Need help on circuit modification

[ahkyo]

Here is the circuit information that powering with 120V (ac mains) 60 Hz, anyone can help me modify the circuit which powering with 230V 50Hz instead of buying an expensive step down tranformer for this simple circuit. I've tried simulate with multisim and changing the capacitor value did not give me the desired result.

I am working on Half-wave capacitive drop circuit. (page 4)
Thankz for the help.

https://www.electro-tech-online.com/custompdfs/2006/10/AND8146-DPDF.pdf

 

[eblc1388]

Take a look at the equation (2) at the bottom of Page 3 in the above AppNote, which gives the relationship between Irms, Frequency and Vac.

Using the 10uF value in the original 120V 60Hz design, you can then find out the Irms value. With new values of Vac and frequency, you can work out the value of capacitor, keeping the Irms the same.

 

[tunedwolf]

Personally I would say his first mistake was to use Motorola anything...
Terrible company to deal with...

 

[ahkyo]

Take a look at the equation (2) at the bottom of Page 3 in the above AppNote, which gives the relationship between Irms, Frequency and Vac.

Using the 10uF value in the original 120V 60Hz design, you can then find out the Irms value. With new values of Vac and frequency, you can work out the value of capacitor, keeping the Irms the same.

Thankz you so much...problem solved...

 

[philba]

If you are going to use that circuit, please be aware that it is not isolated. As such, it can be quite hazardous in the event of certain parts failing - 230VAC can kill some one.

Given your level of questions, I suspect you are fairly inexperienced with electronics. I'd suggest you use a wall adaptor and make a low voltage power supply instead of that approach. It will be much safer.

 

[ahkyo]

If you are going to use that circuit, please be aware that it is not isolated. As such, it can be quite hazardous in the event of certain parts failing - 230VAC can kill some one.

Given your level of questions, I suspect you are fairly inexperienced with electronics. I'd suggest you use a wall adaptor and make a low voltage power supply instead of that approach. It will be much safer.

like what u say, i am still a student and inexperienced at this field, only doing the simulation on multisim for now...so the circuit looks working fine there..

i am doing a small project on this blue LED, do u have any other blue LED powering method that is lousier than this? probaby i need it for writtig the justification of doing this circuit on my report =_=......

Thankz for remind me anyway....by the way, the only expensive components is the Blue LED, willl it burn easily becuase of that reason? the LM317 voltage/current regulator should be able to protect it, isnt it?

 

[Hero999]

A worse option would be to use a current limiting resistor and a rectifier diode in reverse parallel with the LED.

Anyway go for the ful wave option (last circuit) it will work out more compact and probably cheaper since the capacitor can be half the size.

Anyway if I were your lecturer I wouldn't allow you to build this due to the safety implications. I'd insist you buy a transformer. The cheapest and most effective way of doing this would be to buy a cheap and cheerful mains adaptor and power the LM317 constant current source from it.

 

[audioguru]

A blue LED was expensive about 15 years ago. Not today.

 

[CanonMan75]

A blue LED was expensive about 15 years ago. Not today.

They still are if you're in the UK and make the mistake of buying them from Maplin

 

[audioguru]

Before RadioShack got out of Canada they were selling a blue LED at about 5 times to 10 times more than other places.
In Australia, Dick Smith "Surplus electronics (WW2) and Used car parts" also sell stuff at high prices.

 

[Hero999]

They still are if you're in the UK and make the mistake of buying them from Maplin

Tell me about it. Craplin are expensive but even so blue LEDs are much cheaper now, even from Craplins. They started selling blue LEDs in 1995 or so, back then they were £4.70 per piece!

Tandy was the most expensive place, I used to shop there back in 1994. Standard red LEDs were 99p for two, bicoloured LEDs were 99p each and standard NPN transistors were 79p per piece. Compare this to Maplin where at the time red LEDs were about 7p each and transistors were 5p. Think about how expensive it would be at today's prices!

 

[on1aag]

Lousy circuit.

Hi Ahkyo,

You wanted a lousy circuit he, here's one. Enjoy !
I used eight ordinary red led's. If you want to use it on a different
line voltage or at a different line frequency you gonna have to scale
the 330 nF capacitor up or down. The voltage drop over the 220 hm:
resistor should be about 5 volt. Also note that you might have to
increase the working voltage of the 470 µF capacitor if the voltage
drop over the leds increases.

on1aag.

 

[philba]

sigh. first a repeat safety lecture. high voltage can kill you. don't mess around with it until you know 100% what you are doing. Use a wall transformer (aka wall wart) to get to a much much safer voltage.

I will assume that you mean a better circuit. OK, go look up an LM7805 datasheet - there is a circuit that shows how to use it to get 5V. Use a 9V wall wart to power this circuit. (you can find them in thrift stores cheap). assuming your LED has a Vf of 3.5V and a sugggested If of 20 mA, use a 75 ohm resistor. (look up the datasheet) Attach one end of the resistor to +5 and the other end to the LED's anode. attach the cathode to ground. apply power, bask in the blue light.

 

[ahkyo]

Sry for the late reply, i am not able to online few days ago ^^

thankz for the reply and suggestion, as the information i gave above, i think i wil still remain my first choice. The transformer is too expensive for me and that's y i wan a modification circuit here.

this circuit is able to power the LED and maintain current through the LED within the manufacturer's specification. So if i change to others circuit like what you guy suggest, will it sitlll be able to achieve that purpose? And sorry, it is really hard for me to change the circuit now T_T.

and can anyone give me the web for reading the detailed datasheet of the LM317 current regulator?

and on1aag, thankz for the circuit.

I really weak in this electronic thing, but i still neeed to complete it ~_~

 

[philba]

do what you want but I can find wall warts for $1 usd in local thrift shops. and there are always many of them.

good luck, I hope you don't get hurt.

 

[ahkyo]

philba, can u take a look on the demo board circuit for the informaiton link i gave above (last 2 pages)? that is complete circuit i am going to do, the circuit discuss here just for simulation and not for pratical use.

it is connected to this (probably for protection) together with a fuse.
https://www.electro-tech-online.com/custompdfs/2006/10/1715035.pdf

thankz.

 

[philba]

I took a look but really don't understand what you want. If you are just simulating it, no big deal. If you are building the circuit, be very careful.

 

[ahkyo]

ok, thankz for ur advices.....

good luck for me ~_~