He & his wife count the birds entering the bird house during the last 10 mins in the evening with mechanical hand held counters. Then taking the average of the two to reduce the error - simple!
I like it.
Thursday, November 5, 2009
Birds Counting Tip
How would you estimate the birds staying in the bird house? This is how my friend does it.
He & his wife count the birds entering the bird house during the last 10 mins in the evening with mechanical hand held counters. Then taking the average of the two to reduce the error - simple!
I like it.
He & his wife count the birds entering the bird house during the last 10 mins in the evening with mechanical hand held counters. Then taking the average of the two to reduce the error - simple!
I like it.
Wednesday, October 14, 2009
Cleaning Bird Nests - Part 2
I also wanted to improve on the rinsing process in removing fine hairs & particles. So I come up with this DIY filtration process. A small fountain pump circulates water up a tumbler that carries a coarse wire mesh sieve at the top. Water overflow to the next filtration unit and down to the water basin.
The filter unit is made of common household items. A tall plastic cup houses a finer wire mesh sieve and washing sponge form the filter.
Transferring the bird nest from the ultrasonic cleaner into the wire mesh sieve, it is then wash continually by circulating water. The finer wire sieve retains bird nest that overflowed into the filter cup.
I am pretty satisfied with the result. These are fine particles trapped by the filter sponge after cleaning - ones that can't be picked by tweezers.
So I am using a 2 stage process now. First using the ultrasonic cleaner (& hand picked the larger feathers of course) before transferring to the 2nd rinsing/filtration process.
A logical next step is to combine the two into a single process. But I am happy with this arrangement for the meantime. Hope you will find it useful too.
The filter unit is made of common household items. A tall plastic cup houses a finer wire mesh sieve and washing sponge form the filter.
Transferring the bird nest from the ultrasonic cleaner into the wire mesh sieve, it is then wash continually by circulating water. The finer wire sieve retains bird nest that overflowed into the filter cup.
I am pretty satisfied with the result. These are fine particles trapped by the filter sponge after cleaning - ones that can't be picked by tweezers.
So I am using a 2 stage process now. First using the ultrasonic cleaner (& hand picked the larger feathers of course) before transferring to the 2nd rinsing/filtration process.
A logical next step is to combine the two into a single process. But I am happy with this arrangement for the meantime. Hope you will find it useful too.
Cleaning Bird Nests - Part 1
Cleaning bird nest is a simple process but tedious & time consuming. Just soak the bird nest overnight in a bowl of water, it will soften and expand. It is a matter of picking out the feathers with a pair of tweezers!
The tweezers look alike, you will learn to differentiate them after using and appreciate the pair with sharper tips & gentler on fingers.
Then there are finer particles & feathers that seem an endless task to remove! Rinsing many times with water seem the only practical way. Still there are many fine hairs left to pick. So depend how clean you want it, the remaining task is still very time consuming! One can then understand why commercial cleaning resort to bleaching agents.
I did it several times for personal consumption. Each time I was motivated to find a better way. I toyed with the idea of using a ultra-sonic cleaner for a while. Its mechanical vibrations would help to shake loose the feathers & fine particles trapped within.
Recently I found this 35W ultrasonic cleaner that comes with a plastic tray. Fine hairs & particles are attracted to the plastic tray by electrostatics, which I find is a plus.
I tried and it does help and effective to some extend. Rather than to describe my experience here, I suggest it is better for one to experiment & discover for themselves. I merely want to introduce it as a tool here.
The tweezers look alike, you will learn to differentiate them after using and appreciate the pair with sharper tips & gentler on fingers.
Then there are finer particles & feathers that seem an endless task to remove! Rinsing many times with water seem the only practical way. Still there are many fine hairs left to pick. So depend how clean you want it, the remaining task is still very time consuming! One can then understand why commercial cleaning resort to bleaching agents.
I did it several times for personal consumption. Each time I was motivated to find a better way. I toyed with the idea of using a ultra-sonic cleaner for a while. Its mechanical vibrations would help to shake loose the feathers & fine particles trapped within.
Recently I found this 35W ultrasonic cleaner that comes with a plastic tray. Fine hairs & particles are attracted to the plastic tray by electrostatics, which I find is a plus.
I tried and it does help and effective to some extend. Rather than to describe my experience here, I suggest it is better for one to experiment & discover for themselves. I merely want to introduce it as a tool here.
