# Switch light on with rotary switch and dimmable LEDs

#### TogetherInElectricDreams

Joined Jan 23, 2019
48
Hi everyone,

I am trying to create a realistic oven for my son's toy kitchen using lights and dials.

User story:
The oven will have two (matching) dials on the front
The first dial will turn on a white light (2 position rotary switch?)
The second will turn on a red LED strip, the strip will start dim and get brighter as the dial (PWM?) is turned.
You can only turn on the red LED strip when the white light is on.

I think I need a two position rotary switch for this and a PWM. What kind of light would I need for the white light? I was hoping for something like a cupboard light rather than another strip? Can I get any light provided I put the wires in the right way?
How do I go about dimming an LED? I've seen stuff about PWMs but I wasn't sure how I would incorporate that into my setting. Not sure if there's an easier way? All advice is appreciated.

#### dl324

Joined Mar 30, 2015
8,954
How do I go about dimming an LED?
How many LEDs are you talking about? What is the supply voltage? What is the total current?

#### TogetherInElectricDreams

Joined Jan 23, 2019
48
How many LEDs are you talking about? What is the supply voltage? What is the total current?
Hi and thank you for replying to me.

Here are the LEDs they say 12V but I can't answer about the current as I don't know the wattage. I am buying 3m but think I'll end up using half of that.

I was thinking of this kind of light for the white oven light. It says 2.5W but it doesn't say the volts.

#### djsfantasi

Joined Apr 11, 2010
5,614
Hi and thank you for replying to me.

Here are the LEDs they say 12V but I can't answer about the current as I don't know the wattage. I am buying 3m but think I'll end up using half of that.

I was thinking of this kind of light for the white oven light. It says 2.5W but it doesn't say the volts.
The “LEDs” that you have linked to aren’t LEDs. It is EL wire, something very different. Also, that product runs on only 3V. In your other thread, you said all of your features run on 12VDC.

The product description of the white light in the link you provided clearly says 12VDC. Hence, the current used is 200mA

If you use the power supply I recommended in the manner I suggested, there are two things you need to be aware of. Everything must run on 12VDC unless you add other circuitry. And secondly, you need to keep a total of the current needed of all the devices and that cannot exceed 5A.

#### Bernard

Joined Aug 7, 2008
5,267
Same page are LED strips, 120 LEDs/ m. 12V, Red, guessing 4 in series or 30 groups for about 300 mA ?
An AND gate will keep red off if white is off. Like putting switches in series, white feeds into red SW.

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#### TogetherInElectricDreams

Joined Jan 23, 2019
48
Same page are LED strips, 120 LEDs/ m. 12V, Red, guessing 4 in series or 30 groups for about 300 mA ?
An AND gate will keep red off if white is off. Like putting switches in series, white feeds into red SW.
Thank you Bernard, sorry but what does that mean in "real" terms? What would I need to buy to make it work? How could I do it using switches or would I need an arduino?

#### TogetherInElectricDreams

Joined Jan 23, 2019
48
The “LEDs” that you have linked to aren’t LEDs. It is EL wire, something very different. Also, that product runs on only 3V. In your other thread, you said all of your features run on 12VDC.

The product description of the white light in the link you provided clearly says 12VDC. Hence, the current used is 200mA

If you use the power supply I recommended in the manner I suggested, there are two things you need to be aware of. Everything must run on 12VDC unless you add other circuitry. And secondly, you need to keep a total of the current needed of all the devices and that cannot exceed 5A.
So in "simple" terms, firstly. Would I need a limiter of some kind? I think you showed me one before. Also in terms of the EL wire, we are working the other way (as in the light uses too much power but the wire uses too little), would the wire burn if we are running everything on 12VDC? I think the best place to start is to just "make" the light out of an EL strip too. If I do that what "other circuitry" do I need and how would I achieve this with "oven knobs?"

#### djsfantasi

Joined Apr 11, 2010
5,614
So in "simple" terms, firstly. Would I need a limiter of some kind? I think you showed me one before. Also in terms of the EL wire, we are working the other way (as in the light uses too much power but the wire uses too little), would the wire burn if we are running everything on 12VDC? I think the best place to start is to just "make" the light out of an EL strip too. If I do that what "other circuitry" do I need and how would I achieve this with "oven knobs?"
I provided a link to a switching converter but here is another one that can convert 12V to 3V. You wire this to your jack switch and wire the output to the EL wire. Cut one of the output leads and wire your control knob in series.

You need the converter because the wire will fail if connected directly to 12V.

The white light you linked to is a 12V device. There is no reason not to use it.

