DIY LED : Bits 'n' pieces for thought ...

Well ...
Feel free to contribute ...

Making a start ..
( " opening the gate .... " )


{ AC Side } Glass braided-Silicon insulated wires .

-Flame- proof .
( like in holding the wire inside or above the flame of a lighter ...As long as you like ... ***)

http://www.amazon.com/High-temperature-wire-AWG-roll/dp/B001ALK97C/ref=pd_rhf_dp_s_cp_2_FHVY?ie=UTF8&refRID=16YGHKFXWZS2FCT8D5DJ
http://www.amazon.com/SILICONE-GLASS-BRAID-APPLIANCE-TEMPERATURE/dp/B007CMASYC
http://www.alibaba.com/product-detail/AGRP-SiAF-GL-Fiber-Glass-Braided_60069180933.htm

P.S. ***

"Flame-proof "means that the wire insulation will not burst into flames under any situation .
Neither the glass-fiber braided coat ,neither the inner silicon insulation (or teflon coating )
,can be sources of fire/flames.
Still the wire is heat -resistant up to a certain point .
And surely not flame- resistant.
If you hold a piece of this wire inside or above the flame of a lighter ,
for over a min or so ,the wire insulation gets to be permanently damaged .
Both the glass and silicon /teflon become dust particles if the wire is bended three-or more times .

Still ,in any case the wire itself will never burst into flames ,under any circumstances of excessive voltage / current load or spike .
If used ,remember ,that they worthy to be used mainly for over 110 V AC ( or DC )voltages ...
So ..Mainly for AC side ...

Need to find it in 12-3, thats pretty slick.

{ HSF cooling } Diameter matters....Ok...Along with length ...
(of air distance covered ... ): 140-200 mm vs 80-120 mm

Static-pressure optimized fans require higher speeds in order to achieve similar air velocities compared to airflow-oriented designs. This also means they are resistant to stalling and loss of performance. The disadvantage of this is that higher speeds usually mean more noise.

Airflow-oriented designs have greater air velocity to allow air to penetrate farther into the case. They lose out in static pressure. They can also stall easily.

140mm fans can provide more airflow vs 120mm fans at similar RPMs. However, they have lower maximum speeds resulting in less static pressure. They are also not guaranteed to be quieter than 120mm fans. Lastly the blades might come closer to case restrictions.

Summary 5x5 :

80- 120 mm fans :
-Static pressure optimised :Ideal for heat sinks with long fin lengths & long/high, thin and tightly spaced fins .

-High rpm = high air velocity ,but moderate air-flow,
resistant to stalling and loss of performance .

-High / Moderate noise levels.

-Small / Moderate rotor area
( moderate local surface of direct fin coolling = Single fan installed directly above each COB / LED " cluster ",for higher-maximum performance ).

-Short-to-Moderate service life : 30K to 60K hours,(aver.)


140-200 mm fans :
-Air-flow optimised :Ideal for heat sinks with short fin lengths ,short and thick fins and quite spaced-apart .

-Low rpm = low air velocity ,but high air flow ,easy to stall /prone to performance degrading in case of high flow resistance
( i.e. in case of heat sink's fins ,have collected chronic contamination of atmospheric fibrous debris and /or severe dust load ).

-Moderate -to- Low noise levels

-Large rotor area (Large local surface of direct fin coolling= Ideal in case of tightly spaced COBS/ LEDS installed )

-Moderate-to-long service life : 80K to 200K hours,(aver.)

{ 3IN1 dimming control }
Rotary switches ... Neither potentiometers
-neither ammeters ,but still ...

A "resistive" (Viva la resistance! ... ...) approach of human interface,
in order to control the 3IN1 LED drivers.
But it acts as "feedback" interface,also.
In every switch position ,the output current ispretty much known ,to the user .

Rotary switches : The 1x 12 kind ....


^^^ Now ...Imagine that this pic ,
is showing a 12 position ( aka single pole -12x throw ) rotary switch ,as seen looking it from above ...
The black circle with the thick red outline is the knob axis (metal or plastic ) .
The "A" marget point is a contact pin of the rot. switch ,
as also the 12 & 1 marked ones ..
As for the rest contact points ,I bet you that you can imagine them more easily,
effortlessly and much -much quicker ,
than me photoshopin' them,into the pic ... ...

