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Topic: LED lamps esp8266 (Read 253 times) previous topic - next topic

gauravntpl

I have to build a pwm controlled led lamp(9watts) using esp8266. I am going to use 9no of 6 volts 1 Watt led in series so the total voltage will be 54 Volts max. Now the question is can I use 60V mosfet without getting it heated as there is only 6 Volts of difference or should I go with higher voltage mosfet?

Also I am having hard time finding mosfets which are easily available.

ammaralroz

Check the mosfet data sheet.
Usually it is mention when do you need the heat sinks.

DVDdoug

#2
Sep 11, 2019, 05:15 pm Last Edit: Sep 11, 2019, 05:16 pm by DVDdoug
Quote
using esp8266.
That's a 3V device, right?   Make sure your MOSFET turns fully-on at 3V, or you'll need a transistor + MOSFET driver circuit.  If the MOSFET doesn't turn fully-on it will overheat.

Quote
I am going to use 9no of 6 volts 1 Watt led in series so the total voltage will be 54 Volts max.
That's "cutting it close".  What's your actual  power supply voltage?     What kind of current limiting are you using?   You need higher voltage for any kind of current limiting to work properly.

Since you didn't mention it, you may not be familiar with how LEDs work.   Like all diodes, LEDs are highly non-linear (their resistance changes drastically with small changes in voltage).    The specified voltage is approximate...  You supply the required current and the voltage "magically falls into place".   But, that means you need "extra" voltage available.   

With small LEDs we use a series resistor to limit/control the current with about half the voltage dropped across the LED and half across the resistor.   "High power" LEDs (1W or more) are typically powered with a constant-current* switchmode power supply.   That's not an easy thing to build yourself. You can use a series resistor but it's inefficient and you need a power resistor to dissipate the power/heat. 

Quote
without getting it heated as there is only 6 Volts of difference or should I go with higher voltage mosfet?
Usually, heat is more related to current.  If you over-voltage a MOSFET or transistor it usually just dies quietly without any heat, smoke or drama.  (Depending on the circuit, there may be some "drama" after  the MOSFET shorts out!  ;) )       




* Or "controlled current" if you are dimming.

Paul__B

I have to build a pwm controlled led lamp(9watts) using esp8266. I am going to use 9no of 6 volts 1 Watt led in series so the total voltage will be 54 Volts max. Now the question is can I use 60V mosfet without getting it heated as there is only 6 Volts of difference or should I go with higher voltage mosfet?
OK, now unfortunately most of that is completely wrong.  :smiley-eek:

Sorry, complete fail at a question to put to the forum here.  :smiley-lol:

The very first thing you must put in a question is the Web link to the parts you propose to use.

While I could be wrong, I am going to point out that there is no such thing as a six Volt 1 Watt LEDs.  You may have some modules which will operate at 6 V and incorporate a resistor to drop the 6 V to the 3.5 or so V that the LED requires in order to regulate the current that it draws, in which case they are clearly the wrong modules for your purpose.

Six white LEDs in series will require something like 20 to 24 V, not 54.  And you have to provide a constant-current driver.  There are two ways of doing this, one is to provide a somewhat higher voltage such as 28 V and use your FET to control the current in which case it will require a moderately large heatsink as it will get hot.

The other way is to use a switchmode current driver designed for the purpose and if you want the ability to dim it as I suspect, then you need a driver with this capability designed in.

Until you reveal what LEDs you had in mind, it is not worthwhile to discuss the project further than this.

Jack_Arsal

I have to build a pwm controlled led lamp(9watts) using esp8266. I am going to use 9no of 6 volts 1 Watt led in series so the total voltage will be 54 Volts max. Now the question is can I use 60V mosfet without getting it heated as there is only 6 Volts of difference or should I go with higher voltage mosfet?

Also I am having hard time finding mosfets which are easily available.
when you use 9no of 6 volts leds in series then there will be definitely a heat due to resistance you must use heat sink. the rating of heat sinker is depend upon the rating of mosfet

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