LED light help needed (booster? converter? relay?)

Status
Not open for further replies.
D

Dave001

Member
So I have a nurse call system that I need to modify. Currently, when a room call is activated the control panel sounds an audible alarm and illuminates a small 2 volt LED. Each patients room has a call button in both the room and bathroom, and it illuminates a different LED on the control panel for room or bathroom. I want to use the power off the 2V LED as a signal/ trigger to illuminate a LED number to the corresponding room (simple 3D printed plastic backlit number). The purpose for this so that you could see from a distance what room has called and not have to walk right up to the control panel.

I have come up with 2 variations for how I could wire this and need some help to go further. The sketch helps to explain alot.

- Each variation needs to use a buck converter? booster? or relay? to go from the 2V input signal to power the LED number which will be 3-6V.

- Are there other options on a control module?



Variation #1

The signal input wires would join to the same terminals on whatever controller I am using. If the room call 2V LED is activated it would also send power back to the bathroom LED, which will send unwanted power back into the control panel and may cause damage. So the signal input wires would need diodes(?) On every wire? Or just the positive wire?

With this setup I would only need to use 1 control module per room, but have to install diodes.



Variation #2

The output wires would terminate on the number LED. If the room call is activated it would also send power back to the bathroom controller. I would also have to install diodes here, or Depending on what controller I am using it may not be needed. For example a 2 pole mini relay? If that exists?

With this setup I would need to use 2 control modules per room, and not need diodes with a relay?

I need to do this for 8 rooms so the amount of work is something that I am keeping in mind.

The large LED room number (#4 in pic below) is not a display of any kind. Its a plastic 3D printed piece with LED's inside of it that light it up.
I will be using an external power supply for these LED numbers, not getting power from the panel itself.

Thanks in advance!!

 
Last edited:
Sort by date Sort by votes
The status panel most likely operates at eg. 12V and has resistors for the LEDs in it, so you may be able to pick up a higher voltage signal for each channel at its terminals, to feed an optocoupler LED via a suitable resistor.

In that case, you could use diodes from the two inputs to the panel for each room, to give a single signal for the optocoupler. You would have to measure the voltages with the alarm / LEDs not triggered and triggered, to figure out which polarity it operates at (switched ground or switched power).


Otherwise, I'd try an optocoupler with the diode connected in series with the system LED and see if that works?
Or, the diode and a resistor connected across the LED.


Use darlington output optocouplers, so they can control a reasonable current while only needing a low input current to activate.

The signal from the optoisolator output could control a MOSFET to switch the large digit display.

You will need a separate power supply to actually run the bank of large displays, you cannot use power from a LED.


Buck or boost converters (or any other power conversion devices) don't create power, they actually loose a few percent of the input power.

If you fed one on place of an LED - if you could get one that worked on such low input power (eg. 2V, 10mA which equals 20mW), the maximum output would be possibly 18mW, so eg. 2mA at 9V or 1mA at 18V.

Power conversions always loose energy in the converter itself, due to inefficiencies.
 
Upvote 0 Downvote
As noted by JRW, you can't power the large number display directly from the LED volage, you will need an external line-powered supply, unless you can tap into the panel power.

It may also be possible to tap into the signal that drives the present LED resistor, which possibly could generate enough current to power the number display directly..

Do you have any info on the panel wiring or schematic?
 
Last edited:
Upvote 0 Downvote
start every design by defining all inputs , outputs then function.

Set LED voltage?
Reset LED voltage?
combine both room sensors or indicate which?
Acceptable display options ??
Decimal ? On LED per room on the ceiling flashing near central hall when active and steady On if Idle so the position of each LED is diode OR'd from the panel and easy to associate by color or flashing and position.
Options: Yellow , Red, Normally off, Normally On , flashing alert
Position of LEDs (8) are obvious to tell which room by some sign or position.

This is the simplest method then 20 mA LED can easily be seen from the end of a hallway . Tiny but bright.

Otherwise with a shared room number display, what happens when there are two alerts. How do you convert by priority encoder the binary input to to Segment display output in both directions. Fancy but no better.

https://tinyurl.com/2mxcy8of after you define all the voltages and Vcc available outputs can be defined.



To me mirroring the display so it is visible, combined (OR) from a distance on the ceiling
sim https://tinyurl.com/2mxcy8of. This is simple yet effective as long as the room number above each LED is visible from a distance. The alternative is to have the LED outside each room.
 
Last edited:
Upvote 0 Downvote
But always decide on all the acceptable options in a design spec 1st. Do not even think how to implement but consider if it is easy or hard.. This is the most common fault of engineers is to think of a logical realization before simplifying the functional spec.
 
Upvote 0 Downvote
How do you turn LEDs off?
Can more than one room call at the same time?
Can room and bathroom call at the same time?
Can you apply a scope to one of the LEDs to check they're not multiplexed?