The actual connection :
For the sake of a decent example ,let us imagine a CC LED driver ,bearing the 3IN1 / resistive dimming control .
A driver with maximum current output ( 100% ) of 1000 mA ( 1 A ) .

A 10 K resistance connected between the DIM - and DIM + pins / wires of the driver ,will dim down the output current to 10 % of 100% ,thus I output ( Io ) = 100 mA ( 0.1 A )
A 20-K resistance will increase to 20% of 100% ,thus 200 mA ..
And so on ,until 100K resistance or more ,up to infinite resistance value is reached ..
( open circuit between DIM - and DIM+ ) .
Then the driver ,outputs the max current ...= 1 A .

to wire a 12 throw rotary switch we will need at least eleven resistors.

Switch position At #1 + #A :
Let us connect a 10 K resistor at contact point #1 or A ,it does not matter much where really.....
Suppose we connect the resistor at contact point #A ...then the unconnected pin of the resistor to DIM +
(..or DIM -,it does not matter much where ,really......
- "Repetition ,is mostly a form of voluntary,artificial Deja-Vu state ." ,SDS - )

Then connect the c.p. #1 of the rotary switch to the other free & unconnected DIM c.p. of the driver.
Now ,when the knob is positioned at 1 'o clock ,the Io = 100mA ....

.....
We have still 11 unconnected and free switch positions to use up ,until we reach a total resistance of 100 K ..
But in this minimalistic case we will use only 10 !

Now ...
From 100K "limit " we 've already used 10K ...
(Aka the "low limit Io " resistor,we've connected at c.p. #1 )
So 100-10 =90 K to use ,up to 100% output position ....

90 K / 11 positions = 8.1818
So,normally we would need 11 resistors of ~ 8K2 ( 8200 ohms ) ,to reach 100% output
11( #2 to #12 ) x 8.2 =90.2 K ..... +10 K ( #1 ) = 100. 2 K ...
But we will use only ten resistors and final total resistance will be infinite(open ).

Now...
Switch position At #2 + #A :
Between #1 and #2 ,we place the first 8K2 resistor ...
When knob is potitioned at 2 'o clock ,control current flows ,through 10 +8.2 = 18.2 K ...

18,2 K = 18,2 % of 100% in case of a single driver => Io = 182 mA

Switch position At #3 + #A :
Next 8K2 resistor between #2 and #3 ...
10K + 2x 8.2 = 26.4 = > Io = 264 mA calculated

( can also be "250 mA " or "260 " indicated but
at Ta=25C , can actualy be 240 mA or 280 mA,measured .** )


Soo we reach up to the last 8K2 resistor (tenth of the 8K2 ones ) ,
which is placed between #10 and # 11 ....
We stop there ...
We're finished ...
Do not forget-tip : Wash with IPA , to clean from solder flux residues .


Now what we actually 've made ...
( calculated values )

Switch position 1 'o clock : Io= 100 mA
Switch position 2 'o clock : Io= 182 mA
Switch position 3 'o clock : Io= 264 mA
Switch position 4 'o clock : Io= 346 mA
Switch position 5 'o clock : Io= 428 mA
Switch position 6 'o clock : Io= 510 mA
Switch position 7 'o clock : Io= 592mA
Switch position 8 'o clock : Io= 674 mA
Switch position 9 'o clock : Io= 756 mA
Switch position 10 'o clock : Io=838 mA
Switch position 11 'o clock : Io= 920 mA
Switch position 12 'o clock : Io= 1000+ mA (#12 Not Connected=open Dim circuit )

An example of indicated values ....
Switch position 1 'o clock : Io= 100 mA
Switch position 2 'o clock : Io= 180 mA
Switch position 3 'o clock : Io= 260 mA
Switch position 4 'o clock : Io= 340 mA
Switch position 5 'o clock : Io= 430 mA
Switch position 6 'o clock : Io= 500 mA
Switch position 7 'o clock : Io= 600 mA
Switch position 8 'o clock : Io= 675 mA
Switch position 9 'o clock : Io= 750 mA
Switch position 10 'o clock : Io=840 mA
Switch position 11 'o clock : Io= 920 mA
Switch position 12 'o clock : Io= 1000+ mA

Measured Values :
** Accurancy -Performance Tip ...

