Create a multi lamp circuit. One DC source. One switch per lamp. One lamp at a time only

Thread Starter

BSingle

Joined Mar 16, 2022
29
Just joined. Found a reply for a question over 1 yr ago for a similar problem. Was suggested I create a new post. I need a circuit for the following which I think I can create with relays but prefer not to use them. Using one low voltage (9v likely) source I will have 3 LEDs each with its own switch. Example L1, L2, L3. If any one is of these switches closes and its LED illuminates, the other 2 must cut out - can not come on. So if L2 lights, then circuits for L3 and L1 are broken. I found a similar solution in this YouTube link:
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The problem here is that when a second light switch is triggered, it can't power up but this config. also kills power to the one that is on. I need the illuminated one to stay on until it is reset. I could wire the Illuminated one to power relays to the other 2 and physically switch them off but this is too complex. Would prefer switches and circuitry if possible.

Thanks in advance
Brewster
 

dl324

Joined Mar 30, 2015
14,480
Welcome to AAC!
Using one low voltage (9v likely) source I will have 3 LEDs each with its own switch. Example L1, L2, L3. If any one is of these switches closes and its LED illuminates, the other 2 must cut out - can not come on. So if L2 lights, then circuits for L3 and L1 are broken.
The circuit I posted in this thread should do what you want. You need to remove the unneeded flip flop, replace the 3 input OR with 2 input OR, change the power supply to 9V, and add transistors to drive your LEDs.

Schematic from the referenced post:
1647467837017.png
 

crutschow

Joined Mar 14, 2008
29,818
Below is the LTspice simulation of a circuit using one AND gate package and one NOR gate package to provide the desired lockout.
The first light will stay on, independent of what the others do.
That light must be turned off (which I assume is what you meant by "reset") before either of the others can be lit.

The outputs can be used to drive an NPN transistor or N-MOSFET to control the LEDs.

1647471373657.png
 

MrSalts

Joined Apr 2, 2020
1,762
So, are you asking l
- if the switch is off, the bulb is off
- only one can be on at a time max (the one turned on most recently).
 

AnalogKid

Joined Aug 1, 2013
10,065
To the TS: I find the video to be confusing to the point of uselessness. A radio button circuit is very straightforward - press a button, its light latches on and all other lights go out. Release the button and the light stays on. Press another button and the lights change. If that is what you want, then toggle switches as the video will not work for you.

What do you mean by "switch"? There are many different kinds, and the exact switch type determines if a normal radio button circuit will work for you, of if you need a more complex logical structure.

Momentary or not - ?

SPST, SPDT, other - ?

ak
 
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Ya’akov

Joined Jan 27, 2019
5,670
I agree with AK. We need to know the type of switch (momentary or latching, single- or multi-pole).
I don’t think the TS is intending to specify the switch. He just wants the function. I am afraid, based on the “relays are too complicated” he is hoping that some clever wiring arrangement will make this happen rather than needing something that can store state.

This is just surmise, but hey, here at AAC it is the number two hobby among the denizens.
 

Alec_t

Joined Sep 17, 2013
12,818
I don’t think the TS is intending to specify the switch. He just wants the function. I am afraid, based on the “relays are too complicated” he is hoping that some clever wiring arrangement will make this happen rather than needing something that can store state.
+1 on the surmise. I surmise that the three switches will be some way apart from each other (a la game-show use). If it weren't for that (and the 1 switch per lamp spec) then a single SP3T switch would do the job.
 

Ya’akov

Joined Jan 27, 2019
5,670
Thinking about it, three relays, one per switch/lamp, switch energizes its relay, the coil low rail in series on the NC contact, and power for both the respective relay and the corresponding lamp on the NO contact. When you throw your switch it energizes the relay which then latches that relay and disables the others. Reset would be a NC momentary on the high rail which would drop the relay when pressed, and you start all over.

It actually seems pretty simple. Did I miss something there?
 

MrSalts

Joined Apr 2, 2020
1,762
Thinking about it, three relays, one per switch/lamp, switch energizes its relay, the coil low rail in series on the NC contact, and power for both the respective relay and the corresponding lamp on the NO contact. When you throw your switch it energizes the relay which then latches that relay and disables the others. Reset would be a NC momentary on the high rail which would drop the relay when pressed, and you start all over.

It actually seems pretty simple. Did I miss something there?
Of all,the things the TS did specify was, NO RELAYs.
I can create with relays but prefer not to use them.
But redefining the OPs question seems to be the new way to solve a difficult problem - even if the OP specifically doesn't want that.
 

MisterBill2

Joined Jan 23, 2018
11,913
OK, here is one idea BUT with qualifiers: If any one switch turns on, that light stays on and the others do not light, BUT the that switch must switch off before another can light. So if a second switch is operated then one light would switch off and another light. But maybe not. The first concept is just SPDT toggle switches, power to the #1wiper, one side to light#1, other side to wiper of switch #2, one side to light #2, other side to wiper of switch #3, one side to light #3 Only one light at a time, probably not what the TS wants, even though it meets the spec. No relays, no ICs, but it meets the requirement. Can't get any simper, either. Rather sequence sensitive, though..
 
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