Compatibility and Obtainability

Zener diodes, due to their lower cost and greater control, are commonly used in electric devices. They are also compatible with most systems, so they are a preferred method to regulate voltage. They are also used in other applications, such as in solar panels. Though these diodes don't often get damaged due to their current controls, they can still blow out if the current exceeds what they are equipped to handle. If this were to happen, the SCR would also likely blow out and both elements would need to be replaced. Luckily, Zener diodes are fairly easy to obtain due to their common use and low cost.

PERFORMANCE

Zener diodes have a very high performance standard, often more than the electronic device they are placed in needs to operate at maximum efficiency. These diodes are equipped to handle a higher voltage than the standard operating voltage, so they are able to handle more power. These diodes will still operate at standard voltage, but will not blow out if the voltage is still under their threshold. They are also small enough to allow current to flow quickly through their circuits.

ZENER DIODE CONTROL

The ability of the Zener diode to control and reverse part of the current flowing through it means it can be used to regulate and stabilize the voltage in a circuit and prevent problems that can occur when the supply or load voltage varies. Circuit designers can use the Zener voltage of the diode to exactly regulate and stabilize the voltage in the circuit.

ADVANTAGE OF ZENER DIODE

Unlike normal diodes, which allow only forward current, Zener diodes will allow a current to move in reverse when voltage exceeds a specified value, preventing breakdown of the diode. Because of this ability to reverse a portion of the current, Zener diodes offer several advantages in a circuit that normal diodes don't. The idea behind the reverse current used in this diode was proposed by Dr. Clarence Melvin Zener in 1934.

APPLICATION OF TUNNEL DIODE

Although the tunnel diode appeared promising some

years ago, it was soon replaced by other

semiconductor devices like IMPATT diodes for

oscillator applications and FETs when used as an

amplifier. Nevertheless the tunnel diode is a useful

device for certain applications

ADVANTAGE & DISADVANTAGE OF TUNNEL DIODE

One of the main reasons for the early success of the

tunnel diode was its high speed of operation and the

high frequencies it could handle. This resulted from

the fact that while many other devices are slowed

down by the presence of minority carriers, the tunnel

diode only uses majority carriers, i.e. holes in an

n-type material and electrons in a p-type material.

The minority carriers slow down the operation of a

device and as a result their speed is slower. Also

the tunnelling effect is inherently very fast.

The tunnel diode is rarely used these days and this

results from its disadvantages. Firstly they only

have a low tunnelling current and this means that

they are low power devices. While this may be

acceptable for low noise amplifiers, it is a

significant drawback when they are sued in

oscillators as further amplification is needed and

this can only be undertaken by devices that have a

higher power capability, i.e. not tunnel diodes. The

third disadvantage is that they are problems with the

reproducibility of the devices resulting in low

yields and therefore higher production costs.

MODE OF OPERATION

The characteristic curve for a tunnel diode shows an

area of negative resistance. When forward biased the

current in the diode rises at first, but later it can

be seen to fall with increasing voltage, before

finally rising again. The reason for this is that

there are a number of different components to forming

the overall curve. The main two are the normal diode

current across the junction, and the current arising

from the tunnelling effect. It is this last component

that is of interest in a tunnel diode.

Tunnelling is an effect that is caused by quantum

mechanical effects when electrons pass through a

potential barrier. It can be visualised in very basic

terms by them "tunnelling" through the barrier.

The tunnelling only occurs under certain conditions.

This means that it peaks when a certain voltage is

placed across the junction. This results in the

current increasing to a point beyond that which would

be expected for a standard pn junction. As the

voltage across the diode is increased the effect

reduces and the current through the device falls.

This results in a negative resistance region on the

curve of te diode that can be used to provide gain.

STRUCTURE OF TUNNEL DIODE

The tunnel diode is similar to a standard p-n

junction in many respects except that the doping

levels are very high. Also the depletion region, the

area between the p-type and n-type areas, where there

are no carriers is very narrow. Typically it is in

the region of between five to ten nano-metres - only

a few atom widths.

As the depletion region is so narrow this means that

if it is to be used for high frequency operation the

diode itself must be made very small to reduce the

high level of capacitance resulting from the very

narrow depletion region.

