12V DC Motor in Light Fixture with Dimmer & 12V DC to 110V AC Inverter

[CB33]

I have a question regarding a light fixture I'm building that also has a motor in it. It has geometric shapes that spin slowly around the light (almost like a mobile) and this is what I'm using the motor for. The light fixture will be attached to the ceiling like any normal light fixture or chandelier and I want to use a light switch on the wall to be able to turn it on and off. The light bulbs will be powered by 110V AC. The 12V Synchronous DC motor will be powered by 12V DC. I am using an Inverter which is 12 Volt DC To 110 Volt AC which will be able to accommodate turning both the motor and bulbs on with a flick of the light switch on the wall.

The question I have is in regards to a dimmer switch. I want to use a dimmer switch to be able to make the lights brighter or dimmer. However, because the motor is also being controlled by the dimmer switch I want to know if this will be a problem and what will happen. Will it slow down the rotation? Will It damage the motor? If it will pose a problem are there any simple solutions or work arounds? I haven't purchased the dimmer switch yet. Is there a certain type that will work with this or a certain type that won't?

Just to clarify why I'm going about it this way. Initially I was just going to use an AC 110 V motor so it would all be on AC. The problem was getting UL approval because of the motor. Because I'm using a 12 V DC motor instead it is kind of a loophole for me so I can get UL approval without all the headaches. Using a 12V DC motor will not be a safety concern in terms of UL certification.

The motor I'm using is a 12V Synchronous DC geared 1 RPM motor. It's just a simple one you can buy on Amazon and I'll post the link to it: https://www.amazon.ca/gp/product/B07YFJR62T/ref=pp...

Also, on a side note I'm not sure what inverter I should use for this project. The choice is between a constant current inverter/driver vs constant voltage inverter/driver. I'm not sure which one to use here.

Any insights would be greatly appreciated. Thanks!

 

[berkeman]

Welcome to PF.

First and foremost, thank you for saying that you are submitting this to UL for approval. That is an important consideration for AC Mains projects.

I'm confused though, when you mention you have 110Vrms going to the fixture but are adding a 12Vdc to 110Vrms inverter. Why are you needing to do that?

Also, what kind of lights? Probably not incandescent, so LED or Halogen or other? LED lights can be purchased with built-in dimming capability.

 

[CB33]

Welcome to PF.

First and foremost, thank you for saying that you are submitting this to UL for approval. That is an important consideration for AC Mains projects.

I'm confused though, when you mention you have 110Vrms going to the fixture but are adding a 12Vdc to 110Vrms inverter. Why are you needing to do that?

Also, what kind of lights? Probably not incandescent, so LED or Halogen or other? LED lights can be purchased with built-in dimming capability.

Thanks for your reply. I wrote about that in the post. I'll just put that part in quotes below and than elaborate on it:

"Just to clarify why I'm going about it this way. Initially I was just going to use an AC 110 V motor so it would all be on AC. The problem was getting UL approval because of the motor. Because I'm using a 12 V DC motor instead it is kind of a loophole for me so I can get UL approval without all the headaches. Using a 12V DC motor will not be a safety concern in terms of UL certification."

Just to sum it up, because I'm using the 12V DC motor I won't have the problems I would have getting UL certification (it gets tricky getting UL certified with an AC motor). From a UL certification safety standpoint, the motor won't be an electrical hazard if it's 12V DC but it will if it's on 110V AC. In terms of UL certification they basically don't care if the motor is running on 12V and it will pass certification this way. However, because I'm using a 12V DC motor, and want my bulbs and light fixture to be a normal one with standard bulbs I now need the inverter for the 110V AC. This will allow me to use normal light bulbs in the fixture. I will just be using LEDs. I didn't want to use special low wattage bulbs for this light so using the inverter allows for this as opposed to just keeping the whole light and motor on 12V. Hope this clarifies this a bit further.

 

[berkeman]

Where does this 12Vdc come from?

 

[CB33]

Where does this 12Vdc come from?

Sorry, I don't know what you mean where it comes from? I can send you a specific link to the product I'm using to convert 12V to 110V. https://lightsandparts.com/products/veroboard-12v-1a-12w-non-dimmable-led-driver-vbd-012-012nd

 

[berkeman]

Sorry, I don't know what you mean where it comes from? I can send you a specific link to the product I'm using to convert 12V to 110V. https://lightsandparts.com/products/veroboard-12v-1a-12w-non-dimmable-led-driver-vbd-012-012nd

That looks like a 110Vrms input, 12Vdc output (AC-DC converter) to drive non-dimmable LEDs (with series current limiting resistors maybe). It does not appear to be any 12Vdc to 110Vrms inverter device.

