LED Bulbs pt3

[Gary Murphy 1]

Hi Guys, I have used pt3 title hoping previous helpers will look.

All the help as been great BUT I can just not get schematic drawings.

I have drawn a diagram that I would understand if shown. I have tried to show 12 led`s connected to the 10 wire ribbon cable.

Is this correct for all led`s to work? If not could someone draw a similar diagram that IS correct?

Now, If my example does work is that series connection OR parallel?

If I wanted more leds what would that diagram show?

Lastly , the module can vary a bulbs voltage to show 3 brightness`s .would the resistor value be the same as the others that do not dim?

Using 6 cell nimh 7.2 to 8.4v

Sorry to seem dim (no pun intended) . I do appreciate the help.

[Gary Murphy 1]

I have realised that I have made a mistake in that diagram, well 1 that I can see

When I need 2 tail lights,2 head lights etc ,They would need to go to the same output. This is where the parallel or series issue come into play.

I am just going to find the next wall!

[Denis Watkins]

You are not dim Gary, that is a brilliant diagram, and the LEDs look like they will light up

Test one LED on your outputs individually

Your LEDs are wired in Parallel, and you can save a lot of cable running each minus/negative to its neighbour, then ultimately to the negative feed.

A redrawn digram is exactly as yours is but with straight lines to horizontal and vertical points

If you want more LEDs, then just tandem those, in parallel on existing LEDs

At the big Dot, where all minus join, you add a resistor there

But your module may have protective resistance inside on the outputs

[Denis Watkins]

Tricky altering LED brightness with voltage, as high voltage will make them fail

Perhaps have BULBs on the Headlights

[Barryorbik]

Just a quick observation Denis, if he only uses one series current limiting resistor then would need all of the LED's on to calculate its value from (Voltage to be dropped/ total LED current), but if only a couple are then turned on, the resistor value would need to be different. I suspect like you that the control unit already has the current limiting resistors for each LED built in

Barry

[Nigel R]

What is the module?

[Denis Watkins]

Posted by Nigel R on 25/02/2019 17:16:36:

What is the module?

Here Nigel, for a Truck

**LINK**

[Dad_flyer]

I have put two LEDs on channel 1 and only one on channel 2. I have also shown DW's suggestion of using one wire to the positive supply rather than a separate wire all the way for each LED. Either will work.

From page 46 of the manual it seems to day that it uses PWM for dimming. This is slightly different from the PWM for servo control, it basically switches the LEDs on and off rapidly and the amount of on compared to the amount of off gives the brightness. There is something on page 46 that seems to say that you should not use the servo connections at the same time as the switch channels 11 and 12, although both are used in the diagram on page 10. I have not really read the manual, just skimmed through the pictures...

[Gary Murphy 1]

Once again guys thanks very much for the help. Dad flyer`s diagram is spot on for me to understand. I can understand that for 1 and 2 bulb applications. I can see 2 bulb will be wanted more, headlights,tail lights etc.

The voltage varying for brightness is something you can programme. you use 3 percentages upto 100% . I think they suggest 10,30 and 60. I presumed it was safe for the leds. I do not know about the resistor in that application,would it be the same as I single 100% bulb?

I am getting slowly and its all thanks to you guys, its great to get help with no "scoffing"

[Dad_flyer]

I think you are now ready to test it on the bench. This diagram is now basically the same as page 10 of the manual. If you set the resistors for your safe LED current at maximum voltage then whatever method it uses for brightness control will not harm anything.

Then try changing the brightness. If it uses PWM then this should work. If it changes the voltage then the LEDs will dim more rapidly than you expect, and will go out completely somewhere about 20-50%. I don't quite see how it could vary the voltage, as all LEDs take the same supply pin and the separate switches are on the ground side. I think it therefore does use PWM and will just work for you.

Good luck!

[Allan Bennett]

Posted by Denis Watkins on 25/02/2019 15:28:20:

. . . . . Your LEDs are wired in Parallel, and you can save a lot of cable running each minus/negative to its neighbour, then ultimately to the negative feed.

A redrawn digram is exactly as yours is but with straight lines to horizontal and vertical points

If you want more LEDs, then just tandem those, in parallel on existing LEDs

At the big Dot, where all minus join, you add a resistor there

But your module may have protective resistance inside on the outputs

Given that the LEDs are probably different colours -- at least red, white, and amber for a vehicle -- then a common resistor in the common -ve line is probably a bad idea, unless it's there as an overall over-current protection. The reasons are twofold: First, different colour LEDs have different forward voltage Vf and maybe also different forward current, thus, theoretically need different value resistors to achieve their optimum current; Second, as has already been mentioned, the value of the resistor will be different for different numbers of LEDs on at the same time.

[Denis Watkins]

Gary is asking for help Allan

Could you look over his module and assist with your knowledge base

[Allan Bennett]

I've been following this thread for a while, but have refrained from commenting until now because I'm not familiar with the unit in question.

Having looked at the diagram in the manual it seems clear to me that there is probably no current-regulation for the LEDs within the unit, for it clearly shows a resistor in series with each of the LEDs at Output 1 to Output 12. This is quite logical for every LED needs a different value resistor, depending its colour and wattage.

Note that the values of the individual resistors depend on what supply voltage is being used for the module, as well as on the LEDs' characteristics. Page 19 of the manual mentions this, but then gives a table of suggested resistor values which ignores the LEDs' characteristics. To determine the required resistor the simplest way is to use this online calculator for which you will need to know the forward voltage (Vf) of each LED as well as its operating current and the supply voltage. No resistor is needed in the common return wire (the red one in the diagram) if each LED has its own. With 12 individual LED outputs I can't envisage the need for any LEDs in parallel, but if they are needed, then they must be identical, and the calculator I've linked will then give the resistor value for the pair. So a pair of identical LEDs, with one resistor, could replace any of the single LEDs + resistor shown in the diagram.

The manual says that one can individually control each of the LEDs, but at first glance I can't see that it tells you how to do this! Hopefully someone else has covered that in the preceding posts.