Simple 230V AC to DC converter

[ricko_uk]

Hi,
I need to build a 230V AC (mains) to 230V DC converter. It needs to be simple and reliable so the obvious initial thought was just a bridge rectifier with massive capacitors to smooth it out but the output would not be flat DC, it would obviously have smoothed out peaks every cycle.

I remember seeing many years ago an extremely simple circuit that was providing very smooth DC output and at the time I thought it was very clever solution. But cannot find it anymore. It was not just a rectifier and massive caps. It had a few extra components but less than a handful. I googled it for days but cannot find that circuit anymore. Any suggestions?

It is to be used only in the UK and in controlled environment by an experienced engineer So the only safety required is just a fuse for over-current protection.

The specs are as follows:
- 230V AC to DC
- 5A
- when the load is on the voltage should be as steady as possible. This is the most important spec.
- the load is only resistive (heating elements)
- the heating element itself has a thermostat integrated in it to turn it on and off. It switches on/off every 20-30 seconds
- voltage dips transients when turning on and off are acceptable (perhaps an inrush current limiter on the output might help improve those too?)

Does anybody have any clever suggestion/idea?

Thank you as always

[Benta]

I'm unable to see the point of this.

[langwadt]

what's the point of dc for a heating element?

[PCB.Wiz]

- the load is only resistive (heating elements)
- the heating element itself has a thermostat integrated in it to turn it on and off. It switches on/off every 20-30 seconds

Heating elements do not usually need  AC-DC, the thermal inertia is enough, especially if this turns on/off every 20-30 seconds.

- 230V AC to DC  5A
- when the load is on the voltage should be as steady as possible. This is the most important spec.

What you describe is now a voltage regulator.

Do you want to regulate voltage, or power ?  Does the heater resistance change matter to you ?

If you want to regulate voltage, there are some choices :

• Linear is simple, but at 5A a linear control of only 12V (5%) change, means 60 WATTS of heat loss in the regulator.
• Switch mode is much less lossy, but a 230V 5A buck regulator is non-trivial.

Alternatives are Phase control of the AC mains. Here, you can regulate average power/voltage, with some lag.
You pick some control range ( eg +/- 5%) and then regulate at -5% for ideal mains and -10% for Mains +5% etc

eg if the mains changes, you can correct that on the next mains cycle.
Half cycle pairs should have identical phase angles, to keep the mains load free from DC.

[nightfire]

Going DC for touchable parts CAN make sense, IF done correctly- so you would have to stay below the accepted limits for safety voltage, meaning that you would need a transformer for stepping down the 230VAC.
If I understand UK regulations correctly after a very short google search, this would be below 75V DC.

If this is of no concern, and you simply need some nice heater somewhere, it is also easier to switch a AC load than a DC load. Also you can use a simple circuit breaker (RCCB) as overcurrent protection, if there is enough space.

[amyk]

I agree with the others about DC being irrelevant for heating elements, and suggest a ferroresonant transformer for regulating the voltage.

[langwadt]

I agree with the others about DC being irrelevant for heating elements, and suggest a ferroresonant transformer for regulating the voltage.

what's the point of regulating the voltage if it has a thermostat?

[coromonadalix]

whats the point in all of this ...

[Andy Chee]

I envisage the heating elements are being use for some kooky free energy experiment or health quackery device, hence the requirement for DC.

[amyk]

I agree with the others about DC being irrelevant for heating elements, and suggest a ferroresonant transformer for regulating the voltage.

what's the point of regulating the voltage if it has a thermostat?

Ask random questions, get random answers

[Someone]

health quackery device

Probably:
https://www.eevblog.com/forum/projects/ac-infrared-sauna-heaters-driven-with-dc/

[Andy Chee]

Does anybody have any clever suggestion/idea?

My proposal is a power factor correction boost regulator.  You can either build a reference design from a datasheet, or purchase a module and equip it with the appropriate heatsink & capacitor.

https://www.onsemi.com/pdf/datasheet/mc34262-d.pdf

https://product.tdk.com/system/files/dam/doc/product/power/switching-power/ac-dc-converter/catalog/pf1500b_e.pdf

Either way, it's not "simple".

I remember seeing many years ago an extremely simple circuit that was providing very smooth DC output and at the time I thought it was very clever solution.

You could be referring to LM317/7812 circuit variants:



http://web.mit.edu/sp.716/www/datasheets/AN-103.pdf

[bdunham7]

Does anybody have any clever suggestion/idea?

If you use anything other than a PFC SMPS you're going to have terrible efficiency and/or power factor issues.  Converting 230VAC to DC using simple systems like rectifiers and capacitors will necessarily result in the input current being pulsed.  Regulation other than by switching will result in heating losses.  The circuit you are thinking of may be a capacitor multiplier, but it while it may smooth out your DC power it won't solve any of the other problems.

[Haenk]

As Someone already pointed out, this is a complete nonsense discussion.
"Driving an IR heater by DC to reduce "the magnetic field" is the intention. Yeah, whatever. Don't forget to install that aluminium foil to protect you from orgone.