Okay, maybe you could upload a sketch of what you are trying to do? Use the "Attach files" link below the Edit window to upload a PDF or JPEG file with your sketch.

Initially it sounds like your product would be installed in existing 110Vrms areas. If you could get the 110Vrms motor approved easily, the whole fixture would run off of room 110Vrms AC Mains supply. But because using a 12Vdc motor simplifies UL approval, somehow you are turning the room AC Mains 110Vrms into 12Vdc (with that LED driver module?) for the motor.

And were you asking about using an SCR/PWM 110Vrms dimming module to PWM the AC Mains input to that LED driver module? I don't think that would be compatible with that AC/DC converter module. At the very least, there could be some stability issues.

This is all very confusing for me (and likely for others)... Hopefully your sketch will help clarify things. Thanks.

 

[CB33]

That looks like a 110Vrms input, 12Vdc output (AC-DC converter) to drive non-dimmable LEDs (with series current limiting resistors maybe). It does not appear to be any 12Vdc to 110Vrms inverter device.

Okay, maybe you could upload a sketch of what you are trying to do? Use the "Attach files" link below the Edit window to upload a PDF or JPEG file with your sketch.

Initially it sounds like your product would be installed in existing 110Vrms areas. If you could get the 110Vrms motor approved easily, the whole fixture would run off of room 110Vrms AC Mains supply. But because using a 12Vdc motor simplifies UL approval, somehow you are turning the room AC Mains 110Vrms into 12Vdc (with that LED driver module?) for the motor.

And were you asking about using an SCR/PWM 110Vrms dimming module to PWM the AC Mains input to that LED driver module? I don't think that would be compatible with that AC/DC converter module. At the very least, there could be some stability issues.

This is all very confusing for me (and likely for others)... Hopefully your sketch will help clarify things. Thanks.

Thanks very much for your informative response. For the most part I think you understand what it is I'm trying to do. I don't want an SCR/PWM module. I don't really care about controlling the motor speed as this is not may intention at all. It's a 1 rpm motor and I'd like it to stay at this speed or if it goes less than 1 rpm I don't mind mind that also.

The main issue here is this light is being installed in a dining room which has a dimmer like most dining rooms have and typically run on 110V AC. The main purpose in the case of this light or likewise any dining room light with a dimmer is to be able to dim the lights or make them brighter. I don't care at all about controlling the motor speed but it just so happens that the light switch connected to this light will have a dimmer (I can get any dimmer though and install whatever I like). I'm worried how the dimmer will affect the motor in this light.

Because it's in a dining room house it's not like I can just run a separate power cord from the motor and plug it into a wall outlet. This would not be aesthetically pleasing or appropriate for a house. I want to know if the 12V DC gear motor (not a synchronous motor) will get damaged here with this setup? If so, is there any solutions to keep this setup and find out a way to do this without damaging the motor. I've attached a diagram of what I'm trying to do. Thanks for looking.

 

[berkeman]

The diagram helps a lot, thanks. So basically you want a 110Vrms/12Vdc converter that is well behaved while the 110Vrms duty cycle is varied by a typical SCR/PWM dimmer switch. Ideally, the 12Vdc output would remain steady over some PWM range, say 100% to 25%, and the 12Vdc would drop to 0Vdc below that to just smoothly stop the motor and mobile motion.

What is the power input spec for the 12Vdc motor? It's probably a pretty low power motor, if all it has to do is turn a suspended mobile sculpture. If it weren't for the UL approval issue, it would be pretty easy to add a rectification stage input to the power converter to store the input energy on a capacitor for the 12Vdc output converter.

But to keep it all easy to submit to UL, you need to find an AC-DC converter module that can handle low input duty cycle 110Vrms power and still maintain the 12Vdc output at your required motor current. Ideally this module would already have a good size input capacitor inside its input rectifier circuit, to hold up the input voltage across the lower duty cycle waveforms. And ideally, the converter would have some smooth shutdown circuit to turn off the output 12Vdc when the input power drops too low.

Have you had any luck looking for such modules? I doubt that the LED driver module that you showed in your earlier link can do all of that.

 

[CB33]

The diagram helps a lot, thanks. So basically you want a 110Vrms/12Vdc converter that is well behaved while the 110Vrms duty cycle is varied by a typical SCR/PWM dimmer switch. Ideally, the 12Vdc output would remain steady over some PWM range, say 100% to 25%, and the 12Vdc would drop to 0Vdc below that to just smoothly stop the motor and mobile motion.

What is the power input spec for the 12Vdc motor? It's probably a pretty low power motor, if all it has to do is turn a suspended mobile sculpture. If it weren't for the UL approval issue, it would be pretty easy to add a rectification stage input to the power converter to store the input energy on a capacitor for the 12Vdc output converter.

