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Monday, February 15, 2016

How to Build 12V / 20mAh Transformerless Power Supply

ElcoHow. - There are two kinds of power supply according using transformer, these are using transformer and not using transformer or called with transformerless power supply. In here we will give you one project of power supply with the title How to Build 12V / 20mAh Transformerless Power Supply. In here we will give you electronic circuit, component list, description, how to build, and some software that used to build this power supply.

You also can read: How to Build Transformerless Power Supply 30V 1A using Thyrirstor

Electronic Circuit
Component List
  1. Resistors
  2. Capacitors
  3. Zener Diodes
  4. Bridge Diode
Description

Electronic circuit like in Figure 1 above is 12V / 20mAh Transformerless Power Supply circuit. According Zen22142.zen site that published this circuit describe that This circuit will supply up to about 20ma at 12 volts. It uses capacitive reactance instead of resistance; and it doesn't generate very much heat.The circuit draws about 30ma AC. Always use a fuse and/or a fusible resistor to be on the safe side. 

The values given are only a guide. There should be more than enough power available for timers, light operated switches, temperature controllers etc, provided that you use an optical isolator as your circuit's output device. (E.g. MOC 3010/3020) If a relay is unavoidable, use one with a mains voltage coil and switch the coil using the optical isolator.C1 should be of the 'suppressor type'; made to be connected directly across the incoming Mains Supply. They are generally covered with the logos of several different Safety Standards Authorities. If you need more current, use a larger value capacitor; or put two in parallel; but be careful of what you are doing to the Watts. The low voltage 'AC' is supplied by ZD1 and ZD2.

The bridge rectifier can be any of the small 'Round', 'In-line', or 'DIL' types; or you could use four separate diodes. If you want to, you can replace R2 and ZD3 with a 78 Series regulator. The full sized ones will work; but if space is tight, there are some small 100ma versions available in TO 92 type cases. They look like a BC 547. It is also worth noting that many small circuits will work with an unregulated supply. You can, of course, alter any or all of the Zenner diodes in order to produce a different output voltage. As for the mains voltage, the suggestion regarding the 110v version is just that, a suggestion. I haven't built it, so be prepared to experiment a little.
Skill

To build 12V / 20mAh Transformerless Power Supply, you need some skill as follow:
  1. Basic soldering.
  2. Read a basic schematic.
  3. Assembling electronic component
  4. Design PCB layout
  5. Testing voltage and current
  6. Know Thyristor component
Tools and Material

In this project, you must prepare some tools and material that used as the supporting to build 12V / 20mAh Transformerless Power Supply as follow:
  1. Tools: soldering iron, cutter, multitester, and Project Board.
  2. Material: Tin, PCB
Software

When you want to realize this 12V / 20mAh Transformerless Power Supply circuit into real application, you can build it as like design PCB layout using good software as like: PCB Wizard. 
How to do?

For more information about this project step-by-step you can follow this project of 12V / 20mAh Transformerless Power Supply you can read below.
  1. Prepare electronic component listed, material and tools needed.
  2. Firstly you can try this circuit using project board tool.
  3. After you surely with this circuit work properly, now you can begin with design PCB using PCB Wizard.
  4. After designed, now you can make the PCB layout to put these components. You can make PCB by your self or order it according your PCB layout design.
  5. Put all component to the PCB layout and soldering all component.
  6. Now you can test, input and output voltage and current from this circuit. Please read caution below.
Caution
  • Electric Shock Hazard. In the UK,the neutral wire is connected to earth at the power station. If you touch the "Live" wire, then depending on how well earthed you are, you form a conductive path between Live and Neutral. DO NOT TOUCH the output of this power supply. Whilst the output of this circuit sits innocently at 12V with respect to (wrt) the other terminal, it is also 12V above earth potential. Should a component fail then either terminal will become a potential shock hazard.


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