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230V led driver, which one has low failures?

KUMARA SHP

Aug 1, 2014
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led230v_s.gif

extra-bright-led-lamp1.gif

XXXXXXX.png
 

KUMARA SHP

Aug 1, 2014
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please tell me if any problem in designs
I prefer 1st one. I am going to use this for machine. reliability is very important
so please help me
which one should I choose
also cost is an factor

thanks
 

duke37

Jan 9, 2011
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To use a resistor to limit the current will need about 50 times the power to be dissipated in the resistor over that dissipated in the led. This may not be a cost problem but the heat will need to be removed.

I have an aversion to electrolytics for reliability.

I would therefore go with circuit ! but remove R2 (it does nothing here) and use C1 to limit the current. There are special capacitors to run on the mains, one of these should be used.
D1 could be another led to get twice the light from the same current.
R1 is to protect from switch-on surge and should be capable of withstanding a highish voltage. Diddy 200V resistors are not suitable even if they have sufficient power capability.
 

KUMARA SHP

Aug 1, 2014
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thanks for your reply
so I will use 1st design
I have 1 more question

circuit 1 gives AC voltage (so led on and off at 50HZ)
circuit 2 gives DC

so is DC or AC gives maximum life for led?
and reliability?
 

gorgon

Jun 6, 2011
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You should also take into account that 230VAC will have a peak value of 325V if you want to make a long life circuit. The DC circuit(2) is made to supply a chain of 30 LEDs, so you need to recalculate the capacitor if you want to drive only one LED.
You should check the calculations anyway, to see if the values are correct. Normally a lower current will give a longer life.
 

duke37

Jan 9, 2011
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Many led displays are multiplexed so I would think that the intermittent current should not be a problem. I have a clock at least 20 years old still working well.
You could consider keeping R2 and replacing D1 with a zener to limit the turn on current, this could be as high as 150mA if the supply is turned on at maximum voltage.
 

KUMARA SHP

Aug 1, 2014
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Capture.JPG
I changed it to this design.
any comment on this
zenor is 3.3V
I hope this is good design
what can I additional add to protect whole circuit from over voltages
 

KUMARA SHP

Aug 1, 2014
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I hope to replace this zenor with 1N5225B 3.0V zenor . max power dissipation is 500mW.
I think that is enough because it does the same power as LED.
please tell me if there is any problem. this machine should not have any failures in LED circuit
 

KUMARA SHP

Aug 1, 2014
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I am going to turn into the neon indicators now.
what is you think is neon bulb or led circuit has low failure ?
 

duke37

Jan 9, 2011
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The diagram which you show is not what I recommended. The zener should be connected across R2/led1 pair. A value of 6V to 10V or so will limit the peak current on switch on.

I do not see how to protect the whole circuit from over voltage, just make sure R1 and C1 are capable of withstanding any overvoltage.
To get extra reliability you could duplicate the circuit.
Neons should be reliable but they go dim with use due to internal coating of the glass.
 

KUMARA SHP

Aug 1, 2014
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I do so to minimize current through the zenor. because it series with 220 ohm now. but is there any problem or disadvantage?
 

KUMARA SHP

Aug 1, 2014
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and I am going to use 0.5W zenor. hope that will sufficient .won't?
 

duke37

Jan 9, 2011
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During normal running, the current will be controlled by C1 and R1, a voltage drop across R2 will do nothing much.

A zener across the led will either take all the current or none at all depending on the relative voltages of the zener and led. By defining the voltage across R2 and led in series, the maximum current in the led will be defined.. The zener will not conduct in its zener direction under normal running, it will only act as a diode would.

The idea of a zener is to limit the current at turn on when C1 can be considered a short circuit for the first part of the cycle.
220v has peak voltage of 311V
The current will be limited to 141mA by R1, this is high but may be OK for half a cycle.
C! will have a reactance of 14k4Ω at 50Hz.
The reactance of C! and R1 will be 14k6Ω so the running current will be 15mA but only half of this will go through the led.

If you use a 10V zener across R2 and led in series, then the current through the led will not exceed 32mA which the led should easily stand for part of a cycle.

A 0.5W zener should be all right.
R1 will dissipate about 0.5W.

You should check these calculations.
 

KUMARA SHP

Aug 1, 2014
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yes really thank you very much.
I gained all what i need now.
I changed the design as you mentioned
thanks
 

KUMARA SHP

Aug 1, 2014
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hi
finally I built it.
simulation works fine
I designed pcb on eagle.
I used 7.5mm grid distance package for 220nF (400V) capacitor,
but I can't find 7.5mm capacitor,
I am not like to change package due to low on space

do anyone know capacitor for sale woth that specs
 
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