But to keep it all easy to submit to UL, you need to find an AC-DC converter module that can handle low input duty cycle 110Vrms power and still maintain the 12Vdc output at your required motor current. Ideally this module would already have a good size input capacitor inside its input rectifier circuit, to hold up the input voltage across the lower duty cycle waveforms. And ideally, the converter would have some smooth shutdown circuit to turn off the output 12Vdc when the input power drops too low.

Have you had any luck looking for such modules? I doubt that the LED driver module that you showed in your earlier link can do all of that.

"So basically you want a 110Vrms/12Vdc converter that is well behaved while the 110Vrms duty cycle is varied by a typical SCR/PWM dimmer switch. Ideally, the 12Vdc output would remain steady over some PWM range, say 100% to 25%, and the 12Vdc would drop to 0Vdc below that to just smoothly stop the motor and mobile motion." Yes, this is correct.

"What is the power input spec for the 12Vdc motor?". 4 Watts

"Have you had any luck looking for such modules?" I have not. I'm not sure how to even go about finding an AC-DC converter module such as this. One of the reasons I chose the LED driver module that I did was because it was the smallest one I could find that would work for me and it is already UL approved which is also what I need. I specifically want something small since I have to incorporate this into the design of the light fixture and I'm kind of hiding it within the fixture.

 

[berkeman]

Have you looked at the "Smart Home" type of light fixtures? They typically will not need a traditional SCR type dimming module, since the dimming will be done in the fixture itself with communication with the light switch/dial on the wall. Those would just have regular 110Vrms power connected to them, with some sort of powerline or RF communication to control the dimming and on/off.

 

[CB33]

Have you looked at the "Smart Home" type of light fixtures? They typically will not need a traditional SCR type dimming module, since the dimming will be done in the fixture itself with communication with the light switch/dial on the wall. Those would just have regular 110Vrms power connected to them, with some sort of powerline or RF communication to control the dimming and on/off.

That's interesting. I should research that a bit further.

On your previous post you mentioned: "If it weren't for the UL approval issue, it would be pretty easy to add a rectification stage input to the power converter to store the input energy on a capacitor for the 12Vdc output converter." Would it be impossible to get UL approval using this method?

Someone else mentioned to do the following:
"Look for a 12 Volt power supply that will accept the highest input voltage you can find. Feed the power supply from the incoming AC with a diode bridge and possibly a capacitor. You may have to use a voltage divider or small transformer to get the voltage down to what your power supply can accept. If you fed the voltage regulator with about 50 Volts, you will have 12 Volts down to about 25% dimming. Depending on the wave form, it may be even better than that."

I honestly don't know as it goes over my head quite a bit but open to suggestions.

 

[berkeman]

Someone else mentioned to do the following:
"Look for a 12 Volt power supply that will accept the highest input voltage you can find. Feed the power supply from the incoming AC with a diode bridge and possibly a capacitor. You may have to use a voltage divider or small transformer to get the voltage down to what your power supply can accept. If you fed the voltage regulator with about 50 Volts, you will have 12 Volts down to about 25% dimming. Depending on the wave form, it may be even better than that."

I honestly don't know as it goes over my head quite a bit but open to suggestions.

Where is that from? Since it does not have a quote box around it, I'm guessing it's from a different discussion forum thread? It does not make good sense to me without any other context.

On your previous post you mentioned: "If it weren't for the UL approval issue, it would be pretty easy to add a rectification stage input to the power converter to store the input energy on a capacitor for the 12Vdc output converter." Would it be impossible to get UL approval using this method?

So if you were designing this whole system from the ground up, you would put an energy storage stage between the 110Vrms input and the switching power supply circuit that generates your 12V. Most off-line switching power supplies will not operate with too low of an input supply of energy, but if you design or choose your power supply to do it, you could have it still supply an output 12Vdc with a low input power waveform PWM % and a low enough output power demand (like your light DC motor load requirement).

But using a large off-line AC-DC power supply to satisfy this requirement will be expensive and overkill, so not likely a good solution for you. Doing it in a custom way like I mentioned would likely be the least expensive way to do it, but I'll have to think about the UL approval issues involved.

Would running two different 110Vrms circuits to your fixture be an option? One would be SCR/PWM controlled for dimming the lights, and the other would be a straight ON/OFF switched circuit to power the motor.

@Baluncore -- Do you have some ideas on this?

 

[Baluncore]

@Baluncore -- Do you have some ideas on this?

The assumed design constraints make it difficult to see an optimum solution.
The OP's skills will decide the project trajectory.

Post #7 gives a compromise circuit that should work, but that will depend on the dimmer design, for use with LED globes.

