system is working on a powersupply of 12V (not battery)
power dissipation is not that important
12V power because that is present on the alarmpanel
i have four systems and each system should control about 12 to 16 leds

 

Don't dismiss power dissipation issues so cavalierly. If you have four systems with 16 LEDs and each circuit is dissipating 2W, that's 128W of heat that has to be dissipated or else you have a fire hazard.

You can use four transistors and five resistors to hold the total power dissipation per circuit to just the 240mW that you are stuck with as a consequence of drawing 20mA from a 12V supply. That would drop your total heat load to about 15W, which is a lot more managable.

Are these LEDs going to be located in one place (at least per alarm system), such as in a panel. If so, then it would be a simple matter to make a circuit board to mount everything on, which might also allow for a neater, more professional looking installation.

 

Ramusson's solution uses an active device, and hence isn't a suitable counter for the claim that it can't be done without using an active device. I don't know what circuit you had in mind as you mentioned four resistors. So I couldn't very well ask someone to indicate why a circuit that wasn't actually given wouldn't work without the addition of an active device.
...

Seems to be a communication misunderstanding? The important part of Ramusson's circuit re this discussion is AFTER the gate, and uses two resistors and the LED.

Driving it from a open collector input requires minimum one resistor more (the required pullup resistor) and can use the fourth resistor as a series resistor with the open-collector for safety and tunability.

This is such an old standard way to drive a 2pin bicolour LED from 1 pin that I assumed people knew what Ramusson and I were talking about. Maybe I should have posted a schematic.

 

Here is a bone-simple way to have the bi-color LED's illuminate in alternate states

 

Here is a bone-simple way to have the bi-color LED's illuminate in alternate states

It's deja vu all over again. Guess you didn't see my post #23.

 

The values may work, but they don't do what the OP asked for, which is for 20mA in both directions. This gives about 7.2mA when green and about 6mA when red. That may be good enough (I suspect it likely is). The power dissipation isn't too bad, being about 150mW when red and about 400mW when green. It also only asks the alarm output to sink 30mA.

But if you want to achieve what the OP asks for, then you are looking at values more along the lines of what crutschow came up with. I suspect that those are optimal, but you probably aren't going to do a whole lot better, either.

 

so i can make it work with a circuit of three resistors and the bicolor led.
But crutschow talks about resitors about 100ohm and 247 ohm.
in the circuit of sensacell i see values of 500ohm and 1000ohm.
will it still give enought light when working with these values?

 

How are WE supposed to know how much light YOU will consider enough?

Why don't you do a little test and find out?

Do you have an VOM (volt-ohm-milliamp) meter? If so, configure it as a millamp meter and use a battery (like a 9V battery), your LED, the meter, and a resistor all in series and try different resistor values until you think you have enough light. If you don't have a meter, get one. There's not much point doing even a project like this without a meter -- and they can be had for $10. To get a feel for the resistor values that you need to explore, with a 9V battery you will have to drop roughly 7V across the resistor. So to get 2mA you would need 3.5kΩ and to get 20mA you would need 350Ω. So you might try a 1kΩ resistor first, which should give you about 7mA. This is very possibly going to be satisfactory. If it's not bright enough, try a 510Ω, which should give you about 14mA. If it's still not bright enough, then try a 330Ω resistor which should give you about 20mA. But before you do that, be sure to look at the specs for the LED you are using and look up the max forward current.

Be sure to check both the red and the green.

 

It's deja vu all over again. Guess you didn't see my post #23.

Yes, you are right. I am a little slow today.

 

I have forgotten one detail. Although i think it is not a detail.
Every output of the alarmsystem should control two bicolor leds.

I want to make 2 controlpanels with visualisationleds, on for every floor.
so that would mean that i need to control two circuits with a bicolor led.

Is this possible?

 

I don't understand anymore what i should choose,
when i use the circuit with the relay, someone said that this is a shame because the relay would cost so much
whith the passive circuit with only resistors i will have to much power dissipation in the resistors?
what should i do?

I hear that.....I thought I was beginning to understand LEDs, till this thread came along.????

 

Sure, it's possible. But I think you need to take a step back and look at the big picture here for a moment.

Forget about the LEDs for the moment. You've got two control panels. How do they communicate so that whatever is done on one is reflected on the other? This may not impact how the LEDs are handled, but sometimes how other parts of a system are done opens possibilities that can be exploited.

Are the LEDs that are controlled by a panel located at the panel, or off at some other part of the building?

At one point you said that you had four systems and that each system needed to control 12 to 16 LEDs. Does this mean four systems in four different buildings that are copies of the same design but otherwise have nothing to do with each other? Are you now saying that each system will have two control panels and each control panel will control 12 to 16 LEDs?

