Hi, Luciano
Seems not only for the Englishmen ...
3 Phases ... Your home really is a Castle !!!
Alain
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An English man's house ...
Hi, Luciano
Seems not only for the Englishmen ...
3 Phases ... Your home really is a Castle !!!
Alain
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Why insist on using 32 Bits when you're not even able to deal with the first 8 ones ??? ehhhhhh ...
************************************************** ***********************
IF there is the word "Problem" in your question ...
certainly the answer is " RTFM " or " RTFDataSheet " !!!
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Hi Alain,
This is what we get here.
Only this option is available.
Our milking machines use three-phase motors.
Best regards,
Luciano
PS: En réalité j'habite dans un petit village au
sud des Alpes. Avec nos amis et voisins italien
on partage la langue et la culture. Ciao!
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Originally Posted by Melanie
In this case, the circuit will protect itself but kill the user !
--------------------------
"If the Earth were a single state, Istanbul would be its capital." Napoleon Bonaparte
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Neutral And Ground
The big difference between ground and "common" or "neutral" is the voltage drop that is developed on the neutral wire due to the fact that it has the same current flow as the line conductor (What goes out must return) (Load current x DC resistance of neutral conductor between receptacle and breaker box= Voltage difference between neutral and ground at the receptacle). Normally the voltage drop is neglible except in long circuit runs with higher current loads. The neutral and ground wires are normally connected together (bonded) at the breaker box. I totally agree that the fuse definitely needs to be in the "hot" or "line" or "mains" line to perform a safety function.
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Question of costs and safety!
This whole thread, I think, is on the brink of veering off!
When U are choosing a very low cost alternative there are many conditions
which are subject to be adhered. first being a circuit a "live" it is not to be
used as any run of mill usage like powering something which can get body
contact. Secondly if "safety" being prime concern then why use "transformerless " supply at all? If I have to get 'risk' of capacitor shorting
eliminated I would rather use a double wound txr and add the cost to safety
of supply!!! Some people are just attached to fancy of some components and
don't look at overall concept of a circuit or device.
How nice it will be if everyone should consider to buy a Merc or BMW as
it won't let U down in middle of road like small car?
For Melani's information we men like to live dangerous but do consult
our purse before risking our reputation in hotel or pub !
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Transformerless.png
Nice to see the modified diagram but U have missed a vital component.Hi All,
There seems to be a great deal of confusion among hobbyists and new professionals concerning ground and circuit ground.
I post this diagram to help illustrate what Melanie already pointed out.
There should be small resistor like 22 Ohm( Ur LAW) to 47 ohm in serries
with 1uf/250V capacitor ( Melani wont approve of this ).Otherwise in few
days that capacitor will be reduced to open circuit (if of metallised film
type) or get short (if Film foil type) and whole ckt will go up in smoke.
The resistors should be atleast 1/2 watt type ( 1watt better). A high value
resistor like 220K is better placed across capacitor to protect user if he
accidently touches capacitor even when ckt is disconnected from mains.
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Thanks for the information.
Psdayama,
Thanks for the knowledgeable input. Makes the thread valuable to anyone reading it.
http://www.picbasic.co.uk/forum/atta...1&d=1163524317
-Adam-
Last edited by Pic_User; - 14th November 2006 at 17:13. Reason: Adding corrected drawing
Ohm it's not just a good idea... it's the LAW !
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It's not cost saving, but size too...
When this thread started, I put forward an example of a Fan Controller. This fits inside a standard size wall recess which can be as shallow as 15mm. They just don't make transformer bobbins that small - and consider you have to wind around 8,000 turns of 0.01 or 0.008mm wire for a 0.5VA transformer primary - and even then it'll run warm because you really need about 12,000 turns at that rating and you quickly discover that there are minimum sizes for sensible transformer manufacture. Wire that thin is scary stuff to work with as it's so fragile.
Cost of course is a factor. A small Capacitor, a Diode and an Opto-isolator makes for a simple 'Fuse Blown' or 'Power Fail' detect circuit. Whilst a Transformer is nice, it just takes up too much PCB space - and you can't do it for 20 cents.
Finally, my choice of X2 Capacitors is deliberate. If you correctly chose your Capacitor, series Resistors are unnescessary. In all the years I've been designing these kinds of circuits, I've never had any failures of X2 Capacitors. Actually, I can't ever recall having a defective X2 Capacitor in any circuit. Chose your components wisely from reputable sources and you'll not have any troubles.
