LED-lights DIY

[Denis Watkins]

[Birgir]

Hello again everyone

I’m enjoying this discussion very much and hopefully getting better and better understanding of electric circuits.

If I understand Denis’s diagram correctly the important feature in a parallel connection is that the resistor is on the lead before it splits into two or three or even more parallel connected LEDs. This would of course rely on that all the LEDS in the circuit where of a similar kind.

Could I use the metaphor of water running thru water pipes and the resistor being equal to narrowing in the system, only allowing a limited amount of water going thru, at least if the pressure is kept constant?

Then, one narrow part of the pipe would be sufficient to hold back the flow of water for the whole system.

But to keep pressing the laws of electric current I intend to use three different LEDs in my parallel connected circuit J, red, green and white. To be able to do that, I would have to have three different resistors, as Martin suggests, one for each LED that takes into account the different voltage of each coloured LED.

It might be wise to use two serial connected button cells giving 6 volts and 225 mAh

Now I must find a good guess for the voltage of each colour and find me a calculator to make use of Plummet’s, -eh Ohm’s law V = I x R

(PS. As you might have noticed English is not my first language so bear with me if my vocabulary is limited)

B.

[Denis Watkins]

[Plummet]

I have found this:-

**LINK**

which gives nominal voltages for various coloured LEDs.

And this:-

**LINK**

which gives similar information. I have not compared them.

Birgir, your use of water in a pipe is the same idea I use when trying to explain electricity and resistors.

Imagine a tank of water raised up above the ground. The outlet of the tank is connected to a pipe. The end of the pipe is below the level of the water in the tank. Your thumb is blocking the pipe. It is stopping the flow. There is no current in the pipe.

If you raise the end of the ipie the pressure on your thumb reduces. If you move it downwards, the pressure increases.

The pressure in the pipe is like the voltage in a circuit. (Voltage id often called the potential difference.)

You remove your thumb. The water will flow from the pipe.. As you raise and lower your pipe end the flow will decrease and increase. All the water will not suddenly come from the pipe. It will flow steadily. If the pipe is big, the flow will be faster than if the pipe is small. The small pipe provides a high resistance to flow. The larger pipe, a lower resistance.

In electrical terms the rate of water flow (eg, litres per minute) is like the current (amperes, or milliamperes.)

A low value resistor is like a wide pipe, and a higher resistance is like a narrower pipe. Electrical resistance is measured in ohms.

The relationship between them is Ohms Law, as you already know, which is expressed as

V = I x R

V is measured in volts

I is measured in amperes (amps)

R is measured in ohms.

Plummet

[Allan Bennett]

Posted by Birgir on 24/11/2016 20:42:23:

Hello again everyone

I’m enjoying this discussion very much and hopefully getting better and better understanding of electric circuits.

If I understand Denis’s diagram correctly the important feature in a parallel connection is that the resistor is on the lead before it splits into two or three or even more parallel connected LEDs. This would of course rely on that all the LEDS in the circuit where of a similar kind.

As was explained in a thread earlier on, a single resistor can only be used if the parallel LEDs are identical to each other. The preferred method is to use a resistor in each lead, as shown in Denis Watkin's post after yours -- even if there's only one LED in each branch. That will work every time, provided you've calculated your resistors correctly.

[Birgir]

Good morning everyone

At last, the goods have arrived from China, a box with different coloured LEDs and a bag full of resistors, (1/4 W 120 – 910 ohm) so now it is back to bench testing.

I’ve decided to use three resistors, one for each LED (white, red and green) and all three LEDs in parallel connection to one battery pool of two button batteries, giving 6 Volts and 225 mAh.

In this setup the white LED is considerably brighter than the red and green but that is most likely because of the fact that those are different coloured LEDs.

If each LED is about 20 mA, three of them should use 60 mA and a 225 mAh battery pool should keep them lit for up to three hours. The bench testing showed just that. After 4 – 5 hours the white LED started to lose its brightness and this morning it was just a dim glow but the other two green and red seem to last longer.

Next phase is to implement the three navigating lights into my model, perhaps using the wing as an on/off switch, so that when the wing is in place the lights are lit but turns off when the wing is removed. For longer periods with LEDs off, I will place a plastic strip between the connectors to the wing as you often see in new toys that comes with batteries installed.

Comments and ideas, good or bad, are welcomed.

B.

Edited By Birgir on 30/12/2016 09:13:06

Edited By Birgir on 30/12/2016 09:21:43

[Denis Watkins]

Well done B, I use a dial resistor substitute, which goes in circuit via crocodile clips and introduces different values when rotated, then look at the brightness. Also some white LEDs are higher voltage but being a diode they still consume 20 ma but can be above 3 v. Nevertheless they are brighter, and as you say the colours can absorb some of the light. You are near your goal so keep trying

Edited By Denis Watkins on 30/12/2016 09:41:52

[Birgir]

Thanks Denis

I wonder what the price is for a CR2032 in UK.

Here in Iceland, a Duracell costs 3,6 pound a piece in the supermarket but I can get a no name brand in a low-price store for 18 cents a piece.

Enormous price difference but I can't see any difference in performance in my LED circuit.

B.

[Denis Watkins]

More expense B, but these switches let you control most things from your Tx

[Birgir]

Thanks Denis

I went the DIY route and made three contacts on the fuselage. One is the negative, but the other two are the positive lead. When I put the wing in place, the positive connector for the wing lights bridges the two positive connectors on the fuselage closing the circuit for the tail light.

So now the mission is completed and hopefully I can start my spring flying a week or two earlier here in the twilight in the North.

B.

[Mannyroad]

Very informative thread. I know nothing about LEDs but am learning fast - I think

[Birgir]

Good to hear Mannyroad

Here is a sketch of the switch free circuit design

Edited By Birgir on 09/01/2017 16:44:24

[Giuseppe Saroli]

I am not a electronic expert but i am going to make this strobe light

i got the clock bit and a 1 cell lipo just need to find or salvage a led i think is brilliant

Would it be bright

**LINK**

[Denis Watkins]

Piacere Giuseppe,

Look up Ultra Bright LED for this one

A standard LED would be quite dim

[Birgir]

Hi Giuseppe

Even though I had much fun implementing the navigation lights into my Mini Super they came out a bit dim.

Next time I would follow John Stones suggestion earlier in this thread and buy a ribbon to pull the leds out of. It can be bought in any length

The link is: LINK

B

[Giuseppe Saroli]

Sounds good and worth a try there are cheap and ever so small you will need a magnifier glass to cut the wire i think

I am looking for a bright led as Denis suggested i only want 2 to play with not 100 as sold

I do like the beacon light mind you. I saw it first time on a foam glider at my club and you can actualy see it high up in the sky ever so impress i could belived it, but even so it was a button battery powered version very small stuck under the wings i was not impress by the price he paid £30 each

i will report back when i find some led might have raid my son toy box for one

Good luck on you project Birgir

[steve york]

Or go here.................LINK

[Giuseppe Saroli]

Thanks a lot