Selection of some components

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abr

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Selection of some components
May 17, 2021 - 11:16am

Night light project. (My first project.)

 

I need some help to select some components.

 

I have a 240 VAC/50 Hz voltage supplying a Bridge Rectifier (4x1N4007) with an output of 24VDC for 6 blue LED in series.

 

I have to step down the voltage from 240VAC to 24VDC.  I don’t know how drop the voltage from 240VAC to 24VAC.  It is where I need some help.

 

From what I read, to step down the voltage, I need a Cx capacitor (?? µf 400V) and one resistor R1 (??Ω) in parallel  to discharge the capacitor and another R2  (??Ω) resistor on the other side.

 

 

I know the Bridge Rectifiers change the current from AC to DC and I will need another C1 capacitor to smooth the ripples and a resistor of R3 (120 Ω) before my 6 LED.

 

I could use the values already available on different websites but I would like know the step by step for selecting the Cx Capacitor and the 2 resistors before the Bridge Rectifier.

 

Thank you.

Sourav Gupta's picture

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I think this question is addressed in another forum thread.

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abr

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Hi Sourav.  Yes, you are correct, I did post the same request elsewhere as I could not get the information that I am seeking.  I am looking for some guidance to put me in the right direction as my knowledge in electronic is limited.  Can I be blamed for being persistant at understanding how things work?  Regards

Sourav Gupta's picture

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Is not your problem solved? Please share what you want to know.

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abr

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Hi Sourav,  No, my problem is far from being resolved.  I am still at it, working out how to get values for Cx capacitor, R1, R2 and C2.

As I said in my “May 17 request” I  would like to bring down the voltage from 240VAC 50Hz to 24VDC-0.5mA to light 5 or 6 white/blue LED.

I would like to get some help/guidance on how to get these values.  I came up with a Cx value of 1200nf which I think is not correct.

If someone has time to help me, I would appreciate if he/she could show me the steps I should take (with the formulas) to make it work.

 

I am looking for:

Cx1:………………R1: ………………R2:………………..C2:…………………..

  

  1. I know that R1 help discharge Cx but does it had an impact in selecting Cx or on the circuit itself.
  2. What impact does R2 have on the circuit? Only to deem or bright a little the LED?

 

I have attached my working sketch project if that can help.

 

Thank you for your time.

 

Regards,

 

 

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abr

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Joined: May 17, 2021

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Hi Sourav,  No, my problem is far from being resolved.  I am still at it, working out how to get values for Cx capacitor, R1, R2 and C2.  
As I said in my “May 17 request” I  would like to bring down the voltage from 240VAC 50Hz to 24VDC-0.5mA to light 5 or 6 white/blue LED.
I would like to get some help/guidance on how to get these values.  I came up with a Cx value of 1200nf which I think is not correct.
If someone has time to help me, I would appreciate if he/she could show me the steps I should take (with the formulas) to make it work.

I am looking for:
Cx1:………………R1: ………………R2:………………..C2:…………………..
  
I know that R1 help discharge Cx but does it had an impact in selecting Cx or on the circuit itself.
What impact does R2 have on the circuit? To bring down the voltage at the bridge rectifier?

I have attached my working sketch project if that can help. 

Thank you for your time.

Regards,