3 amps of power are taken. I tried it with 0.33ohm 5w resistors I have and the results were great. One more 0.33 OHM resistor can be added and with a lower ohmic load (3.7 ohm), 8 amps are taken, but I don't have resistors or loads. With the materials I have, various current and voltage tests did not cause problems. Note: The original shunt resistor value is probably 0.05 Ohm 50mR metal tip. The power supply circuit can be used with a current of 3A or 5A. For example, you can get about 3 amps with one TIP3055 transistor, with a series resistance of one 0.22 OHM. The filter capacitor is 3300uf, and the diode is KBU8M. The transformer power decreases, 100W is enough for 3A, and the cost decreases. For 5 amps, you need at least three transistors. You must adjust the minimum and maximum current settings accordingly. The BDX54C transistor can be used instead of the T3 BD646 transistor. For 3 amps, you will probably need a heat sink, a thick small heat sink can be used or directly mounted on the main heat sink. The dimensions of the heat sink to be used for the output power transistors are in the Velleman K7200 manual, but it is a large type that will be hard to find. Instead, you can use a smaller heat sink and add a fan. Also, you need to make a probe for current measurement with a multimeter, although it says that current can be measured with 10A...20A on measurement instruments, the probes of the multimeter do not carry high currents and they heat up and show incorrect values. "For high current long-term tests, a 35A metal bridge diode may heat up, it is advisable to install a small heat sink or directly mount it on the main heat sink, but the transistors should be slightly away. I made the PCB drawings for the DC rectifier, filter, relay solid and transistor solid single-layer for easy implementation. There are also double-layer drawings available. In double-layer PCB drawings, you don't need to struggle to thicken the tracks."
I checked the drawings, I didn't see any problems, but I haven't printed and used them yet. Please check according to the diagram before using. Remember to use thermal conductive paste and insulator in the heat sink mounting of TIP3055 transistors in the power source. See the relevant article on heat transfer and insulators. Note: For 2SC5200 transistors, only an insulator is needed because the screw-mounted sections have plastic insulation in the original design. Power source current settings The instructions are translated from the Velleman K7200 document. I just set the trim pots randomly for maximum current and went directly to implementation. You can access the original document in the file. 1. Connect an ammeter that can measure minimum 1A to the output. 2. Turn the current limiting potentiometer to the maximum. 3. Turn the voltage regulator potentiometer (COARSE-KABA) to the intermediate position. 4. Turn RV1 trim pot fully to the left (maximum current setting). 5. Turn RV2 trim pot fully to the right (minimum current setting). 6. Connect the power source to the network (the current limiting LED is likely to light up). 7. Carefully adjust RV1 until the ammeter reads 1A. 8. Set the current setting potentiometer to 1A (center position). 9. Carefully adjust RV2 until the ammeter reads 1A. Update: Control and DC Solid PCB I tried to fit the DC part of the power source control board into a 100X100 size as a single layer because the dimensions of the control board PCB were quite small. It may be useful for those who have printed the circuit from China. It is necessary to fill and thicken the AC lines with solder. There are no major changes in the control layer, only the emitter-collector jumpers of the BDX54C transistor were adjusted according to the DC layer, and the 1000uf capacitor was removed. The main filter capacitors are directly on the board, so this capacitor is not necessary. The original design also does not have it, but since the DC and control layers are combined with cables, cable losses have been well thought out. The new PCB design has been added to the file. 4700UF capacitors are ideal for 8 amps, if 10 amps are used frequently and for a long time, 6800UF can be used. The capacitor diameter is 25.5mm and the area on the PCB allows for 6800UF if possible. New generation capacitor sizes are getting smaller. I visually checked the controls according to the diagram, I didn't see any problems. I haven't printed and used the design, please check and make sure before using. Update: A reader from abroad has used the new PCB design and there were no problems, a visual check is recommended before using. "I have an empty UPS case, I will share pictures if I can install it in the future. Lastly, the PCB design is not mine, I only corrected a critical error that would prevent it from working and made some modifications. I couldn't trust the design when I saw the error, so I checked it from start to finish according to the schematic. I have source Sprint layout PCB designs and gerber files for the control board, DC, and transistor cards. The material list is written in the manual_k7200.pdf file. Comments from those who applied the circuit abroad: I made this power supply on the 2nd PCB version, I can say I am satisfied with my 2x13.5VAC toroid transformer, 10mF and 6300uF DC filter capacitors. The only thing I had to buy was the bdx54 transistor, I found the rest in various piles of scrap in my workshop. When I put everything together (body, front panel, multimeter, and soft start toroid), I will attach some photos. I am also considering thermal protection such as a 95-degree thermal fuse and relay (because I have 15 in stock) to cut power to the ICs and turn on the indicator. This can be easily connected to the jumper next to capacitor C10 and diode D2. I tested the power supply with a large heatsink and a bd249, it lasted about 5 minutes at 5A in a short circuit, and the capacitors (of course, excluding C9) were cold."
