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Some advice please?

raspberrypitechguy

I’m a challenger for 1 Meter of Pi, I’ve been designing a lightning system for the plants, however, I realize that the LEDs would require 5A total of current, so I split them into 5 parts, for 1A per section. This still is too much for an arduino pin to handle- at most they can handle one or two, while each had 5.

I’ve considered using multiple pins and boards but my friend says that would likely overload the regulators and fry the chip, or damage.

He said using buck converters, and MOSFETs, would be an ideal solution.

can someone please eleaborate on this part, like a bit of conceptual explanation, and/or other ideas? Thanks!

  • 0

    I would need to know more about the lights setup to give you my opinion but off the top of my head using a simple relay would allow you to do that then you can use the appropriate power output and use the arduino for switching the relay.

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    Hi!

     

    You can either use a relay to turn on/off the lights, which will work good, or you can go the route of using MOSFETs where you can also control how bright the LEDs are using PWM. Here is a project I did where I've done that using MOSFETS Ski Lamp . I've used 3 MOSFETs because the LED strip was RGB, so I was controlling each of the channels, one would be sufficient if you're using a single color LED. If you plan on doing that just make sure in the datasheet what are the voltages that can turn on the MOSFET so you don't need a comparator before it like me, as well as the max current, though, the second one shouldn't be an issue. Hope this helps!

     

    Milos

  • 0

    I'm going with - a simple relay would allow you to turn the lights on and off using just 3v or 5v - depending on the relay. The raspberry pi (or an arduino) would never touch the mains voltage.

  • 0

    Thanks everyone-

    Im doing a 5x5 5530/5730 array, I was originally going to use a DAC to control voltage.

    From what I understand, the relay acts as a barrier?

    I’ll look into that.

    Thanks!

  • 0 in reply to raspberrypitechguy

    A relay is like a switch that you can trigger with a signal.

     

    You would usually have two connections: Normally Closed or Normally Open. When you send a signal via the Arduino for example, the relay would "switch" to the reverse. For example, if you connect your external circuit to the Normally Open terminals, that circuit would be "open" (no electricity flowing) until you trigger the relay, which would then close the circuit and allow electricity to flow.

     

    A relay is great when you want to isolate sensitive equipment (like your Arduino) from a circuit that is either high current (like the LEDs you have) or high voltage (like mains). The only downside with relays is that they are slow, so you can't do PWM on the LEDs to lower their brightness for example.

     

    But for regular turn on/off scenarios, a relay is perfect and really simple to use.

  • 0

    A buck (reduce)/boost (increase) board enables you to move the output voltage up or down in relation to the input. I use them extensively in my personal projects. I have base 12VDC power supply that is used to power strings of LED's. I then use a buck/boost board to produce 5VDC and 3VDC for the digital electronics.

     

     

    I have had good success with LM2596 DC-DC Adjustable Step Down Power Supply Module from banggood.com. They are inexpensive if bought in quantity and have yet to replace any from burning them out. Trust me I have done some not to smart stuff!

     

    I tend to not use relays if I need to control a load. Solid state devices vs mechanical devices are less problematic. I switch 12 VDC LED strings with an IRFZ44 FET.

     

  • 0 in reply to parasquid

    Thanks! I've heard that they have voltage spikes though?

  • 0

    Thanks again everyone- I think it's best if I use relays and Step down modules.

     

    I currently have 25 LED's... that's 5 Amps. I thiink it's best if I turn it down to 8 LED's or 10. (After all, it's a mini model).

     

    That will use just under 2.1 Amps...

     

    I think that's the most likely...

  • 0 in reply to raspberrypitechguy

    I think you're referring to https://resources.altium.com/p/using-flyback-diodes-relays-prevents-electrical-noise-your-circuits

     

    They cause damage to the relay, yes. But if you use something like a breakout board for a relay like the ones found in Arduino kits, they usually already have the flyback diode integrated (and they have indicator LEDs too which help a lot with troubleshooting).

     

    Unless you know what you're doing, I'd recommend staying away from the bare relays. They are cheaper, but relays usually need have a few extra passives added for best performance.

     

    But if you really want to use a bare relay, there are many tutorials around on how to setup the flyback diode.

  • 0 in reply to parasquid

    I do have a relay module for Arduino that I got in an Arduino kit or something when I first started.

     

    I'll probably use that...