Newbie alert....I would like to run something by everyone to make sure I'm on the right track.
A little background. I live in an RV by a lake. All lighting is 12V from an inverter (If the RV were to move this 12V would be from car batteries). I have changed all of the bulbs to LED for power savings and no heat. All of the switch boxes are very small so there is not a lot of space to add anything.
I would like to add my lights to a home automation system (The IoT Gateway). For each switch box I would add a Moteino and an N channel FET like a IRLML6344. The LED bulbs (Sometimes 2 or 3 in a fixture) are around 4W each so max of around 13W
Does anyone see any problems with this idea? Would heat be a problem? Supposedly a Moteino can run from 12V OK. I don't know what the heat output of the FET would be but it's meant to be able to handle 30V. The Light fixtures would only draw a max of around 1A.
Rather than paralleling the switch I would add it to a pin on the Moteino so that the gateway would know when the switch was used manually to turn the light on/off.
There is not a lot of extra space in the switch boxes so was wondering if I could get a pre-programmed Moteino with DualOptiBoot BootLoader so wouldn't need to solder on the FTDI header to program and then desolder it.
The LED loads for that FET would not be a power problem. With only 37mOhm on resistance, there would be virtually no power dissipated in the FET at 1A. What you do need to watch is the power dissipated in Moteino's voltage regulator. At normal car battery voltage you'll have about 10V x Moteino current wasted as heat. As long as you keep the Moteino in lower power conditions (ie, limit your transmissions to brief, occasional bursts), you'll be fine there as well.
Re not soldering the FTDI connector, I have successfully used a technique I first saw on Sparkfun. Don't solder the connector, but insert the header into the pins and keep it tilted with light pressure to keep a continuous pressure on the pins. This works ok for the standard sized holes for the brief time you're programming. On my own boards I use smaller diameter holes (so the pins are force fit) or used the Sparkfun footprint that slightly offsets every other hole making the row a 'jam' fit.
That Sparkfun technique is good to know. I can definitely use that.
So, the best idea is to power down the Moteino transmitter and only turn it on when needed. Great. I'll push ahead with a small development environment.
Thanks for the quick response.
Quote from: Valdhor on August 31, 2018, 03:36:16 PM
So, the best idea is to power down the Moteino transmitter and only turn it on when needed.
You don't have to power off the radio, you can stay in RX mode (about 16-20mA worth = <1/4W), but only go to TX occasionally.