ESP8266 Community Forum

- Wed Mar 23, 2016 3:36 pm #43899

You're not going to like this but from RFP30N06LE datasheet
1) Absolute Maximum continuous drain current 30A (not 33A)
2) Even with 5V on Gate, at 30A, RdsOn=0.047R
SO using nothing more than Ohms Law, Vds =30A x 0.0.47R = 1.41V
Power=VxI = 1.41x30 = 42.3Watts = smoke + molten mess

With a 1'C/W heatsink you might get away with it but with a 3.3V Gate drive even this huge chunk of Aluminium won't be enough.

Also, what PSU, cable and connectors are you planning on using

again your are giving me a big advise and in same time broke my dreams haha

summery is that i shouldn't go far in Amps , for that do you think is should divide the LED strip in enough length that will be in safe Amps power consumption to drive with a MOSFET- still not selected- and use my Software power by make my boards listing to the same MQTT so they will act together as one maybe with small acceptable delay of some ms.

and the highest Power supply i found that can give up to 50A is this one @ $40

so any suggestion which MOSFET i should use to 3.3V signal from ESP8266 to drive 10 meter LED strip (almost 20 A/3 ≃ 7) without the need of heatsink and package can be TO-220

- Wed Mar 23, 2016 5:42 pm #43902 Yes, this is why I said many posts ago to tackle this in a modular fashion. That's also true for the power supplies. To you Amps may just be numbers, but you should treat them with respect... they are what drive electrical fires. Consider this: Power (Watts) correspond to heat. Watts=I x I x R (current squared times resistance). You know how squares go! If you've never played with long lengths of RGB tape before, I may have more bad news for you... beyond 5m the volt-drop in the tape (I x R) drops enough volts to push the colour towards red (because red has more headroom that green and blue, which both begin to dim down).

So I advise feeding in power every 5m (sometimes the tape has a Y junction at the end to allow this but not often). Also, several 10A PSU's are preferable to one really big one. The risks are much lower. I'm reminded of all the problems rookie RepRappers have with heated print beds - just 10A@12V has been enough to cause fires and ruin PCB's.

I'm so busy telling you all this I will leave you to hunt down the ideal Mosfet. All the info I've given you in this topic so far is all you need. I would only add that you should ignore any Mosfet with a Gate threshold above 2V. This will narrow down your search.

One last suggestion (a repeat of a previous one) consider using a dedicated Mosfet Gate driver chip that runs off the 12V supply and make it pay for itself by parallel driving a bunch of Mosfets as an alternative to using Multiple ESP's and MQTT. This way the Rds on will be as low as possible and you will get the benefit of using cheaper Mosfets. The very low threshold ones are the expensive ones!

- Thu Mar 24, 2016 2:21 am #43916 thanks for all of the information and the advises , that makes every thing clear and the concepts of Driving MOSFETs
and take Power and temperature in the equation.

and as you know that i am still building my knowledge so i am not strong enough to go far and deep in that , an to keep
my self and my home also safe - without any thing catching fire - i am about to use RGB amplifier every 5 Meters , with a separate 10A power supply , as using you more advanced chips like Mosfet Gate driver is need more and more research and once i go there i will found myself need to know more and more - i have that problem - and that's to fare for me in the electronics designing .

so last thing let me know if using the RGB amplifier is good approach or no as it's rated to have maximum 4A per channel
i will only go for 2A per channel and that is enough for 5 meter strip.
in my PCB i will drive directly the MOSFETs with Gate threshold less than or equal to 2V , and with max 2A
and going for less RdsOn i can find

- Thu Mar 24, 2016 6:52 am #43933 I personally think you've made the right decision. You should have no trouble driving your first 5m and then build upon that as you like. I have no experience with the RGB amplifiers you linked to but the principle is certainly sound.