A DIY humidifier cum ventilator
This is not my DIY project but an excellent idea I picked up during a recent trip to southern Thailand.
In essence it is a combination of ventilation & humidifier all-in-one. Like it immediately soon as I seen its construction and operation.
The bricks used in the wall construction have 4 extrusion holes each. A dripping tap keep the wall moist always (as seen in photo). In-coming air passes through the damp brick wall and pick up moisture. Excess water is drained off from the bottom water pool.
A very clever arrangement indeed! I give top marks to its originator!
In essence it is a combination of ventilation & humidifier all-in-one. Like it immediately soon as I seen its construction and operation.
The bricks used in the wall construction have 4 extrusion holes each. A dripping tap keep the wall moist always (as seen in photo). In-coming air passes through the damp brick wall and pick up moisture. Excess water is drained off from the bottom water pool.
A very clever arrangement indeed! I give top marks to its originator!
Sunday, August 23, 2009
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.
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.
Saturday, August 22, 2009
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.
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.
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.
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.
Saturday, June 20, 2009
Converting a shop unit into a bird house
In recent months, I came to know of another bird nucleus in town. Just established over a year, it is a relatively new area with only 2 bird houses. Both front and back has wide open spaces as roving yards.
As this is not a big exercise, guess it may fit in as another DIY undertaking. These shop houses are 2 1/2 storey. The ground floor has a high ceiling, to its rear is another 1/2 storey like a mezzanine floor.
So it can be easily converted into 2 nesting floors. Steel beams added to support the new floor areas. The nesting planks too provide additional support to floor boards.
Behind the roof is an open terrace, another floor extension converts it to a 4-storey bird house. Top floor walls and ceiling were lined with internal layer of styrofoam for heat insulation.
On ground level, the steel roller shutter door was replaced by a double layer brick wall with steel door.
The equipment room is tappered at one end to maximize internal nesting areas. I don't favor a corner jutting out into the nesting area.
The roving room extends over the stairway. Stair case roof is removed to provide added entry path. But the wall is retained to control light.
Workers putting up the ceiling boards of the roving room. The roving room is painted with water based black paint to minimize light reflection to internal areas.
It is pretty straight forward - every bird house is different in some ways, no hard and fast rules & more of exercising common sense. Often swiftlets populated vacant houses/temple attics to begin with. In this instance is at the top of a nearby hospital.
As this is not a big exercise, guess it may fit in as another DIY undertaking. These shop houses are 2 1/2 storey. The ground floor has a high ceiling, to its rear is another 1/2 storey like a mezzanine floor.
So it can be easily converted into 2 nesting floors. Steel beams added to support the new floor areas. The nesting planks too provide additional support to floor boards.
Behind the roof is an open terrace, another floor extension converts it to a 4-storey bird house. Top floor walls and ceiling were lined with internal layer of styrofoam for heat insulation.
On ground level, the steel roller shutter door was replaced by a double layer brick wall with steel door.
The equipment room is tappered at one end to maximize internal nesting areas. I don't favor a corner jutting out into the nesting area.
The roving room extends over the stairway. Stair case roof is removed to provide added entry path. But the wall is retained to control light.
Workers putting up the ceiling boards of the roving room. The roving room is painted with water based black paint to minimize light reflection to internal areas.
It is pretty straight forward - every bird house is different in some ways, no hard and fast rules & more of exercising common sense. Often swiftlets populated vacant houses/temple attics to begin with. In this instance is at the top of a nearby hospital.
Tuesday, June 16, 2009
A motorized trolley
As my new bird house is approaching completion. With a ceiling height of 3.5m, a motorized trolley platform reaching up to nesting areas for installation work is handy. It is useful for harvesting and service failed tweeters in future too.
Some time ago, I saw this mini-hydraulic platform at a Melbourne shopping mall - for hire!
Hmm.. wouldn't it be nice to have one to harvest my bird nests? That is certainly wishful thinking!
So this became another DIY project I have been cooking in mind for the past weeks. The implementation idea actually came from my neighbor, P'Wah. He was contracted recently to wire the sound system of some new bird houses. To save him trouble climbing up & down on the wiring job, he built a motorized platform to mount his ladder on.
I took his idea further to have a more secured platform instead. The basic design looks like this. I'll add a few ladder steps during fabrication. You might want to do the same if you have a fair size bird farm building with high ceiling.
What motor drives & control did he use?