Looking forward to seeing the coming episodes but what I don’t like is mixing switching power supply with linear one, this defeats the purpose of building linear ps low noise but bad efficiency, if you use ATX as the input stage you will introduce the switching noise to the linear stage. I would suggest that you make a different episode modding the ATX to work as variable and with your experience and knowledge I know you are capable of doing so and we will enjoy it, yes it will have a drawback that it will not reach very low voltages, but will get a lot of current without worrying about lot of heat dissipation. Good luck 👍
Sure - I really just want to see how well it works in this configuration as it is probably the cheapest option for most people to make a high power bench PSU. Modding an ATX to produce a variable output voltage would still not give us a proper bench PSU which has a variable CC mode down to 0 Amps and short circuit protection. I have three commercial bench power supplies, two linear and one SMPS. To be honest I haven't found anything yet that I can do with the single linear one that would not also work using the SMPS one. I'm starting to wonder if it is another myth that you must have a linear bench PSU 🤔 The other linear one is a dual bench PSU so that does have it's own specific uses.
@@LearnElectronicsRepair Yes having good smps will satisfy 90% of all our needs, me too having both linear and switching, I found myself using the smps more it’s Riden RD6012 a lot of features and can provide very high power, but when it comes to playing with audio and filters I use the linear Korad and I am too building linear dual channel one as it is mostly required for audio the positive and negative supplies.
@@ultimateworkshop2000 Well as you see, I will build both types in the upcoming parts of this video. I am most excited about the dual channel linear one using the transformer and other parts from the scrap amplifier. Adding a second 18V-0-18V @2A using the other winding will make it ideal for amplifier fault finding, I would imagine. 😉
They claim it's a 0-30v supply, but I don't see how this can reliably work at for instance 0.5 V. Does it stabilise well at such low voltages? It look like a 1-30V design to me, but I could be wrong.
I was wrong. The ground voltage of the output is at another level than the ground of the rectifier output. This way they solve the minimum 2 v input that the regulator chip needs.
I watched up until I saw the current sensing was low side and therefore any grounding (true ground) will cause the current sensing to stop limiting current. I have to say low side sensing is pretty rubbish for the above reason. Are you going to cover a high side sensing one at some point? I do love watching most of your videos though as you do cover everything very well, keep up the great work!
Shame you didn't watch the rest as when I tested it everything was working well apart from the current sensing which did not work. High side current sensing is not so difficult using an op-amp and you can the reference the voltage across the sense resistor to ground if you like. I mentioned in the later parts of the video that I am going to recreate the schematic (the download link does not work for me) and redesign the PCB so your suggestions could be needed on the next installment
@@LearnElectronicsRepair In that case I'll watch it till the end tomorrow and then post any ideas on the high side sensing. I seem to remember that TI does a broad range of devices as does Maxim and Analog Devices, you can easily create the sense amp yourself with a fairly accurate sense resistor and decent opamp...
For this one www.pcbway.com/project/shareproject/Laboratory_Power_Supply_0_30V_10A.html 320volt.com/laboratuvar-guc-kaynagi-0-30v-10a-ayarli/ I'll update the video description on Monday to link to all the other ones. I have the links in a word document but I'll have to do it when I am back at the office after the weekend 😉
Love your videos Richard! Thank you for your inspiration, hard work and sharing your knowledge.
Holy Crap! ...a ua723 design, now that goes back a few centuries! I remember some design that used the ua723 in switching supplies (not very reliable). Int the 70-80's the ua723 was the GO-TO chip for PSU design, as was the 2N3055! ...Love It, gonna watch for the nostalgia, thank you! :)
A wonderful selection of boards that can keep any enthusiast busy for long. Great work and stay well.
