Dispensing aroma with humidifier

The idea of using humidifier to dispense aroma is not new. One other blog suggest the use of ultrasonic mist maker for this purpose - which I do not favor.

What is my approach then?

A simple arrangement - a plastic tank that feeds aroma solution to the humidifier water pan by gravity. My initial thought was to use an electronic timer to add some aroma solution daily. But it is not synchronized to the humidifier operation.















So I wired the solenoid valve to the hygrostat controller. Picture below shows the attachment of solenoid valve in-line with a manual valve which control the flow rate. The aroma solution is diluted as the humidifier operates over a variable period.




















My hygrostat controller relay has 2 pole, 10A relay contacts (wired in parallel can handle 20A) that easily handle the extra electrical load of the solenoid valve. The 'turn-on' switching current pulse is generally quite high.

Cases of recurring amplifier failures

Recently I met two bird farmers with recurring amplifier failures. Tweeters connection are parallel in both cases - one with just 15 tweeters a channel.

It is common knowledge load impedance (Z, as in fig. below) to the amplifier drops rapidly towards a short circuit with parallel connections:
e.g. (ignoring wiring resistances)
A 10 tweeters in parallel reduce its load impedance to 10%;
20 tweeters in parallel reduce load impedance to 5%;
50 tweeters in parallel reduce load impedance to 2%!

What happens?
The amplifier has its output impedance (Zout) too. So together with the load impedance, the combined behavior is like a voltage divider.

What then?
If Z is high relatively to Zout, things are pretty normal. But when the external load impedance, Z, is at the same level as Zout, sound level is halved: i.e. only half power is delivered to the load, other 1/2 power dissipates within the amplifier as heat! We then tend turn up volume higher close to its limits.











So the amplifier heats up even more until thermal runaway occurs leading to amplifier failure.

What are the solutions?
1) Employ series-parallel connection can improve the situation a little and hence not favored. Connecting adjacent tweeters in series doubles the load value - but still limited by the overall parallel connection. Besides when one tweeter fails the other in series will not work too, then extra effort to trouble shoot.














2) The proper solution is to choose an amplifier with lower output impedance. This is the reason I chose amplifiers with 100W r.m.s. per channel. I have 40-50 tweeters to a channel. Once I turned up volume close to max. during endurance tests, the amplifiers did heated up and failed too after 2 days!

So just beware - I normally touch the amplifier heat sink when I visit the farm house. Best should be just warm.

Mounting tweeters at corner planks

It is normal practice to nail the tweeter below the nesting plank.

In a recent new bird house, I try to improve on this. We all know birds like to hang close to tweeters and build nests around it, so the tweeters are installed higher up on nesting planks with space for birds to perch beneath it.

Using smaller tweeters to fit in a cut circular hole. Consideration of tweeter replacement in future should be taken into account.















A more close up view.















There are small surface mount 'button-like' tweeters, much easier to install.















I'll update pictures here in time to come.

When and how humidifiers would fail?

This Taiwanese made humidifier is perhaps the most common in use. If you are using such humidifiers for a year or two, it is prudent to do some preventive maintenance such as cleaning and oil its bearings. You will be surprise how dirty it can become!

















One that I have been using with a plastic cover to direct the mists sideways and prevent young birds falling in.




















Recently I noticed the motor didn't turn when the hygrostat controller indicator was "ON". The first thought came to mind was to check the hygrostat output control or relay. I used a 10Amp Omron relay with built-in an LED indicator - which is useful for visual check. Next I gave the fan with a little spin and the motor kicked into life. That helped to kick start it so too much frictions at the bearings I thought.

I took it home to do some cleaning and oil the moving parts. I have dismantled such unit several times before, so it is a familiar routine. A good exercise if you are doing it first time and discover its working principle.

Picture below is a dismantled unit turned upside down. I normally remove the metal 'squirrel' cage as it can be easily damaged. Beware of its sharp edges too!



















The tip of the spindle sucks water up a cone and spin outwards to the 'squirrel' cage. In the process kinetic energy of water increases and breaks into fine droplets as it hit the blades. The fan on top draws the water droplets upwards into a fine spray. Simple and very clever!















After removal of plastic housing, there are only two electrical parts: the motor and a capacitor.















Beneath the metal cap plate is rubber O-ring to prevent water sipping into the motor. It does add friction to the motor shaft - so I oiled both top and bottom rings.



















The top O-ring.



















& the bottom O-ring.




















The motor housing must be opened in order to reach the bearings. Below is a burned out motor & capacitor. The bearing is seen around the motor shaft. By now you will have many loose screws lying around and should keep track of them for re-assembly!















It worked fine as I put the unit back together - the problem fixed so I thought!
A week later, I noticed the same problem again! So I scratch my head - only 2 working parts, what can be wrong? The capacitor looks normal without any bulge. Common sense was to replace it and see what happens - BINGO! That was the problem - the starting capacitor!















Fortunate I detected sign of early failure. My lesson was I did not suspect the capacitor without any bulge - the sign of failing capacitor. Oiling the moving parts did help somewhat but gave a false impression the problem was fixed!

So the failure mode begins at the capacitor. Without sufficient starting torque, the motor stalls without cooling. Heat builds up gradually within the motor until its stator wire insulation breaks down creating short circuit and even melts wire! A failed unit (one shown above) I inspected had its plastic enclosure warped by the heat, pretty hot it must be!

It is very essential to have an external mains protective fuse or circuit breaker. I use a 20A circuit breaker to protect the power points in the bird house.