TUNNEL DIODE?

The tunnel diode was found many microwave 

applications because semiconductor devices of the day 

could not reach these frequencies. Although not 

widely used today, it is still sometimes mentioned 

and it is a fascinating device.

The tunnel diode was discovered by a Ph.D. research 

student named Esaki in 1958 while he was 

investigating the properties of heavily doped 

germanium junctions for use in high speed bipolar 

transistors. In the course of his research he 

produced some heavily doped junctions and as a result 

found that they produced an oscillation at microwave 

frequencies as a result of the tunnelling effect. It 

was subsequently found that other materials including 

gallium arsenide also produced the same effect.

BASICS OF VARACTOR DIODE

The varactor diode or varicap diode consists of a standard PN junction, although it is obviously optimised for its function as a variable capacitor. In fact ordinary PN junction diodes can be used as varactor diodes, even if their performance is not to the same standard as specially manufactured varactors.

The basis of operation of the varactor diode is quite simple. The diode is operated under reverse bias conditions and this gives rise to three regions. At either end of the diode are the P and N regions where current can be conducted. However around the junction is the depletion region where no current carriers are available. As a result, current can be carried in the P and N regions, but the depletion region is an insulator.

This is exactly the same construction as a capacitor. It has conductive plates separated by an insulating dielectric.

The capacitance of a capacitor is dependent on a number of factors including the plate area, the dielectric constant of the insulator between the plates and the distance between the two plates. In the case of the varactor diode, it is possible to increase and decrease the width of the depletion region by changing the level of the reverse bias. This has the effect of changing the distance between the plates of the capacitor.

MAIN FUNTION OF VACTOR DIODE

Varactor diodes are widely used within the RF design arena. They provide a method of varying he capacitance within a circuit by the application of a control voltage. This gives them an almost unique capability and as a result varactor diodes are widely used within the RF industry.

Although varactor diodes can be used within many types of circuit, they find applications within two main areas:
Voltage controlled oscillators, VCOs:   Voltage controlled oscillators are used for a variety of applications. One major area is for the oscillator within a phase locked loop - this are used in almost all radio, cellular and wireless receivers. A varactor diode is a key component within a VCO.
RF filters:   Using varactor diodes it is possible to tune filters. Tracking filters may be needed in receiver front end circuits where they enable the filters to track the incoming received signal frequency. Again this can be controlled using a control voltage. Typically this might be provided under microprocessor control via a digital to analogue converter.

What is a varactor diode

Varactor diodes or varicap diodes are semiconductor devices that are widely used in the electronics industry and are used in many applications where a voltage controlled variable capacitance is required. Although the terms varactor diode and varicap diode can be used interchangeably, the more common term these days is the varactor diode.

Although ordinary PN junction diodes exhibit the variable capacitance effect and these diodes can be used for this applications, special diodes optimised to give the required changes in capacitance. Varactor diodes or varicap diodes normally enable much higher ranges of capacitance change to be gained as a result of the way in which they are manufactured. There are a variety of types of varactor diode ranging from relatively standard varieties to those that are described as abrupt or hyperabrupt varactor diodes.

USES OF LED(A note)

The operational life of current white LED lamps is 100,000 hours. This is 11 years of continuous operation, or 22 years of 50% operation. The long operational life of an led lamp is a stark contrast to the average life of an incandescent bulb, which is approximately 5000 hours. If the lighting device needs to be embedded into a very inaccessible place, using LEDs would virtually eliminate the need for routine bulb replacement.

There is no comparison between the cost of LED lights vs. traditional incandescent options. With incandescent bulbs, the true cost of the bulb is the cost of replacement bulbs and the labor expense and time needed to replace them. These are significant factors, especially where there are a large number of installed bulbs. For office buildings and skyscrapers, maintenance costs to replace bulbs can be enormous. These issues can all be virtually eliminated with the LED option.