Mike.
 
Upvote 0 Downvote
Thanks to everyone for all the responses! Pommie rjenkinsgb crutschow Tony Stewart

I made a these updates/ Corrections to the original post:

- Each variation needs to use a buck converter? booster? or relay?
I was under the impression that these were like a electronic adjustable relay. Having clarified that it is just a converter, it is no longer an option.

The large LED room number (#4 in pic) is not a display of any kind. Its a plastic 3D printed piece with LED's inside of it that light it up.
I will be using an external power supply for these LED numbers, not getting power from the panel itself.


I think I may have made it seem more complicated than intended with the first post. Its a simple setup of wanting to use the small 2V LED as a signal (relay activator) to power on a larger LED number. I am just stuck on how to prevent electricity from flowing back to the control panel (as described in the first post.)
 
Upvote 0 Downvote
I assume that the 2 Volts you measured is directly across the LED.

LEDs can be driven either by switching the positive side, or the negative side.

I need to know which it is in your case. Can you find a common ground (negative) point in the panel? Then measure the voltage on each side of the LED both when is lit and when it's not.

Also. Could you take a picture of the back side of the panel?
 
Upvote 0 Downvote
Pommie said:
So, what happens if 4, then 5 call? Do both light up? What should be displayed in this case?

Mike.
Click to expand...

Since each set (room/bathroom) of red signal LED's will have its own independent controller/relay system, you can have any amount of rooms call at the same time, and corresponding large LED numbers will light up.
I have room #4 in the drawing example as one independent system. Every room will need to have such system to not have any conflicts or add to the complexity of the system.
 
Upvote 0 Downvote

Yes the 2V was measured directly across the LED

LEDs can be driven either by switching the positive side, or the negative side
By this you mean one lead has constant power (does not go through a switch), and the other one does go through a switch?

Roger that, I will check and get a pic.
 
Upvote 0 Downvote
Yes. But the switch can be in either the positive lead, or the negative lead.
 
Upvote 0 Downvote
Here's my take on a circuit (sim below) to do what you want, that avoids any concerns about how the LED circuitry is configured, and requires no ground connection between the indicator panel and the number circuitry.
It uses one opto isolator to detect the Room LED and one to detect the Bathroom LED, with outputs paralleled to a MOSFET that drives the number LED.

The circuit detects the signal across either the Room or Bathroom LEDs and lights the corresponding number LED.
(How much current will the number LED require?)

The yellow trace shows when the Room LED is on and the red trace shows when the Bathroom LED is on.
The green trace shows that the number LED is lit when either the Room or Bathroom LED is on.

The number power supply voltage is somewhat arbitrary and can be different if you want.

 
Upvote 0 Downvote
Wow,you are really good at it. wish you guys can make the design reality.
 
Upvote 0 Downvote

You are an intelligent man, and I appreciate your feedback and effort, but after looking at it for some time and trying to understand it all its way beyond my current skill level. In between expanding my business and learning more about CNC, and trying to buy a house, I dont have any more brain space at them moment to be learning something like this...
 
Upvote 0 Downvote
I have been tinkering with my design idea for some time though, and I realized I can simplify the circuitry.

So disregard any need for diodes or anything that I was saying in the past. The system will be much more simple like this and easier to service in the case something stops working. I will keep each circuit as a separate system, avoids any conflicts, easier to build. I now just need help finding a suitable relay that will work with the 2V signal input to power up 3-6V LED number.


Any leads on a suitable relay would be appreciated!!
Preferably an electronic relay so that its not making any clicking noises, if there is such an option.

Thanks in advance!
 
Upvote 0 Downvote
The Vishay VO14642 is a possible solution. I have not used these but remember finding them when looking for opto isolators. If the existing LED on the control uses a resistor or constan current source to limit it's current then the input on these solid state relays could kust be wired in series with the existing LED.
Rather than getting numbered caps engraved you could use 7 sement displays with the segments hard wired to display the required digit.

Les
 
Last edited:
Upvote 0 Downvote
Thank!!
 
Upvote 0 Downvote
Just to make sure I am understanding this correctly:
- My 2V signal input wires would go to 1&2
- 4&6 would be the inline switch going to the LED number
Is that correct?




Also, would this Vishay chip work on a standard breadboard to bridge the gap? Or is it of a different size?
 
Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

I
Need help adding a manual temp-on pushbutton switch to an alexa controlled relay.
Replies
1
Views
402
Les Jones
L
  • Question
Help with boost converter circuit
2
Replies
25
Views
7K
audioguru
D
  • Question
SRD-12VDC-SL-C Relay Module
Replies
3
Views
2K
Tony Stewart
N
  • Question
Light pulse then on
2
Replies
22
Views
6K
danadak
S
  • Question
Help needed for 24V Charging w/ Variable Speed Gen
Replies
10
Views
3K
Roff
Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…