You seem to have a basic misunderstanding of how to wire your devices. There are three important considerations:
1. Voltage must match. If you have a 3V device, it won’t work at 1-1/2V or 12V
2. Polarity must match (with DC). Plus must go to plus; negative or ground must go to negative or ground
3. Current available (from the power supply) must be greater than the current needed. When powering multiple devices. The total current required must be less than the total current available.
Note that in item 3, I state that current available must be greater than current needed. Your devices only draw what they need, so a higher current available is not bad, unlike too much voltage. An 12V Light that needs 200mA can easily run on a 5A supply

#### djsfantasi

Joined Apr 11, 2010
5,614
Oh, and I suspect that you may be disappointed in this appearance of EL wire. It provides a narrow line of light, which may not look like a burner.

As far as dimming and control, dimming EL wire is more difficult than LEDs.

For those reasons, I’d use multiple LEDs for the burner effect as in the photo you posted

You can dim them using PWM from a microprocessor.

#### TogetherInElectricDreams

Joined Jan 23, 2019
48
Oh, and I suspect that you may be disappointed in this appearance of EL wire. It provides a narrow line of light, which may not look like a burner.

As far as dimming and control, dimming EL wire is more difficult than LEDs.

For those reasons, I’d use multiple LEDs for the burner effect as in the photo you posted

You can dim them using PWM from a microprocessor.
Thank you as always for your explanations, yes I do have a basic misunderstanding but I am learning as I go and that's why I appreciate it so much that you take the time to spell it out for me. I was trying to go for a "glowing" look like an oven filament which is why I liked it. I thought it was an LED strip as it's what came up when I searched so when you say multiple LEDs is that the same as a strip? Like in the photo you mean? Where can I see a schematic or a project? I have struggled to find anything online.

#### Bernard

Joined Aug 7, 2008
5,267
Do you have a drawing of the kitchen unit showing arrangement of all of the parts.?
For LED dimming something like 3 AMP DC MOTOR SPEED CONTROLLER CAT# MSC-35, @ US$5.75 from All Electronics. Has speed control pot. with a switch.. Would probably need a different pot for panel mounting TL-50k @$ .85like CAT# .
If at all possible would use gravity feed water supply with small, 8 oz?, reservoirs with 12V pump & level switch.
Old version of PWM speed control from All Electronics.

#### TogetherInElectricDreams

Joined Jan 23, 2019
48
Do you have a drawing of the kitchen unit showing arrangement of all of the parts.?
For LED dimming something like 3 AMP DC MOTOR SPEED CONTROLLER CAT# MSC-35, @ US$5.75 from All Electronics. Has speed control pot. with a switch.. Would probably need a different pot for panel mounting TL-50k @$ .85like CAT# .
If at all possible would use gravity feed water supply with small, 8 oz?, reservoirs with 12V pump & level switch.
View attachment 182335 Old version of PWM speed control from All Electronics.
No I haven't but I will try to make one. Can that dimmer be used for the EL wire I showed earlier?

#### djsfantasi

Joined Apr 11, 2010
5,614
No, it can’t be used for EL wire. Looking at your link, it appears that the wire included an inverter in the plug. EL wire runs in AC, not DC. Normally you just buy the wire and then buy an inverter to drive/light the wire. Dimming it doesn’t work with PWM or a motor controller. You need a circuit to vary the frequency supplied to the wire.

You can purchase 12V LED strip, which has the LEDs and current limiting resisters all on one strip. To make the shape in your picture is a little difficult.

To use individual LEDs, you will need to design series/parallel wiring to connect them to a 12V source.

If you decide to use individual LEDs, I can provide you with s series/parallel wiring design. This construction can be controlled with a PWM or motor controller. You can then mount the potentiometer of the controller on your kitchen facade.

#### TogetherInElectricDreams

Joined Jan 23, 2019
48
No, it can’t be used for EL wire. Looking at your link, it appears that the wire included an inverter in the plug. EL wire runs in AC, not DC. Normally you just buy the wire and then buy an inverter to drive/light the wire. Dimming it doesn’t work with PWM or a motor controller. You need a circuit to vary the frequency supplied to the wire.

You can purchase 12V LED strip, which has the LEDs and current limiting resisters all on one strip. To make the shape in your picture is a little difficult.

To use individual LEDs, you will need to design series/parallel wiring to connect them to a 12V source.

