Capacitive transformerless power supply schematic for PIR motion sensor NV-1111.35

In the previous article I have explained how a PIR motion sensor works. There you can also find the schematic for the NV-1111.35 PIR sensor which is based on a popular three stage op-amp topology. Understanding this can help you understand other pyroelectric sensors as well.

This sensor is powered by a capacitive transformerless power supply with an output of 8V and 7mA of current.

How an outdoor motion PIR sensor switch works with schematic

In this article I will be explaining how a pyroelectric (PIR) sensor works and show the reverse engineered schematic simulated in LTspice. The schematic is for NV-1111.35 outdoor PIR sensor used to switch a mains light and has 3 potentiometers for setting SENSITIVITY, LUX and TIMEOUT.

This sensor is based on a popular three stage op-amp topology. Understanding this can help you understand other pyroelectric sensors as well and also something about active filters using LM324 and removing and setting a DC voltage bias.

 

Using USBTinyISP programmer with Atmel Studio 7 | AVR programming

In the last article I talked about Programming any AVR microcontrollers using WinAVR and USBTinyISP but recently I found that USBTinyISP can be easily used together with Atmel Studio.

Using an external programmer in Atmel Studio 7

Program any AVR microcontrollers using WinAVR and USBTinyISP - Getting started with AVR tutorial for beginners

Nowadays Arduino is the platform of choice for programming AVR microcontrollers and for good reasons. But there are times when you want to have full control over what is added to your code. 

For example Arduino is enabling by default Timer0 for use in millis function and other functions and includes some interrupt routines that perhaps your project is not using and so adding to the code size or perhaps those interrupts can interfere with your code.

What you need:

• ATmega328P (used in this tutorial as an example)
• USBTinyISP programmer 
• WinAVR software (more on this later)

What you can learn:

• how to program an AVR microcontroller using an In-System Programmer such as USBTinyISP and WinAVR
  
• some bitwise operations for handling the registers

There are two ways to program a microcontroller:

- ISP (In System Programming) using SPI protocol and a ISP programmer

- With a bootloader using UART protocol and a USB to Serial programmer. Some microcontrollers come with a bootloader already pre-programmed on them.

 

This tutorial will cover the ISP programming way.

Programming software

There are many tools for programming an AVR microcontroller such as Atmel Studio, PlatformIO, Eclipse with an AVR plugin, etc but the simplest and light weight solution that I found is using WinAVR.

Programming hardware

Apart from development software there is also the need of a hardware programmer that the software uses to communicate with the microcontroller and upload the code to it. Searching online for 'avr programmer' reveals lots of options. The most popular I believe is the USBTinyISP and is very cheap. There is also Atmel-ICE from Atmel. A bit more expensive but it has the benefit of being able to debug and see in real time what happens inside the microcontroller.

Getting started with WinAVR

How a POV propeller display works

In part 1 on How to make a POV display we talked about the hardware and schematic. In this part 2 we will dive in how the code works and why the POV (Persistence Of Vision) display is so cool and fun to play with.

Build a wireless energy POV display propeller clock with Android app

A POV display aka propeller display/clock is a display that uses the Persistence Of Vision (POV). By turning just a few LEDs on and off at a specific position around a circle, a full display that would normally require hundreds of LEDs can be created. This illusion of a still image is due to the eye's slow refresh rate. Without this perk we would see moving pictures instead of videos and obnoxious LED lights caused by PWM in daily life.

If you think about it is is an interesting and fun project to experiment with. This will be more obvious in part 2 where we will discuss the code and the basic principles. It can be used as a clock or display text from internet in real-time or for image display.

Here is a video with the POV display controlled by an Android app. Needless to say it looks better in person. The display can be styled by different LED colors.

Build a double sided UV LED exposure box for making PCB

I found a broken Samsung MM-N6 audio system and so I've decided to build myself a double sided UV exposure box using it's front panel since it already had an LCD display and buttons and the sliding motorized panel looked cool.

Before I get into more details about how it was build, take a look at this overview video.