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LED help

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Cbello44

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Hi there,

I realize this might be a silly problem but I'm a video guy much more than an electric guy.. I'll start by explaining my end goal and then tell you where I've landed. I am trying to put recessed ceiling LED fixtures in to a fire station sleeping quarters. There are 4 rooms, I wanted to put one fixture in each. Each room would have a wall switch for WHITE light, but the same fixture (all four) would come on in RED automatically when the station received an emergency call.

I researched DMX and a few other automated routes, but this seemed too pricey or above my skill level. So I bought a simple 12 watt RGB+Warm White LED fixture that comes with an in-line remote control receiver. The second I opened the box I ripped that receiver open to figure out its outputs, cut the receiver out of the picture and moved on to old-school 12 volt powering. The wires leftover going to the light are a 12v+ and then 4 grounds (a red, a green, a blue, and a warm white) I also had a 12v PSU and a 12v PWM dimmer wall switch on hand. So you give the 12v+ power, and ground out the white and you get a white. switch the ground to the red and you get red..combine 2 and you..you get the picture.

Okay so where I stand is, I know I can make a switch turn on the light for white which is one of my goals... but now I need to know what to do to override that white light and get the red grounded instead of white when we get a call. When we get a call there is a 12v circuit that closes (right now it powers one rotating light in another room), so I can use that, we'll call it "Alert", circuit to either fire another relay or I can also power the new fixtures off of it entirely..

But if the white light was on and we got an Alert, I'd be sending two power supplies to the same fixture. Or if the switch was off and I was only switching grounds from red to white there would be no 12v+

So basically i know how to make the light do one or the other and I would like some help trying to make it switch between the two on command.

Thanks!
 
Hy Cbello,

Welcome to ETO. I am sure most members would be happy to help anyone connected with the fire service.

I think a solution to you problem is quite simple and will give it some more thought and should be able to post a suitable approach. Many other ETO members will also be able to post suggestions.

In the meantime, can you tell us where you are in the world- it helps to know what components you can get. Also mains supplies and safety standards.

spec
 
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Thanks for the quick reply! I am from Maryland in the US... I updated my profile to help out on that! My main supply is 120VAC. Safety standards, I'm not too sure how to answer that?
At this point I have a 200W 12vDC power supply to use on this setup. But typically the way I've seen these things set up is with a smaller 12v supply near to the wall switch for just normal single color fixtures.

Also this is the fixture that I am playing with https://www.amazon.com/GENSSI-Recessed-Ceiling-Downlight-Flood/dp/B01CPTANIW
 
Thanks for the quick reply! I am from Maryland in the US... I updated my profile to help out on that! My main supply is 120VAC. Safety standards, I'm not too sure how to answer that?
At this point I have a 200W 12vDC power supply to use on this setup. But typically the way I've seen these things set up is with a smaller 12v supply near to the wall switch for just normal single color fixtures.

Also this is the fixture that I am playing with https://www.amazon.com/GENSSI-Recessed-Ceiling-Downlight-Flood/dp/B01CPTANIW

No sweat about response.

And thanks for your fast response too- we really appreciate that on ETO

You don't need to worry about safety standards. Now that we know that you are in Maryland we can sort that.

I have a few questions for you which I will post quite soon. The answers will help with the solution.

spec
 
Hy Cbello,

I didn't bother with the questions as there is sufficient information in your original post. Here is a schematic which I think meets your requirements.
There is one point of concern. It is normal to drive LEDs with a constant current but you are driving them with a 12V supply, or do the LEDs have built-in constant current generators?

2016_04_14_Iss01_ETO_LED_COLOR_CONTROLLER_VER_01_Sh04.png

DATA SHEETS & SOURCES
(1) Relay 1 1PDT Automotive
**broken link removed**
(2) Diodes 1 & 2 1N5822
https://www.mouser.com/ds/2/149/1N5822-888313.pdf
https://www.mouser.co.uk/ProductDetail/Fairchild-Semiconductor/1N5822/?qs=UY9CvlAIy0ilZt8GFdM7Zg==&gclid=CjwKEAjw_7y4BRDykp3Hjqyt_y0SJACome3Tdb1gYcsns3Jn9Rh2t0kYh-5rlDNVD3kBJlJaHol5GBoCJB3w_wcB

NOTES

(1) Relay 1 is a common car (automobile) 12 Volt single pole change over (SPCO) type which are freely available and cheap.
(2) Diodes 1 & 2 are rectifier diodes of 2A minimum current capacity and 24V minimum peak inverse volts. Many types will be suitable but Schottky would be best because of the low forward voltage drop. The diodes are also low cost.