-For higher accurancy use at least 1% tolerance resistors.
0.1 % are even more precise and will offer superb accuracy .
Not worthy to use less than 0.1% tolerance resistors.
(=high priced resistors ).

-Choose also of LOW thermal coefficient ( ppm / C ) resistors ,
to improve stability of resistance values ,in relation with temperature changes .

stop

PICOGRAV said:

stop

Click to expand...

Give me a good reason and I might think about it ...
Here where I have been risen and now standin' and will be burried Sir ,
we do not accept orders ,from nobody .

{ Galvanic Corrosion }Aluminium .

Galvanic corrosion
Galvanic corrosion may occur where there is both metallic contact and an electrolytic bridge between different metals. The least noble metal in the combination becomes the anode and corrodes. The most noble of the metals becomes the cathode and is protected against corrosion. In most combinations with other metals, aluminium is the least noble metal. Thus, aluminium presents a greater risk of galvanic corrosion than most other structuralmaterials. However, the risk is less than is generally supposed.
Aluminium corrosion resistance
Aluminium corrosion resistance is very good in untreated aluminium. Untreated aluminium has very good corrosion resistance in most environments. This is primarily because aluminium spontaneously forms a thin but effective oxide layer that prevents further oxidation.

Aluminium oxide is impermeable and, unlike the oxide layers on many other metals, it adheres strongly to the parent metal. If damaged mechanically, aluminium’s oxide layer repairs itself immediately.

This oxide layer is one of the main reasons for aluminium’s good corrosion properties. The layer is stable in the general pH range 4 – 9.

Jump to:

1. Galvanic corrosion
2. Pitting
3. Crevice corrosion
4. Aluminium in the open air
5. Aluminium in soil
6. Aluminium in water
7. Aluminium and alkaline building materials
8. Aluminium and chemicals
9. Aluminium and dirt
10. Aluminium and fasteners
11. Corrosion checklist

The most common types of aluminium corrosion are:

• galvanic corrosion
• pitting
• crevice corrosion

Stress corrosion, which leads to crack formation, is a more special type of corrosion. It occurs primarily in high-strength alloys (e.g. AlZnMg alloys) where these are subjected to prolonged tensile stress in the presence of a corrosive medium.
This type of corrosion does not normally occur in common AlMgSi alloys.


Galvanic corrosion
Galvanic corrosion may occur where there is both metallic contact and an electrolytic bridge between different metals. The least noble metal in the combination becomes the anode and corrodes. The most noble of the metals becomes the cathode and is protected against corrosion. In most combinations with other metals, aluminium is the least noble metal. Thus, aluminium presents a greater risk of galvanic corrosion than most other structural
materials. However, the risk is less than is generally supposed.


Close-up of galvanic corrosion in an aluminium rail post (25 year’s use). The rectangular hollow profile was held in place by a carbon steel bolt. The contact surfaces between the steel and the aluminium were often wet and attack was aggravated by wintertime salting.

Galvanic corrosion of aluminium occurs:

• Only where there is contact with a more noble metal (or other electron conductor with a higher chemical potential than aluminium, e.g. graphite).
• While, at the same time, there is an electrolyte (with good conductivity) between the metals.

Galvanic corrosion does not occur in dry, indoor atmospheres. Nor is the risk great in rural atmospheres. However, the risk of galvanic corrosion must always be taken into account in environments with high chloride levels, e.g. areas bordering the sea. Copper, carbon steel and even stainless steel can here initiate galvanic corrosion.

Problems can also occur where the metallic combination is galvanised steel and aluminium. The zinc coating of the galvanised steel will, at first, prevent the aluminium being attacked. However, this protection disappears when the steel surface is exposed after the consumption of the zinc.

