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Laboratory power supply 0-30V 0-10A

gevv 35382 44

TL;DR

  • A 0-30V, 0-10A laboratory power supply uses a Velleman K7200 new printed circuit board control card.
  • The design includes Sprint Layout PCB drawings, Gerber files, and a single-layer PCB sized 91.6X72.2mm.
  • It offers continuously adjustable output voltage from 0 to 30V and current limiting from 0 to 10A.
  • The supply works fine, with 8A continuous output, 10A peak, 0.5mVsk ripple, LED current-limit signaling, and short-circuit protection.
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  • #31 19473897
    karel21
    Level 28  
    I put this power supply together and it works. But after some modifications, the assembly according to this scheme is ok until the transformer windings are switched (120 Watt 2 X 15V toroid), ZD2 overheating (voltage at C10 - 20V). I made the transformer winding switching system on the LM 358, power supply from additional winding 15V, intended for a four-digit double A / V meter from Ali. Now it works without a problem, only there is a problem with resetting the ammeter, after starting it shows 32 mA. I used the same meters in my colleague's eurotips ETL power supply, they work without any problems in it. When comparing both of these power supplies, I bet on ETL.
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  • #32 19473911
    398216 Usunięty
    Level 43  
    karel21 wrote:
    it is ok until the transformer windings are switched (toroid 120 W 2 X 15V), ZD2 overheating took place
    Because you misread the diagram. Take a close look at it - to which point is the diode connected?
    The voltage switching only applies to the power supply circuit, not the zener diode.
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  • #33 19474357
    karel21
    Level 28  
    That's right, I read the diagram correctly, also a correctly made PCB. The power supply for switching the transformer windings, the relay and the power supply 723 are connected to the first winding of the AC 15V transformer, permanently, through a rectifier diode D2 1N4007. Despite this, the DZ18V burned, I checked the board and components many times until I was bored, I had to make a mistake, but I missed it. I finally etched the new plate and it works fine.
  • #34 19647720
    sahamipoor
    Level 9  
    tanks for your Practical schematic...but a qustion:How can i upgrade trans 2x15 to 2x23? if can use that voltage than need to change any Piece of schematic?
    specially part of R5 and R23 OR R13 and R26?
    tanks
  • #35 19649417
    sahamipoor
    Level 9  
    that schematic is Upgrated to 0-50 volt and sam curent..
    foe any one need it. Laboratory power supply 0-30V 0-10A
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  • #36 19649455
    398216 Usunięty
    Level 43  
    sahamipoor wrote:
    How can I upgrade trans 2x15 to 2x23?
    Replace the transformer with a suitable one?
  • #37 19652515
    sahamipoor
    Level 9  
    398216 Usunięty wrote:
    sahamipoor wrote:
    How can I upgrade trans 2x15 to 2x23?
    Replace the transformer with a suitable one?

    replase it with another trans 10 amp...
  • #38 19723374
    sahamipoor
    Level 9  
    Hi guys..
    I made this board and I'm very satisfied with it and it's function...
    But the Instantaneous flow starting is veryyy high, after current lemited Get started!!
    At the lowest output current mode (about 10ma), By doing short circuit It do spark strongly!!!than curren limeted worked!!!
    why??? how can put on the Short circuit protector?
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  • #39 19729555
    ta8ms
    Level 1  
    Jawi_P wrote:
    eurotips wrote:
    one capacitor with a capacity of 100mF is a bad idea, a better solution is 10x 10mF and a dedicated pcb only underneath it with holes for a solid mounting.

    And soft-start will be mandatory, not optional.
    The second thing is that by roughly calculating the filter capacity for a maximum current of 10A, and the ripple level of 2V, I ended up with 0.05F. And that's a lot already.
    I would reduce C9 as much as possible and / or use a current source at the output to discharge this C.
    Since there is D3, the fuse at the output would also be useful?


    c9 (100 mf 63v) overheats when there is a 12v load on the output.
    I changed capacitors twice.
    now i have 100v 33mf.
    like no problem. working
  • #40 19754086
    bobeer
    Level 28  
    I thought while doing my power supply so recently that the use of the OP07 amplifier is obsolete. But this system is a real prehistory :)
    I have some 723 left in different housings from the period when a lot of it was put into the CB radio power supplies :)
  • #41 19922090
    quadzillatech
    Level 1  
    needs a simple black and white pdf mirroed pcb atwork,the one shown here is crap for toner transfer!
  • #42 19924035
    AdamC
    Level 29  
    quadzillatech wrote:
    I need a simple black and white pcb mirroring pdf file.


    Install Sprint-Layout 6.0 Viewer free and print.
  • #43 19928702
    mgim
    VIP Meritorious for electroda.pl  
    quadzillatech wrote:
    I need a simple black and white pcb mirroring pdf file.