I caught up with him a week ago to learn from his exercise. He is very helpful to share and I expressed my gratitude to him again here.
He used 2 x windscreen motors (12V DC with built-in reduction gears). Use the ones for trucks if you need more torque, he advised. Those are 24V DC. Like a front wheel drive arrangement, one motor each side. The rear wheels are free turning.
The driving wheel shaft is supported by 2 bearings. A rubber coupling serves as a universal joint between the motor & wheel shafts! Simply clever! I'll try to get a picture of it in future.
A typical automobile windscreen motor.
What about the direction control? Joystick I would thought.
"No, I use one finger", showing me his index finger as he replied.
His solution is genius! He mounted 4 micro-switches (one as seen below) with the lever tab facing each other orthogonally (a square arrangement) inside a box. Cutting a round hole, he can put his finger in to trigger any switch to steer the trolley, effectively like a joystick control!
Hmm.. a photo illustration here will be clearer & do away with such cumbersome explanations!
Each micro-switch is wired for the 4 directional controls:
1) Forward
2) Reverse
3) Turn left
4) Turn right
This is really neat! I could work out the relay controls from there. It is my good fortune to know such resourceful people around.
Some time ago, I saw this mini-hydraulic platform at a Melbourne shopping mall - for hire!
Hmm.. wouldn't it be nice to have one to harvest my bird nests? That is certainly wishful thinking!
So this became another DIY project I have been cooking in mind for the past weeks. The implementation idea actually came from my neighbor, P'Wah. He was contracted recently to wire the sound system of some new bird houses. To save him trouble climbing up & down on the wiring job, he built a motorized platform to mount his ladder on.
I took his idea further to have a more secured platform instead. The basic design looks like this. I'll add a few ladder steps during fabrication. You might want to do the same if you have a fair size bird farm building with high ceiling.
What motor drives & control did he use?
I caught up with him a week ago to learn from his exercise. He is very helpful to share and I expressed my gratitude to him again here.
He used 2 x windscreen motors (12V DC with built-in reduction gears). Use the ones for trucks if you need more torque, he advised. Those are 24V DC. Like a front wheel drive arrangement, one motor each side. The rear wheels are free turning.
The driving wheel shaft is supported by 2 bearings. A rubber coupling serves as a universal joint between the motor & wheel shafts! Simply clever! I'll try to get a picture of it in future.
A typical automobile windscreen motor.
What about the direction control? Joystick I would thought.
"No, I use one finger", showing me his index finger as he replied.
His solution is genius! He mounted 4 micro-switches (one as seen below) with the lever tab facing each other orthogonally (a square arrangement) inside a box. Cutting a round hole, he can put his finger in to trigger any switch to steer the trolley, effectively like a joystick control!
Hmm.. a photo illustration here will be clearer & do away with such cumbersome explanations!
Each micro-switch is wired for the 4 directional controls:
1) Forward
2) Reverse
3) Turn left
4) Turn right
This is really neat! I could work out the relay controls from there. It is my good fortune to know such resourceful people around.
A conceptual DIY long range bird caller
I have been looking at simple ways to project sound forward too. It is well established that the parabola curve has the property of directing a parallel beam from a focal point. Such application are seen commonly in light reflectors; satellite receiver dish applies the principle in reverse.
It is not a new or novel idea. I've toyed with such a parabolic microphone years ago. It is amazing the clarity of conversations it picked up across the road. Just reverse the application with the tweeter at the focal point, turn it around to project sounds far away.
Instead of a dish, one can also use a cylindrical shape parabolic reflector to project the sound energy forward as a beam. Seen below is an application of a cylindrical parabolic solar collector to heat water.
Easier to build than a dish, so this is my favorite DIY choice for a long range caller.
Scaling up its size, I believe it can handle alot more power than a 'bazooka' horn.
By sitting it on a rotating table & also tilt on the vertical axis, the combination can be automated to scan the sky in all directions - like a radar!
Of course, what is the over-powering effect of the high SPL (Sound Pressure Level) at short range?
I have thoughts about its solution too.
This is just a conceptual model.. yet to be tested and proven; one that I have been thinking for a while now. I am pretty sure it will work. The effective range is of course dependent of the applied sound power and physical laws governing sound transmission through air.
Anyone out there game enough to try? I have several more ideas in the pipe line, may sound like science fiction or could be stupid ideas to some! No rocket science actually, all based on applying existing know how.