As it has a thicker zinc coating than electroplated material, hot dip galvanised material gives longer protection. Thus, in combination with aluminium in aggressive environments, hot dip galvanised material should be used.

Preventing galvanic corrosion

The risk of galvanic corrosion should not be exaggerated – corrosion does not occur in dry, indoor atmospheres and the risk is not great in rural atmospheres.

Electrical insulation

Where different metals are used in combination, galvanic corrosion can be prevented by electrically insulating them from each other. The insulation has to break all contact between the metals.

The illustration shows a solution for bolt joints.



Breaking the electrolytic bridge

In large constructions, where insulation is difficult, an alternative solution is to prevent an electrolytic bridge forming between the metals. Painting is one way of doing this. Here, it is often best to coat the cathode surface (i.e. the most noble metal).

A further solution is to use an insulating layer between the metals.

Cathodic protection

Cathodic protection can be gained in two ways. The most common is to mount an anode of a less noble material in direct metallic contact with the aluminium object to be protected. The less noble material “sacrifices” itself (i.e. corrodes) for the aluminium. It is thus referred to as a sacrificial anode.

For the above to work, there also has to be liquid contact between the surface to be protected and the sacrificial anode.

Zinc or magnesium anodes are often used for aluminium.

Another way of obtaining cathodic protection is to connect the aluminium object to the negative pole of an exterior DC voltage source.

The illustration below shows the cathodic protection of an outboard motor.





End of part #1 ....

Pitting
For aluminium, pitting is by far the most common type of corrosion. It occurs only in the presence of an electrolyte (either water or moisture) containing dissolved salts, usually chlorides.

The corrosion generally shows itself as extremely small pits that, in the open air, reach a maximum penetration of a minor fraction of the metal’s thickness. Penetration may be greater in water and soil.

As the products of corrosion often cover the points of attack, visible pits are rarely evident on aluminium surfaces.

Preventing pitting

Pitting is primarily an aesthetic problem that, practically speaking, never affects strength.

Attack is, of course, more severe on untreated aluminium. Surface treatment (anodising, painting or other coating methods) counteracts pitting.

Cleaning is necessary to maintain the treated surface’s attractive appearance and its corrosion protection. Rinsing with water is often sufficient. Alkaline detergents should be used with care. Mild alkaline detergents are now available. These are used in, amongst other areas, the industrial cleaning of aluminium.

Pitting can be prevented by cathodic protection (above). It is also important to design profiles so that they dry easily.


Avoid angles and pockets in which water can collect. Instead, use a shape that promotes draining.


Stagnant water is avoided by suitably inclining the profile and/or providing drain holes. The ventilation of "closed" constructions reduces the risk of condensation.

back to top

Crevice corrosion
Crevice corrosion can occur in narrow, liquid-filled crevices. The likelihood of this type of corrosion occurring in extruded profiles is small. However, significant crevice corrosion can occur in marine atmospheres, or on the exteriors of vehicles. During transport and storage, water sometimes collects in the crevices between superjacent aluminium surfaces and leads to superficial corrosion (“water staining”).

The source of this water is rain or condensation that, through capillary action, is sucked in between the metal surfaces. Condensation can form when cold material is taken into warm premises. The difference between night and day temperatures can also create condensation where aluminium is stored outdoors under tarpaulins that provide a tight seal.

Preventing crevice corrosion and aluminium corrosion resistance

Using sealing compounds or double-sided tapes before joining two components prevents water from penetrating into the gaps.

In some cases, rivets or screws can be replaced by, or combined with, adhesive bonding. This counteracts the formation of crevices.





Aluminium in the open air
The corrosion of metals in the open air depends on the so-called time of wetness and the composition of the surface electrolytes. The time of wetness refers to the period during which a metal’s surface is sufficiently wet for corrosion to occur. The time of wetness is normally considered to be when relative humidity exceeds 80% and, at the same time, the temperature is above 0°C (e.g. when condensation forms).

In normal rural atmospheres, and in moderately sulphurous atmospheres, aluminium’s durability is excellent. In highly sulphurous atmospheres, minor pitting may occur. However, generally speaking, the durability of aluminium is superior to that of carbon steel or galvanised steel.