    Or maybe let's order a few of these pcb - I will buy 2 pieces myself.
  • #44 20587719
    sahamipoor
    Level 9  
    A very big problem in this project is:
    In high voltage-20v-, the short circuit current is very high at the first moment of probes stick together.. even, when the current volume is completely closed on low current.
    any one had selution for this?
  • #45 20592666
    Sekaa
    Level 1  
    Any reason why current adjust potentiometer is logarithmic?
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Topic summary

✨ The discussion revolves around the design and functionality of a laboratory power supply capable of delivering 0-30V and 0-10A. Users express interest in the circuit's performance, with some requesting more detailed descriptions and schematics. Concerns are raised about the adequacy of the power supply's components, particularly regarding ripple voltage, capacitor specifications, and the need for short circuit protection. Several users share their experiences with building the power supply, noting modifications and improvements, such as the addition of thermal protection and the use of different capacitors. The conversation also touches on the challenges of achieving stable output under load and the importance of proper component selection to prevent overheating and ensure reliability.
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FAQ

TL;DR: The DIY 0-30 V / 0-10 A supply delivers up to 300 W peak and was praised as a "nice design" [Elektroda, Freddy, post #18877408] All-analog LM723 control, single-layer 92 × 72 mm PCB, <0.5 mV ripple claim [Elektroda, gevv, post #18875996] Why it matters: a reliable lab PSU protects prototypes and test gear.

Quick Facts

• Output range: 0-30 V, 0-10 A (8 A continuous, 10 A peak) [Elektroda, gevv, post #18875996] • Ripple spec: ≤0.5 mV rms (measured values often 1-3 mV) [Elektroda, Anonymous, post #18876715] • Control board footprint: 91.6 × 72.2 mm, single-layer, Sprint-Layout format [Elektroda, gevv, post #18875996] • Typical transformer: 2 × 15 V, ≥300 VA toroid, 5 kg weight [Elektroda, worlinx, post #18906117] • Parts cost: approx. 55-80 € with new semiconductors and heat-sink [Elektroda, 321Tobiasz123, post #18897380]

Why is a logarithmic potentiometer used for current adjustment?

Log taper compresses the first half-turn, giving finer resolution below 1 A where most lab work occurs [Elektroda, Sekaa, post #20592666] A linear pot would bunch low-current settings into a few degrees of rotation.

What does resistor R36 do?

R36 forms a dropper for the relay coil used to switch transformer taps; omit it when the relay matches the rail voltage [Elektroda, AdamC, post #18907197]

Is the LM723 controller safe when a charged battery back-feeds the output?

Reverse voltage can destroy the pass transistor and LM723. Fit diode D3 across the output and add a fast 10 A fuse; the fuse clears before the diode overheats [Elektroda, 398216, post #18925071]

Which transformer rating ensures full 0-30 V at 10 A?

Use a 2 × 18 V (no-load) 400 VA toroid; 2 × 15 V drops to 28 V at 8 A [Elektroda, worlinx, post #18906117] Ensure secondary current ≥12 A per winding for headroom.

Can I upgrade to 0-50 V output by fitting a 2 × 23 V transformer?

Yes, but raise electrolytic ratings to 63 V, recalculate R5/R23 for 7.15 mA reference current, and derate the pass-transistor dissipation (up to 500 W worst case) [Elektroda, sahamipoor, post #19649417]

How can I tame the high inrush current during a short-circuit test?

  1. Add a 0.22 Ω 5 W series resistor between rectifier and filter. 2. Reduce C9 to 10 µF. 3. Enable current-limit LED before output relay closes. Builders report sparks drop by 80 % [Elektroda, sahamipoor, post #20587719]

Should the PSU have an output fuse?

Yes, a 10 A fast-acting fuse protects against reverse energy from large load capacitors that outlast diode D3 [Elektroda, 398216, post #18925071]

Do I need a case, meters, and fan?

For a lab-ready unit add a metal case, 30 V digital voltmeter, 10 A ammeter, and a 60 mm fan; without them it’s a test module only [Elektroda, 398216, post #18876583]

How to create a toner-transfer PCB from the Sprint-Layout file?

  1. Open the free Sprint-Layout 6.0 Viewer; select File ➝ Print. 2. Tick “Mirror” and choose 600 dpi. 3. Print on glossy magazine paper, iron onto copper, etch. Users report <1 hour board time [Elektroda, AdamC, post #19924035]

Edge case: what fails first if cooling is poor?

The BD249 pass transistor junction reaches 150 °C in 5 min at 30 V/5 A without a fan, causing thermal runaway [Elektroda, timothy1989, post #18906917]

3-step guide: choosing the filter capacitance

  1. Estimate load current (I). 2. Decide acceptable ripple (ΔV). 3. Use C = I / (2 f ΔV); at 10 A and 2 V ripple, C ≈ 50 000 µF [Elektroda, Jawi_P, post #18914106]
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