ERRATA
(1) The top traces to each 12V power supply are the positive outputs.
 
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Thanks spec, This is greatly appreciated! I think I almost understand what you've made for me...

I'm not sure what you mean about the power supply versus current generator?

With regards to the + supply to the LEDs I am a little confused because there isn't a 5th wire shown. I probably shouldn't have called it a constant 12v+ for that fifth wire. The way the PWM dimmer works is by pulsing via both the + and -. So the wall switch needs to be connected to both in order to dim.... This is all unless, I can instead dim the 120vac side like a normal light switch. So, reduce power going to the 12v supply instead of PWM dimming downstream.. Does that make sense? It was my understanding that LED fixtures don't dim as smoothly unless you use PWM.
 
Let's see if I understand the requirements correctly:

1. Normally, four rooms have completely independent control of their white lights with four independent wall switches.

2. In the alarm state, any white lights that are on go off.

3. In the alarm state, all four red lights come on regardless of the wall switch position.

If all of that is correct, then one question - do the 12 V power supplies have a low-voltage input signal for output enable, output disable, global shutdown, something like that? Many industrial supplies do, and if they are there then all of the control can be done at the low energy level. Starting with spec's two supply scheme:

4. All red lights go directly to one supply #1 without any wall switches. This supply is enabled by the house alarm signal. We'll have to work out the interface for that, but I've done a lot of these and it's pretty simple.

5. All white lights go to supply #2 through their individual wall switches. This supply is enabled/disabled by the 12 V output of the supply #1. No relays, no diodes in any power path. Both supply outputs and all lights common-grounded.

If the supplies don't have output enable signals, then one SPDT relay will be needed with an alarm control circuit (maybe just a relay coil driver), but now you're down to a single power supply.

6. The signal coming from the station that changes the lighting, "a 12v circuit that closes" - sounds more like a 12 V source that is turned on in the alarm state. Can it handle another 0.1 A of relay coil current?

ak
 
Thanks spec, This is greatly appreciated! I think I almost understand what you've made for me...

I'm not sure what you mean about the power supply versus current generator?

With regards to the + supply to the LEDs I am a little confused because there isn't a 5th wire shown. I probably shouldn't have called it a constant 12v+ for that fifth wire. The way the PWM dimmer works is by pulsing via both the + and -. So the wall switch needs to be connected to both in order to dim.... This is all unless, I can instead dim the 120vac side like a normal light switch. So, reduce power going to the 12v supply instead of PWM dimming downstream.. Does that make sense? It was my understanding that LED fixtures don't dim as smoothly unless you use PWM.

Hy Cbello,

I obviously have not understood what your layout is like.

It was my understanding that you were going to power the LEDs, not with the mains supply, but with a separate 12V supply.

It was also my understanding that the alarm signal was also a 12V supply line with sufficient current capacity to drive the red LED.

When you drive a LED you don't put a voltage across it, insted you put a constant current through it. This is because the forward voltage of a LED (when it is on) is not accurately defined so with a voltage applied the LED may take excess current (and fail) or too little current (and not be sufficiently bright).

I do not understand what you say about the dimming function at the moment.

We need to sort out what you circuit is. Could you sketch a schematic.

In the meantime treat my schematics as tools for discussion until things can be fully defined.

Here is another version of the schematic where the alarm line does not power the red LED which instead is powered by the same 12V supply that powers the white LED. The alarm signal only has to supply 80mA to operate the relay.

Once again this circuit is only a vehicle for discussion.

spec

2016_04_14_Iss01_ETO_LED_COLOR_CONTROLLER_VER_02_Sh04.png
 
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Cbello,

I may have figured the way the light is wired. I will post a schematic so that you can see if it is correct.

spec
 
I will try to post a diagram later when i am at my desk.

To AK, yes you have points 1.2.3 correct. But no there is not any analog control of the unit.

So let me back up... the current system is a simple 12v wall mounted light that comes on solid because it is being closed by a computer controlled relay when an alert is sent. There is currently a 120 to 12 volt power supply in the basement that is always on, but the circuit doesn't complete until that closure takes place.

