Why useless? Didn't the hum go away? All toroids hum more or less. Yours maybe was the one with "more" hum?DIAR said:
Is the schematic in the first page truley accurate?
What is this circuit supposed to do?
Very curious!
What is this circuit supposed to do?
Very curious!
poobah said:
Main target is to filter dc which is mixed up with 100v-240v ac supply. Main purpose is to improve the audio/video system quality.
Regards
jH
AndrewT said:
Hi,
It is of little use to preach safety while advocating the placement of circuitry of any type in series with the neutral line! Very dangerous practice that.
As far as performance is concerned it would make no difference which line, so pick the safer option.
This has to be without doubt one of the most expensive DC blockers I've seen. Is meant to work with an isolation transformer or instead of?
There are far cheaper alternatives.
Regards,
Chris
Hmmmm,
This circuit will not remove DC. What this circuit WILL do is increase the diode noise and the harmonics in the AC signal. You can only have DC in an AC signal if you have a point of reference to call Ground or ZERO volts. Even then, this circuit will not remove a DC BIAS.
Am I missing something???
This circuit will not remove DC. What this circuit WILL do is increase the diode noise and the harmonics in the AC signal. You can only have DC in an AC signal if you have a point of reference to call Ground or ZERO volts. Even then, this circuit will not remove a DC BIAS.
Am I missing something???
Poobah, I'm afraid you have missed the main issue and also how to solve it.
jh6you, your filter is a massive overkill but you are aware of this I'll suppose.
Main purpose accordning to me is to reduce audiable (mechanical) hum from the (toroid) transformer.jh6you said:
jh6you, your filter is a massive overkill but you are aware of this I'll suppose.
Does this circuit go between the wall plug and the input to the equipment?
What point do you declare as zero volts? Ground?
What point do you declare as zero volts? Ground?
Hi,
if given the choice, I would fit this inside the same box as the mains transformer. Then all the danger is at the same location.
Class4,
if fitted inside the same box as above then no one is exposed to any extra danger. However the area of high voltage terminations will be massively reduced by inserting the DC blocker into the neutral line. For the DC blocker to fail open circuit both the caps and the diodes would have to fail open circuit since they are in parallel. This possibility is real and could occur but is unlikely. Conversely the improvement in safety wrought by reducing the areas of danger will, I believe, bring about an overall improvement. Compare this to the noise reduction systems based on caps to ground and CMMR toroid inserted into both lines.
Please let us hear more of your opinion.
I tried raising this debate in a previous thread but you must have missed my comments then. or is this thread jacking?
if given the choice, I would fit this inside the same box as the mains transformer. Then all the danger is at the same location.
Class4,
if fitted inside the same box as above then no one is exposed to any extra danger. However the area of high voltage terminations will be massively reduced by inserting the DC blocker into the neutral line. For the DC blocker to fail open circuit both the caps and the diodes would have to fail open circuit since they are in parallel. This possibility is real and could occur but is unlikely. Conversely the improvement in safety wrought by reducing the areas of danger will, I believe, bring about an overall improvement. Compare this to the noise reduction systems based on caps to ground and CMMR toroid inserted into both lines.
Please let us hear more of your opinion.
I tried raising this debate in a previous thread but you must have missed my comments then. or is this thread jacking?
Peranders,
So in this circuit, the diodes are simply for safety and do not normally conduct. The capacitors charge to an average dc level to correct (buck) asymmetry in the input AC voltage. The small DC current hiding in the AC voltage is blocked and the toroidial input transformers do not saturate.
Is this how it works?
I had to redraw the circuit to understand it.
So in this circuit, the diodes are simply for safety and do not normally conduct. The capacitors charge to an average dc level to correct (buck) asymmetry in the input AC voltage. The small DC current hiding in the AC voltage is blocked and the toroidial input transformers do not saturate.
Is this how it works?
I had to redraw the circuit to understand it.
Thanks,
I went off the deep end wondering why somebody would snub antiparallel diodes to block DC. The cap values don't show up readable for me.
Cheers
I went off the deep end wondering why somebody would snub antiparallel diodes to block DC. The cap values don't show up readable for me.
Cheers
poobah said:
poobah said:
No. The diode normally conduct when it is forword biased.
If you refer to mine, the value of each cap is 10,000uF/50V.
Overkill . . . ? Probably . . .
I made it using the leftover from my Pass F1 project.
And, this one box covers Pass F1, SOBOZ, CD player, DVD player, projector and TV.
In addition, Pass F1 and BOSOZ have their own dc-blocker inside.
Yeah . . . overkill . . . 😀
Regards
jH
AndrewT said:
Hi,
I don't recall you having mentioned the transformer being in the same box, which makes a bit more sense, but then as you say, what if you drop the lid on, what if you take the lid off ? 🙂
It's not considered safe practice to put circuitry in the neutral line.
Arguments can be made for both cases, but the fact is no one unqualified should be sticking their hands in there or taking it apart to service anything. Should it fail with caps/diodes in the neutral line the rest remains active.