The key strength of LED lighting is reduced power consumption. When designed properly, an LED circuit will approach 80% efficiency, which means 80% of the electrical energy is converted to light energy. The remaining 20% is lost as heat energy. Compare that with incandescent bulbs which operate at about 20% efficiency (80% of the electrical energy is lost as heat). In real money terms, if a 100 Watt incandescent bulb is used for 1 year, with an electrical cost of 10 cents/kilowatt hour, $88 will be spent on electricity costs. Of the $88 expense, $70 will have been used to heat the room, not light the room. If an 80% efficient LED system had been used, the electricity cost would be $23 per year - there would be a cost savings of $65 on electricity during the year. Realistically the cost savings would be higher as most incandescent light bulbs blow out within a year and require replacements whereas LED light bulbs can be used easily for a decade without burning out.

Our white LED lights currently come in packages which contain 36 or 48 LED lamps and can be adapted for use with any power supply or casing. Our clusters allow for conversion to operate from all common caving batteries, e.g. FX5/Kirby pack down to two AA cells, in case portability is needed. We have produced a seven-LED cluster light source as an alternative to low wattage light bulbs and a possible portable light source.

The main limitation to the adoption of white LED lighting as a lighting standard is the current high cost of led bulbs. Although the cost keeps going down, LED light bulbs are still expensive. A single AC bulb (17 LED), replacing a 25 watt incandescent, will cost about $40. Although LED's are expensive, the cost is recouped over time and in energy cost savings. Factor in that it is significantly cheaper to maintain led lights, the best value comes from commercial use where maintenance and replacement costs are expensive. Traffic lights and outdoor signs, for example, are being switched over to LED's in many cities. Smaller arrays, such as those in flashlights, headlamps and small task lights are great for specialty and outdoor use. LED based automotive headlights are current being used in high end luxury cars.

It will be interesting to see what developments are coming for more residential applications of LED lights. LED lighting technology has been researched and developed for the past two decades and we are beginning to see practical applications from this work. There is already wide spread use of LED traffic signs and LED headlights where a premium is placed on a reliable light source that is cheaper and less labor intensive to maintain. We in the industry are certain that tomorrows LED lights will last longer and consume even less power than todays energy efficient led light bulbs. LED lighting will be used to replace virtually every type of light, bulb, and lamp that is currently in use.

PIPE INSULATION in solar cell

Insulate all tubes for safety and efficiency. Insulation should have at least 1/2” wall thickness.
In particular, be sure that any sensors are well insulated. Be sure that any exterior pipe insulation
is resistant to UV radiation and moisture.

FILL THE SOLAR LOOP WITH FLUID

WARNING !!! Do not do this work in strong sunlight unless the solar collectors are covered!!!
If you feed water to a stagnating solar collector, the water can flash to steam and cause
considerable damage to the collectors and even present a safety hazard. Serious burns
and even death could result.
With that warning noted, attach a garden hose to the fill valve of the Plumbing Mechanical
Package (PMP). To make the connection, you will need to find or make a short length of hose with
two female ends on it (a washing machine hose is ideal).
Then, attach one end of another length of garden hose to the drain valve, and take the other end
outside to an appropriate place.
Close the ball valve between the fill and drain valve so that the water is forced through the whole
system. Close the air vent in the PMP so that it will not function (it could become plugged up).
Flush the system thoroughly with water to get out any flux, solder, air, dirt, and anything else that
is not wanted in the system.
Then close the drain valve and allow the system to pressurize. You can open the air vent after the
system has been flushed.
Get the system running well with water. Fix any leaks before you add antifreeze.
Then add a predetermined amount of pure anti freeze based upon a calculation of the total
amount of fluid in the system
EXAMPLE: If you want the final solution to be 30% antifreeze, and the system calculates to be
60 gallons total, add 19 gallons of pure antifreeze and take out 18 gallons of water, and you will
have it.
Let the system run for a while and then test with a hydrometer or test strip to make sure of the
concentration.
Consult the appendix to find typical amounts of fluid per linear ft of tubing and typical fluid
capacity for Radiantec solar collectors, so that you can calculate total fluid volume.

BRING THE SOLAR PANELS TO THE ROOF AND SECURE THEM

With planning and proper equipment, it is possible to do this work without stepping on the
roof.
It is best to build a secure scaffold. If a sign crane is used, consider making a sling out of wire
cable and cable clamps, even if it is only used once. The materials are cheap and a proper sling
will save a lot of time and aggravation on the job. If you use a heavy rope, it will be difficult to
retrieve from behind the solar panel. If you use a lighter rope, sharp metal edges may cause it
to fail at a bad time. If it is windy, use anchor lines on either side of the collectors.
When the panel arrives at the roof, the workman first assembles what plumbing connections
need to be made. He does not solder the connections at this time. He will drill a pilot hole for
the mount with reference to the earlier made chalk line.
He may then insert a screwdriver through the hole in the mount and then into the pilot hole.
This will temporarily secure the panel in place and prevent the plumbing connection from
becoming undone.

