Motion Sensing Micro-Processor Controled Night Light




About: Why would i buy something ready made when i can make it myself with half the features for twice the money? DIY!

Getting up at night to go to the bathroom or whatever has just gotten a whole lot better on the account of my motion sensing nightlight
I place this under the bed and as soon as you get up the sensor will detect motion and on comes the light.  

This night light uses the popular PIR sensor to detect movement.
Then the ATtiny 2313 processes the signal and turns on the LED's for the set 2 minute, then off and waiting for another signal. 
Repeat and repeat.

Step 1: ATtiny2313 Vs ATtiny85

So why use a ATtiny2313 and not an ATtiny85, when a ATtiny85 seams to be the more logical one to use?

The ATtiny2313 has many more pins than this project could ever use. Over kill on the pin count.
That also makes it psychically bigger that say a ATtiny85. 20 pins instead of just 8.
It doesn't have the byte capacity of a ATtiny85. ATtiny2313 has 2K bytes verses the ATtiny85 8K bytes.

Like most everything it comes down to cost. The ATtiny2313 is the cheapest micro-processor i can get in my area, when shipping ect is factored in.
ATtiny2313 is $1.75 USD. Where as an ATtiny85 is $4.50 each if i buy 2. 

ATtiny2313 PDF

Step 2: Code

 The ATtiny2313 only has 2000 bytes of flash memory available, but this sketch has 2572 bytes.
So how do we get all that is there?

We comment out all the serial communication in the sketch. 
Those 3 lines of code took up a whopping 1438 bytes of flash that aren't used in the completed project anyway.
Use the serial communication when you are testing with your Arduino board.
Later when the sketch is transferred to the ATtiny2313, comment the serial out.

With the serial commented out and the code we will add for this project the sketch size will only be 1324 bytes total.
Great we are defiantly under the 2000 byte max limit.

This sketch is from ladyada, but has a 2 min delay add by me.

/* PIR sensor tester*/

int ledPin = 9; // Chip Pin Number is 12. choose the pin for the LED

int inputPin = 11; //Chip Pin Numbre is 14. choose the input pin (for PIR sensor)
int pirState = LOW; // we start, assuming no motion detected
int val = 0; // variable for reading the pin status

void setup() {
pinMode(ledPin, OUTPUT); // declare LED as output
pinMode(inputPin, INPUT); // declare sensor as input


void loop(){
val = digitalRead(inputPin); // read input value
if (val == HIGH) { // check if the input is HIGH
digitalWrite(ledPin, HIGH); // turn LED ON
if (pirState == LOW) {
// we have just turned on
//Serial.println("Motion detected!");
// We only want to print on the output change, not state
pirState = HIGH;
delay(120000);           // <<<<<<<<<<< This delay was added giving us the 2 minute LED on time - Change as needed
} else {
digitalWrite(ledPin, LOW); // turn LED OFF
if (pirState == HIGH){
// we have just turned of
//Serial.println("Motion ended!");
// We only want to print on the output change, not state
pirState = LOW;

Step 3: Programming

For programming i used the methods found in this Instructable and this one as well. 

Step 4: Power Supply

I really like these cellphone charger type power supplies. Al-tho this one happens to be from a D-Link router.
I have found they always output more than the rated amount. This is rated at 5v. Actual output is 7v.
After running it through the LM7805 voltage regulator i measure 5.01v output. Just write.

Step 5: Diagram

This is about as simple as i could make it.

Step 6: Board and LEDs

The board is fairly simple with only 8 components.
For the LM7805 voltage regulator i used 2 #104 capacitors. That is not what the book calls for but i have found it works well enough i can not measure the difference with a DMM. 
There is a 20 pin socket for the ATtiny2313 to sit in, then a 4K7 ohm resistor from pin 12 ( set as an output ) to the base of a 2N2222 transistor that is used to switch the ground on and off of the LED's. The positive side of the LED's are always connected to VCC.
Pin 14 is an input for the PIR sensor.. Pin 10 is ground and pin 20 is VCC.
The voltage regulation is set up like in the picture.

            That's it, 4 connections.
  1. Pin 10 GND
  2. Pin 12 out to Transistor
  3. Pin 14 in from PIR
  4. Pin 20 VCC 


  1. Attiny2313
  2. 20 Pin socket
  3. 4K7 resistor
  4. 2N2222 Transistor
  5. LM7805 Voltage Regulator
  6. #104 cap
  7. #104 cap
  8. Power Jack
  9. 9 components if you count the perf board

Step 7: Prepare the Case

These are some containers i bought, 83 cents for 5 with lids. Affordable! 
They are about 7x5x2 inch measurements.

