Transformer wires

[123hotchef]

thanks mate ill look at some boards tomorrow

 

[mike 109444]

Don't forget that the plug you put on that transformer may come with a 13amp fuse but for the load you are going to put it under get some 3amp or even 1amp fuses !! and keep the mains away from the water and instead have long leads from the DC side.

 

[anjum]

Judging by the size of your transformer (no builders mug for reference but looking at the water bottle in the background) the bridge you are proposing to use is too lightweight (not rated for enough amps). I would use at least least the 35amp one at maplins and secure it to the case or a heatsink with some heatsink compound.

You also need to limit the available current at the output as putting a short across the leads WILL cause it to go BANG!!!
The voltage may not be critical but the current ratings are.

The least you could get away with is a large power metal clad resistor on a heatsink. Work out the power it would consume connect right across the bridge and capacitor (i.e. the output leads are shorted) and limit the current to not exceed the bridge or transformer or the power resistors continuous rating. The same applies for the capacitors ripple rating.

(maybe a light bulb would work but would limit your current too much)

Those 'simple' battery chargers weren't just slung together!

How much current do you need?

Another way, the best, would be to design/ buy a regulator circuit.

 

[123hotchef]

It is only for a rust removal tank @anjum so a capacitor will be the easiest and cheapest option

the bridge I ordered was a 35amp one from China too.

 

[123hotchef]

Just acquired a nice pair of transformers putting out 30V or 60V at 2amps so I think Ill give these a go instead, nothing to loose

 

[123hotchef]

 

[123hotchef]

 

[WorkshopChris]

i might be tempted to see how your existing transformer goes the 30v ac will be 40+v once rectified , might be on the high side.

 

[123hotchef]

this one already had DC coming out of it see the circuit board attached to the transformer 2 big bridges and 4 big caps

 

[WorkshopChris]

OK see how it goes, will try to get mine finished this week , want to keep it outside under a cover. Just need a dry day to get it finished.

 

[123hotchef]

I want to keep mine outside too hence the transformers in a plastic box, mine is ready to go now washing soda gets delivered thursday

 

[bigegg]

i might be tempted to see how your existing transformer goes the 30v ac will be 40+v once rectified , might be on the high side.

Could a dimmer switch be fitted on the input side to reduce the voltage?
Full voltage to blast through any paint/crud then turn it down once it gets going

 

[skotl]

Could a dimmer switch be fitted on the input side to reduce the voltage?
Full voltage to blast through any paint/crud then turn it down once it gets going

Depends how the DC regulator works. If it's all discrete components then it will likely track down with the "dimmed" AC input voltage but if it's IC-based then it may get a bit miffed if fed with less voltage from the transformer than it expects.

I doubt it would hurt it though - worst case is that turning down the dimmer means 0VDC out, so then just remove the dimmer - worth giving it a try!

 

[WorkshopChris]

All depends on the dimmer as skotl said, some dimmers as they are designed for lighting rather reduce the voltage they chop it up and switch the light on and off ever so quickly this has the effect to the eye in reducing its brightness. however the bulb is still getting 240v.
To reduce the voltage correctly a rheostat would be required, but a dimmer might work. it cant do much harm with the size of transformers we are looking at.

 

[123hotchef]

great idea ull be better off with a led dimmer and stick it after the trannie

 

[skotl]

great idea ull be better off with a led dimmer and stick it after the trannie

Errr... probably not, cos even LED dimmers are normally 240VAC

 

[123hotchef]

huh no 12-24v dc

 

[123hotchef]

like this one http://www.lightinthebox.com/8a-1-c...BcHsW42a2qKaLvkHKoIj6Xc4RMnM30UIyZRoCNuPw_wcB

 

[skotl]

huh no 12-24v dc

Fair enough not seen an ELV dimmer before - first time for everything!

Looks like it's max 24V though so you may still need to step down from your transformer output. I doubt it will carry much current, either (odd that there's no specs on that website) so you'll need to be careful about drawing too much current.

Edit: just spotted that it reads 8A, which would seem plenty

 

[123hotchef]

and £4 aint bad price either,