Worth A Look

[nitro7]

The power supply he has used has a proper EI core transformer in it. An RCD would do nothing for protection as the secondary is fully isolated from the primary.

Get some current limiting on those LEDs swiftly though - they will not last long as you have them. Those transformers are notorious for being poorly regulated (if at all!)

He has wired the LEDs in parallel so one LED failure will not cause the others to fail, although they will all fail anyway because they're being overdriven!!

A transformer is NEVER a guarantee of ABSOLUTE safety... less so when you employ the cheapest rubbish the inevitable far east manufacturer has put in there ! A primary/secondary fault WOULD cause mains voltage to appear at the LEDs, AND in your tank water... This could be caused by overheating of the PSU, a fault in the wiring causing a short... etc etc - so there is STILL a NEED for an RCD.

Because they are wired in parellel, they are all sharing the load, so if one pops the others will suffer a voltage spike at best - at worst the voltage will jump up due to the drop in current. (more so if the PSU is not regulated... and by regulated, I DO NOT mean the crappy zener that cheapo units use !)

after all your lovely comments
i think i have it sorted?
out goes the transformer and in goes the solar pannel
ive got 1 that runs about 40 white leds at 3v for about 4 to 5 hours in winter ,8 to 10 hours in summer
with only 5 leds i hope they will run for longer,switch on at dusk ,off at dawm
job for the weekend
thanks again for all your useful info

 

[keenonfish]

I would NEVER run LEDs without a resistor, and in the way yours are wired, failure of one would probably cause the rest to fail...

Voltage is irrelevant - its current that kills (LEDs and people) , and the resistor that controls it.... you may find them TOO bright, in which case increase the value of the resistor.
...and make SURE the power supply is "double insulated" AND is plugged into a "RCD" even though you are playing with supposed low voltage, you are only ever a tiny amount away from mains voltage ! (transformer fault)

I admire a DIYer... but water+electricity only lets you #### up ONCE... So PLAY SAFE

Voltage is VERY relevant. You cannot specify a resistor for an LED without knowing the voltage. Not only that but if you have an led with a forward voltage of 3.6 volts and ran a regulated supply of 3v while not the 'correct' as long as the led doesn't heat up it would not exceed it's maximum I[sub]f[/sub].

However I generally agree with your sentiments that those transformers are cheap as you get and are in no way regulated! Also the OP must make sure all connections are water tight i.e. use some sort of non toxic epoxy to seal from water.

To OP Resitor = Voltage out of transformer (measure this) e.g. 12V - (subtract) Forward voltage for LED (normally quoted as V[sub]f[/sub] @ xxmA e.g. 3.2v) and divide that answer by the current you want to drive the LED at (normally about 30mA divide by 0.03 in this example) but never go near the maximum quoted mA specification of the led you have chosen.

In above example 12 - 3.2 = 8.8v (voltage drop across resistor) divide by 0.03 (30ma) = 293 R.

Having resistors to each individual LED ensures that a power hungry led won't nick all the juice and lower the output of the others.

 

[Rooster]

Often thought about striiping one of the solar garden lights... and placing the solar panel in the hood - after all, we are simulating daylight in there !

 

[Gun]

nitro7 - hide your heater/wires to complete the effect in your 4th pic

Guys, what safety device/equipment should I have in place with a multiple tank set up? (20-40 tanks-various). Electric Shock worries me, sometimes

ps, don't mean to hijack..seems there's a lot of knowledge floating around here, though

 

[keenonfish]

Often thought about striiping one of the solar garden lights... and placing the solar panel in the hood - after all, we are simulating daylight in there !

wouldn't be a bad idea to use some of that stray light in the hood to charge some batteries for night lights - if you could get them bright enough!

 

[keenonfish]

nitro7 - hide your heater/wires to complete the effect in your 4th pic

Guys, what safety device/equipment should I have in place with a multiple tank set up? (20-40 tanks-various). Electric Shock worries me, sometimes

ps, don't mean to hijack..seems there's a lot of knowledge floating around here, though

To protect you kill all power whenever you service the tank. At the very least an independent RCD (normally sold at garden centres etc) is mandatory! However it is essential you get the an RCD that doesn't reset itself in the event of a power cut. I have one that does this the other one locks on and stays that way until needed!

Also check cables whenever you take a heater or pump out look for signs that things don't look right.

You could get one of those volt sticks but they should never be relied upon for safety! If it ever lit up when dipping in the tank then you would know there was a problem!