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Microchip application note
This App note has a lot of good information on transformerless PSU's
http://ww1.microchip.com/downloads/e...tes/00954A.pdf
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Self contradictory!!
Your very first statement is exactly opposite to end one.
Check size of X2 capacitor and normal metallised film capacitor. You will
find X2 atleast 2times bigger than normal. Obivously no manufacturer can
provide X2 at same price so they are atleast 3times expensive.
Metallised film caps which are supplied by UL approved manufacturers will
NEVER short. They may become open with overload. So either way the
argument is pointless! A serries resistor costs less than a cent and it is
wise to limit inrush current.(In all situations). You may have not recieved any complaint with
X2 capacitor as they if not used properly become open circuit SLOWLY. If
anybody notices difference in EMI after 6months or years later, it will be
sheer accident!
I have designed and made a fridge controller (Blind type) with 555 and
similiar transformerless power supply some 3-4 years ago. I have used
normal 680n / 250V capacitor --( our system is 240V 50Hz) and those are
working nicely last 3-4 years and saving 100s of Rs. every month for the
users without any recall.
Last edited by psdayama; - 15th November 2006 at 09:44.
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Now it would be a good time to post that schematic here.
BTW; let me remind you that Melanie has a Klingon cloaking device.
----------------------------------
"If the Earth were a single state, Istanbul would be its capital." Napoleon Bonaparte
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Take a hundred engineers and give them the same problem, and you're likely to get a hundred different solutions, and each will argue that thiers is the best approach. I think this thread has been pretty much done to death, and there's more than enough information here for anyone but the most inept to design their own. And they, through natural selection when playing directly with the supply mains, will ensure that the standards remain high for the rest of us on the forum.
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Just do a web search for X-10 schematics. They've been using a metallised film cap and series resistor for many years in the millions of UL approved switches and modules they've sold.
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Hi,
About the resistors:
(Click to enlarge the picture).
Best regards,
Luciano
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Fridge controller
Hi sayzer,
well here is the schematic. Im not so good in drawing like U.
I had a fridge which had thermostat gone bust. So I made this ckt and
saved lot of energy 0.75KWHr /day instead of 5KWHr/day. I also found
that most of fridges have improper settings evenif the thermostat is OK and
there is lot of frost and they consume abt 3-4 KWHr/day. So making a
commercial unit costing Rs.400/- ( $9 appx.) have installed in abt 20-30
homes and they are all saving energy down to 1KWHr/day.
The consumption of unit is less than 05VA and there is no area even feeling
warm. I cant afford to use X2 capacitors in this as that will push cost of unit.
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Hi all
All said and done, we have to accept that what we try to design and implement will be used by us only and that there would not a future occassion to extend the equipment using such PSU to other eqpt, which might create ground loops- a possible shock.
many times we will be pre occupied and would like forget the non isolated psu and take it for granted that we will be safe--
AS SUCH I SUUGEST THAT WE SOULD NOT PRACTICE THIS MODE AT ALL-- ok for academic interest.
Regards,
Sarma
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transformerless PSU
Melanie i was wondering if you could suggest a manufacturer of the VDR used in your design.
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The VDRs (aka Varistors) we use are made by Joyin Co of Taiwan. They work out between 5-15 cents (US) each depending on the flavour. If finding Joyin is a bit elusive in your neighbourhood, then push this link...
http://www.motionnet.com/cgi-bin/sea...?a=cat&no=2149
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Dangerous Stuff
Early last year I designed mark II of my PC-Controlled Mains Switch. As with the original design, I opted for a transformer-less solution. 240VAC directly feed to three paralleled X2 class rated caps, then to a full wave bridge powering two shunt regs to produce 5, 12V rails respectively. The entire circuit is optically isolated from the PC at all times.
During development of the Windows-based software which drives it, one of the opto's shorted when my multimeter probe slipped. This turned out to be disastrous! It took out the entire parallel port on my notebook weighing in at the time around $3,000 !!! &*@!()K
The paramedics managed to revive me after several hours. When I came to, had a beer and faced the inevitable reality of my "accident". The notebook was sold at a bargain price to someone who wasn't terribly concerned with the absence of the parallel port.
The project was finally completed on a desktop PC and published in the Silicon Chip magazine last July. Unlike the first version, it was a complete flop. No kits were produced. Double the features but twice the price to build. The system is easily expandable - (up to 8 units can be daisy chained together) - Windows-based software to boot, undoubtedly there will be no MK III, and I'm certainly in no rush again for a cost-effective transformer less solution.
