Powering multiple 12v arrays using one power source

Thread Starter

Long_p1

Joined Nov 2, 2011
14
Hi guys, I hope you are all well.

I'm fairly new to electroincs and keep getting ideas that sound simple but then as I look into them (to make sure they are safe) I just confuse myself!

Basicly I have a some LED modules that I want to use to light my aquarium. They are in modules of 4 leds in a string of 20. That is to much light for my needs.
What I want to do is cut the array/string down so I have 2 or 3 which I can then turn on independantly when an increase/decrease in light (or colour) is needed.
This is an idea of the scematic

I know ive prob got the negitive rail wrong (that my 1st ever attempt of a scematic)
My driver is
Specifications
Model no: NV1230C Input Voltage AC170-240v,
Output Voltage
DC 12+0.5v
Output Power
30w max
Output Current
DC 2.50A

Will the basic concept work, or will i need to add some form of transistor/capacitor
/regulator?

I have found similar threads but none seem to answer my question in a direct manor.

Many, many thanks for any help of suggestions
 

iONic

Joined Nov 16, 2007
1,650
Well, there is no negative rail. You need to tie all resistors together then directly to the negative terminal of the battery. Right now you have the positive terminal on both sides.
What are the specs of the LED's, any clue? Are they white? If so probably about 3V and 20mA.
You'll probably get no light with 4 LED's in series with a 180 ohm resistor if the power supply is a regulated 12V. You will need to cut back to 3 LED's and the 180 ohm resistor.

The switching idea is sound. one switch for Low, the other for Med, and both for High Lighting.

We really need to know what the specs are on the LED's however... can you post a pic of these LED modules??

 
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SgtWookie

Joined Jul 17, 2007
22,220
I prefer to have the resistors on the positive side of the LEDs. Electrically, it really makes no difference - as long as the resistor is in series, the current flow will be controlled. However, from a practical standpoint it does make a difference; as generally there are many more connection points to ground than there are to the positive supply. If a short develops from ground to the low side of the resistor, the resistor might burn up - but that's better than losing a string of LEDs.
 

Thread Starter

Long_p1

Joined Nov 2, 2011
14
Cheers guys, was just coming back to put that info in
The modules are sealed unit shop brought in a string of 20




Description:
20pcs of SMD 5050 4-LED modules connected in parallel circuit

  • Waterproof construction
  • Low power consumption, high energy efficient
  • Luminous: 15LM
  • Viewing Angle: 120 degrees
  • Grade of Waterproof: IP65
  • Emitting Color: White
  • Operation Voltage: 12V
  • Current: 0.12A
  • Power Consumption: 1.44W per module
I'm thinking I want to run 10 + 6
 

Thread Starter

Long_p1

Joined Nov 2, 2011
14
The idea/thought of the switches and one power supply for more than one string was my main qestion. Addional info is great as it makes sense when the info is coming about a project you are undertaking!
Thanks again so far

Paul
 

SgtWookie

Joined Jul 17, 2007
22,220
Even if you operated all 16 strings in parallel, just one supply would be more than enough. You would be operating at ~77% capacity of the supply; 80% is generally considered to be a conservative practical limit for a supply.
 

Thread Starter

Long_p1

Joined Nov 2, 2011
14
Yea, I had seen some posts previously Re the 80% so wanted to stick below that.

Thanks for the confirmation on that.

Whould it be ok to use some pref board & equipment wire to connect/split the power supply to internal connections.

I would also like to use 2.5mm DC sockets to make the lights removeable/replacable.
Will these connections bring up any problems in terms of volt/current loss ect?

p.
 

iONic

Joined Nov 16, 2007
1,650
The switch looks OK, but my circuit drawing is not right for the LED's specified.
Still not sure the forward voltage for the LED's are, but as you posted the forward current is 120mA. So I'm still trying to figure out how they are lighting 4 LED's in series (If they are in series) with a 180 ohm resistor and Just 12V. Actually, if I ca see the picture well enough, they look like 200 ohm resistors (Printed - 201).