You can build any or all. I will watch each one no matter what
The EasyOne electronic load só,show seems back-to-basics and easy to do anywhere. And if you could do some brainstorming and digressing around, they would be greatly appreciated.
Probably because I have some unexplained pleasure to see minimalist circuits working, go figure.
Thanks for asking us all!
Surely the DIY’s Bench power supply is the most important hobbyist project - and the most useful one, just not so simple to assemble and follow for a novice, I guess. The good thing is that is a fully ‘analog’ electronics, 0% cpu/MCU.
heya 00:30 yes love to see more DIY bild's for learning ( with a good explanation of the workings ) and maybe some new tools for repairs. oh yeah bilding a dual psu would be great even better wen you can switch between 0-12, 12-24, 24-36 36-48 or something like that, like a mixing console goes up to 90V I don't know I'm learning from you so probeble you know better what are commen used voltagges in differant aplications (sorry for my english) lol
WooHoo first comment, I would like to see the Tiny Load build, looking forward to it! Keep up the great content.
OK I will order the parts that I don't have. That one should be ready to build in a month or so.
Regarding the boards you showed, all of them seem very interesting projects I would like to see. The soldering iron driver projects are specific to a type of iron, of course, but even those would be interesting to watch. Thanks!
Great explanation thanks 😊
BC547 and BC557 are just standard low power NPN and PNP transistors (50V 100mA). You can replaced them with nearly any other modern low power transistor.
Thanks for the info. I like to keep these things in stock (as you probably noticed) so when I come across things like this that I don't have, and I can buy 25 pairs for a couple of euros, I just go on and hit the button. Probably I just enjoy adding stuff to my component collection 😉
Great vid , so much more than just populating a pcb. Excellent . As you went along you were answering my questions without hearing them .PS even ocd types touch a charged cap now and again😂
wow amazing projects in the intro. I'm very interested to see all of them
That's weird as I had a puzzling moment a couple of days back exactly the same as you with a transistor, mine is 2N5401 has EBC and the 2N5401C has ECB ! the 'C' however isn't always used by sellers so you have to be very careful as Base and Collector can swop, sometimes you have to be aware about letters and numbers after the code ! I wish Digikey did....cheers.
Built something similar 30 years ago! Trouble is, 3055s (often with 3053s) were generic and everywhere in PSUs and other class A amp designs but at times the power dissipation can be horrible. I had a mahoosive passive heatsink (about 0.5C/W) and it still cooked! The switched transformer windings will help the maximum dissipation but it will be interesting to see the switching transient at high currents.
Hi Richard, if you use atx psu as a power source, you can use a duo relay to switch on and off the second PSU if not in duty, just need to switch the ground to PSON pin of the ATX PSU.
Regards, Mark
I don't see why not. Or as you suggest put it into standby, that would be really easy 🙂
Excellent project. But I think it is Zero-AC, not Oh-AC for the center transformer secondary wire.
did I put 0h? I suppose it is how you like to call it. Like in a hotel would you be in room one-zero-one or would you be in room one-oh-one? And is James Bond Double-oh-seven or..... I look forward to your reply 🙂
The centre contact on the relay is the "common" terminal - relays don't have wipers :-). I'm not just being pedantic - some people may scratch their heads when looking in vain at datasheets...
OK 😊
Thanks Richard for the videos, I’m wondering where do you guys get the components from? Are you using mouser or digikey or aliexpress?
Aliexpress
To connect 2 ATX (or any PC/server) PSUs in series, go into the high side PSU (the PSU to go from 12V point of the first PS .. the PSU that will measure 24V from the 0V point) and remove the connection to ground from the DC negative.
Then, ohms test for no connection/isolation from ground on the high side PSU from ground.
Add a thyristor as a crowbar to protect against over voltage. Need to let the gate follow the adjustable set point. Then you won’t get full DC out if the transistors short circuit. That can ruin your expensive DUT.
Translation of original text of builder
The adjustable power supply has a power output of 10A, but the number of output transistors and the value of the series resistors can be configured for power levels such as 3A, 5A. Based on my experience, higher currents can also be obtained, and the output voltage can even be modified for 0-50V, but this requires effort and tests. For now, 0-30V is sufficient.
I applied the "0-30V 10A Power Supply (LM723 TIP3055)" circuit that was previously shared. The PCB design is regular and small (91.6 X 72.2mm) and is single-layer.