 

[SteveyG]

A transformer is NEVER a guarantee of ABSOLUTE safety... less so when you employ the cheapest rubbish the inevitable far east manufacturer has put in there ! A primary/secondary fault WOULD cause mains voltage to appear at the LEDs, AND in your tank water... This could be caused by overheating of the PSU, a fault in the wiring causing a short... etc etc - so there is STILL a NEED for an RCD.

I disagree. You would need at least THREE faults for mains to appear on the secondary. Remember the coils are never wound directly onto the laminations - there is a plastic former which the coils are wound around, which can either be two completely separate mouldings to maintain isolation or a single moulding with a separator.

There is no requirement for an RCD to be used at all with SELV, even the regs say it is not required.

 

[Gun]

To protect you kill all power whenever you service the tank. At the very least an independent RCD (normally sold at garden centres etc) is mandatory! However it is essential you get the an RCD that doesn't reset itself in the event of a power cut. I have one that does this the other one locks on and stays that way until needed!

Also check cables whenever you take a heater or pump out look for signs that things don't look right.

You could get one of those volt sticks but they should never be relied upon for safety! If it ever lit up when dipping in the tank then you would know there was a problem!

Thanks keenofish

'To protect you kill all power whenever you service the tank'...I've never really thought about it like that...damn I'm slow sometimes

 

[keenonfish]

To protect you kill all power whenever you service the tank. At the very least an independent RCD (normally sold at garden centres etc) is mandatory! However it is essential you get the an RCD that doesn't reset itself in the event of a power cut. I have one that does this the other one locks on and stays that way until needed!

Also check cables whenever you take a heater or pump out look for signs that things don't look right.

You could get one of those volt sticks but they should never be relied upon for safety! If it ever lit up when dipping in the tank then you would know there was a problem!

Thanks keenofish

'To protect you kill all power whenever you service the tank'...I've never really thought about it like that...damn I'm slow sometimes

You know I should take my own advice sometimes ; )

Olly.

 

[nitro7]

A transformer is NEVER a guarantee of ABSOLUTE safety... less so when you employ the cheapest rubbish the inevitable far east manufacturer has put in there ! A primary/secondary fault WOULD cause mains voltage to appear at the LEDs, AND in your tank water... This could be caused by overheating of the PSU, a fault in the wiring causing a short... etc etc - so there is STILL a NEED for an RCD.

I disagree. You would need at least THREE faults for mains to appear on the secondary. Remember the coils are never wound directly onto the laminations - there is a plastic former which the coils are wound around, which can either be two completely separate mouldings to maintain isolation or a single moulding with a separator.

There is no requirement for an RCD to be used at all with SELV, even the regs say it is not required.

hi steveyG
so what you are saying is if the transformer goes wrong the mains electric wont go into the fish tank.
i use a rcd on my tank any way just to be on the safe side
thanks for the comments

 

[keenonfish]

You can never say it impossible, but almost impossible

Just bear in mind you are working with electricity and there are always risks, so it is best to minimise risk and assume something could be dangerous unless you absolutely know otherwise!

 

[nitro7]

Love this forum
get loads of help&lots of people with electrical no how
heres couple of pics
i took this off what i took the L.E.D.s off.
do you think i should replace it ?
and could you explain what its for
sorry to be a pain in the butt
many thanks eric (nitro)

 

[Rooster]

At the top we have an electrolytic capacitor.... under that a couple of resistors, under those 4 diodes - no doubt arranged as a "bridge rectifier"
The thing to the left, marked as "Q1" (?) could be a transistor, or voltage regulator... probably an "amplified zener" regulator circuit...

Thats my guess....

 

[nitro7]

At the top we have an electrolytic capacitor.... under that a couple of resistors, under those 4 diodes - no doubt arranged as a "bridge rectifier"
The thing to the left, marked as "Q1" (?) could be a transistor, or voltage regulator... probably an "amplified zener" regulator circuit...

Thats my guess....

cheers rooster,
tried it out but it just flashes the L.E.Ds on and off (worth a try.lol)
could i use one of the resistors ?

 

[keenonfish]

Yes rooster is correct that circuit will accept a.c. (or d.c.), rectify then crudely regulate using the big resistor (20 ohm) and zener to the left of the rectifier diodes. The transistor will be part of the flasher circuit or maybe as rooster pointed out part of the regulator if it used to drive reasonable load. I suspect there maybe a component or two underneath? Either that or the flashing is due to a fault?

Don't bother using those resistors if you are in the states you should have your 'circuit cities' or whatever and over here you have Maplin's for consumers. Work out the resistor value you require find the nearest match then spend a few cents or pennies on new resistors...