Hardware

@jendrush At the moment 5v use one of the [image: 1427712052724-20150330_160334.jpg]

@m26872 This is mostly a matter of opinion. There are several options available. Personally, I will design so that I have three options to choose from depending on the sensor type (and long term measurement data)

this will work i think, but not sure what will happen, after removing the regulator from the pro (http://iot-playground.com/2-uncategorised/9-arduino-low-power-sensor). I hate it, that i don't find any useful documentation about my usbtiny grml :disappointed:

Yes, Nano is a bit bigger, but have own usb-serial chip so you can program it directly and have onboard 5-3.3 output. Keep forgetting that:) So if size is not an issue, got with the Nano...

@dakky No, it can not set fuses.. You need a ISP programmer for that. There are lot's of "cheap" isp programmers around, even an arduino can be made into a ISP programmer.

I don't know .. but ideally is if nrf24l01 set ack with payload .. and this payload will contain random number or rtc time .. encrypted with xtea . all node or repeater if receive ack then got this number or rtc time .. and use in next packet .. nrf24l01 chip can make 50%work alone .. node if send data packet then wait for hardware ack . and this ack can contain payload .. this payload will be starting point ..gw will generate actual payload for ack sequence .. It's just idea ..

Of cource it's powered down :-) - but is his done by a sw-command via SPI (and also the pwr-up) or by transistor ? I'm surprised about the quality of the rNF - the power down seems very good?

Absolutely

That lib only supports HW SPI(from what I can see) and I would need it for Pro Mini's. But tried it on a mega, almost same issue. Did some more testing with same result. I checked the datasheets , and from what I can see, it is depending on a stabel reference voltage. Was driving my pro mini with 5v and then regulating it to 3.3v for the MAX31855. So dataline was 5v and max31855 was 3.3. Even if this is within spec the macx31855 board I got was as cheap one, so it did not filter the voltage/data input for the chip.(Looks like the Adafruit board does?) Moving the regulator in front of it all, driving everything with 3.3v it's as stabel as could be expected. [image: 1426927325919-screenshot-2015-03-21-09.41.14.png] Green is a DS18B20, Blue a DHT21 and the black is the ThermoCoupler.

If the sensor and the gateway are at the same level or about the same level I think using a half-wave dipole or "rubber duck" antenna pointed vertically is a good idea. That will focus the energy in the horizontal plane and not into the ground or to the air giving about 2 dBi of gain.

It is possible to connect the radio, you can find instructions for example here. CE/CSN to any unised digital pin, IRQ not needed. However there are 2 pitfalls: voltage: You need to have 3.3v to power the radio. Pro Micro module is sold in 5V version or 3.3V version. 5V version don't have 3.3V pin output, so you have to arrange that by an external regulator. If you have 3.3V version, then it's fine for the radio, but such board is working on 8MHz, so it's not compatible with Leonardo target in Arduino IDE, you need to have hack that there. MCU there is different than Arduino Uno/Pro Mini, sleep modes are different; someone here reported that sleep is not working with MySensors, you can search here for experience with that. I made some helper PCBs for pro micro, you can check here. [image: upload-57ad0499-3d7e-4dfd-bfe1-b666f9b05fb8.jpg]

@Mickey What would be the use case? One can't do much with 4kB flash on the controller there.

@Ozal I had similar board which **pcbbasket made it for me, the cost was a bit higher, but they made exactly as I wanted. So I recommend them www.pcbbasket.com **

I finally made them work :) I was not using the right clock for programming, 16MHz instead of 8MHz... Thanks @AWI ;)

@AWI said: Can you share what is in the box? I am getting curious.. [image: upload-b4b8c6d2-ace5-400e-90c9-4c4dcfd4d4aa.jpg] arduino_nrf24l01.rar

If you look at the Netatmo devices you can see that they have plastic caps and a long plastic notch. I'd bet that the antenna can be found in such an area... I dont think that a small thickness will help to let the radio signal pass. Think of that very thin µ-metal sheet covers on high frequency circuits e.g. in TV or Radio inputs (where you want to stop a radio transmission). They are built to not let radio waves pass and they are thin - so I dont think the thickness plays a major role. As Bulldog wrote paramagnetic blocks radio waves. And aluminum stays paramagnetic even if you reduce the thickness. But I made the experience that relatively small areas, where the radio waves will not get blocked (e.g. plastic caps) can make the difference between no signal and "its working". Also keep in mind that nearly all antennas have a direction. So changing the orienation of the antenna might dramatically change the transmitting capabilties.

@Session Yes, there are plenty of "certified" dimmers that are controlled by PWM or 0-10V input. However, there are also plenty of "certified" LED drivers that you can also use by connecting the (-) negative side of the DC output to the Arduino ground, and the (-) negative side of your LED to the mosfet output. Certification is for the AC part of the Driver. The great thing about the new LEDS is that you can control the DC side and not worry about controlling the AC. You don't need a triac, you don't need a zero crossing detector, simply switch on and off (PWM) the negative side of the DC part of the light.

@tbowmo The last time I needed a non-standard thread (for a camera tripod-like mount) I had to go to Würth. They charge about an arm and a leg for a few screws, but on the other hand the metal is probably very high-grade and resistant to corrosion.