12V DC Motor in Light Fixture with Dimmer & 12V DC to 110V AC Inverter 4

[CB333]

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=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

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!

 

[TugboatEng]

Modern power supplies can often accommodate a wide range of input voltages. If you were to use a 110 to 12 volt power supply, it might not be sensitive to the changes in voltage created by the dimmer switch. If your power supply has a good filter, it will be even less effective by dimmer switch. Dimmers don't reduce the peak voltage, they only reduce the average voltage.

 

[waross]

Self contradictory? Let me count the ways.

It is unusual to see such a high DC frequency.
DC frequency is most often zero.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[3DDave]

The sellers note:

*Attention: The applicable voltage of this motor is DC 12V, using AC power supply, the motor does NOT work; too high voltage will burn the motor.If you can't judge whether your power supply is AC or DC, and you have any questions about the voltage, please ask the custcome service before buying the motor.

What is "custcome service"?

My guess, they are juicing the search engines to get clicks by adding the frequency and "synchronous" to their listings, which also appear on ebay and Walmart, and many, many others.

I won't include a link to their website but the first image I was presented with was a tiny motor to use as a tablesaw with a blade on one end of the shaft and a drill chuck on the other end. Maybe they make great motors, but their advertising is nuts.

Edit:

More nuts than I thought. I think they are running some sort of scam.

Here's the text from one listing on the company home site:

High Quality Synchronous Motor TYC-50 AC 110V 0.8-36RPM Brushless Motor Long Life

Fine-tuned acoustics for clarity, breadth and balance
Streamlined design for a custom-fit
Durable and foldable so you can take them on-the-go
ake calls and control music with RemoteTalk cable

I suspect they change the product but keep the reviews.

 

[BrianPetersen]

There is no such thing as a "synchronous" motor powered by DC. And how the heck is something simultaneously "12V DC" and "50/60 Hz"? There is no such thing as DC power that has a frequency.

I don't know what the eff is inside that little enclosure, but it isn't what the label says is inside it, and it isn't what the ad says it is.

I would strongly suggest that you have separate power supply to the motor (not fed through the dimmer switch) and to the lights (dumb resistive load). If you insist on using that particular motor, I would suggest that you get one in hand and do some testing on it before you commit to a circuit design. See what happens if you put 12 volts DC to it (jumper cables to a car battery). If it really is a "synchronous" motor, thus expecting AC input, I suspect the motor will stay put and let out heat and smoke. Maybe even fire. Might be spectacular. I have an old electric lawnmower that let out smoke and stink a couple months ago. I should take it apart to see what it looks like (and smells like). Doesn't work no more. (Popped the circuit breaker before setting anything on fire)

I don't know if you've seen the waveform that comes out of a dimmer switch, but it is not pretty. Very, very choppy and loaded with harmonics. Resistive loads like incandescent lamps won't care about the nasty waveform. I've never tried using a motor on such power.

 

[waross]

After checking on 12 VDC operation;
Look for a 12 Volt power supply that will accept the highest input voltage you can find. (the grammer is a little mixed up but you know what I mean)
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.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[TugboatEng]

I was referring to the diac+triac type dimmer. I don't know if there are more modern options. I built a bunch of these to control universal motors for window wipers. They worked ok but were much better than the rheostat controllers supplied by the OEM. This style of dimmer still passes peak voltage, it just clips out part of the sine wave. An AC to DC power supply with sufficient filter shouldn't be affected by this clipping for such a small load.

 

[waross]

I think that our thinking more or less aligns, Tug.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[TugboatEng]

The stars do align.

I had a confusing situation recently where I had a boat with a DC 32 volt to 12 volt converter. I was confused because the highest DC voltage on the boat was 24V. After digging through datasheets, I found that the converter's max nominal input voltage was 32 but it could operate on a wide range of voltages below that, including 24v, and still be able to output 12 volts.

 

[CB333]

@TugboatEng and @waross thanks for your informative responses. You both touched on a few things such as "power supply filter", "diode bridge", "capacitor". I have to make sure any parts I get are UL approved and/or when this light is finished it will pass a UL inspection and need to be conscious of this with what I do. Any chance you could elaborate a bit more on what I can potentially do here?

One idea that I floated was to add a rectification stage input to the power converter to store the input energy on a capacitor for the 12Vdc output converter. Any thoughts on this? Not sure if this would pose a problem with UL certification. Would really appreciate any advice or suggestions.

Also, I added a diagram just to show with a bit more clarity what I'm trying to do. Thanks for looking!

 

[CB333]

Having trouble uploading the .png file that has my diagram on it. Hopefully it worked this time.

 

[3DDave]

Use the image button. If that button isn't working, allow Javacript to run for this forum.

 

[waross]

Something like this.
Look for a device that is approved as a component.
Approvals of unapproved components may be extremely difficult.
I suggest buying a converter and trying it to see how it will work behind a dimmer and how low you may set the dimmer before the output fails to drive the motor.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[waross]

Worst case, many ceiling fans have a light included.
These are typically three wire devices.
If, after several fails with various converters, you may have to add a third wire.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[CB333]

@waross thanks for the info. I'm still a bit worried what will happen to the motor since it will be on a the dimmer. Do you think it will damage the motor?

 

[zlatkodo]

Read the product description before you buy that junk.
BTW, this kind of post doesn't belong on electrical engineering. It's more suited for a hobby forum.

 

[TugboatEng]

The motor won't be on the dimmer. The motor will be on the power supply. The power supply is on the dimmer.

 

[waross]

With the power supply on the dimmer, and with a chopping dimmer, the power supply should output 12 VDC even as the input is dimmed.
It depends on both the waveform of the dimmer and the internal circuitry of the power supply, as to how far the AC voltage may be dimmed before the motor voltage drops.
A higher wattage power supply may hold up the output voltage under the motor load at lower levels of dimming.
My suggestion is to buy one (or two or three) power supplies and a generic dimmer and try some tests.
You may also be well to try several different brands of dimmers. (Different manufacturers, not the same dimmer with a different name slapped on by a reseller)

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[OperaHouse]

I remember hearing of a company that used a 100A power supply just to power a single relay so it wouldn't drop out with short line dropouts. The concept is the same of getting a converter with enough internal capacitance. Are these lights LED? Those typically have a higher voltage they start out with giving converter a longer on cycle.

 

[CB333]

Thanks for letting me know that concept. Yes, they are LED.