Tag Archives: arduino

12 Volt trigger for NAD-D3020 amplifier

Update 3 January 2021 – mention that I am now using Tasmota firmware.

The NAD D3020 is a hybrid digital audio amplifier with a combination of analog and digital inputs. I have been using it for quite some years now to play the sound of my Samsung smart TV over the living room speakers and for digital radio, iTunes and Spotify from my Mac mini. The Samsung is connected with an optical Toslink cable, the Mac mini is connected with a USB cable.

In the way the D3020 is placed in our media cabinet, its on/off button is not so easy to access. The D3020 remote control is really crappy and I find it anyway annoying to have to use multiple remotes to switch the power of all devices. Also, the status LEDs of the D3020 are dim and got considerably worse over time, especially for the OPT1 and the USB inputs that are for the TV and the Mac mini, and hence on most of the time. I guess that it uses OLEDs, which have degraded over time. Consequently, it happened quite often that we forgot to switch the amplifier off for the night.

However, the D3020 features a 12V trigger input port which allows the amplifier to be switched automatically on/off along with other gear. Of course, neither TV nor the Mac mini has a 12V output port, but both are connected to my home network; hence it is possible to detect over the network whether these are powered on.

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Monitoring the central heating with an Arduino and two DS18B20 sensors

This post is part of a series on Arduino-based energy and climate monitoring.

About 40% of our energy bill is spent on electricity and 60% on gas, which we use to heat our house and for hot water. Although we do have a relatively recent HR central heating installation, I don’t think that it has been tweaked for efficiency. After reading this post on optimising the yield of the central heating installation, I decided it would be worthwhile to try and acquire some data.


I wired up a Arduino pro mini (3.3V) with a RFM12b and a pair of DS18B20 temperature sensors to measure the temperature of the outgoing and returning water of our central heating system.


Power is provided by connecting a rechargeable 18650 LiPo battery to VCC on the programming header of the Arduino. This battery provides nominally 3.7V, which in my experience is close enough for the board to work fine. The whole module is mounted in a battery holder for two 18650 batteries.

Every 66 seconds a temperature reading of both sensors is performed and transmitted it to the central relay module. The central module forwards it to ThingSpeak to acquire a long-term log of the behaviour of our central heating system.

You can find the sketch for the Arduino here.

Arduino kWh and M^3/h energy meter – gathering the components

I am working on an energy meter that is to show the instantaneous electrical power (kWh ) and natural gas usage (M^3/h) in our house. A bit like <a href=”http://juerd.nl/site.plp/kwh”>http://juerd.nl/site.plp/kwh</a>, but with two recordings, data logging to an SD card and with some buttons to switch the display from the instantaneous recording to usage per-minute, per-hour, etc.

I just managed to get all components hooked up to the Arduino nano. See the photo for an impression.

The project includes

  • Arduino Nano
  • RTC
  • CRT5000 Infrared Reflectance 2x
  • SD card module
  • 1602 LCD

I am still waiting for the two pushbuttons. Once those arrive I’ll finalize the electronics and software and transfer it to a perfboard.