rsimpson4365
Posts: 1
Joined: Sun Mar 18, 2018 9:49 pm

Lighting with raspberry pi3b+

Sun Mar 18, 2018 10:06 pm

Thanks in advance for any insight you guys can offer. I'm a beginner in all aspects of this so please explain like I'm five.

I am trying to wire different led chips and affect their intensity or brightness. The brightness of each different type of led must be controlled separately by the raspberry pi

3 x 50W warm white led chips
3 x 50W cool white led chips
5 x 20W red led chips
5 x 20W blue led chips
4 x 20W IR LEDs

Each type of led is driven separately by a DC to DC booster run off of an AC to DC converter. They run at 36V (and Im very iffy on the wiring math)

Is it even possible to control the lights without directly driving them with the raspberry pi?

wh7qq
Posts: 1330
Joined: Thu Oct 09, 2014 2:50 am

Re: Lighting with raspberry pi3b+

Mon Mar 19, 2018 2:35 am

I have no idea of the dimming tolerance of the LED's you are using but the 50W units are drawing about 1.4 amps from your 36 volt source. Individually, any of them can be controlled with a power MOSFET like the MRF520 or better from the RPi, a FNP30N06L, either, cheaply available on ebay. The way to control them is probably best done with PWM (pulse width modulation) that is much easier to do with an Arduino than an RPi but there is python code out there to do it with the RPi. You will probably want to heat-sink the MOSFETs at that power level. The Arduino UNO has multiple pins that can be driven with PWM and examples of the code abound. More advanced Arduino models have more digital pins that can be controlled with PWM

If this is some kind of automotive application or camp lighting using a 12V source, you could eliminate the AC inverter and just follow this: http://henrysbench.capnfatz.com/henrys- ... r-battery/.

Your project has some wiring complexity and you need to get yourself a better grasp of electronic theory so that basic power calculations, heat dissipation and the like are second nature. Otherwise, you could end up with a fire.

W. H. Heydt
Posts: 10907
Joined: Fri Mar 09, 2012 7:36 pm
Location: Vallejo, CA (US)

Re: Lighting with raspberry pi3b+

Mon Mar 19, 2018 5:00 am

rsimpson4365 wrote:
Sun Mar 18, 2018 10:06 pm
3 x 50W warm white led chips
3 x 50W cool white led chips
5 x 20W red led chips
5 x 20W blue led chips
4 x 20W IR LEDs
Are you sure about those power output figures? IIRC, a LED equivalent to a 100W incandescent is 23W. A 50W LED would be the same as an incandescent bulb of over 200W. That's a *lot* light. The kinds of LEDs you'd hook up to a Pi would be drawing mW to--maybe--a watt or two.

saltydog
Posts: 39
Joined: Mon Dec 24, 2012 10:40 am

Re: Lighting with raspberry pi3b+

Mon Mar 19, 2018 7:20 am

The easiest way is to find a LED driver with 3.3v PWM dimming, to match the specs of your LED chips.
What your trying to achieve is very common in the Reef Aquarium hobby.
Try googling: reef meanwell ldd led diy
That should help with understanding some of the basics.

Chris

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