As far as something like a CM choke it's it's a little more reliable than a cap being a piece of wire I'd think, and a failed bypass cap won't leave the rest of the circuitry live & unoperational.
You're right though proper insulation would have been prudent.
I don't think it's thread jacking to bring up a safety issue, nor do I read all posts.
jh6you, I guess you made it with parts you had kicking around already so cost wasn't the issue (or maybe it was), I can't help but think an isolation transformer would have come up to about the same in total, had you not already had those parts laying around, and been a bit safer, in case anyone else is considering this as a solution.
Regards,
Chris
Hi,
I would normally accept that nothing be put in the neutral line. Your observation that the mains part of the circuit becomes live if the DC blocker fails open circuit is spot on.
In event of failure the repairer, hopefully the builder, will remember when he opens the unit (or has it well labelled) that the mains components may be at elevated (dangerous) voltages.
I would normally accept that nothing be put in the neutral line. Your observation that the mains part of the circuit becomes live if the DC blocker fails open circuit is spot on.
In event of failure the repairer, hopefully the builder, will remember when he opens the unit (or has it well labelled) that the mains components may be at elevated (dangerous) voltages.
Hi,
the DC blocker using 10mF caps back to back will have an impedance at 50Hz of 0.64ohms.
At a current of 1amp the rms voltage across the blocker is 0.64Vac. Obviously at 1.5A the voltage has risen to 0.9Vac = 1.27Vpk. This is just below the double diode threshold. The diodes should not conduct for all currents below 1.5Arms = 330VA when on 220Vac mains.
The chosen size of caps should never see a peak current exceeding root2 times 1.5A = 2.1Apk, with only one exception:- during unit start up when transformers (all types) draw an increased current, the diodes conduct for a few dozen mS until the magnetic field establishes itself.
10mF =10,000uF can operate equipment upto a maximum of 330VA (@220V 50Hz) or 200VA (@110V 60Hz)
If you intend running more equipment, then the caps need to be recalculated to suit the normal maximum load you expect for your situation.
Remember the double diodes are there to prevent excessive voltage building up across the caps under overload conditions.
the DC blocker using 10mF caps back to back will have an impedance at 50Hz of 0.64ohms.
At a current of 1amp the rms voltage across the blocker is 0.64Vac. Obviously at 1.5A the voltage has risen to 0.9Vac = 1.27Vpk. This is just below the double diode threshold. The diodes should not conduct for all currents below 1.5Arms = 330VA when on 220Vac mains.
The chosen size of caps should never see a peak current exceeding root2 times 1.5A = 2.1Apk, with only one exception:- during unit start up when transformers (all types) draw an increased current, the diodes conduct for a few dozen mS until the magnetic field establishes itself.
10mF =10,000uF can operate equipment upto a maximum of 330VA (@220V 50Hz) or 200VA (@110V 60Hz)
If you intend running more equipment, then the caps need to be recalculated to suit the normal maximum load you expect for your situation.
Remember the double diodes are there to prevent excessive voltage building up across the caps under overload conditions.
Hi Jh6,
the wiring diagram was not live in post 1 when I first looked at this thread.
The connections are WRONG.
Disconnect the unit from the mains immediately.
the wiring diagram was not live in post 1 when I first looked at this thread.
The connections are WRONG.
Disconnect the unit from the mains immediately.
Hi Andrew
Thanks for the comment.
By the way, kindly let me know where and why wrong?
Regards
jh
Thanks for the comment.
By the way, kindly let me know where and why wrong?
Regards
jh
Hi Jh6,
the diode bridges are wired wrongly.
remove the shorting link across the ~ & ~ . Keep the shorting link across the + & -. Connect the input AC to ~ and to cap -ve. Connect the output AC from ~ and cap +ve.
You then have 2 diodes in series and these in parallel with the cap.
You have separated the back to back caps putting one pair on the live input and the other in the neutral input. I think it would be better to put both the caps on either the live or the neutral.
You have duplicated all the caps and diode bridges. Strictly this is not necessary but you have gained by increasing the redundancy and improving the failure risk to go open circuit.
You have also used 2*10mF in // giving half the impedance I quoted earlier. The safe loadng would be increased to 660VA (220V 50Hz) and 400VA (110V 60Hz).
The caps, although spare, do not need to be 50Vdc. 10Vdc or 16Vdc would do saving a lot of space and money.
the diode bridges are wired wrongly.
remove the shorting link across the ~ & ~ . Keep the shorting link across the + & -. Connect the input AC to ~ and to cap -ve. Connect the output AC from ~ and cap +ve.
You then have 2 diodes in series and these in parallel with the cap.
You have separated the back to back caps putting one pair on the live input and the other in the neutral input. I think it would be better to put both the caps on either the live or the neutral.
You have duplicated all the caps and diode bridges. Strictly this is not necessary but you have gained by increasing the redundancy and improving the failure risk to go open circuit.
You have also used 2*10mF in // giving half the impedance I quoted earlier. The safe loadng would be increased to 660VA (220V 50Hz) and 400VA (110V 60Hz).
The caps, although spare, do not need to be 50Vdc. 10Vdc or 16Vdc would do saving a lot of space and money.
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