The presence of salts (particularly chlorides) in the air reduces aluminium’s durability, but less than is the case for most other construction materials. Maximum pit depth is generally only a fraction of the thickness of the material. Thus, in marked contrast to carbon steel, strength properties remain practically unchanged.


The picture shows an untreated sample after 20 years off the south-west coast of Sweden. UV radiation, sulphuric acid and nitric acid in combination with chlorides have not left any deep marks. After 22 years in a marine atmosphere, examination of an untreated aluminium sample (alloy AA 6063) showed that corrosion attack was so limited (max. depth approx. 0.15 mm) that strength was not affected.

Aluminium and chemicals
Thanks to the protective properties of the natural oxide layer, aluminium shows good resistance to many chemicals. However, low or high pH values (less than 4 and more than 9) lead to the oxide layer dissolving and, consequently, rapid corrosion of the aluminium. Inorganic acids and strong alkaline solutions are thus very corrosive for aluminium.

Exceptions to the above are concentrated nitric acid and solutions of ammonia. These do not attack aluminium.

In moderately alkaline water solutions, corrosion can be hindered by using silicates as inhibitors. Such kinds of inhibitors are normally included in dishwasher detergents.

Most inorganic salts are not markedly corrosive for aluminium. Heavy metal salts form an exception here. These can give rise to serious galvanic corrosion due to the reduction of heavy metals (e.g. copper and mercury) on aluminium surfaces.

Aluminium has very good resistance to many organic compounds. Aluminium equipment is used in the production and storage of many chemicals.

Aluminium and dirt
Coatings or build-ups of dirt on the metal’s surface can reduce durability to a certain extent. Very often, this is attributable to the surface now being exposed to moisture for considerable periods. Thus, depending on the degree of contamination, dirty surfaces should be cleaned once or twice a year.

End of part #2 ...

Aluminium and fasteners
When choosing fasteners for use with aluminium, special attention should be paid to avoiding galvanic corrosion and crevice corrosion (above). Galvanic corrosion of aluminium occurs where there is metallic contact with a more noble metal. It should be pointed out that, indoors and in other dry atmospheres, aluminium can be in permanent contact with brass and carbon steel with no risk of galvanic corrosion.

The pictures below show the results of an accelerated corrosion test, the Volvo indoor Corrosion Test (VICT). The test cycle is 12 weeks and corresponds to five year’s use of a car in a moderately large town.



Left – Zinc/iron-coated steel nut and bolt. The fastener is completely rusted. In the aluminium, 0.43 mm deep pits have formed.

Right – Dacrolit-coated steel nut and bolt. The fastener has not been attacked. No pits have formed in the aluminium.

Corrosion checklist
The summary below is intended to give a picture, from the perspective of durability, of aluminium as a construction material. Used correctly, aluminium has a very long life.

Environments
Rural atmosphere Aluminium has excellent durability.

Moderately sulphurous atmosphere Aluminium has excellent durability.

Highly sulphurous and marine atmosphere Superficial pitting can occur. Nonetheless, durability is generally superior to that of carbon steel and galvanised steel.
Corrosion problems can be overcome
Profile design The design should promote drying, e.g. good drainage.Avoid having unprotected aluminium in protracted contact with stagnant water.Avoid pockets where dirt can collect and keep the materialwet for protracted periods.

pH values Low (under 4) and high (over 9) values should, in principle,be avoided.

Galvanic corrosion In severe environments, especially those with a high chloridecontent, attention must be paid to the risk of galvanic corrosion. Some form of insulation between aluminium andmore noble metals (e.g. carbon steel, stainless steel, copper)is recommended.

Closed system (liquid)

In closed, liquid containing systems, inhibitors can often be used to provide corrosion protection.

Severe, wet environments In difficult, wet environments, the use of cathodic protection should be considered.

http://www.aluminiumdesign.net/design-support/aluminium-corrosion-resistance/

..The end ...