I had the PCB board made and printed a double-layer PCB for hole filling and jumps. The circuit works really well with precise voltage adjustment. I used 2SC5200 transistors instead of TIP3055 for the power transistors. If you can find it, use TIP3055 in a TO218 case. Also, calibrate the potentiometers well, meaning rotate them thoroughly left and right before operating the circuit. I had a problem in a few circuits because of the potentiometers, but I solved it with this method.
1. 0-30V 10A K7200 Power Supply Circuit Diagram
2. Power Supply Test Video
3. 0-30V 10A Power Supply Installation Details
4. Power Supply Connection Diagram
5. Current Adjustments of the Power Supply
I actually implemented the power supply circuit with limited resources, but it is sufficient for me. The initial tests were successful. I have a toroidal transformer with an estimated voltage of 250W...300W 2X15VAC, so I tested it with that. A normal transformer can also be used as long as its power is at least 300W or more. I directly wired the DC rectifier, filter, and solid state relay (I made a PCB for these parts of the circuit).
0-30V 10A K7200 Power Supply Circuit Diagram
Adjustable power supply based on 2 LM723 (UC723) ICs. Normally, LM723 can control voltage and current on its own, but in this design, separate LM723s are used for voltage and current control. LM741 opamp is used for AC voltage stabilizationization.
Power Supply Technical Specs:
Adjustable output voltage range: 0V to 30V
Adjustable output current range: 0V to 10A
Fine adjustment over 1V
LED-indicated current limiting indicator
Output current: 8A continuous / 10A max
Maximum ripple of 0.5mV RMS
All connections for 2SC5200 output transistors are made with separate cables, which is not necessary, but was done this way for the lack of proper cooling during testing (a PCB layout for the output transistors has been prepared). The transistors can be mounted on a single row cooler, and the collector and base terminals can be connected with thick single cables or wires.
The output of the 0.22 OHM 5W balancing resistors can be combined with a thick single cable or wire. I used a radial resistor, and did not make any additions, using cables salvaged from a PC power supply.
Power Supply Test Video
The assembled power supply, including short-circuit tests, load tests, and notes, is quickly shown in the video below. The video is short but fairly detailed.
Setup Details for 0-30V 10A Power Supply
If I had them, I would use low-power metal film resistors with a 1% tolerance, but since not all values are available, some of them are using metal film. The metal film resistors you see in the finished product are not specific to the circuit. If possible, let the resistors be metal film and the potentiometers be high-quality Alps brand.
I recommend cleaning the power supply control board with soldering tin after material assembly and checking the solders.
I don't use an integrated socket in circuits I'm confident in, but I used an integrated socket for this one because I'm testing it for the first time and there's a chance of problems.
In the material list for the control board, 33nF, 68nF, and 1uF capacitors are listed as MKM type, but I used standard polyester type. Voltage values are 63V.
In the power supply circuit, the voltage sensing resistor in the bypass circuit used to reduce the power consumed by the transistors is fixed at 8.2K, but I used a 10K multi-turn trimpot instead. With an 8.2K resistor, the output is approximately 11V and the relay pulls in when the input is 42V, but I set it to activate when the output is between 12V and 13V. For example, if we set the output to 13V, 42V DC will be applied to the DC input of the circuit and the dual winding of the transformer will be used (15VAC + 15VAC = 30V, 30 x 1.41 = 42). When the output is below 13V, 21V DC is applied and only one winding of the transformer is used and the bypass circuit automatically adjusts this.
As I said, I built this part directly, but those who don't want to work can use the PCB design I made. Capacitors can be 4700uf 50v or 6800uf, bridge diode 35-50 amp metal type, relay 12V 16 amp.
In the original document, only the measurement information for the current sensing shunt resistors is given, and no value is given. In a shared document, 4 pieces of 1ohm 11w are noted, but this value is incorrect. With 4 pieces of 1ohm, only about 3 amps of power are taken. I tried it with 0.33ohm 5w resistors I have and the results were great. One more 0.33 OHM resistor can be added and with a lower ohmic load (3.7 ohm), 8 amps are taken, but I don't have resistors or loads. With the materials I have, various current and voltage tests did not cause problems.
Note: The original shunt resistor value is probably 0.05 Ohm 50mR metal tip.