How many of these are to be produced?
UL certification suggests a manufacturing run, yet such an agglomeration of available modules is not suited to ongoing production.

 

[Rive]

It has geometric shapes that spin slowly around the light (almost like a mobile) and this is what I'm using the motor for. The light fixture will be attached to the ceiling like any normal light fixture or chandelier and I want to use a light switch on the wall to be able to turn it on and off.

That sounds like a work for a hybrid switch (don't know the exact naming for the thing) made for ceiling fan/lamp combination thingies.
A switch for the fan and a dimmer for the lamp, so no need to mix them.

 

[CB33]

Where is that from? Since it does not have a quote box around it, I'm guessing it's from a different discussion forum thread? It does not make good sense to me without any other context.


So if you were designing this whole system from the ground up, you would put an energy storage stage between the 110Vrms input and the switching power supply circuit that generates your 12V. Most off-line switching power supplies will not operate with too low of an input supply of energy, but if you design or choose your power supply to do it, you could have it still supply an output 12Vdc with a low input power waveform PWM % and a low enough output power demand (like your light DC motor load requirement).

But using a large off-line AC-DC power supply to satisfy this requirement will be expensive and overkill, so not likely a good solution for you. Doing it in a custom way like I mentioned would likely be the least expensive way to do it, but I'll have to think about the UL approval issues involved.

Would running two different 110Vrms circuits to your fixture be an option? One would be SCR/PWM controlled for dimming the lights, and the other would be a straight ON/OFF switched circuit to power the motor.

@Baluncore -- Do you have some ideas on this?

Unfortunately running two 110Vrms circuits isn't an option for me. The intention is that this would be going into already finished homes where the wiring is already finished and the expense of adding another line is not really feasible for most people. I'm trying to come up with another solution for this.

 

[sophiecentaur]

The intention is that this would be going into already finished homes where the wiring is already finished and the expense of adding another line is not really feasible for most people

If this is a ceiling fitting then used the existing mains supply and fit a 12v power supply in the cavity. Motor and lights can be varied with readily available 12V wireless controls. Everything would be dead safe and would need no major adaptation of the house wiring.

 

[berkeman]

If this is a ceiling fitting then used the existing mains supply and fit a 12v power supply in the cavity. Motor and lights can be varied with readily available 12V wireless controls. Everything would be dead safe and would need no major adaptation of the house wiring.

That would work, up until the homeowner went, "I wonder what this dial does on the light/fan control"... (the AC Mains SCR dimming circuit)

 

[Tom.G]

To satisfy UL, local Electrical Code, and the building owners Fire Insurance, please consider something that is not a hard-wired installation.

For instance:
https://www.google.com/search?hl=en&q=screw-in+ceiling+fan+with+light

Cheers,
Tom

 

[Rive]

Unfortunately running two 110Vrms circuits isn't an option for me. The intention is that this would be going into already finished homes where the wiring is already finished and the expense of adding another line is not really feasible for most people. I'm trying to come up with another solution for this.

Then it's just engineering.
Though the really difficult part would be not about circuitry but about the safety and EMI standards, at the end this means you cannot cut corners and has to do all the work and paperwork.

 

[Baluncore]

A controller regulates all features, including dimming. Communication from the controller to the ceiling unit, could be wireless, or over the power line.

Power could be delivered to the ceiling unit continuously, or only when required by the controller. EMI radiated by the dimmer would be reduced.

 

[CB33]

A controller regulates all features, including dimming. Communication from the controller to the ceiling unit, could be wireless, or over the power line.

Power could be delivered to the ceiling unit continuously, or only when required by the controller. EMI radiated by the dimmer would be reduced.

Thanks for your reply. That's a great idea. I was considering putting a wireless dimmer just on the light portion of this and it would be controlled by a remote and would be installed within the ceiling box or within the light fixture itself. Is this what you mean? Just to reiterate the challenge I'm facing is that this is in a finished house and we don't have control with anything before the ceiling box that the light fixture is going to. I realize it makes it more difficult but I can't change the way the house is wired and can't expect the homeowner to incur additional electrical costs and labor to the wiring within there home. I'm trying to find a solution to avoid this.

 

[berkeman]

Well, you only have one option, IMO, and I'm going to close this thread pretty soon because of your constraints. We can help with a lot of questions, but when you overconstrain the problem statement to this level, well, there can be no solution.

You need to find a way to supply 100% duty cycle energy to the fixture when it's turned on, and control the light duty cycle some other way. You cannot fundamentally power your motor mobile with low duty cycle SCR PWM energy unless you invest in the UL approval costs of an energy storage stage.

Thread is closed. *

* If anybody has more to add, including the OP, please send me a PM to request reopening the thread.