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How to Convert 18-36V Adjustable AC from Converter to 15Vdc/14Vdc 2A DC - Ready Devices

Wiejuk 8241 13
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  • #1 16769721
    Wiejuk
    Level 7  
    Posts: 7
    Hello.

    I have a problem, namely I have the need to convert alternating current from the converter to direct current. The converter has an adjustable voltage from 18 to 36V and 2A. Finally, it needs a current of 15Vdc / 14Vdc and 2A. I would not like to solder rectifier diodes, so I am asking for links to ready devices.

    Thank you, please help me quickly.
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  • #3 16769971
    Wiejuk
    Level 7  
    Posts: 7
    Thanks, but could you send me the diagram and the bridge. I don't know anything like that, so please. And what kind of capacitors
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  • #5 16770060
    marekhab
    Level 33  
    Posts: 1349
    Help: 251
    Rate: 267
    The scheme is very simple.
    You select capacitors according to the catalog note of the L78S15 stabilizer
    on input C1-0.33uF
    behind the stabilizer C4 - 0.1uF
    Electrolytic I give about 100uF at the input (at the appropriate voltage)
    behind the stabilizer 470uF - 1000uF
    In the diagram, I misspelled the stabilizer instead of the L78S15, I described the LM78S15
    Attachments:
    • ZASILACZ.pdf (12.14 KB) You must be logged in to download this attachment.
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  • #6 16770064
    cyann
    Level 20  
    Posts: 278
    Help: 44
    Rate: 18
    wojtek 9007 wrote:
    Capacitor of your choice;

    Any from here? My friend probably deigns to joke.
    Wiejuk wrote:
    needed to convert alternating current from the converter to direct current.

    What is this inverter?
  • #7 16770069
    marekhab
    Level 33  
    Posts: 1349
    Help: 251
    Rate: 267
    wojtek 9007 wrote:
    Hello - you can assemble such a thing; How to Convert 18-36V Adjustable AC from Converter to 15Vdc/14Vdc 2A DC - Ready Devices

    Without a stabilizer, about 24V will come out, as you can see the founder of the topic needs 15V
  • #8 16770077
    398216 Usunięty
    Level 43  
    Posts: 34017
    Help: 3914
    Rate: 9192
    Wiejuk wrote:
    I would not like to solder rectifier diodes
    You can buy a bridge ... but I'm not entirely sure if Schottky diodes will not be necessary in the case of the converter ...
  • #9 16771177
    Wiejuk
    Level 7  
    Posts: 7
    Thanks marekhab but could you tell me where I can buy all this ??
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  • Helpful post
    #11 16771227
    marekhab
    Level 33  
    Posts: 1349
    Help: 251
    Rate: 267
    Any electronics store, start with looking for a stabilizer (L78S15), the rest should be standard capacitors, very common.
    http://www.sklep.monster.pl/78s15-2a-to-220-stabilizator,4,36627,17445
    http://www.sklep.monster.pl/6a-400v-piny-kwadrat-kbpc-604-mostek,4,36121,635
    http://www.sklep.monster.pl/470uf-35v-10x17-105-lea-elko,4,45038,14694
    these capacitors must be purchased at least 10 pcs
    http://www.sklep.monster.pl/100nf-50v-kond-ceramiczny-100szt,4,36872,2509

    http://www.sklep.monster.pl/100uf-35v-100szt-6x11-105-lea-elko,4,45038,15385
    If you have any questions, write to me and I will try to help.
    In another store you can also buy these items, I chose the first one where I buy and they have a large selection.
    IMPORTANT L78S15 stabilizer (15Volt 2 Amps), stabilizer on the heat sink.
  • #12 16771238
    Wiejuk
    Level 7  
    Posts: 7
    I don't understand a bit of the last sentence. Should I mount a heat sink on the stabilizer?
  • #13 16771245
    jdubowski
    Tube devices specialist  
    Posts: 21595
    Help: 2511
    Rate: 2792
    Wiejuk wrote:
    I have a problem, namely I have the need to convert alternating current from the converter to direct current.


    What frequency?

    Wiejuk wrote:
    I would not like to solder rectifier diodes, so I am asking for links to ready devices.


    If we are dealing with frequencies over 400Hz, it is rather a bridge made of fast diodes.

    Wiejuk wrote:
    I don't understand a bit of the last sentence. Should I mount a heat sink on the stabilizer?