*Always take extreme care when working with mains power!
http://www.siliconchip.com.au/cms/A_107104/article.html
Best regards,
Trent Jackson
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transformerless PSU
Melanie,
I have tried to emulate your schematic and have found that without the 5V Regulator the ciruit provides 11.7 V, but as soon as I add the regulator or put any kind of load across the circuit it drops to almost nothing. Does anyone have any idea of why this may be happeneing?
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and yet another SIM victim... trust me and Melanie, it's circuit works.
Just for my own curiosity, which SIM did you used?
Steve
It's not a bug, it's a random feature.
There's no problem, only learning opportunities.
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Have designed a similar circuit.
Interestingly, I designed a similar circuit myself early last year. Few variations with mine. Used two TO220 regs. (LM7805 & LM7812 1 amp packages) Plus I also have a bit more available current due to full wave rectification. This arrangement also makes the circuit a little safer too. The low voltage rails are tied close the Neutral line of the 240VAC mains, so provided you connect to a correctly wired GPO (240VAC socket), most of the circuit is nominally at low potential. (*Claimed by Silicon Chip publications)
Anyhow, I discovered a whole bag full of problems with this circuit on the bench. In theory, it all should have worked. In practice, I found that the 5 & 12V regs were unable to deliver the goods. The circuit was pre-calculated and should have been good for about 1.2W of power- 100mA on the 12V rail. The 12V rail failed to provide even a third of this. I have no explanation to the problem and my thoughts are entirely inconclusive. I discovered only about 20mVPP of ripple in the raw DC rail supplying the regs. This is more than an acceptable level of AC component.
In the end I settled for two zener-based shunts to produce 5 & 12V rails respectively. Circuit works well.
Trent Jackson
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Off-Load the VDR clips the upper voltage from climbing too high. But if your supply is crashing, then you are trying to draw too much current - that actually is an additional safety feature. If you measure the volts across the supply Capacitor, you'll find the whole lot appearing there.
If you just put a 5v Reg (like a 78L05) in circuit and your output crashes, then (a) your Regulator is defective, or (b) your main supply Capacitor is the wrong value for the current you're drawing or itself defective.
That circuit and the values given is good for 10-30mA total. You can measure how good the circuit is by putting some Resistors in series with a meter set to mA across the 11v VDR. Put another voltmeter across the VDR. Now increase the load (ie decrease the Resistance) until the voltage just starts to drop to say to 10v. That will the the maximum (total) useable current from your PSU based on the main Capacitor you're using.
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To ease my mind I'd like to tell myself that I had two faulty regs.
20-30mA?, lets see...
XC = 1/ 2Pie(FC)
= 1 / 6.283185307 x (50Hz x 0.00000047F)
= 1 / 6.283185301 x 0.0000235
= 6772Ω
Now, there's a 470K bleed resistor in parallel with the cap.
XC = 1 / (1/ 6772) + (1 / 470K)
= 1 / ( 0.000147666 + 0.000002127)
= 6675Ω
As you can see the 470K only knocks about 100Ω off the total reactance.
For those who don't know, reactance in an AC circuit is like resistance.
Rectified high voltage rail from RMS value (full wave rectification)
= 240VAC x 1.414
= 339.36VDC 'Peak value, has same heating effect as 240 RMS
(half wave rectification)...
= 0.637 x 339.36VDC
= 216.17VDC Average
Absolute max current (short circuit)
= 216.17VDC / 6675Ω
= 32.38mA
There's a 5V rail being produced from a LM78L05. It's input VCC must always be at least 2.5V greater than the output in order for it to maintain adequate regulation.
Absolute max current @ 5V
= (216.17VDC - 7.5VDC) / 6675Ω
= 208.67VDC / 6675Ω
= 31.26mA
Absolute max power @ 5V
= 31.26mA x 5
= 156mW
Spot on. In the perfect World, Melanie's supply should be good for about 30mA.
Component tolerances often compromise the accuracy of calculated events. Such is life.
Trent Jackson
Last edited by T.Jackson; - 7th March 2007 at 12:38. Reason: Typo
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Getting more power
Want more power from this circuit? No problem...
Clearly, the third calculation - (full wave rectified high voltage rail from RMS value) - shown in the previous post tells us that rectifying both sides of the sine wave is beneficial.
Lets see how much current we can squeeze out using full wave rectification.
XC = 1/ 2Pie(FC)
= 1 / 6.283185307 x (50Hz x 0.00000047F)
= 1 / 6.283185301 x 0.0000235
= 6772Ω
Now, there's a 470K bleed resistor in parallel with the cap.
