my rust removal tank

[123hotchef]

maybe i went ott then with 6 brake discs and 20 odd gallons of water

 

[123hotchef]

 

[123hotchef]

well thats the first power supply dead i am thinking that 6 brake discs might be too much for the power supply

 

[123hotchef]

Put a current limiter in.

how would i do that mr pdg

 

[WorkshopChris]

If you put a 12v bulb in series it will limit the current it can draw.

a 12v 21 w indicator bulb would limit you to around 2amps

 

[123hotchef]

i used my clamp on amp meter and it seems to be drawing less than 1 amp

 

[WorkshopChris]

Sounds strange is your clamp meter rated for ac & dc ?
What was the voltage.
Mine normally sits at about 2 to 3 amp depending on voltage when useing a bench power supply. if its a charger then i normally stick the bulb in to limit.

 

[WorkshopChris]

If you wrap the wire around the clamp a few times then divide the reading by the amount of turns it will give you better accuracy on small loads.

 

[123hotchef]

ok yes it was a ac clamp on meter so i pulled my other meter out just now and its pulling 0.9amps at the power supply

i am now using a old cb power pack 12v

the psu was from a dell surround sound amp it was 20V and It blew the rectifier

how does the lamp limit the current then just want to know the science behind that

 

[123hotchef]

so the lamp only lets 2amps max flow through it

 

[WorkshopChris]

how does the lamp limit the current then just want to know the science behind that

Ok will give it a go ( brain a bit fried today but will try),
The filament in the bulb is just a resistor, as the current flows around the circuit the resistor heats till its bright red and glows. in this situation the bulb is self regulating it will use the power available to glow and no more.
So if we now stick your tank between the bulb and supply it doesn't matter how much power the tank wants it still cant use any more than will pass through the filament.

Hope that helps.

 

[123hotchef]

got it thanks Chris but surely if the tank is not drawing more than an amp the lamp is not needed? I have a few lamps knocking about i might give it a go

so the lamps gets put in the circuit on the + before the tank and the - after?

 

[WorkshopChris]

With the lamp in circuit if the tank only needs half a amp it can still get it but if something in the tank touches or get to close to one of your disks the current is limited at 2amp, even in a direct short you power supply will still be safe.

 

[123hotchef]

got it so its a safety thing too maybe something touched the disc earlier that is why the psu burnt out,

 

[123hotchef]

a 12v 21 w indicator bulb would limit you to around 2amps

so the lamp will not illuminate just wire it in the + side of the circuit

 

[WorkshopChris]

Maybe, i am still new to this but i have found if the solution is strong and a large part gets to close to the steel around the edge the current will go up even if there is no direct contact so it pays to move parts around carefully.

The more current flowing the brighter the bulb will glow.

 

[The_Yellow_Ardvark]

Do you have a in line fuse?
Must PSU have one inside, some are solder in place. Others are normal fuses. One of my PSU states.
NO Serviceable Parts Inside.
Look inside and there was 2, one for mains and one for the DC O/P.

 

[123hotchef]

the fuse was replaced with tin foil!

 

[123hotchef]

the actual transformer is knackered no resistance across the input maybe a thermal fuse in the windings somewhere although i couldnt find one

 

[123hotchef]

thanks that is what i figured just checked the tank its drawing 1.1 amps now the power supply is hot but it always got hot when i use to use it to power my cb back in the day