You had also mentioned the possibility of transitioning from 12V to 24V at some point.

The 12V supply that you are using now (or planning to use), what is it's current rating and how much current does the alarm panel itself consume? The point here is to estimate how much current you have available to run your LEDs.

I would strongly recommend incorporating a voltage regulator into this design and stepping the voltage down to 5V or even 3.3V. A suitable regulator doesn't cost much more than a transistor and is about the same size.

 

yes lets make a resume:

i have four alarmpanels, each alarm panel is located in a different building and will be working separately from each other.
on each panel i need to connect 2 remote panels with each 12 leds, one of the four panels wil controll two remote panels with each 16 leds.
on the aux connectors of the alarmpanel I have 12VDC 600mA
the remote panels will be placed at a distance of about 25 to 50meters away from the alarmpanel and i would like to connect them with a multicalble SVV 16x0,8
I have never spoken of 24V power supply, that was only suggested in some of the given circuits. I have only 12VDC available at the alarmpanel

 

yes lets make a resume:

i have four alarmpanels, each alarm panel is located in a different building and will be working separately from each other.
on each panel i need to connect 2 remote panels with each 12 leds, one of the four panels wil controll two remote panels with each 16 leds.
on the aux connectors of the alarmpanel I have 12VDC 600mA
the remote panels will be placed at a distance of about 25 to 50meters away from the alarmpanel and i would like to connect them with a multicalble SVV 16x0,8

Okay, so it would appear that our constraints are wanting to power 16 LEDs with a supply that can deliver a max of 600mA at 12VDC. Is it safe to assume that the aux connectors will ONLY be powering the LED circuits and nothing else?

Assuming that, then each circuit can only be given a budget of about 35mA to work with. As you saw from the numbers being thrown around, that is going to be hard to do with the three-resistor topology, at least from a 12V supply. But until I look at things a bit closer, I'm not positive that dropping the supply voltage would reduce the total current draw that much -- or at least enough. If you were really wedded to that topology (and there really isn't a compelling reason to be), then you could use a DC-DC converter to step down to 5V and that would probably about double your current budget, where using a linear regular, while simple and cheap, would not. But you can get a switcher from Digi-Key for under $5.

But at this point I'd recommend just going with a relay. I'm sure a couple people put up schematics earlier in the thread, but here's one I just threw together so we have it handy here:

You can get a small relay for under $5 (again, single-quantity Digi-Key prices). If you have any kind of an electronics surplus store (and some DO still exist), you can probably beat that price by a factor of two or more.

I'm pretty sure I asked at one point, but don't think I saw an answer. What kind of budget are you thinking in terms of for the LED portion of the project? Also, how are the LEDs and any other components going to be mounted? On a custom PCB?

I have never spoken of 24V power supply, that was only suggested in some of the given circuits. I have only 12VDC available at the alarmpanel

This is the post I was referring to:

http://forum.allaboutcircuits.com/showpost.php?p=635463&postcount=37

But I'll assume that the 24VDC thing is off the table, which simplifies things.

 

I also think that the circuit with a relay is the most simpel solution for my problem, but this will have to say that i need to control 2 relays for each output of my alarmsystem.
two different panels with the same leds

that means in three of the four cases 2 times 13 relays
in the last case that would mean 2 times 21 relays


i see that the relays that i have here consume about 33.33mA
so that would mean that al the relays together would consume
in one case a total of 26x33.33 = 866.58 mA
in the other case 42x33.33mA=1399.89 mA

and that is only for powering the relays, then we also have the leds who need power.

I think i wil have to use an extra powersupply. I have an power supply 12VDC who can give 3amp.

 

the budget is for me not the most important issue.
it needs to be working good and stabel and not to complicated to make.

 

Does each remote panel have it's own auxillary output, or just the main panel that is controlling the other two?

How many relays do you presently have? If you only have a few, then go ahead and purchase relays that draw less current. The ones I was referring to in Digi-Key consume less than 10mA.

If you only have one aux output per system, then you would need to get the current per LED circuit down to 600mA/(2*16) = 18.75mA. With 10mA relay coils and 8mA LEDs, you are there.

 

at this moment is can purchase what i want
i have just ordered a couple of components so i can do some test
I've orderded them online by conrad.
have you got a tecnical or an ordernummer of these relays?

if the 600mA is not enough for making it work i can Always place an extra power supply.

the remote panels, that is just a plate in pvc with a layout of the building in this plate i will make some wholes to place the bicolor leds .
so it is only the main alarmpanal who has an power supply of 600mA 12VDC