How would you attempt to use 2 or three of them in series. They appear to have a waterproof coating over the entire PCB?

I think I'd be inclined to work with each 4 LED module as a whole, and parallel them with the specified 12V.

I'm led to believe that since there are 4 LED's and 4 Resistors that the module is wires as 4 LED's in parallel. But with a 200 ohm resistor and 12V that leaves less than 60mA for each LED.

Oops, now 2 resistors are 200 ohms and 2 are 1K ohms! I'm perplexed!
 
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Thread Starter

Long_p1

Joined Nov 2, 2011
14
Yes, sorry for confussing you with my drawing, was just trying to show set up as I understood it.
Your right there is 2 x "201" & "2 x 102" resistors per module.
 

SgtWookie

Joined Jul 17, 2007
22,220
Would it be ok to use some [perf] board & equipment wire to connect/split the power supply to internal connections?
What did you have in mind?
What do you mean by "perf board"?
Equipment wire?
What internal connections?
That entire sentence is quite vague.

I would also like to use 2.5mm DC sockets to make the lights removable/replaceable.
Will these connections bring up any problems in terms of volt/current loss ect?
Any time you add connectors, you add points where there can be losses and failures - even failures as simple as coming unplugged.

2.5mm sockets/plugs can be very difficult to solder. They are frequently nickel plated, which requires a very hot iron.
 

Thread Starter

Long_p1

Joined Nov 2, 2011
14
......perfboard, stripboard, proto board?
As this is going to control lights on my aquarium which is in my lounge I would like to make the connections within a box to keep it all neat and dry (Although it wont be much rish of water splillage near it).

My plan/idea was to have the power cable from the driver to enter the box, split so it can be attached to the 2 switches which attach to the sockets/plugs to which the lights can then be attached (& removed if needed as the LED's will be attached to the hood of the aqaurium)

So internal connections; I was referring to any/all wiring within this "box".
I have a decent varible iron, even though I've not used too much basic soldering i'm fairly confident with.

Hope thats a little clearer....??
Any thoughts, suggestions or recommendations are happily received.

Thanks so much

P.
 

SgtWookie

Joined Jul 17, 2007
22,220
Ahh, ok. Well, you should be able to do that then.

Keep in mind that your LEDs will be generating some heat. 12v * 1.92A = ~23 Watts. Don't forget to provide a way for that heat to dissipate, or you will have problems.
 

Thread Starter

Long_p1

Joined Nov 2, 2011
14
and equipment wire I was reffering to the wire used to connect these parts.

Thinking about it, I'm over complicating it. I could use a block connector to directly wire the "power in" to the switches and then wire the switches to the 2.5mm connectors for the lights. This sound ok.

It doesnt have to be 2.5mm sockets, any suggestions?

Thanks

P.
 

Thread Starter

Long_p1

Joined Nov 2, 2011
14
Hey guys, got all of my bits to build a switched box delivered today and in the process of putting it together. I am usind STDP (on-on)toggle switches. There are 3 connections on them, using my multi meter I can see that I connect incoming power to one side and "outgoing" power/lights to the centre.
Can I just confirm that I dont connect the neg lead to the switch but directly to the lights/LED's that they are for?

Sorry for a bit of a stupid question, just wanna make sure im not blowong myself up! :)

Cheers

Paul
 

SgtWookie

Joined Jul 17, 2007
22,220
You don't connect the negative wire to the switch.

Connect the positive LED wire to the center terminal.
If it is a bat-handled or rocker switch, connect the supply positive wire to the lower terminal. If it is a slide switch, connect the supply positive wire to the upper terminal.
That way when you flick the switch up, the lights turn on.
 

Thread Starter

Long_p1

Joined Nov 2, 2011
14
Thanks again to you guys. Just thought I'd throw a couple pics of the (almost) completed project.
I decided to add my new digital temp gauge (which I've now found out is faulty!) to the switch box & ruined the box!! I've enjoyed putting it together so will order a new box and do it again.
Thanks again for your time & input..... Back to learning Arduino!





 
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