    And what is difficult to understand here - the stabilizer converts excess voltage into heat (simplified), so a heat sink will be necessary.
  • #14 16773412
    Strumien swiadomosci swia
    Level 43  
    Posts: 27411
    Help: 1403
    Rate: 6379
    Wiejuk wrote:
    I have a problem, namely I have the need to convert alternating current from the converter to direct current. The converter has an adjustable voltage from 18 to 36V and 2A


    Buddy, specify whether the converter has an alternating voltage at the output, which is very strange and unlikely.
    Does it have unstabilized constants.
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Topic summary

✨ The discussion revolves around converting adjustable AC voltage (18-36V) from a converter to a stable DC output of 15V or 14V at 2A. Users seek ready-made solutions instead of DIY soldering rectifier diodes. Recommendations include using a bridge rectifier and specific capacitors for voltage stabilization. The L78S15 voltage regulator is suggested for achieving the desired output, with advice on necessary components such as capacitors and heat sinks. Links to purchase components and diagrams are provided, emphasizing the importance of selecting appropriate diodes and ensuring proper heat dissipation for the stabilizer.
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FAQ

TL;DR: For a 2 amps rectified supply, use a ready bridge, filter capacitors, and an L78S15 regulator. “At 2 amps, you'll probably need a small heat sink.” [Elektroda, jgorsk, post #16771211]

Why it matters: This FAQ helps beginners convert an adjustable AC output to a stable 14–15V DC, safely and with off‑the‑shelf parts.

Quick Facts

How do I convert 18–36V AC at 2A to a stable 15V DC using ready parts?

Rectify with a ready bridge, smooth with electrolytics, then regulate with an L78S15. Use 0.33µF input and 0.1µF output capacitors on the regulator, plus ~100µF at input and 470–1000µF at output. Mount the stabilizer on a heat sink. [Elektroda, marekhab, post #16770060]

Can I avoid soldering individual diodes for rectification?

Yes. Use an off‑the‑shelf rectifier bridge module. Add two capacitors for filtering and a voltage stabilizer to reach 15V. This keeps wiring simple and reliable for beginners. [Elektroda, marekhab, post #16769825]

What exact capacitors should I pick around the L78S15 regulator?

Use 0.33µF at the input and 0.1µF at the output of the L78S15. Add an electrolytic of about 100µF at input and 470–1000µF after the regulator. Select appropriate voltage ratings. [Elektroda, marekhab, post #16770060]

Do I need a heat sink on the stabilizer, and why?

Yes. The linear stabilizer turns excess voltage into heat during regulation. “The stabilizer converts excess voltage into heat,” so a heat sink prevents overheating at 2A. Ensure good thermal contact. [Elektroda, jdubowski, post #16771245]

Which bridge rectifier works for 2A, and should it be cooled?

A KBPC‑style bridge (e.g., KBPC5010) is suitable and can bolt to a small heat sink. At 2 amps, added cooling improves reliability and temperature margins. [Elektroda, jgorsk, post #16771211]

What happens if I skip the voltage regulator after rectification?

Without the stabilizer, the DC after the bridge and filter will be around 24V. That exceeds 15V device limits and risks damage. Always regulate to the target voltage. [Elektroda, marekhab, post #16770069]

Does AC frequency matter when choosing the rectifier?

Yes. For frequencies over 400 Hz, use a bridge made from fast diodes. Standard bridges can overheat or fail at high switching frequencies. [Elektroda, jdubowski, post #16771245]

Do I need Schottky diodes when the source is an inverter?

It can be necessary. A contributor warned that Schottky diodes may be required for converter outputs. They reduce losses and handle faster waveforms better. [Elektroda, 398216 Usunięty, post #16770077]

Where can I buy all the parts in one go?

Any electronics store should stock an L78S15, a rectifier bridge, and capacitors. One poster listed sample shop links and reminded to heat‑sink the stabilizer. [Elektroda, marekhab, post #16771227]

Quick 3‑step: How do I wire the bridge, capacitors, and L78S15?

  1. Connect AC leads to the bridge’s “~” terminals, then bridge “+” to the filter input.
  2. Add ~100µF and 0.33µF at the regulator input; wire L78S15 input to the smoothed “+”.
  3. From regulator output, add 0.1µF and 470–1000µF, then feed the 15V load. [Elektroda, marekhab, post #16770060]

My source says 18–36V and 2A—will a 2A regulator be enough?

Yes for current, but ensure thermal design. L78S15 is a 2A class part; use a heat sink because drop times current equals heat. Add adequate airflow if enclosed. [Elektroda, marekhab, post #16770060]

Is the converter’s output truly AC or unstabilized DC?

Clarify this first. A participant found AC at a converter output unusual and asked whether it was unstabilized DC instead. Verify with a meter before rectifying. [Elektroda, Strumien swiadomosci swia, post #16773412]

What if my AC frequency is unknown?

Measure it or check the converter’s datasheet. If it exceeds 400 Hz, choose fast‑recovery diodes or Schottky types for the bridge. This avoids excessive heating. [Elektroda, jdubowski, post #16771245]

Can I get 14V instead of 15V from this setup?

The thread solution centers on 15V using L78S15. It does not detail a 14V regulator choice. If 14V is essential, seek a regulator rated for 14V output. [Elektroda, marekhab, post #16770060]

Any beginner mistakes to avoid with this build?

Do not skip the regulator, or the output sits near 24V after rectification. Always add the small 0.33µF and 0.1µF capacitors close to the regulator pins. Heat‑sink the stabilizer. [Elektroda, marekhab, post #16770069]
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