Recommendation: power supply

[dakky]

Greetings @sundberg84

I'm looking for a "non-in-wall" solution to power an pro mini / bare atmega.
At the moment i want to build a simple button-relay. Of course i could by any phone charger, but they cost about +- 10€. And i don't have soo many spare chargers lying around at home :P
The size is important for me, because my wife would kill me, if i put medium sized packages near everthing i want to switch on/off :D

i'm already following the thread u mentioned, but i have to admin: my understanding in these topics is not very deep :D

[sundberg84]

Ok, have you seen petewills relay thread: http://forum.mysensors.org/topic/775/8-lamp-outlet-smart-plug-module ?
There are some examples how to power as well... I hear you about that wife thing... they dont like big plugs for some reason :)

[Denke]

have you had a look at transformer less designs? One capacitor some zener diodes and a rectifier bridge
You need to know what you are doing, but if all is in the same box then i think it is safe. The design can give you around 25mA. I will use it myself for a 2 channel dimmer project that I am working on.

If you rip apart a Nexa Switch box or similar you will find this designs in there.
http://www.jula.se/catalog/el-och-belysning/elinstallation/plug-in-produkter/fjarrstrombrytare/fjarrdimmer-408053/
or
http://www.jula.se/catalog/el-och-belysning/elinstallation/plug-in-produkter/fjarrstrombrytare/dimbar-fjarrstrombrytare-408051/
Also LED light bulbs seems to use this principle

But you have to read up if this is something that suits your need.

Also dont connect your computer to the programming port at the same time as it is powered on.

[ToniA]

I've been using Nokia phone chargers (ones with the USB type A connector, so that I could use any USB cable on them, like USB mini on the other end for Arduino Nano).

But how about powering the SenseBender? Do you guys have any good recommendations for a similar, small, sleek design wall outlet power adapter? Or should I use a low-dropout 5V to 3.3V regulator with some capacitor? Would be nice if there was a USB micro -powered version of the Sensebender...

[Dwalt]

@ToniA The Sensebender was designed with battery power in mind. I have several with attached PIR and LDR running near to 7 months off a single CR123 and they all report battery near 90%. Powering off AC would be possible with addition of voltage regulator but would be a waste of a beautiful low powered design.

[dakipro]

@Denke I was also trying to reuse power from similar Nexa Switch box to power an arduino pro mini node, but it seems that there is just not enough power for arduino in there. I purchased 4 different similar plugs (some with remote and some with timer) in order to find one that can power up the arduino mini, but none of them does it. One timed power switch from Clas Ohlson gets it up and running but when the node starts sending the radio then all LEDs on the mini fade and device reboots.
Did you manage to reuse some of the Switch boxes in order to power up the arduino with mysensors?
It would be much cheaper to just take out the guts from some Nexa Switch and put mysensors node inside, and then have two-way communication and all the MySensors benefits.

[ToniA]

@Dwalt But if the idea is to run some actuator (like relay) on it, it must be on all the time.

[mfalkvidd]

Creating one design that is useful for battery and mains power would lead to a design that't half-good at both.

Lots of discussion was put into making the sensebender good for battery-powered sensors. There are some hardware designs for mains power as well, for example the in-wall pcb that aims to create a design that doesn't need cooling.

[Dwalt]

@ToniA This thread is veering off topic but to clarify my comment, powering the Sensebender off of mains runs contrary to the design of the board. For your example, this board would be a more efficient design - a compact relay board designed for mains powering, ~$9.50 US. It still requires a 5V power supply 😉 .

[ToniA]

What I'm after is a (physically) small device acting as an actuator ('always on'), to send IR codes. So, I need to be able to send IR using 38 kHz PWM frequency, and I need to have it externally powered as it's an actuator. And 5V is easily available. The mini rboard would be perfect for a relay, thanks for the tip :)

So, would the SenseBender + radio run fine, if I power it from a cell phone USB charger using a 'LE33ACZ 5V-3.3V Step Down Regulator' (I already have these, SenseBender is on its way). Do I need to use some capacitors?