When he is ready, the workman will apply a silicone-based sealant to the pilot hole and
put a lag bolt in, but not tighten it all the way. When the lag bolts are inserted, the silicone
sealant will be squeezed under the pressure and fill any cracks or voids that water might
leak.
Only when the lag bolts are in the bottom mounts is it safe to undo the sling from the
crane and the solar panel.
It may be necessary to lift the solar panels a little bit in order to retrieve the sling or to
make the plumbing connection. Tighten the lag bolts completely when this work is done.
Do not choose the drill bit for the pilot hole haphazardly. This detail is important for both
structural strength and water tightness.Guess at the size and then drill a pilot hole in a
piece of scrap wood. Drive a lag bolt in. If you hear cracking noises and the bolt seems to
be splitting the wood, the pilot hole is too small. If the bolt goes in very easily and strips
easily, the pilot hole is too large. Each workman should drive a lag bolt into a piece of
scrap wood until it strips the hole. Then he will know how much force can be applied to
the bolt. The attachment will be both strong and watertight if made properly, and might
be something less if it is not.
The copper connections, top and bottom, may be done at this time, or they can all be
done at the same time if the work will not be delayed too long (not overnight).
Solder the connections using standard, no lead solder. Do not use 95/5, or silver solder
and do not braise it. It is not necessary and the excess heat will damage seals and insulation
within the panel. The person who does this work should be good at it.
If high quality solar collec tors are used with tempered glass, it is possible to set a ladder
directly on the collectors.

PREPARE THE Solar PANELS FOR MOUNTING

1. Attach the mounts to the panel. It is important to avoid the use of different kinds of metals when
fastening to the solar collectors. When different kinds of metals are used, the metal that is more
stable will corrode the metal that is less stable. Use stainless steel fasteners that are especially
resistant to corrosion, or use materials that are all made of the same material. Rubber from an inner
tube or roofing material could insulate one material from another, but it is not a real good detail, and
it won’t help at all in a moisture situation. Better to avoid the problem in the first place.
2. Mounting kits supplied by the Radiantec Company will be compatible with the solar collectors.
3. Attach the mounts so that the solar panels are held about 1”off the roof in order to prevent
moisture from damaging the roofing materials.

INSTALL THE BLOCKING BEHIND THE ROOF:solar cell

1. Blocking transmits the solar collector loads to the rafters and provides something solid to screw the
lag bolts into. Do not just lag the solar panels to the plywood sheathing; it is not acceptable. If
blocking can not be installed (as in a retrofit situation), the lag bolts must be drilled directly into the
rafters, or something else solid. Mounts provided by Radiantec can slide along the top and bottom
edges of the solar collec tor so that mounts can be installed directly into the rafters.
2. Blocking should be installed whenever possible because the collector array will be more attractive if
the mounts are spaced evenly and the rafters can be difficult to locate exactly.
3. The blocking should be close fitting and square. They may be 2”x 4”or 2”x 6”, and they can be
installed with the flat side up (towards the plywood). It will be easier to hit them squarely, and they
will be just as strong. They must be securely nailed with 16d nails or better.

PLAN THE LOCATION OF THE SOLAR PANELS

1. Plan and locate the position of the panels with chalk lines so that their appearance can be
visualized. Solar panels are generally more attractive if they are placed at or below the midline of
the roof area.
2. The customer should approve the location of the panels before the work begins. Take a sheet
of plywood up to the roof if it will help to visualize the finished work.
3. Keep in mind that work will have to be done behind the roof to prepare a solid support for the
solar collector legs. Do not put the collectors in a place where this work is inaccessible.
4. Coordinate with the General Contractor. Make sure that the General understands that solar
panels will be placed upon the roof and that the roof must be built to the proper dimensions.
Building insulation should not be installed in the solar work area until the solar work is roughed
in and pressure tested.
5. Snap another chalk line in the place where holes will be drilled for the collector mounts. Hold
the line tight enough that it does not dip in the middle.
6. Start in the middle of the roof and work outward. That way, you can be sure that the work will
be centered on the roof.
7. Measure twice before drilling holes in important locations.
8. Foresee everything that needs to be done before starting work. Read the entire manual
before starting. In particular, note the following:
a. Blocking should be installed behind the solar panels in new construction.

