Reducing 220V AC to 24V AC without Transformator

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Discussion Overview

The discussion revolves around methods to reduce 220V AC to 24V AC without using a transformer. Participants explore various circuit options, safety concerns, and the implications of using alternative methods such as resistors or capacitors.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Exploratory

Main Points Raised

  • One participant suggests using a resistor, but others warn that this method poses significant safety risks due to lack of isolation from mains voltage.
  • Several participants advocate for the use of a transformer as the only safe option, emphasizing the dangers associated with other methods.
  • A participant mentions that using a resistor might only be feasible with a constant load, raising concerns about varying load demands.
  • Another participant proposes using a series capacitor as a potential method, but highlights similar safety considerations as with resistors.
  • Some participants discuss the availability of transformers, noting that 12V transformers might be more accessible than 24V transformers.
  • There is a suggestion to use two 12V transformers in series to achieve 24V, with caution regarding phase alignment.
  • Participants express concern about the original poster's level of experience and the implications of their proposed methods.
  • One participant shares a calculation method for determining capacitor values based on load requirements, indicating a more technical approach.

Areas of Agreement / Disagreement

There is no consensus on the best method to reduce voltage safely. While many participants agree that a transformer is the safest option, others explore alternative methods, leading to a range of opinions and concerns about safety and practicality.

Contextual Notes

Participants emphasize the importance of safety and the risks associated with working with high voltage AC. The discussion includes various assumptions about load characteristics and the environment in which the circuit will operate, which remain unresolved.

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Need reduce 220V AC to 24V AC without transformator and I'm not sure about circuit.
Should I use resistor? Title is wrong (AC-AC)

Thanks.

[title corrected. -Russ]
 
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you could, but that would be a dangerous way of doing it. as there is no isolation between the mains voltage and the equip running from the 24V and any faults could easily cause the equip to have 220V potential present., causing serious electric shock or electocution.

in 4 words... DO NOT DO IT

one has to ask, why would you even consider it ?? what are you trying to achieve, other than a possible listing in the "Darwin Awards' list ?

Dave
 


Use a transformer.
 


When one refers to a transformer as a transformator, it would be best to just lock the thread. I mean seriously, what level of experience does this show?
 


It's not for me, and transformator is out of reach. My advice was to use resistor and protector (fuse) in series. Is there any better way?
 


A transformer is your only good option. Using a resistor would only work if you have a fairly constant load, and has many kinds of danger associated with it.

I'll repeat, buying a transformer is your only good option.
 


I agree 100%. But, transformator is not available.
 


Where are you from that they say "transformator"? I've never heard it called that.

Why is it unavailable? BTW, a lot of us here are engineers and have an ethical obligation to discourage the creation of circuits that can seriously hurt or kill a person. We're not trying to be unhelpful or dodge the question.
 


I know. East Europe. And I know name is "transformer", i didn't overlook text i wrote...i was in hurry maybe...
 
  • #10


"Transformator" is german for transformer; and Germany is nearer to Eastern Europe than GB or USA, so that´s that.
@track: you might tell us which application really needs 24V AC. Maybe somebody can suggest a workaround.
On the other hand, 12V tranformers may be more easily available than 24V. Take two 12V transformers and put the secondaries in series. (take care of the phase, or you´ll get 0V). You´ll find 12V transformers in halogen lamps resp. their mains adapters, in wallwarts, mains adapters, battery chargers, doorbell transfomers or ...
Find something you can cannibalize. Even in Eastern Europe, people throw away things which still have working parts inside.

Good luck with your project
 
  • #11


You need to consider two things to determine the viability of using a dropping resistor: 1) safety, and 2) current demand. If you cannot insulate this circuit from human contact, then it is not a viable option. If the load requires too much current or has a varying load demand then this option is probably not viable. Until you provide more information about the load, I do not think you will get any more useful information from this thread, other than - use a transformer.
 
  • #12


It depends on the load, but the cheapest and least power hungry option to get low voltage AC from higher voltage is sometimes a series capacitor. I have seen this trick with some indicator light, I think it was a diode.
 
  • #13


maimonides said:
On the other hand, 12V tranformers may be more easily available than 24V.
Heating and air conditioning controls run on 24VAC. There are tons of them available.
 