XC = 1 / (1/ 6772) + (1 / 470K)
= 1 / ( 0.000147666 + 0.000002127)
= 6675Ω
High voltage DC rail - (full wave rectification)...
= 240VAC x 1.414
= 339.36VDC
Absolute max current (short circuit)
= 339.36VDC / 6675Ω
= 50.84mA
Absolute max current @ 5V
= (339.36VDC - 7.5VDC) / 6675Ω
= 331.86VDC / 6675Ω
= 49.71mA
Absolute max power @ 5V
= 49.71mA x 5
= 248mW
% More power
(248mW / 156mW) x 100
= 59%
That's quite a significant increase. You could also push things even further by
decreasing XC - use a larger cap or parallel a few together. Practical limitation of such a circuit is about 1W. Takes up too much real estate and defeats the cost-effectiveness of it otherwise.
All told, it's better to use a transformer...
Trent Jackson
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Why is it better to use a transformer?
Short answer is because it's much safer. But there are also other advantages
as I will spell out here...
1. Cleaner power, typically around 5mVPP of ripple - (AC component) - with the usage of sufficiently sized reservoir caps. General rule of thumb: 10uF for every 5mA of current. So, at 1 Amp you want at least 2200uF.
2. Well designed transformers are extremely efficient. Typically 95% or better.
3. Power transformers are reasonably immune to interference.
4. Isolation transformers are critical for the novice for when it comes to taking
high voltage measurements on an oscilloscope. In fact, no one should really take measurements without using it.
Trent Jackson
Last edited by T.Jackson; - 8th March 2007 at 05:59. Reason: Error / typo
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Transformers have their place, but...
I agree that it's better for hobbyists to include a transformer, but I do disagree with some things you write...
A Transformer will RARELY hit 95% efficiency. The reality is a figure somewhere between ZERO (yes ZERO percent efficient!!!) and somewhere approaching 90%. Let me explain...
The higher the frequency, the greater the transfer ratio between the Primary and Secondary. Hence, the most efficient are Switching Power Supplies which usually run at a few tens of kHz. However at the frequencies of the incomming AC Mains Supply (ie 45-65Hz depending where on the planet you happen to be), the efficiency is governed by the amount of iron (and quality of iron) you can shove into your transformer. Generally, the more iron, the greater the transfer ratio which conversely applies the law that the smaller the transformer the more inefficient it will be.
Now for this ZERO percent efficiency (100% waste of energy) bit...
The efficiency of a Transformer is simply calculated as Power Out divided by Power In. Actually we can reduce that to just Current In viz Current Out with regard to the turns ratio. So in a 100% efficient Transformer, 1A at 12V OUTPUT should equal 50mA at 240V INPUT as there's a 20:1 reduction ratio. Sadly, take any Transformer out of your parts box, put a series Ammeter with the Primary and plug it in completely OFF-LOAD. You will have a standing current... ie you are sucking energy in, but not taking any out. All this is doing is heating up the core, and it's worse the smaller the Transformer becasue of the smaller amount of iron. So from this you can gather, that the less current we draw from a Transformer from it's optimum design point, the more inefficient it will be. If a Transformer is designed to be most efficient at say 100mA, then any current draw less than that is heading towards the ZERO efficiency point when it is completely off-load. Likewise if you exceed the optimum design point (which is usually just below the Magnetic Saturation Point of the core), you then risk driving the core into saturation and again your efficiency plumets as all you end up doing is pumping more current in which just heats up the core.
From the above, you can gather that a Transformer is really the root cause of global warming as before it was invented we didn't have the problem!
Notwithstanding that, it does give you galvanic isolation and as proof that countless hobbyists are alive today posting silly questions on internet forums that otherwise wouldn't be, is it's most commendable feature.
Finally, there is a place for everything... even the humble Transformerless design. For small current supplies, the size and cost beats the transformer every time. For a typical Washing Machine or Freezer or Cooker or Microwave or Boiler or Central Heating or Air Conditioning or ..., or... or (add your own domestic appliance to the list) controller, losing the transformer would save about 50 cents (and save some weight too), multiplied by a typical 300,000 production run for the design and you can do the math.
As for hobbyists that play with mains... well we all gotta die sometime (it's a hereditary trait), just some sooner than later...
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Eddy loss current
I think you've have described the term "Eddy loss current" ?
Just having a quick flick through some of my old college notes, I have %95 written down as a typical rate of efficiency...