[Siwastaja]

- the heating element itself has a thermostat integrated in it to turn it on and off. It switches on/off every 20-30 seconds

And you are 100%, like 200% sure and certain that this thermostat definitely accepts DC? I mean, mechanical thermostats that accept 230VAC cost like $1, while the DC ones cost hundreds of $, if you are able to find any. Driving DC into a normal thermostat causes a fire, nearly 100% guaranteed.

I get you are into some kind of new age nonsense bullshit, but what you are now doing is highly risky, you are very likely to burn the houses of your victims down. Please stop.

Alternatively, I think we should start gathering some information about this guy and report to authorities to prevent loss of life.

[themadhippy]

just bolt a 240v dynamo onto a 240v AC motor,2 components job done

[eutectique]

- It needs to be simple
- the voltage should be as steady as possible

Do I see contradicting "requirements" ?

[Spar59]

I think I am pretty much in agreement with others in that this is a pointless exercise but there nis an important point I haven't yet spotted:

Applying 230V aC to a simple rectifier (presumably a bridge) and smoothing capacitor circuit will NOT get you 230V DC on the capacitor!

The capacitor will charge to the peak value of the AC wave i.e. 325V, the actual waveform of the output would be a steady 325V DC with huge capacitor and little load but more typically when load is applied it would start from that peak of 340V and ramp downwards until it reaches the same value as the rising value of the next AC half cycle at which point it will track it back to the peak (well almost track it due to rectifier drops and charging path resistance).

[soldar]

- when the load is on the voltage should be as steady as possible. This is the most important spec.

I agree with others that the project is pointless and a waste of time.

BUT

The simple way to meet "the most important spec" is to filter the rectified voltage with a pi filter with capacitors and inductors (one or more sections).

[Johnny B Good]

Hi,
I need to build a 230V AC (mains) to 230V DC converter. It needs to be simple and reliable so the obvious initial thought was just a bridge rectifier with massive capacitors to smooth it out but the output would not be flat DC, it would obviously have smoothed out peaks every cycle.

I remember seeing many years ago an extremely simple circuit that was providing very smooth DC output and at the time I thought it was very clever solution. But cannot find it anymore. It was not just a rectifier and massive caps. It had a few extra components but less than a handful. I googled it for days but cannot find that circuit anymore. Any suggestions?

It is to be used only in the UK and in controlled environment by an experienced engineer So the only safety required is just a fuse for over-current protection.

The specs are as follows:
- 230V AC to DC
- 5A
- when the load is on the voltage should be as steady as possible. This is the most important spec.
- the load is only resistive (heating elements)
- the heating element itself has a thermostat integrated in it to turn it on and off. It switches on/off every 20-30 seconds
- voltage dips transients when turning on and off are acceptable (perhaps an inrush current limiter on the output might help improve those too?)

Does anybody have any clever suggestion/idea?

Thank you as always

 As many have already  questioned the whole point of this exercise, I have to wonder what it is you're trying to achieve. The only thing that makes any sense is that you're trying to test and verify the actual heat output from these (1KW ?) thermostatically controlled heaters. For this, all you need is a suitable variac and / or a ferro resonant voltage stabilising transformer with a modern day plug in "energy consumption monitor" (AKA "wattmeter".

 In fact, since these heaters include a built in thermostat switch designed with ac current supply in mind, a dc supply has to be avoided if you wish to prevent the switch contacts becoming welded into a permanently closed state.

 As for "inrush current", the nichrome resistance wire typically used in heating elements, unlike tungsten filament incandescent lamps which typically demonstrate a 10 to 1 inrush current (even higher for tungsten halogen lamps), only suffers a moderate ( circa 1.2 to 1.3 to 1 afaicr) cold to operating temperature inrush current effect which normally isn't an issue unless you're explicitly testing this characteristic.

 If my assum(e)ption is wide of the mark (ASS-U-ME), please feel free to clarify what it is you're trying to achieve.

[coppercone2]

heater with DC might sag because of the non alternating magnetic field when hot

[Andy Chee]

As many have already  questioned the whole point of this exercise, I have to wonder what it is you're trying to achieve.
 If my assum(e)ption is wide of the mark (ASS-U-ME), please feel free to clarify what it is you're trying to achieve.

A few posts up give a link to another thread by the OP which gives much greater context.

In summary, the OP is trying to eliminate AC power due to perceived human health impacts of electromagnetic radiation.  The load is an infrared lamp for a health sauna.

[coromonadalix]

 


yeah   remove all wireless  cell phone signals around you  loll

but seriously  you have many conversion losses etc ...    and it seems you deal with anxious people ?

[p.larner]

looks like another closet lunatic posting this b.s to me!.

[Terry Bites]

Unless there are very stringent e and m field constraints, it seems pretty pointless to run a resistor on DC.
Have you considered a 24 pulse three phase rectifier, a much smaller cap will do nicely.