If the reflector shape is appropriately modified, it could be used for external call sounds to provide a wider beam and reduce noise pollution to the neighborhood.. think about it!
It is not a new or novel idea. I've toyed with such a parabolic microphone years ago. It is amazing the clarity of conversations it picked up across the road. Just reverse the application with the tweeter at the focal point, turn it around to project sounds far away.
Instead of a dish, one can also use a cylindrical shape parabolic reflector to project the sound energy forward as a beam. Seen below is an application of a cylindrical parabolic solar collector to heat water.
Easier to build than a dish, so this is my favorite DIY choice for a long range caller.
Scaling up its size, I believe it can handle alot more power than a 'bazooka' horn.
By sitting it on a rotating table & also tilt on the vertical axis, the combination can be automated to scan the sky in all directions - like a radar!
Of course, what is the over-powering effect of the high SPL (Sound Pressure Level) at short range?
I have thoughts about its solution too.
This is just a conceptual model.. yet to be tested and proven; one that I have been thinking for a while now. I am pretty sure it will work. The effective range is of course dependent of the applied sound power and physical laws governing sound transmission through air.
Anyone out there game enough to try? I have several more ideas in the pipe line, may sound like science fiction or could be stupid ideas to some! No rocket science actually, all based on applying existing know how.
If the reflector shape is appropriately modified, it could be used for external call sounds to provide a wider beam and reduce noise pollution to the neighborhood.. think about it!
How far can your bird calls reach?
When we do bird calls, normally we would simply turn up the volume knob, wait and watch. Sometimes we see birds circling far above.. they must be responding to the calls, one could only guess.
I have also been pondering how far could one extend the calling range of external sounds?
I guess there is no straight answer to this - it is dependent on:
1) Power of the sound source i.e. to the tweeter
2) How the sound energy is projected in one direction
3) How sound energy is dissipated (or absorbed) while travelling in air
4) How sensitive are the birds' hearing
Well, I don't have all the answers.
As for (1), it is simply the raw power one can pump into the tweeter and how much it can handle without too much distortions.
For (2), it can be improved by design with better engineering solutions. The tweeter horn is to project the sound forward. Then there is the 'bazooka' design to extend the range further.
On (3), I did some readings and gained some insights on the subject.
At room temperature & R.H. 65%, a 1KHz sound travels 35Km to loose 6dB SPL (i.e. half amplitude) through absorption loss!
Sounds good but there is the inverse square law that affects the higher frequencies. What this says is that doubling the frequency would mean the same loss occurs at 1/4 the distance; or a 10KHz sound would be 1/2 level a distance 100 times shorter - to about 350m! A 20KHz sound would be 88m at 1/2 level.
I suppose the bird sounds is within the 10KHz - 20KHz range, so this gives an idea what it is like after the sound leaves your tweeters into the air.
What is worthy to note from above is that the medium of sound transmission, i.e. air itself, has a low pass filter characteristic inherently. Higher frequencies are attenuated much more relatively at further distances. In other words, it loose clarity through the losses of its higher frequencies. So no matter how good are your tweeters, sound quality degrades as distance increases is inevitable.
For (4)... totally no clue! If somebody know something, I would love to know.
I have also been pondering how far could one extend the calling range of external sounds?
I guess there is no straight answer to this - it is dependent on:
1) Power of the sound source i.e. to the tweeter
2) How the sound energy is projected in one direction
3) How sound energy is dissipated (or absorbed) while travelling in air
4) How sensitive are the birds' hearing
Well, I don't have all the answers.
As for (1), it is simply the raw power one can pump into the tweeter and how much it can handle without too much distortions.
For (2), it can be improved by design with better engineering solutions. The tweeter horn is to project the sound forward. Then there is the 'bazooka' design to extend the range further.
On (3), I did some readings and gained some insights on the subject.
At room temperature & R.H. 65%, a 1KHz sound travels 35Km to loose 6dB SPL (i.e. half amplitude) through absorption loss!
Sounds good but there is the inverse square law that affects the higher frequencies. What this says is that doubling the frequency would mean the same loss occurs at 1/4 the distance; or a 10KHz sound would be 1/2 level a distance 100 times shorter - to about 350m! A 20KHz sound would be 88m at 1/2 level.
I suppose the bird sounds is within the 10KHz - 20KHz range, so this gives an idea what it is like after the sound leaves your tweeters into the air.