  • #14


0xDEADBEEF said:
It depends on the load, but the cheapest and least power hungry option to get low voltage AC from higher voltage is sometimes a series capacitor. I have seen this trick with some indicator light, I think it was a diode.

The same safety considerations apply to this as to a resistor, and as a minimum safety requirement you need a specially rated capacitor which is designed to minimize the chance of creating a short circuit if it fails. Remember that AC mains can pick up very high voltage spikes (1000V or higher) from electrical equipment switching on and off, lighning strikes, etc.

Given the low level of knowledge that OP seems to have, IMO the only safe options are a transformer or a complete "ready built" power supply.
 
  • #15


maimonides said:
"Transformator" is german for transformer; and Germany is nearer to Eastern Europe than GB or USA, so that´s that.
@track: you might tell us which application really needs 24V AC. Maybe somebody can suggest a workaround.
On the other hand, 12V tranformers may be more easily available than 24V. Take two 12V transformers and put the secondaries in series. (take care of the phase, or you´ll get 0V). You´ll find 12V transformers in halogen lamps resp. their mains adapters, in wallwarts, mains adapters, battery chargers, doorbell transfomers or ...
Find something you can cannibalize. Even in Eastern Europe, people throw away things which still have working parts inside.

Good luck with your project

Thank you maimonides. My friend works on ocean and he asked me for advice. He said there is no more transformers around to use. I don't know anaything about device but I think it's not some huge load. I told him about resistor and to be extremely careful. He did it on test board and it works for now. Told him about possible heating and safety too. Here, on forum, I just wanted to ask is there any other option. Thanks everyone.
 
  • #16


track said:
Thank you maimonides. My friend works on ocean and he asked me for advice. He said there is no more transformers around to use. I don't know anaything about device but I think it's not some huge load. I told him about resistor and to be extremely careful. He did it on test board and it works for now. Told him about possible heating and safety too. Here, on forum, I just wanted to ask is there any other option. Thanks everyone.

i have a way. But it will use for only a load. that capacitor in resonant course. capacitive reactance. xc=1/(2*pi*f*c) unit is Ohm. So you need to know full load current.

ex.

Load 3A 24Vac
source 220 Vac 50Hz

direction. 1. 220-24 = 196 Volt Volt on Capacitor
2. 196/3 = 65.33 Ohm Current pass Capacitor
3. 1/(2*pi*50*65.33) = 48.723 uF

try connecting the capacitor 50 uF 650 V by 220Vac---->Capator---->load
GND ----------------->load
 
  • #17


Re: resistor, that would really depend on what you're powering, it's load characteristics and requirements etc.

Averagesupernova said:
When one refers to a transformer as a transformator, it would be best to just lock the thread. I mean seriously, what level of experience does this show?
quit complaining. Several languages call the transformer "transformator".
 
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  • #18
track, is the 220 VAC grounded (perhaps not the right word to use on the ocean)? Will the circuit using the 24 VAC be accessible? Can the circuit be touched while operating? Can objects be inserted through holes in the enclosure while operating? Will the resistor or the wiring be exposed to moisture?

How much current does the load draw and how much does it vary? If the load varies you may want to consider a voltage divider instead of just a dropping resistor. Is there an on off switch and on which side of your dropping resistor is it located. If it is on the load side then when the switch is off, the load side of the resistor will be at 220 VAC, unless you use the voltage divider. If the dropping resistor is some distance from the switch, the wire between them must be in conduit. It would be best if the dropping resistor and the 24 VAC circuit can be in a moisture tight enclosure however that may create overheating inside the enclosure.

Televisions do not use power transformers and considering the number that have been built there have been very few problems.
 
  • #19


Dmytry said:
quit complaining. Several languages call the transformer "transformator".

Oh give me a break. You really expect anyone here with a conscience to advise someone to work with 240 volt mains by calling a transformer a transformator while otherwise displaying NO evidence of English being a second language also wondering about using a series resistor as a proposed solution? Regardless of the expertise of the OP the first post was all there was to go on at the time.
-
So lighten up.
 
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  • #21


AlephZero said:
Given the low level of knowledge that OP seems to have, IMO the only safe options are a transformer or a complete "ready built" power supply.
I strenuously agree!

I'm locking the thread due to the danger of humoring an alternate solution.
 

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