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NB59S Technical Notes

Table of Contents

  1. How do I vary the output?
  2. What kind of transformer?
  3. What about the water?
  4. Draining down
  5. What is the life of the transducer
  6. Premature death
  7. Legionella
  8. More design information

How do I vary the output?

The output from the humidifier modules may be varied by changing the voltage supplied to the modules between 38v and 48v.  This can be done very economically by using a multi-tapped transformer.

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What kind of transformer?

You must use an ordinary transformer with separate primary and secondary windings.  If you use an auto-transformer, which is one where the secondary winding forms part of the primary winding, then this may put the primary voltage onto one or other of the module input terminals.  This will then cause the output from the bridge rectifier to be at the line (high) voltage which can short to earth through the heat sink.  This makes pretty blue sparks and an interesting noise as it destroys the PCB!

Note that most Variac transformers are of the auto-transformer type and so must not be used, even for test purposes.

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What about the water?

There should be 40mm of water above the transducer disk.  If you power up the driver circuit without any water then the transducer and driver circuit will die instantly and permanently.

As the water will end up in the air space, you must ensure that it is free of any impurities that will affect the equipment or personnel within the space as the water evaporates.  In a computer environment the calcium salts in hard water will collect on screens and tape heads etc.  This is easily dealt with by using demineralised water produced by a reverse osmosis plant.

Whilst tests have shown the Legionella bacteria to be killed by exposure to the ultrasonic shock waves from the transducers, it is essential that the statutory legionella controls and inspections be undertaken.

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Draining down?

When humidifiers are operated in a dirty environment, the dust and dirt is washed out of the air and it collects in the reservoir.  We recommend therefore that all humidifiers should be drained down on a regular basis when in use.  They MUST  always be drained when humidification is not required for an extended period.

We have designed a fully automatic control module that will drain the humidifier on a regular basis.  It accepts inputs from float switches and from building management systems and has outputs to the NB59S boards, solenoid valve and status indication.  Click here for more information.  Whilst these modules were developed to suit the Electrosonic range of humidifiers, they can easily be adapted to other humidifiers.

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What is the life of the transducer?

TDK quote 10,000 hours continuous running at the end of which time the output will be about 70% of the new output.  At this stage, it will be noticed that the plating is starting to peel off the centre of the disc.

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Premature death?

Normally, the driver circuits and transducers are very robust and will last for years of intermittent use.  However, as with any equipment, abuse will shorten their life - drastically!

Operating without water over the transducer kills the board and transducer instantly.

Powering up the NB59S board without a TU20A transducer correctly attached kills the NB59S instantly.

Powering up the NB59S board with the Orange and Yellow wires on the wrong terminals destroys the NB59S and the transducer.

Using an auto-transformer can destroy the driver board as noted above. You must use an isolating transformer.

The heatsink MUST be mounted on a surface that can conduct the heat away from the TO1A transistor.  If this is inadequate then the transistor will overheat and fail.

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Legionella

Concerns have been raised about the risk of Legionella when using misting humidifiers.  As with many devices, ultrasonic humidifiers can be dangerous if they are not properly installed, operated or maintained.

More information about Legionella

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More design information

TDK publish comprehensive design information. The button below will take you to TDK's web site where they give lots of detail on the application of the NB59S nebulisers.  They also give information on a couple of other units but we only stock the NB59S and TU20A.

Visit TDK's web site

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All information and advise on this site is given in good faith and no liability is implied or accepted by BSDesign Limited.
Copyright 2002  [BSDesign Limited] rights reserved.
Revised: April 16, 2016 .