What is worthy to note from above is that the medium of sound transmission, i.e. air itself, has a low pass filter characteristic inherently. Higher frequencies are attenuated much more relatively at further distances. In other words, it loose clarity through the losses of its higher frequencies. So no matter how good are your tweeters, sound quality degrades as distance increases is inevitable.
For (4)... totally no clue! If somebody know something, I would love to know.
Monday, June 15, 2009
A word of caution on mist maker
I just came across mention of such mist maker at another blog...
Commonly installed as part of ornamental water feature with a little fountain, it is wonderful to watch the fog coming out like smoke over water.
Well, just like to add a word of caution here. I studied its use about 2 years back and decided it is not a good practice.
Why?
Such devices use ultra-sonic transducer that vibrates at around 1MHz! It is the finest fog generating machine, sounds good & I like it initially from that perspective!
Did you know it can pose some health hazard?
Studies by U.S. health authorities had shown that such devices eject fine particles (mineral impurities & bacterias) contained in water into the air as well!
One needs very pure water for its safe use - just take note of this.
Otherwise you may introduce bacterias into your bird house atmosphere unwittingly & unnecessarily.
Suits one of my favorite axioms: Half knowledge can be dangerous!
Commonly installed as part of ornamental water feature with a little fountain, it is wonderful to watch the fog coming out like smoke over water.
Well, just like to add a word of caution here. I studied its use about 2 years back and decided it is not a good practice.
Why?
Such devices use ultra-sonic transducer that vibrates at around 1MHz! It is the finest fog generating machine, sounds good & I like it initially from that perspective!
Did you know it can pose some health hazard?
Studies by U.S. health authorities had shown that such devices eject fine particles (mineral impurities & bacterias) contained in water into the air as well!
One needs very pure water for its safe use - just take note of this.
Otherwise you may introduce bacterias into your bird house atmosphere unwittingly & unnecessarily.
Suits one of my favorite axioms: Half knowledge can be dangerous!
Monday, June 8, 2009
Cooling the roving room
This is the bird house I've been improving its micro-environment lately. The roving room is long and its design allows 3/4 of it to be converted into nesting areas in future - so it is good to get the temp & humidity close to the desired levels too.
The data collected showed it is too warm & temp reaching 38 deg around 3.30pm on warmest days with R.H. ranging between 50-60%. On cooler days the max. temp reached 35 deg and R.H. between 60-65%.
My first experiment was to see if too much heat is getting in through the roof. There is an aluminum foil under the roof and some air space between ceiling, insufficient insulation I thought. A sprinkler with timer control was installed on the roof in an attempt to cool it from there. The reduction in room temperature was insignificant. It simply points out much heat came in through the two long side walls.
I do not intend to add more wall insulation at this stage, so how to address the situation?
Good that the humidity was on the lower side. I set up a humidifier in the roving room (near the entrance hole) with a timer control; turned on from 10am to 5pm during the warmest period.
The principle is to extract the thermal energy from the air by using water vapor, similar to misting fan.
Evaporative coolers are commonly seen in countries where humidity is low. It is effective even with high outside air temperature because the heat in the air is being absorb by fine mists as latent heat converting to water vapor.
Humid air vents out through entrance hole via convection air currents. The outcome is quite satisfactory - the highest temp is now between 30-32 deg most days. The humidity is improved too - lowest R.H. of the day is about 75% and highest between 85% to 90% around 5am in the morning.
Logged data with the humidifier in use.
The lowest temperature registered so far is about 25 deg on colder rainy days at about 7am. As a roving room it don't bother me yet. At least I get the day temperature a few degrees lower. It is just a stop gap measure until the time to convert to nesting areas.
The data collected showed it is too warm & temp reaching 38 deg around 3.30pm on warmest days with R.H. ranging between 50-60%. On cooler days the max. temp reached 35 deg and R.H. between 60-65%.
My first experiment was to see if too much heat is getting in through the roof. There is an aluminum foil under the roof and some air space between ceiling, insufficient insulation I thought. A sprinkler with timer control was installed on the roof in an attempt to cool it from there. The reduction in room temperature was insignificant. It simply points out much heat came in through the two long side walls.
I do not intend to add more wall insulation at this stage, so how to address the situation?
Good that the humidity was on the lower side. I set up a humidifier in the roving room (near the entrance hole) with a timer control; turned on from 10am to 5pm during the warmest period.