The power supply circuit can be used with a current of 3A or 5A. For example, you can get about 3 amps with one TIP3055 transistor, with a series resistance of one 0.22 OHM. The filter capacitor is 3300uf, and the diode is KBU8M. The transformer power decreases, 100W is enough for 3A, and the cost decreases. For 5 amps, you need at least three transistors. You must adjust the minimum and maximum current settings accordingly.
The BDX54C transistor can be used instead of the T3 BD646 transistor. For 3 amps, you will probably need a heat sink, a thick small heat sink can be used or directly mounted on the main heat sink. The dimensions of the heat sink to be used for the output power transistors are in the Velleman K7200 manual, but it is a large type that will be hard to find. Instead, you can use a smaller heat sink and add a fan.
Also, you need to make a probe for current measurement with a multimeter, although it says that current can be measured with 10A...20A on measurement instruments, the probes of the multimeter do not carry high currents and they heat up and show incorrect values.
"For high current long-term tests, a 35A metal bridge diode may heat up, it is advisable to install a small heat sink or directly mount it on the main heat sink, but the transistors should be slightly away. I made the PCB drawings for the DC rectifier, filter, relay solid and transistor solid single-layer for easy implementation. There are also double-layer drawings available. In double-layer PCB drawings, you don't need to struggle to thicken the tracks."
I checked the drawings, I didn't see any problems, but I haven't printed and used them yet. Please check according to the diagram before using. Remember to use thermal conductive paste and insulator in the heat sink mounting of TIP3055 transistors in the power source. See the relevant article on heat transfer and insulators. Note: For 2SC5200 transistors, only an insulator is needed because the screw-mounted sections have plastic insulation in the original design.
Power source current settings
The instructions are translated from the Velleman K7200 document. I just set the trim pots randomly for maximum current and went directly to implementation. You can access the original document in the file.
1. Connect an ammeter that can measure minimum 1A to the output.
2. Turn the current limiting potentiometer to the maximum.
3. Turn the voltage regulator potentiometer (COARSE-KABA) to the intermediate position.
4. Turn RV1 trim pot fully to the left (maximum current setting).
5. Turn RV2 trim pot fully to the right (minimum current setting).
6. Connect the power source to the network (the current limiting LED is likely to light up).
7. Carefully adjust RV1 until the ammeter reads 1A.
8. Set the current setting potentiometer to 1A (center position).
9. Carefully adjust RV2 until the ammeter reads 1A.
Update: Control and DC Solid PCB
I tried to fit the DC part of the power source control board into a 100X100 size as a single layer because the dimensions of the control board PCB were quite small. It may be useful for those who have printed the circuit from China. It is necessary to fill and thicken the AC lines with solder.
There are no major changes in the control layer, only the emitter-collector jumpers of the BDX54C transistor were adjusted according to the DC layer, and the 1000uf capacitor was removed. The main filter capacitors are directly on the board, so this capacitor is not necessary. The original design also does not have it, but since the DC and control layers are combined with cables, cable losses have been well thought out.
The new PCB design has been added to the file. 4700UF capacitors are ideal for 8 amps, if 10 amps are used frequently and for a long time, 6800UF can be used. The capacitor diameter is 25.5mm and the area on the PCB allows for 6800UF if possible. New generation capacitor sizes are getting smaller.
I visually checked the controls according to the diagram, I didn't see any problems. I haven't printed and used the design, please check and make sure before using.
Update: A reader from abroad has used the new PCB design and there were no problems, a visual check is recommended before using.
"I have an empty UPS case, I will share pictures if I can install it in the future. Lastly, the PCB design is not mine, I only corrected a critical error that would prevent it from working and made some modifications. I couldn't trust the design when I saw the error, so I checked it from start to finish according to the schematic.
I have source Sprint layout PCB designs and gerber files for the control board, DC, and transistor cards. The material list is written in the manual_k7200.pdf file.
Comments from those who applied the circuit abroad:
I made this power supply on the 2nd PCB version, I can say I am satisfied with my 2x13.5VAC toroid transformer, 10mF and 6300uF DC filter capacitors. The only thing I had to buy was the bdx54 transistor, I found the rest in various piles of scrap in my workshop.
