electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
That is what we have been discussing, why it says that.
Can you answer my question: do you find it odd for something to say it require DC yet have no way to tell polarity?
Would this work fine on AC?
- Thread starter electrofelon
- Start date
Can you answer my question: do you find it odd for something to say it require DC yet have no way to tell polarity?
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
You have the bulb on hand and can see that its base is symmetrical? Because from the picture, the bottom wedge has a half-cylinder protrusion on the side facing the camera. If the opposite side of the wedge base does not have the protrusion, that's an asymmetry that could be used to enforce polarity.
Cheers, Wayne
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
Yes I have one in my hand. Definitely symmetrical and no markings of any sort.
It's DC. The polarity is +ve on one side and -ve on the other. How else could you describe it?
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Since you have one, could you please try it on DC both ways and on AC and let us know the results?
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
The Topic title asks if 'this' will work fine on AC.
The attached picture shows a bulb, very clearly says that the bulb uses 12V DC. That statement very clearly implies +ve and -ve. But there are _no_ polarity markings on the bulb.
Most every polarized device has clear polarity markings on it. If you zoom in on the picture, you see that the LED emitters have a notch cut out of the corner, intended as a polarity marking.
But the entire bulb does not have a polarity marking. There is nothing on the bulb that informs the user which terminal is +ve and which is -ve.
Thus the question: would this device, specified for 12V DC, function on 12V AC, and if so what problems or issues could be expected.
Hopefully @electrofelon will test and provide us with the results.
-Jonathan
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
Ok but you did not answer my question: I will try again:
Do you find it odd for something to say it requires DC yet have no way to tell polarity?
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
I will be messing with them tomorrow and I will let y'all know!
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
That is actually a great example.
On the left side there are clear polarity markers. I'd expect appropriate terminal markings on the actual hardware.
The controlled rectifiers are drawn with polarity symbols.
On the right side at the input transformer there are no polarity symbols, because AC input is expected.
Once you know what is happening under the hood, you know that this device would not tolerate DC input. The transformer would saturate and draw huge primary current.
Now back to the original post. The device is specified to use DC, everyone agrees on the spec. But the input terminals are not marked for polarity, and we don't have the schematic. The question is how the device will function when driven out of spec.
What is your guess? @electrofelon will be trying it out.
On the left side there are clear polarity markers. I'd expect appropriate terminal markings on the actual hardware.
The controlled rectifiers are drawn with polarity symbols.
On the right side at the input transformer there are no polarity symbols, because AC input is expected.
Once you know what is happening under the hood, you know that this device would not tolerate DC input. The transformer would saturate and draw huge primary current.
Now back to the original post. The device is specified to use DC, everyone agrees on the spec. But the input terminals are not marked for polarity, and we don't have the schematic. The question is how the device will function when driven out of spec.
What is your guess? @electrofelon will be trying it out.
Good man !
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
Again you have not answered my question: I will try a third time:
Do you find it odd for something to say it takes a DC source yet have no indication of polarity on the input terminals?
It's a simple question.
I have shown the polarity with my own fair hands. Can you not see that?
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
You posted a diagram of a 3 phase rectifier system, which clearly shows the polarity of that specific device.
I bet we could post millions of diagrams and pictures of devices which show polarity.
But what is being discussed is the lamp shown in the original post.
Can you
a) identify the terminal polarity markings on that device (maybe there is a really hard to see '+' somewhere, or some subtle difference that none of use are seeing)
or b) post a picture or a diagram of a device which both is polarized and doesn't have a polarity marking? (Maybe there are tons of devices that really should only be used with + on one terminal and - on the other terminal, with no clear identification of which terminal is which.)
In my experience, if polarity is relevant to device operation, that polarity is clearly marked.
In which post did you show the polarity of the lamp in the OP?
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
What I expect:
On DC, correct polarity: On
On DC, reversed polarity: Off
On AC: On (at full brightness)
The very first post is DC. I have shown a diagram which is polarised. Also DC. C'est la vie..........
Wedge base LEDS in theory should hopefully follow compatibility with whatever incandescent lamp they replace;
looking at the spec sheet for the lamp
www.1000bulbs.com
presumably that is designed to replace these incandescent filament lamps;
the originals are just '12 volts' and not polarized, so presumably they can run off AC or DC in any polarity at around 12 volts.
So the LED manufacturer includes low cost bridge rectifier allowing the lamp to be inserted in any DC polarity, but skips the filtering needed to have it run on AC.
looking at the spec sheet for the lamp
LED Wedge Base Bulb- 2 Watt - 2700 Kelvin - Incandescent Match - 140 Lumens - 10 Watt Equal - 12 Volt DC - PLT-300273 | 1000Bulbs.com
Use PLT T10-13SMD5050-27K LED mini wedge base lamps as halogen replacements in your car lighting. Save on LED mini indicator lamps at 1000Bulbs.com!
looking at the specs for a similar T5 Incandescent Landscape Low Voltage Light Bulb
the originals are just '12 volts' and not polarized, so presumably they can run off AC or DC in any polarity at around 12 volts.
So the LED manufacturer includes low cost bridge rectifier allowing the lamp to be inserted in any DC polarity, but skips the filtering needed to have it run on AC.
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
Agreed, the very first post _says_ DC in the text in the image. But nothing that I can see on the device shows polarization of the lamp supply pins.
You posted a diagram of a three phase rectifier system, which is a great example of polarization labeling in a schematic.
Is there anything that you can see _on the picture of the lamp_ that conveys polarization?
What are your guesses for what will happen if DC of the wrong polarity or AC is applied to the _lamp_ shown in the original post?
You posted a diagram of a three phase rectifier system, which is a great example of polarization labeling in a schematic.
Is there anything that you can see _on the picture of the lamp_ that conveys polarization?
What are your guesses for what will happen if DC of the wrong polarity or AC is applied to the _lamp_ shown in the original post?