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-   -   [offtopic] need it for a led lamp. (https://www.diyaudio.com/forums/power-supplies/343689-offtopic-led-lamp.html)

e3k 8th October 2019 08:25 PM

[offtopic] need it for a led lamp.
 
i upgraded to LEDs last year. i did know that the light can be bit shaky due to AC/DC conversion.


the lamp has a module of questionable origin with parameters on the output 700mA 34-47V.


is there some other power supply with more stable Voltage you could recommend me?


I am thinking right now about to dismantle some old audio PS and to use it there. :geezer:

ubergeeknz 9th October 2019 06:51 PM

LEDs are current driven devices. You want to limit current and not worry too much about the exact voltage (as the required voltage varies).

e3k 9th October 2019 07:25 PM

well in my opinion you want to have a stable power supply. the wire based bulbs stabilize the light output trough inertia of the heat of the wire.


leds in oposite are able to emit changes in the electrical signal much more quicker.


that is why you need a really calm machine. a battery would be ideal.

ubergeeknz 9th October 2019 07:30 PM

LEDs require a stable current source. A small change in voltage through an LED equates to a large change in current. Yes it needs to be stable but it needs to have stable current, not a fixed voltage.

e3k 9th October 2019 07:33 PM

Quote:

Originally Posted by ubergeeknz (https://www.diyaudio.com/forums/power-supplies/343689-offtopic-led-lamp-post5939283.html#post5939283)
LEDs require a stable current source. A small change in voltage through an LED equates to a large change in current. Yes it needs to be stable but it needs to have stable current, not a fixed voltage.

i have only a voltmeter to measure it.
this is how it looks like. i mean just from the visual observation you might think this is cheap shaky China: power supply for a led lamp - Album on Imgur

ubergeeknz 9th October 2019 07:37 PM

What you can do is find the nominal voltage for the LED cob, use a fixed DC supply, then you calculate a suitable ballast resistor to limit current to the desired level.

Probably (I didn't look) the cheap supply is not producing DC but chopping line frequency.

e3k 9th October 2019 07:53 PM

i measured now the voltage when turned on and shining. 51,5V.
did not manage the Amperes as am not sure about the settings of the device.

ubergeeknz 9th October 2019 07:55 PM

Your meter have a current setting? I would measure that, then you have a good starting point.

ubergeeknz 9th October 2019 07:56 PM

Just to make sure as I don't know your level of knowledge - current reading needs to be done in series ie. You will need to break the connection.

e3k 9th October 2019 07:57 PM

Quote:

Originally Posted by ubergeeknz (https://www.diyaudio.com/forums/power-supplies/343689-offtopic-led-lamp-post5939310.html#post5939310)
Your meter have a current setting? I would measure that, then you have a good starting point.

my meter has but i am have no practice with this. you have to switch the red cable from position mA to 10A... further the lamp blinked once i was measuring i don't want to screw things up.


what exactly should i setup on the meter to measure ~700mA?


-add yes i have done it in series that was ok...


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