Can anyone help me find what specific transformer is this, the only marking on it is HLB 21. It seems to be a double winding transformer, there are 4 pin on one side and 2 on the other. I salvaged it from an old phone charger.



Or possibly i might need a help on converting 220AC to 5VDc, currently this is what i have done



Much thanks in advance. Im a new electronics engineering student, any help is very appreciated.

 

It is unlikely that you will find a datasheet for that transformer. It will be made to meet the manufacturers requirements and will not be an item you can buy from stockists such as Farnell or RS components. It could be a simple 50/60 hz transformer or if it was from a switch mode power supply it would be working at several tens ot hundreds of Khz. looking at the design of the power supply should tell you what type of transformer it is. If you post pictures of the power supply it was removed from members of the forum should be able to tell you if it is a switch mode supply. If the core is made up of laminations it is probably a mains fequency transformer. If the core is ferrite then it will be a high frequency transformer.
Les.

 

It is unlikely that you will find a datasheet for that transformer. It will be made to meet the manufacturers requirements and will not be an item you can buy from stockists such as Farnell or RS components. It could be a simple 50/60 hz transformer or if it was from a switch mode power supply it would be working at several tens ot hundreds of Khz. looking at the design of the power supply should tell you what type of transformer it is. If you post pictures of the power supply it was removed from members of the forum should be able to tell you if it is a switch mode supply. If the core is made up of laminations it is probably a mains fequency transformer. If the core is ferrite then it will be a high frequency transformer.
Les.

Ohhh, got it. i might just scratch that idea, and look for other solution. Thanks for that.

 

IF the transformer supply is to provide DC at 5 volts from a 220 volt mains source, the rectifiers will not be the first item in the string. First the 220 volts will go to the transformer, and then a much lower voltage will be fed to the rectifier .
AND, the apparent multiple connections may also be to assure that the transformer is only inserted into the circuit board correctly.

 

IF the transformer supply is to provide DC at 5 volts from a 220 volt mains source, the rectifiers will not be the first item in the string. First the 220 volts will go to the transformer, and then a much lower voltage will be fed to the rectifier .
AND, the apparent multiple connections may also be to assure that the transformer is only inserted into the circuit board correctly.

Got it, upon not finding a transformer I can use, I resorted to this.


I just fed the 220v dc to a bunch of resistor and potentiometer, so that i could power the LED, will that cause problems?
The resistance values are not based on anything, i just did trial and error, on what value will work but if you have other ways to go through this, that would be very much appreciated.

just a note, im making a fan speed controller with power level indicator.

 

There will be a problem it seems. LEDs are diodes that do not survive very much reverse voltage.
That circuit will certainly ignite that 1K resistor with the rectified mains voltage across it, if the short circuit created by the two ground connections short circuiting the diode bridge to not trip a breaker first.
That circuit has a number of fatal problems in the indicator section.

 

There will be a problem it seems.

Ohhh, I see, won't the potentiometer and the 10k ohms eat most of the voltage?

Also will increasing the 1k ohms help, if not, may i kindly ask on how i should tackle this.

For the ground, can i possible remove the ground connection on the speed controller circuit? Or is it essential. Based on what you state, i also think that those ground might cause a problem.


The less/no IC restriction our prof gave us is a headache.

 

NONE of those "ground" connections are needed. BUT the two segments of the DC portion do need to be connected to each other. AND, given that it is a mains powered circuit, no portion should be connected to any portion that a person could come in contact with. It is probably in some sort of violation of the shock hazard rules of this site.
The issue with the 1K resistor is that it will have the peak to peak value of the mains supply voltage across it, so the current will be quite a bit, and I see no real purpose for it being there.
RV2 100K ohms will discharge the capacitor eventually, and it will consume a lot less power.

 

Got it, let me try your advice. Thanks for that, I would be back after trying this out.

Just another question, is dual gang potentiometer what I think it is. Is it just two potentiometer controlled by one shaft or there something else in it?

 

A dual gang potentiometer is indeed two of them driven by a single shaft, not anything more. BUT there are also some of them with concentric shafts that are independently controlled. Like the volume and tone controls on simple radios had for many years.