Luckily this container had a ring all the way around it at the middle that i used a a guide line.
Just measured out 1 inch spacing and got the hot soldering iron out and started making holes.
7 holes 5 mm in diameter so the LED's had a snug fit.



  • Classroom Science Contest

    Classroom Science Contest
  • Beauty Tips Contest

    Beauty Tips Contest
  • Pets Challenge

    Pets Challenge

22 Discussions


4 years ago on Step 1

With just a quick look I got the program down to 984 bytes (in IDE 1,0) and 916 bytes (in IDE 1.6). that way it would fit in an attiny10 that is even cheaper than the 2313.
getting those last bytes off:
dont use constants for the pin numbers, just use the pin numbers.
shorten the names of your variables to 1 character

don't use 'int' for only storing small numbers, use 'byte'


4 years ago on Step 1

with regard to cost: if you havent already.... check out aliexpress. I know this instructable is 2 years old, but even then 4.80 for an attiny85 is outrageous.
I think currently when bought in bulk the attiny2313 is 70 euro cnts and the 85 some 95 eurocents


5 years ago on Step 2

Is it possible to have this only turn on at night?
Somewhere between 11pm and 5am or so?

1 reply

Reply 5 years ago on Introduction

That would be different. This a motion sensing light not a light operated by a timer.
If you search on here you will find what you are asking about.


5 years ago on Introduction

I was wondering if i can set this up with a 12v dc adapter and the led strip lights, I want to make it so the stairs light up when someone it at the top or the bottom of the stairs, thanks

3 replies

Reply 5 years ago on Introduction

You are wanting to use 12v because your led strip uses 12v i am guessing.
The answer is yes, BUT in supplying 12v to the circuit board that only requires 5v then you will have to burn off 7v. Instead of using the 78L05 voltage regulator that i have used I would switch to a LM7805 voltage regulator and use a heat sink for it if it is getting hot.

Are you planning on making 2 circuits, one for the top of the stairs and one for the bottom or connecting 2 PIR sensors together into one circuit?


Reply 5 years ago on Introduction

Thanks for the info, Well i was hoping that i could get 1 to work, but i thought i might need 2 pir sensors , which way would be best ,


Reply 5 years ago on Introduction

You would need 2 PIR sensors what ever way you build the system. One for the top and one for the bottom. I would take the fresnel lens off of them and put a small tube over the eye to make it very directional or else they will pick up movement other that what you want.
Other than that which way is better is subjective depending on who is building it ect. Either way you will have wires running up and down the stairs several times unless you went wireless.
The 2 main ways i spose is have each PIR go into one controller or build 1 controller for each PIR, that you will have to decide.
One thing is if you used 2 controllers you would not have to change the program. If you used one controller you will need to change the program. I don't know how comfortable you are with Arduino programming.

I would like to see what you build.
Good Luck

Toby Robb

5 years ago

sorry im not sure what you mean. don't call it in a separate function? like an interrupt?

1 reply
Toby Robb

5 years ago

Nice one. Ive made something similar. However i used a mosfet transistor to switch a single high power led. I used the atmega 328. but im going to build an attiny85 version. have you used the chip much?

5 replies
WWCToby Robb

Reply 5 years ago on Introduction

Yes i have. One thing you want to watch out for with the ATtiny85 is not to use analog read. It has the ability but the function is already understood so it doesn't like to be called.

Toby RobbWWC

Reply 5 years ago on Introduction

Ahh ok thanks I was gonna use tue analogRead function but thats disappointing if it doesnt work.


6 years ago on Introduction

cool circuit,you could even fix this inside a laundry room or somewhere else so that in case you walk in with your hands full it will automatically turn itself on.

1 reply

Reply 6 years ago on Introduction

Great idea. There is many variations of this that could conkocked.


6 years ago on Introduction

Voted: Clever and useful. You might consider developing this. At least run it by quirky or the like.

As an enhancement, you should consider using the red LED. You might need to check the spectrum but red light does not interfer with night vision. So, if your light goes off, the power goes off, you go to another dark room etc, you can still see.

I had a red light night light years ago I put in my bathroom. Made a big difference sliding back into bed trying not to wake the spouse. With the red light, I could see plainly in the dark when I came back to bed, without it, well, there was spousal grumpiness in the morning. Wish I could find those again. 

1 reply