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Power supply

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adrianvon

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Hi all,

I am planning to build a power supply for a project that i am currently doing. The input will be connected to the mains (230VAC) and therefore a transformer is needed. I want to use the 7812 and 7805 as voltage regulators and i want the current to be 2A.

Does someone knows of a good tutorial for building such power supply with formulas used to determine the components used??

Thanks in advance.
Adrian
 
Hi all,

I am planning to build a power supply for a project that i am currently doing. The input will be connected to the mains (230VAC) and therefore a transformer is needed. I want to use the 7812 and 7805 as voltage regulators and i want the current to be 2A.

Does someone knows of a good tutorial for building such power supply with formulas used to determine the components used??

Thanks in advance.
Adrian

The 78XX series are not guaranteed to do 2A of load current.

I believe you want the LT1085 or LT1086 series devices.
 
Last edited:
Hi,

Thanks for the reply. I was planning to use pass transistors to increase the output current, but i will consider using the mentioned components.
 
Hi,

Thanks for the reply. I was planning to use pass transistors to increase the output current, but i will consider using the mentioned components.
The problem with pass transistors is that they are not generally over-current or over-temperature protected as the regulator circuit is.
 
The problem with pass transistors is that they are not generally over-current or over-temperature protected as the regulator circuit is.

Hi,

Thanks for that info. I will use the LT1085 or LT1086 instead of using pass transistor.

Does anyone know of a good tutorial to guide me on building a similar supply please? Or any formulas for determining the components values please (such as smoothing cap etc) ??

Thanks
 
You may want to start with the videos found in this section of the forums. Then move on to the manufacturer's data sheets for the linear regulators you are considering using. The data sheets provide schematics and a wealth of information. For example this data sheet for the LT1085 and its family.

Ron
 
Hi adrianvon,

The 7812 and 7805 are manufactured for an output current of 2A as well as for 1A.

The 2A regulators you need are 78S12 and 78S05.

Select a smoothing capacitor of 4,700uF at the input pins of the regulators. Also use 100nF caps from input to ground and from output to ground to avoid oscillations caused by sudden load changes.

Boncuk
 
Last edited:
Hi,

Thanks for your reply Boncuk . I will do some research on those transistors and on different types of transformers.
 
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