I just realized trying to word this is difficult, let me go paint a picture haha, I'll get back to you
 
Here is my interpretation of the requirements. Many other options are possible, such as moving the relay to switching the returns, replacing the relay with a pair of power MOSFETs or power BJTs, etc.

ak
FireHouseLights-1-c.gif
 

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  • FireHouseLights-1-c.pdf
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Let's see if I understand the requirements correctly:

1. Normally, four rooms have completely independent control of their white lights with four independent wall switches.

2. In the alarm state, any white lights that are on go off.

3. In the alarm state, all four red lights come on regardless of the wall switch position.

If all of that is correct, then one question - do the 12 V power supplies have a low-voltage input signal for output enable, output disable, global shutdown, something like that? Many industrial supplies do, and if they are there then all of the control can be done at the low energy level. Starting with spec's two supply scheme:

4. All red lights go directly to one supply #1 without any wall switches. This supply is enabled by the house alarm signal. We'll have to work out the interface for that, but I've done a lot of these and it's pretty simple.

5. All white lights go to supply #2 through their individual wall switches. This supply is enabled/disabled by the 12 V output of the supply #1. No relays, no diodes in any power path. Both supply outputs and all lights common-grounded.

If the supplies don't have output enable signals, then one SPDT relay will be needed with an alarm control circuit (maybe just a relay coil driver), but now you're down to a single power supply.

6. The signal coming from the station that changes the lighting, "a 12v circuit that closes" - sounds more like a 12 V source that is turned on in the alarm state. Can it handle another 0.1 A of relay coil current?

ak

I think the OP also stated (in post #1) that the LEDs are switched from the ground side with the positive side common to the power supply.
 
Return side switching.

ak
FireHouseLights-2-c.gif
 

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  • FireHouseLights-2-c.pdf
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Thanks, I apologize, I haven't yet had a chance to get to my desk yet.

This is close.. The fixtures are 5 five wire. There's 4 grounds (one for each color LED) and 1 positive that has to be energized to make any of these work. The problem lies in me wanting to dim the white light.. because that requires both the + and - running through a pulse width mod dimmer.

After some consideration, I think we might just go with something simpler. We might just mount 2 fixtures in each room. One red and one white on two totally separate systems. It's not as fun, but will require much less low voltage wiring.

I can't express how grateful I am for all of your ideas and help with this. Ultimately this LED fixture's white light mode isn't quite bright enough and would mean doubling my fixtures.
 
Yeah, given the incredible amount of R&D in the last 10 years, nothing is going to get you the white light efficiency of a true white LED.

And separate circuits, as in either schematic, means the white LEDs can have dimmers, remote controls, whatever, that don't affect the red LEDs.

ak
 
Since you are only using about 1amp per bulb, some cheap rj45 phone wire is able to run each ground wire, it is also just enough to run 12v power line to each bulb per wire, but not enough to power more than 1 bulb per wire.

control systems can consist of just simple light switches, or transistors for computer control to do more complex patterns and the dimming you want,
there are lots of pwm circuits which are easy enough to build, and prolly purchase but could add up to wiring mess in the panel, and still need additional circuitry to change dim levels, but i think if you are going to get in to patterns you should just use adruino micro-controller with ramps stepper motor shield & drivers which makes building circuits simpler & cleaner, but adds programming to the learning curve. this makes it easier to programmatically change your patterns instead of bread board rewires

back to your original question:
diagram will show how to wire a kill switch in for all the rooms, it is the last switch in the row of control switches and can be replaced with relay..... but you will need to wire the kill switch relay to the NO(naturally off ) contact so that the White LED flips off when relay is getting power from the "alert circuit", so for that relay you will need to find one with Naturally ON, and Naturally Off contacts...

also note that each bulb is about 1 amp, so the switches/relays need a rating of over 1amp per bulb (so round up when choosing), this also goes with any wires past that point
 

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Maybe this is a simpler question, what's the easiest way to make w ramping/fading up of a series of LED's occur? so that they don't come on so fast
 
A relatively fast ramp, like 1 second or less from dark to full bright, can be done with a series power transistor without generating so much heat that it needs a big heatsink. PWM has much lower thermal issues no matter how slow the ramp is. If this is to eliminate the visual shock of the LEDs going to full brightness in a microsecond, I would go with a 100 ms linear ramp.

ak
 
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