When I put everything together (body, front panel, multimeter, and soft start toroid), I will attach some photos. I am also considering thermal protection such as a 95-degree thermal fuse and relay (because I have 15 in stock) to cut power to the ICs and turn on the indicator. This can be easily connected to the jumper next to capacitor C10 and diode D2. I tested the power supply with a large heatsink and a bd249, it lasted about 5 minutes at 5A in a short circuit, and the capacitors (of course, excluding C9) were cold."
Would there be much modification to make a 50 amp power supply. I got a big ass transformer
Looking forward to seeing the coming episodes but what I don’t like is mixing switching power supply with linear one, this defeats the purpose of building linear ps low noise but bad efficiency, if you use ATX as the input stage you will introduce the switching noise to the linear stage. I would suggest that you make a different episode modding the ATX to work as variable and with your experience and knowledge I know you are capable of doing so and we will enjoy it, yes it will have a drawback that it will not reach very low voltages, but will get a lot of current without worrying about lot of heat dissipation. Good luck 👍
yes a lot of people would build this with a linear ps including me add other bits and bobs as needed but keep it linear
Sure - I really just want to see how well it works in this configuration as it is probably the cheapest option for most people to make a high power bench PSU. Modding an ATX to produce a variable output voltage would still not give us a proper bench PSU which has a variable CC mode down to 0 Amps and short circuit protection. I have three commercial bench power supplies, two linear and one SMPS. To be honest I haven't found anything yet that I can do with the single linear one that would not also work using the SMPS one. I'm starting to wonder if it is another myth that you must have a linear bench PSU 🤔 The other linear one is a dual bench PSU so that does have it's own specific uses.
I'm thinking the same thing. 👍
@@LearnElectronicsRepair Yes having good smps will satisfy 90% of all our needs, me too having both linear and switching, I found myself using the smps more it’s Riden RD6012 a lot of features and can provide very high power, but when it comes to playing with audio and filters I use the linear Korad and I am too building linear dual channel one as it is mostly required for audio the positive and negative supplies.
@@ultimateworkshop2000 Well as you see, I will build both types in the upcoming parts of this video. I am most excited about the dual channel linear one using the transformer and other parts from the scrap amplifier. Adding a second 18V-0-18V @2A using the other winding will make it ideal for amplifier fault finding, I would imagine. 😉
They claim it's a 0-30v supply, but I don't see how this can reliably work at for instance 0.5 V. Does it stabilise well at such low voltages? It look like a 1-30V design to me, but I could be wrong.
I was wrong. The ground voltage of the output is at another level than the ground of the rectifier output. This way they solve the minimum 2 v input that the regulator chip needs.
I watched up until I saw the current sensing was low side and therefore any grounding (true ground) will cause the current sensing to stop limiting current. I have to say low side sensing is pretty rubbish for the above reason. Are you going to cover a high side sensing one at some point? I do love watching most of your videos though as you do cover everything very well, keep up the great work!
Shame you didn't watch the rest as when I tested it everything was working well apart from the current sensing which did not work. High side current sensing is not so difficult using an op-amp and you can the reference the voltage across the sense resistor to ground if you like. I mentioned in the later parts of the video that I am going to recreate the schematic (the download link does not work for me) and redesign the PCB so your suggestions could be needed on the next installment
@@LearnElectronicsRepair In that case I'll watch it till the end tomorrow and then post any ideas on the high side sensing. I seem to remember that TI does a broad range of devices as does Maxim and Analog Devices, you can easily create the sense amp yourself with a fairly accurate sense resistor and decent opamp...
can we have the links for all these projects from pcbway?i want to order some of them but i cant find them
For this one
www.pcbway.com/project/shareproject/Laboratory_Power_Supply_0_30V_10A.html
320volt.com/laboratuvar-guc-kaynagi-0-30v-10a-ayarli/
I'll update the video description on Monday to link to all the other ones. I have the links in a word document but I'll have to do it when I am back at the office after the weekend 😉
Umm 1 side of the transformer is loaded more with a single diode for the circuitry of the realy..
Where is the link for this pcb
Here you go
www.pcbway.com/project/shareproject/Laboratory_Power_Supply_0_30V_10A.html
320volt.com/laboratuvar-guc-kaynagi-0-30v-10a-ayarli/
L I K E 👍👍 👍 👍👍💯🤍💯🤍💯😻😻😻 😻😻😻😻
I guess there is nobody supporting this channel anymore. Questions dont get answered.