The principle is to extract the thermal energy from the air by using water vapor, similar to misting fan.
Evaporative coolers are commonly seen in countries where humidity is low. It is effective even with high outside air temperature because the heat in the air is being absorb by fine mists as latent heat converting to water vapor.
Humid air vents out through entrance hole via convection air currents. The outcome is quite satisfactory - the highest temp is now between 30-32 deg most days. The humidity is improved too - lowest R.H. of the day is about 75% and highest between 85% to 90% around 5am in the morning.
Logged data with the humidifier in use.
The lowest temperature registered so far is about 25 deg on colder rainy days at about 7am. As a roving room it don't bother me yet. At least I get the day temperature a few degrees lower. It is just a stop gap measure until the time to convert to nesting areas.
Sunday, June 7, 2009
Did you know - water vapor is lighter than air?
Every school going kid would know water is heavier than air. Yet many of us may not be aware of the fact - Water vapor is actually lighter than dry air!
The density of water vapor is 0.804g/litre, which is significantly less than that of dry air at 1.27g/litre at STP (i.e. 0 deg C & 14.504 psi).
If you are not convinced, check it out at: http://en.wikipedia.org/wiki/Water_vapor
What is the implication?
"More humid" air is lighter than "less humid" air. This is what happens in our weather system every day. Warm moist air rises several Km high up in the atmosphere to form clouds.
Somebody labeled this as "stupid logic"..
If you recall the lessons of high school chemistry (elementary science):
Water molecule is H2O - 2 Hydrogen atoms & 1 Oxygen atom -> molecular mass of 2+16 =18 units (neglecting the electrons mass).
Likewise, air is about 21% Oxygen & 79% Nitrogen
Molecular mass of O2 is 16x2 -> 32 units
Molecular mass of Nitrogen N2 is 14x2 -> 28 units
I'll leave the rest to common sense.
What this means to our bird house micro environment?
For simplicity of putting the idea across, let's assume the bird house has the same temperature & pressure between floors. If we create "more humid" air on lower floors, the "more humid" air will drift upwards to upper floors gradually.
How do I made use of this principle?
At a 4-storey shop unit bird house, the 2nd storey has the most birds - i.e. many nestlings are around during the day too. I wouldn't set up the humidifier at that level. What I did was to place the humidifier (with hygrostat control) near the staircase on the ground floor & let the humid air drift upwards slowly.
I did achieve 75% to 80% R.H. most of the time.
Lately, I am testing another approach. I have a dripping tap just enough to keep the ground floor wet but not flooded. The idea is using the floor surface to provide a wide evaporation surface. If this works out well, then the humidifier on the ground floor is not required.
The density of water vapor is 0.804g/litre, which is significantly less than that of dry air at 1.27g/litre at STP (i.e. 0 deg C & 14.504 psi).
If you are not convinced, check it out at: http://en.wikipedia.org/wiki/Water_vapor
What is the implication?
"More humid" air is lighter than "less humid" air. This is what happens in our weather system every day. Warm moist air rises several Km high up in the atmosphere to form clouds.
Somebody labeled this as "stupid logic"..
If you recall the lessons of high school chemistry (elementary science):
Water molecule is H2O - 2 Hydrogen atoms & 1 Oxygen atom -> molecular mass of 2+16 =18 units (neglecting the electrons mass).
Likewise, air is about 21% Oxygen & 79% Nitrogen
Molecular mass of O2 is 16x2 -> 32 units
Molecular mass of Nitrogen N2 is 14x2 -> 28 units
I'll leave the rest to common sense.
What this means to our bird house micro environment?
For simplicity of putting the idea across, let's assume the bird house has the same temperature & pressure between floors. If we create "more humid" air on lower floors, the "more humid" air will drift upwards to upper floors gradually.
How do I made use of this principle?
At a 4-storey shop unit bird house, the 2nd storey has the most birds - i.e. many nestlings are around during the day too. I wouldn't set up the humidifier at that level. What I did was to place the humidifier (with hygrostat control) near the staircase on the ground floor & let the humid air drift upwards slowly.
I did achieve 75% to 80% R.H. most of the time.
Lately, I am testing another approach. I have a dripping tap just enough to keep the ground floor wet but not flooded. The idea is using the floor surface to provide a wide evaporation surface. If this works out well, then the humidifier on the ground floor is not required.
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