Qns on DC Power Supply

[audioguru]

In fact, if the puny little 79L05 has a 100mA load then it would shut-down due to over-heating, wouldn't it? :?: :?:

 

[adrian22]

so how will u indentigy the different sub-sections that make up the power supply on the schematics diagram?


Regards
Adrian

 

[audioguru]

It has only a few sub-sections. Why don't you try to identify them yourself?

 

[JimB]

As i m from singapore. i saw a fuse 13A use in all kind of electronics, so i tot it will b using a 13A fuse.

In Singapore you use the same 13 Amp mains plugs as the UK.
A 1 amp fuse in the plug should be OK for this.

The problem is, it may be difficult to find a 1A fuse, a GOOD electrical shop should have them.
All to often, a 13A fuse is fitted and is far too high a rating for the appliance.

JimB

 

[Nigel Goodwin]

In Singapore you use the same 13 Amp mains plugs as the UK.
A 1 amp fuse in the plug should be OK for this.

The problem is, it may be difficult to find a 1A fuse, a GOOD electrical shop should have them.
All to often, a 13A fuse is fitted and is far too high a rating for the appliance.

I didn't think 1A was an available plug fuse size?, I've never seen one!, either fitted in plugs, or offered for sale?.

What you SHOULD do, is fit a small fuse in the plug (3A is usually the lowest), and fit an internal mains fuse in the casing of your project, 20mm fuses have been commonplace in the UK and the rest of Europe for over 30 years, and are available in a huge range of values, starting about 35mA or so - you can get 500mA, 630mA, 1A, 1.25A or 1.6A, for a range of values around the suggested 1A.

 

[JimB]

I didn't think 1A was an available plug fuse size?, I've never seen one!, either fitted in plugs, or offered for sale?.

RS Components p/n 412-986

JimB

 

[adrian22]

the plug itself has 1 but we must place other 1 in the ciruit so i guess is should b 1A.

i have actually written 1 copy n let c wat can b impove:

An AC input 230V is supply into the supply starting from the 1A fuse to the on/off switch then to the center-tapped transformer (15-0-15V). After going though the center-tapped transform, the voltage drop down from 230V AC to 15V AC. Then the 15V AC will be connected to the bridge rectifier and rectifier to a fullwave +15V and –15V.

From there a +15V will be supply to C1 anode (2200uF, 50V) and provide the output of +15V DC. Same thing, a –15V is supply to C2 cathode (2200uF, 50V) and due to ground is higher voltage with respect to –15V. A +15V Dc is supply into LM7815, as a result the output is regulated to a constant +15V DC and once again it is filter to a more purely +15V DC.

From the output –15V from C2, it is connected the LM7915, as a result the output is regulated to a constant –15V DC and once again it is filter to a more purely –15V DC.

Just after the filter, LM7915 regulated output in connected to the input of the LM7905, as a result the output is regulated to a constant +15V DC and once again it is filter to a more purely –5V DC.

Lastly the ground will be connected as a reference to a common point.









Regards
Adrian

 

[audioguru]

An AC input 230V is supply into the supply starting from the 1A fuse to the on/off switch then to the center-tapped transformer (15-0-15V). After going though the center-tapped transform, the voltage drop down from 230V AC to 15V AC.

The voltage is dropped down from 230V AC to two 15V AC outputs.

Then the 15V AC will be connected to the bridge rectifier and rectifier to a fullwave +15V and –15V.
From there a +15V will be supply to C1 anode (2200uF, 50V) and provide the output of +15V DC. Same thing, a –15V is supply to C2 cathode (2200uF, 50V) and due to ground is higher voltage with respect to –15V.

Then the 15V AC outputs allow the bridge rectifier to charge C1 and C2 with full-wave to the peak voltage less a diode drop of about +20VDC and -20VDC. (These 15V regulators operate poorly if their input voltage is less than 18V).

....LM7815....LM7915....LM7905

An LM7815, LM7915 and LM7805 regulator can supply up to 1.5A of current. Your last schematic shows 78L15, 79L15 and 79L05 regulators that can supply only 100mA. Which regulators are you using?

 

[adrian22]

How can we explain abt the peak to peak 20V i tot two secondary wings of 15V give 30V?(15V+15V=30V) :roll:

Is LM7915 same as 79L15?
the circuit written should be LM7915 sorry is my mistake.


Regards
Adrian

An AC input 230V is supply into the supply starting from the 1A fuse to the on/off switch then to the center-tapped transformer (15-0-15V). After going though the center-tapped transform, the voltage drop down from 230V AC to 15V AC.

The voltage is dropped down from 230V AC to two 15V AC outputs.

Then the 15V AC will be connected to the bridge rectifier and rectifier to a fullwave +15V and –15V.
From there a +15V will be supply to C1 anode (2200uF, 50V) and provide the output of +15V DC. Same thing, a –15V is supply to C2 cathode (2200uF, 50V) and due to ground is higher voltage with respect to –15V.

Then the 15V AC outputs allow the bridge rectifier to charge C1 and C2 with full-wave to the peak voltage less a diode drop of about +20VDC and -20VDC. (These 15V regulators operate poorly if their input voltage is less than 18V).

....LM7815....LM7915....LM7905

An LM7815, LM7915 and LM7805 regulator can supply up to 1.5A of current. Your last schematic shows 78L15, 79L15 and 79L05 regulators that can supply only 100mA. Which regulators are you using?

 

[audioguru]

The peak voltage of 15V AC is 21V (15 times the root of 2) minus about 1V for the forward voltage drop of a rectifier diode for each 15V AC output from the transformer. Therefore C1 charges to about +20V and C2 charges to about -20V.

 

[adrian22]

ohh.. so if we hav a 30V transform is will b 42.4V?

so the is a standard?



copy of feasibility study:

An AC input 230V is supply into the supply starting from the 1A fuse to the on/off switch then to the center-tapped transformer (15-0-15V). After going though the center-tapped transform, the voltage drop down from 230V AC to two 15V AC outputs.

Then the 15V AC outputs allow the bridge rectifier to charge C1 and C2 with full-wave to the peak voltage less a diode drop of about +20V DC and –20 V DC.

A +20V DC is supply into LM7815, as a result the output is regulated to a constant +15V DC and once again it is filter to a more purely +15V DC.

From the output –20V DC from C2, it is connected the LM7915, as a result the output is regulated to a constant –15V DC and once again it is filter to a more purely –15V DC.

Just after the filter, LM7915 regulated output in connected to the input of the LM7905, as a result the output is regulated to a constant -15V DC and once again it is filter to a more purely –5V DC.

Lastly the ground will be connected as a reference to a common point. As an output for the result, LM7815, LM7915 and LM7905 produce 1.5A of current. And outputs voltage of +15V DC, –15V DC and –5V DC.

 

[d4d4ng]

Hi adrian22,
Please check the following link : http://www.kpsec.freeuk.com/powersup.htm to get some understandings on role of transformer, bridge rectifier and capacitors filter in a power supply.
Hope this help.

Amri.