b. For even flow, the solar fluid will flow into one side of the solar array at the bottom, and
come out on the other side at the top (called reverse return). The “C” type fluid return
where the fluid comes out on the same side of the collector array that it went in is only
acceptable for no more than three solar collectors. Be sure that there is a good way to run
and insulate these supply and return pipes

c. Two temperature sensors will be located at
the outlet of the solar array. Two sets of
wires, (18g thermostat wire, two wire), must
be run from the outlet to the mechanical
room before the work is closed up.
d. Plan for expansion and contraction of the
header pipes within the solar panel. Solar
collector temperatures could vary between the
coldest expected outdoor temperature, and
the stagnation temperature of the collector in
full sun. This temperature difference could
be up to 300 degrees F.

INSTALL THE SOLAR PANNELS

PLEASE CONSIDER THE FOLLOWING SAFETY RECOMMENDATIONS

1. Hard hats - The worksite is a hard hat area while work is being done on the roof. There are
a number of hazards, and tools or other materials could be dropped accidentally. Rope off the
area beneath the roof and consider posting a sign saying that the area is a hard hat area. Keep
onlookers at a safe distance.
2. Do not work underneath an unsecured solar panel.
3. Solar panels get hot when bright sunlight is shining upon them and nothing is taking away
the heat. Wear gloves. Avoid working with solar panels in the middle of the day. Cover the
panels with part of the shipping carton or with a sheet.

4. Wear sunglasses when working with solar panels on sunny days. The glare reflecting from
solar panels in bright light is very uncomfortable and distracting to the point of causing a safety
problem. Workmen who do not wear sunglasses are likely go home early with a headache.
5. Consider using a crane. It might be safer to use a crane for mounting the solar panels and it is
less expensive in the long run because of lowered labor costs. A crane could mount all solar panels
for a typical residence in less than one hour. It can be economical to rent a crane and operator
from a local sign contractor. Use of a crane allows workmen to stay off of the roofing material.
6. Erect a proper and safe scaffold. It is safer and will save many trips up and down the ladder.
7. Use a proper tool belt. It will also save many trips up and down the ladder. A tool belt will
leave your hands free to hold onto the ladder. Do not carry any extra tools. If you drop a screwdriver
with a tempered bit onto a solar collector with tempered glass, the glass could break
immediately, or it could break up to a week later.
8. Never, ever work with untemperd glass on the roof.

THE SOLAR COLLECTORS

The solar collector, as used in a Radiantec Solar Heating System, is a shallow aluminum box with
a tempered glass cover sheet. Typical nominal dimensions are 4 ft x 8 ft x 4 in, although other
sizes are available. The weight will be about 125 pounds. Several collectors are usually connected
to each other so that they form one large solar collector array. The collectors have “internal
headers” which go across the top and bottom and have outlets on the sides. When the collectors
are connected, the headers of one solar collector are soldered to the headers of the other. A
water based antifreeze solution flows into the bottom of the collector on one side and comes
out the top on the other side after being heated by the sun

SOLAR LOOP

The “Solar Loop” is where solar energy is collected by solar collectors, turned into heat, and then
pumped where it needs to go in order to fill our needs. It is a “closed” system consisting of solar
collectors, a plumbing mechanical package and one or more heat exchangers. “Closed” means
that the system has its own working fluid that stays in the system and is not removed except for
maintenanceWhen the sun shines upon the solar collectors, the solar energy heats an antifreeze solution.
When the solar heated antifreeze solution is warm enough, a circulating pump turns on and
circulates the warm antifreeze solution to one or more heat exchangers, where the heat energy
is put to a use such as the production of domestic hot water, or space heat, or some other use.
The antifreeze solution then returns to the solar collectors to be reheated.