Kitchen2 breadboard prototype

using a fet to dim a ledstrip

During the last week I was able to build the breadboard version of the kitchen2 device.

Learning from my previous problems with just partially prototyping the circuit. I’ve built it fully …i’ve connected the “production” power supply to it and the ledstrip too.

The led strip is dimmed by a fet…because this was new for me I’ve consulted with some experts on the arduino irc channel about what i want to build and they have taught me the simplest cases of using Fets:

  • Fet is under pwm control? Use logic level fets
  • Turning a fet on is like “hitting a dead short” I like this phrase ;) there are various options to do this..depending on the desired control precisity requirements:
    • use transistors to minimize delay - have a look at this article: its very intresting
    • use resistors…less precise i think mostly at low duty cycles
      • One should go betweeen control pin and the gate itself: it should be sized to totally burn the output current of the controlling device
      • Another one should go between earth and the controlling pin: this will help in ruding the disable delay and will prevent noises to turn on the fet (in case the mcu is not controlling it)
  • If your load is inductive, a “rubber diode” should be added - the function of this diode is to protect the fet from recieving above ground voltages.
    • This diode should be around the load; from the fet controlled ground to the positive

Because I will just control a simple ledstrip (which is clearly not inductive), and I dont really care if the control is not really precise: i went the resistor way, without any diodes.

Learning from my earlier experiences with switch mode regulators, i just plugged in a linear regulator for first tests…besides some programming mistakes the sample appliation worked without any problem.

I’ve added the nrf module without any issue..and replaced the 7405 with the desired switch mode counterpart (I’m using these becasue they dosent heat up so much - and I have a lot of them hanging around.) …and the same thing happend as earlier; so i’ve added the LC filter.

It worked as expect on the breadboard - I called it a day and went sleeping ;)

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