SIDE -NOTE :
It is unusual to see galvanic corrosion on aluminum in contact with stainless steel (passive).
In contrast contact between copper, bronze, brass and different kinds of steel alloys (passive and active) and aluminum can cause severe corrosion so it is advisable to provide insulation between the two metals.

http://aluminumsurface.blogspot.gr/2009/04/corrosion-between-anodized-aluminum-and.html

stardustsailor said:

Give me a good reason and I might think about it ...
Here where I have been risen and now standin' and will be burried Sir ,
we do not accept orders ,from nobody .

Click to expand...

I think he meant to say don't stop =P.

Since you're going into dimming circuits a bit. Do you have any advice for digital potentiometer s?[/B]

bicit said:

I think he meant to say don't stop =P.

Since you're going into dimming circuits a bit. Do you have any advice for digital potentiometer s?[/B]

Click to expand...

Never used one.
They seem to me quite complicated in operation and programming ...
Or maybe ,in reality i'm really out of courage to learn and use them ...( aka " bored " ) ...
Have nothing to say about them ..
What I know is that plenty if not all of them are compatible ,
through quite of a few protocols ,with many microcontrollers ..
I think ...

"Stop" , as analysed from my poor brains ,is a word that has only one meaning ...

On the contrary , if it was written , back-ways ....
"POTS " ..
Then ,indeed can have quite of a few different meanings ...
But, then I'm also sure that I'm not usually looking to my screen ,through a mirror ...
...

Furthermore ...
"Can you stop ? " sounds much nicer and can probably contribute to getting more access into
"knowledge of self " and probably much more than that, for both of "sides" implicated .

Cheers.

...my grain of salt...
...notes on …Protections on AC side…
…Tipical Spanish Main Distribution Panel…



…Interruptor de Control de Potencia (ICP)…
+
…Interruptor General Automatico (IGA)…
+
…Interruptor Diferencial (ID)…
+
…“Pequeño” Interruptor Automatico (PIA)…

…ICP 2 polos (bipolar) 20 A… (grado de electrificacion basico)
…normalmente curva de disparo ICP-M similar a la C…...
…La intensidad de disparo magnético Im es entre 5 y 8 In (UNE-20317)…

…IGA 2 polos (bipolar) 25 A… (grado de electrificacion basico)

…ID 2 polos (bipolar) 40 A 30 mA… (grado de electrificacion basico)

…IPAs 2 polos (bipolar)… …normalmente curva de disparo C…
…La intensidad de disparo magnético Im es entre 5 y 10 In (UNE-EN-6089).

…IPA C1 2 polos (bipolar)… …10 A… …wire 1,5 mm2… …ilumination…

…IPA C2 2 polos (bipolar)… …16 A… …wire 2,5 mm2… …tomas de corriente uso general (20 tomas + toma de frigorifico como maximo)…

…IPA C3 2 polos (bipolar)… …25 A… …wire 6 mm2… …kitchen and oven…

…IPA C4 2 polos (bipolar)… …20 A… …wire 4 mm2… …lavadora, lavavajillas, termo electrico…

…IPA C5 2 polos (bipolar)… …16 A… …wire 2,5 mm2… …tomas de corriente of bath room (6 tomas como maximo)…

…cables libre de halogenos… …wires halogen free…

Notas en enchufes …tomas de corriente o bases y clavijas o fichas de conexión…

…Tomas de corriente o Bases de 10 A… …solo para iluminacion… …ojo no suelen llevar conexión para tierra…
…Tipo schuko de 16 A… …general…
…de 20 A… …para lavadora, lavavajillas, termo electrico…
…de 25 A… …para cocina y horno…

…Clavijas de conexión o Fichas de 10 A… …solo para iluminacion… …ojo no suelen llevar conexión para tierra…
…Tipo schuko de 16 A… …general…
…de 20 A… …para lavadora, lavavajillas, termo electrico…
…de 25 A… …para cocina y horno…

…my pov about an Auxiliary Distribution Panel… ...for an litle room or a tent…

...ID 2 polos (bipolar) 20 A 10 mA…

...IPA C2 2 polos (bipolar) 16 A… …wire 2,5 mm2… curva de disparo Z…
…La intensidad de disparo magnético Im es entre 2 y 3 In...





...sorry for my short english...and large posts...

Saludos