Trent Jackson
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Hardest part of electronics is with AC
Extract of taken from college notes 16/06/98
Transformers are very efficient components. Typically they boast efficiency levels of better than 95%. This means that only a mere 5% of the total power is lost. Consumed / wasted in the form of heat. Transformers work on the principle of self-induction, and because of this, there is almost perfect isolation between the primary & secondary windings. With this infinite impedance between the two windings, power transformers are deemed very safe.
By Faraday's law of magnetic induction, when an alternating current is applied to the primary windings, a voltage will be self-induced in the secondary. These windings must be close wound. Secondary power is introduced from the primary because of the changing magnetic field between the two.
When a voltage is applied to the primary a magnetic field is set up, and if the frequency is high enough the primary windings will begin to radiate its power to the secondary. The voltage that is produced on the secondary is directly proportional to the turns ratio.
In short, minus all the math, magnetism theory, that's how a transformer works.
Trent Jackson
Last edited by T.Jackson; - 8th March 2007 at 10:15. Reason: Typo
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Time college lecturers got out a bit more and got dose of the real world.
In theory everything is lovely.
In practice I challenge you to take ANY transformer you've got, and plot Input Current & Output Current from off-load, thru to full rated load in say 5% steps. From that you can calculate and plot a graph of efficiency to prove my point. Enjoy the experience. Then take the efficiency graph and tell your college that life in the real world is far from theory - so far that it's not even close!
For example... let's try to prove the theory of the International Ampere (you know Amps... it's that unit of measurement all of us use every day of our lives... so really we should try to prove the definition before we use it)...
Quote from my University Notes "That constant current which when flowing down two straight parallel conductors of infinite length and negligible cross section, separated by a distance of one meter in a vacuum, produces a force between them of 2 × 10-7 newtons per meter of length."
You get full marks for reciting this like a Parrot in your exam... but let's try to prove it...
1. You go down to your local store and ask for two drums of cable of infinite length and negligible cross-section... you lug them home...
2. You borrow the space shuttle and unravel them in the (supposed) vaccum of space from planet Earth out towards infinity.
3. When you've reached infinity, you join the far ends together and come home.
4. Then you hook up the wire to your PSU with a DVM in series switched to the famous "Newtons per Metre Length" setting on the dial.
5. Take a second DVM in series and switch it to Amps.
6. When DVM No.1 shows 2x10-7 Newtons the other should be showing 1.0000 Amps (assuming it's in calibration).
Worked when I tried it...
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Doubt I'll ever challenge Melanie.
Unfair game here. Someone has a UNI degree...
Where's the referee?
I'm in the process of doing a degree in Applied Science In Information Technology. Only done two years of electronics in college. I'm only at trade level
with most of the theory.
Cheers
Trent Jackson
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Can someone explain to me how the 240VAC after rectification can come down to +12VDC?
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Are you kidding me? I have enjoyed the arguments a lot, and from the first post to the third last (subtracting yours & mine of course), I have come across 2 to 4 circuits all making 12VDC. Check them out going back few posts (Remember to use X2 capacitors with mains - else Melanie would not like it - in case she comes across your circuit)
___________________
WHY things get boring when they work just fine?
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Strangely, i have a design for a transformer-less PSU in the making...
My reason for not using a transformer is because to have a transformer that drops 110V and 240V down to a more usable voltage and supply the current i need would be massive and it costs >£50 each...
I'm not going to post details of the PSU because i intend on filing for international copyright.
The reason for this is because it will handle any single phase voltage, frequency and amount of noise (or noise only) you can throw at it.
It will even operate in a brown out with sustained unstable voltages as low as 24V (maybe lower).
It can also handle stepped AC, Square wave and saw tooth signals provided it is alternating...
Also, Mel is absolutely right, that AN is written for one purpose and one purpose only... TO KILL PEOPLE!
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Something like this PSAA60W-120
AC Input Voltage Rating: 100 to 240V AC
AC Input Frequency: 50 to 60Hz
Input Current: 1.6A at 100V AC, 0.7A at 240V AC
Output: 60W
Efficiency: 85% average
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Re: Transformerless Power Suppply
transformer-less... the above has a transformer, i can tell because of the input specification.
Here in the UK the current code for mains wiring dictates the use of an ELCB.
Earth Leakage Circuit Breaker. If more than 50mA flows up or down the earth wire the ELCB will trip isolating both live and neutral.
every time I've diagnosed wiring faults, their has always been a 50 to 60 V AC difference between earth and ether neutral or live...
If you use an isolation transformer you can connect the negative after rectification to ground. This is what most PC PSU's do.
edit:
That efficiency rating is crap!
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