Transformer smoked

[R791945]

I bought an AC 240v input /Output 24v 2A DC. Connected a fountain mist maker (24v 19w). They produce their effect with ultrasonic sound.

The transformer's led came on, the mister worked and then I saw smoke coming from the transformer and there was a strong smell from the transformer. I quickly turned the power off. The mister's spec makes it suitable for the transformer. The transformer is giving a voltage out of 24.3v.

The supplier has replaced the transformer. I do not wish to have a repeat with the new one. Any ideas how to protect the transformer if the problem is overload?

 

[Minder]

The fountain unit would not be AC by any chance?
M.

 

[davenn]

The fountain unit would not be AC by any chance?
M.

yeah, that was going to be my Q as well

 

[Arouse1973]

We have one of the metal encased types and it's 24 Volts D.C. Current draw is about 500 mA.
Thanks
Adam

 

[ramussons]

Measure the voltage supply. If it drops appreciably when connected to the "mist maker", there is a problem with the mist maker.

maybe it's a smoke maker.....

 

[R791945]

The fountain unit would not be AC by any chance?
M.

The mister can be either AC or DC according to the description.



working voltage: AC or DC 24V
power: 19W

http://www.ebay.co.uk/itm/321548707355?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT


R

 

[R791945]

Measure the voltage supply. If it drops appreciably when connected to the "mist maker", there is a problem with the mist maker.

maybe it's a smoke maker.....

How do I measure the voltage supply when the mist maker is connected to the transformer? Do I do it by measuring the neg and pos output with the volt meter in parallel with the mist maker? I assume I should not try to connect the meter in serial with the mister.

What is the way to protect the transformer when connecting to the mist maker? Should I separately fuse it? Would plugging the transformer into an earth loop detector be useful?

 

[poor mystic]

Hi
It might be best to measure the resistance of the mist maker, using a multimeter, if you suspect that it might be faulty.
Calculating resistance:
P=E^2/R, hence R=E^2/P.
Then R=(24*24)/P
= 576/19
= approx 30Ω

However, if the device was working, it's hard to see how it could also be faulty.

 

[R791945]

Is this an indication that the mister is poorly wired?

I connected the pos of a 1.5v continuity tester to either the + or - power cable of the mister, and the neg to the casing of the mist maker. In both variations there is continuity.

 

[R791945]

Hi
It might be best to measure the resistance of the mist maker, using a multimeter, if you suspect that it might be faulty.
Calculating resistance:
P=E^2/R, hence R=E^2/P.
Then R=(24*24)/P
= 576/19
= approx 30Ω

However, if the device was working, it's hard to see how it could also be faulty.

The ohm reading shows 1 when I connect the + and - cables to the volt meter. There is no continuity between + and - cables using 1.5v continuity tester.

 

[Tha fios agaibh]

Any ideas how to protect the transformer if the problem is overload?

How about adding an inline 2A fuse?

 

[ramussons]

It's also possible that the first Power Unit was faulty and its transformer blew. Yes, a 2 Amp fuse would help.

 

[R791945]

If you look at reply #9 and 10# above you will something I find very strange. No continuity between +- but continuity between each cable and the chassis of the mist maker. How is that possible?

 

[Minder]

If you look at reply #9 and 10# above you will something I find very strange. No continuity between +- but continuity between each cable and the chassis of the mist maker. How is that possible?

One odd explanation is if the mist maker has a bridge on the input for AC/DC and either polarity DC.
And one side of the input connected to GND.
Most modern meters on Resistance range will not measure a SS device.
M.

 

[Tha fios agaibh]

You could measure the resistance, but Imo, the readings are not going to be of much help. I would venture a guess that the ultrasonic waves are compromising the internal insulation, or water has gotten in the thing. (Could explain your continuity readings)
You could monitor the current by putting your meter in series with the wiring, provided it can measure amps. Might want to move the wires around and see if the current spikes (short circuit) or if it fluctuates at certain times.
If you get a steady current (ma) reading, I would feel pretty confident that the previous problem was just a bad transformer.

 

[poor mystic]

A trick I've used when testing audio amplifiers is to put a tungsten filament light bulb in as a fuse.
If you have a 24V automotive tungsten filament interior light bulb you could put it in series with the load, and if there's a short in the load the light will glow brightly and the transformer will not be damaged.

 

[R791945]

I will have to now buy a few extras and see how it goes. I didn't expect to be buying a light bulb as a fuse but it is a good idea as are the other comments. Thanks. I will report back if I have further problems.

 

[poor mystic]

I will have to now buy a few extras and see how it goes. I didn't expect to be buying a light bulb as a fuse but it is a good idea as are the other comments. Thanks. I will report back if I have further problems.

Pick a lamp about the same wattage as the device under test.