LM338 Voltage and Power Questions

[bertus]

Hello,

That is a nice build you made.

As @Bluejets said, the TO3 has better thermal properties:



If you want a beefier regulator with a lower drop-out voltage, have a look at the LT1083.
That is capable of 7.5 A, with a drop-out voltage of about 1 Volt.

Bertus

 

[Harald Kapp]

Please find the below pictures and final schematic I used:

Just one note: Your schematic shows the primary side fuse opposite to the mains switch.
Afaik in the US the mains outlets have dedicated positions for live and neutral. To increase safety both fuse and switch should be in the life wire. This way the switch will separate the power supply from live as will the fuse do in case of overload. In both cases it is less risky to have the rest of the power supply being connected to neutrral.
Whereas in your schematic if the fuse is triggered, the other side of the power supply's input is still connected to life. But you will not be aware of this possibly dangeroues situation because the neon lamp will be off and the supply will show no output.
This should be an easy change to your otherwise great looking build.

See here and here.

 

[Electromotive]

Yes, I agree but: I found the TO3 to be unobtainable unless I wanted Bulk for too much money. I tried the oversea's versions and had issues. Settled on the Lesser TI made ones I could find. Thank you... Tom

 

[Electromotive]

Just one note: Your schematic shows the primary side fuse opposite to the mains switch.
Afaik in the US the mains outlets have dedicated positions for live and neutral. To increase safety both fuse and switch should be in the life wire. This way the switch will separate the power supply from live as will the fuse do in case of overload. In both cases it is less risky to have the rest of the power supply being connected to neutrral.
Whereas in your schematic if the fuse is triggered, the other side of the power supply's input is still connected to life. But you will not be aware of this possibly dangeroues situation because the neon lamp will be off and the supply will show no output.
This should be an easy change to your otherwise great looking build.

See here and here.

You caught me. The lamp is a 110V neon and is on the mains side..Duhhh.... Thanks...Tom

 

[Electromotive]

The Difference between pure regulated DC and Digital output. Interesting...

 

[Electromotive]

Just one note: Your schematic shows the primary side fuse opposite to the mains switch.
Afaik in the US the mains outlets have dedicated positions for live and neutral. To increase safety both fuse and switch should be in the life wire. This way the switch will separate the power supply from live as will the fuse do in case of overload. In both cases it is less risky to have the rest of the power supply being connected to neutrral.
Whereas in your schematic if the fuse is triggered, the other side of the power supply's input is still connected to life. But you will not be aware of this possibly dangeroues situation because the neon lamp will be off and the supply will show no output.
This should be an easy change to your otherwise great looking build.

See here and here.

Sorry, a little confused here. My fuse is connected to the mains hot line via a non reversible 110 volt plug. If the fuse blows, the hot line is disconnected. Can you show me a schematic of what you are describing as a better way to be safe? Thank you... Tom

 

[Bluejets]

To increase safety both fuse and switch should be in the life wire.

Actually, any portable device run on a lead and plug should use double pole switching as there is never any certainty whether an outlet or the plug is correctly wired.

 

[Bluejets]

My fuse is connected to the mains hot line via a non reversible 110 volt plug.

This may be true but if this is the case, switching only the neutral is not allowable.
See #27.

If the unit is hardwired ,(permanently wired into the house wiring system) single pole switch is allowed but then the switch must be in the active conductor.

 

[Electromotive]

This may be true but if this is the case, switching only the neutral is not allowable.
See #27.

I have the switch located on the hot line, the one with the Hot oriented prong plug. The schematic is not drawn correctly, as I referred to in my first response but not precisely communicated.

 

[Harald Kapp]

The schematic is not drawn correctly,

Please provide a revised schematic, To me it is by now totally unclear where switch and fuse are located with respect to mains and neutral