If you decide to use individual LEDs, I can provide you with s series/parallel wiring design. This construction can be controlled with a PWM or motor controller. You can then mount the potentiometer of the controller on your kitchen facade.
I might just stick with an on/off then. You don't really dim ovens anyway that's more a cooker. It would have been fun to do it but if it's not possible I think having the the light glow will be enough so all I would want then is switch one to operate the light then switch 2 only works when switch 1 does, like a real electric oven where you have the settings and temperature.

#### Bernard

Joined Aug 7, 2008
5,267
Equate brightness to temperature, almost every thing is possible.
Wiring individual LEDs is not hard. To see what LEDs look like mounted in drilled holes might look at top of this page " Search Forums ", enter in Key Word box " Buzz Game - Steady Hand .", hit Search. All the way down to post # 90. You can have any number of LEDs in any pattern you desire. Drop by & I'll drill the holes for you.

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#### djsfantasi

Joined Apr 11, 2010
5,614
I might just stick with an on/off then. You don't really dim ovens anyway that's more a cooker. It would have been fun to do it but if it's not possible I think having the the light glow will be enough so all I would want then is switch one to operate the light then switch 2 only works when switch 1 does, like a real electric oven where you have the settings and temperature.
That part with the two switches is pretty easy... When I get back to my laptop, I’ll draw up a schematic showing you how to wire two switches the way you want.

I’ll also draw up a schematic using individual LEDs that you could dim! In case you change your mind.

One thing that has me confused. A real oven has a light, but the heating coils run without the light lit AND the light lights without the heating coils being on. So while I can show you how to light the way you want, I don’t think it’s really realistic.

#### djsfantasi

Joined Apr 11, 2010
5,614
Do you have a drawing of the kitchen unit showing arrangement of all of the parts.?
. . .
If at all possible would use gravity feed water supply with small, 8 oz?, reservoirs with 12V pump & level switch.
You’re late to the party, Bernard!

First, the TS has several threads on this project. Which is confusing because people in one thread suggest things that have been eliminated as a solution in another thread.

This is a work in process. The TS doesn’t have a list of all the parts, never mind an arrangement of all the parts.

Additionally, discussion of gravity feed is a been there, done that scenario. If you missed the point, the TS does NOT want to use gravity feed. Final answer.

We’ve gone through discussions of modules requiring different voltages and the TS is at the point where he can grasp using a single supply voltage for his project. Further discussion requiring multiple modules requiring multiple power supplies will confuse the situation.

I apologize for my tone, but I’ve been involved in all of the TS’ threads and have a global picture of what’s feasible for this particular project.

#### djsfantasi

Joined Apr 11, 2010
5,614
It’s too late for me, but I’ll provide what I promised... It just may take me an extra day (I had a wake today and funeral tomorrow).

This is the story I’m basing my designs on!

“The oven will have two (matching) dials on the front. The first dial will turn on a white light (2 position rotary switch?). The second will turn on a red LED strip, the strip will start dim and get brighter as the dial (PWM?) is turned. You can only turn on the red LED strip when the white light is on.”​

It’s that last sentence I’m confused about. But that’s the way my design will work. I’ll respond as soon as I can.

#### Bernard

Joined Aug 7, 2008
5,267
Some of the " parts" that have been alluded to are: microwave, dishwasher, oven, pump, sink, & stove top. All have not been addressed yet?
Is that two ovens ?

#### djsfantasi

Joined Apr 11, 2010
5,614
Some of the " parts" that have been alluded to are: microwave, dishwasher, oven, pump, sink, & stove top. All have not been addressed yet?
Is that two ovens ?
“Dishwasher”? I missed that feature...

Recovering from the death in the family. We’ll provide a diagram soon.

I do have a moment to verbally describe what I think you need.

The first switch to the oven light is straightforward. One terminal if the switch goes to the power supply. The second is writer to the light. To prevent the “burner” LEDs from lighting unless the first light is lit, instead of wiring the switch to the power supply, wire it the the same output terminal connected to the oven light.

To use individual LEDs for the burner, they have to be wired in groups which are then wired in parallel. Using 12VDC as the supply and red LEDs with of forward voltage if 2V and current draw of 15mA, you can wire five LEDs in series with a 130Ω resistor. Note that the LED maximum current may be 20mA but it’s better to run then with a lower current. Look at the calculations:
R = (12V -5 * 2v) / 0.015A
= 2V / 0.015A
= 133 Ω​

So, depending on how many LEDs you need for the burner, try to design it so the total number is a multiple of 5.

To dim the burner, use a PWM module as suggested about. You can externally mount the potentiometer to use as a switch for the burner. Connect the PWM supply to the oven light switch for the effect you said you wanted. And connect the PWM output to the LEDs.