Phatmatt
Vroom Vroom
+298|6452|Canada

I got two transformers that are 0.7amps each, and will be on the same fuse (car fuse) I have no idea how to calculate what fuse I need.

I thought about just adding up 0.7+0.7=1.4amps  but I'm not too sure it's this simple. what size fuse should I use? I'm a noob when it comes to electricity.

also what size wire should I use?



here is a basic layout of the circuit im doing
https://i16.photobucket.com/albums/b14/phatmatt0005/bdaef976.jpg
Freezer7Pro
I don't come here a lot anymore.
+1,447|6461|Winland

Fuck fuses. 7AWG wire is all you need

And it would probably be easiest to just use a 2A slow fuse. Can't tell more without specifics.

What kind of transformers are they? What are you driving with them? You do know that standard transformers only work with AC, right? Is the 0.7A in or out? What voltage do they output?

Last edited by Freezer7Pro (2009-03-22 11:01:48)

The idea of any hi-fi system is to reproduce the source material as faithfully as possible, and to deliberately add distortion to everything you hear (due to amplifier deficiencies) because it sounds 'nice' is simply not high fidelity. If that is what you want to hear then there is no problem with that, but by adding so much additional material (by way of harmonics and intermodulation) you have a tailored sound system, not a hi-fi. - Rod Elliot, ESP
Phatmatt
Vroom Vroom
+298|6452|Canada

the transformer draws 0.7 amps, so I'm guessing that's in?
the transformer takes DC and turns it into AC.
the lights are AC (cold cathodes)

The transformer is designed to use 12 volts DC, and output approximately 650 volts AC that is needed to power the cold cathode.
Each cathode transformer draws about 0.7 amps of power at 12 volts.
Freezer7Pro
I don't come here a lot anymore.
+1,447|6461|Winland

Ah. That's called an inverter

They often have a bit of a surge when they start, so yeah, 2A slow fuse.
The idea of any hi-fi system is to reproduce the source material as faithfully as possible, and to deliberately add distortion to everything you hear (due to amplifier deficiencies) because it sounds 'nice' is simply not high fidelity. If that is what you want to hear then there is no problem with that, but by adding so much additional material (by way of harmonics and intermodulation) you have a tailored sound system, not a hi-fi. - Rod Elliot, ESP
rdx-fx
...
+955|6855
Design to handle the start-up load, not the steady-state load. 

Cold startup is generally much higher of a load, in most electrical systems.

There are circuit designs to handle surge loads like that, so you can put a fuse in for the steady state load.
Surge & startup get handled by the overload/startup circuit - steady state load goes through the fuse.
One of the two detects an overload outside their design limits, they shut the sysem down (i.e., sustained high-current demand = short= shutdown)

PSU -> fuse -> overload cap circuit -> transformer/inverter circuit -> bling lights.
Phatmatt
Vroom Vroom
+298|6452|Canada

Freezer7Pro wrote:

Ah. That's called an inverter

They often have a bit of a surge when they start, so yeah, 2A slow fuse.
alright, 2A it is
what's the "slow" for? Like I said I'm a noob
Freezer7Pro
I don't come here a lot anymore.
+1,447|6461|Winland

There are two kinds of fuses, fast and slow. Fast burn pretty much the same ms as the current limit is exceeded, slows take a second or two. Slows are better for things like this, as they can draw a lot of current when they're starting up.
The idea of any hi-fi system is to reproduce the source material as faithfully as possible, and to deliberately add distortion to everything you hear (due to amplifier deficiencies) because it sounds 'nice' is simply not high fidelity. If that is what you want to hear then there is no problem with that, but by adding so much additional material (by way of harmonics and intermodulation) you have a tailored sound system, not a hi-fi. - Rod Elliot, ESP
rdx-fx
...
+955|6855

Freezer7Pro wrote:

There are two kinds of fuses, fast and slow. Fast burn pretty much the same ms as the current limit is exceeded, slows take a second or two. Slows are better for things like this, as they can draw a lot of current when they're starting up.
Pfft.  and there you go.  Give him the easy solution, with the fewest parts.

complicated circuit designs?  Noooo..  just a slow fuse.


No fun, I tell ya
Phatmatt
Vroom Vroom
+298|6452|Canada

alright thanks for the help!

I just have one last question.
the switches I got are rated for
10A 277VAC
20A 125VAC

I shouldn't have any problems right?



edit: @rdx-fx, it's probably a better idea to give me the easiest solution, else I'll find a way to blow it up

Last edited by Phatmatt (2009-03-22 12:53:01)

Freezer7Pro
I don't come here a lot anymore.
+1,447|6461|Winland

rdx-fx wrote:

Freezer7Pro wrote:

There are two kinds of fuses, fast and slow. Fast burn pretty much the same ms as the current limit is exceeded, slows take a second or two. Slows are better for things like this, as they can draw a lot of current when they're starting up.
Pfft.  and there you go.  Give him the easy solution, with the fewest parts.

complicated circuit designs?  Noooo..  just a slow fuse.


No fun, I tell ya
Over-elaborating is the best way to kill a project tbh.
The idea of any hi-fi system is to reproduce the source material as faithfully as possible, and to deliberately add distortion to everything you hear (due to amplifier deficiencies) because it sounds 'nice' is simply not high fidelity. If that is what you want to hear then there is no problem with that, but by adding so much additional material (by way of harmonics and intermodulation) you have a tailored sound system, not a hi-fi. - Rod Elliot, ESP

Board footer

Privacy Policy - © 2025 Jeff Minard