# 555 timer - motion LED circuit

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#### rj_uk

##### New Member
Hi, I need some help with a side project I have going on. I have an extremely limited knowledge of electronics, so please excuse the lack of the schematics or incorrect terminology.

The objective is to make a small light that is activated by motion and will remain on for 20 seconds and then deactivate. i.e.you pick up the light it illuminates you put it back down and it remains on for 20 seconds then turns itself off...until it is picked up again.

I have been guessing at what I need so far but already have some of the components:

4x AA batteries <this is a must due to size.
icm7555ipa Timer
Non-mercury Tilt switch
10x colour changing LEDs (could be more cant be less)

I have a load of 510ohm 1/4w resistors(came free with tthe LEDs) but can easily buy more once I know what is needed. I dont have any capacitors but guess I'll need some of those also, what size?I dont know where to begin?.Anything else I might need?

Could someone help me out in getting these components onto a circuit to do the above task. If possible explaining it in layman terms so a simpleton like myself can purchase any extra parts and solder it all together.

Here are the specs for the LEDs:

and if needed here is the info on the timer: Link

Any help warmly welcome, thank you

#### ericgibbs

##### Well-Known Member
Code:
4x AA batteries <this is a must due to size.
icm7555ipa Timer
Non-mercury Tilt switch
10x colour changing LEDs (could be more cant be less)
hi,
Looks a nice simple project.

What sort of housing/enclosure are planning for the batteries/circuit.?

#### rj_uk

##### New Member
All electronics will be concealed inside the device which is being made out of 3mm translucent acrylic, Ive tested and 10 LEDs is suffient to illuminate through this. The batteries will be held in a battery holder(similar to this) on the underside of the light box. I have some stripboard to mount the circuit.

What info is required on the LEDs?
Im not sure if I have any more than I have already provided...they look exactly like the normal 5mm two legged ones...only difference is they change colour slowly.

#### ericgibbs

##### Well-Known Member
All electronics will be concealed inside the device which is being made out of 3mm translucent acrylic, Ive tested and 10 LEDs is suffient to illuminate through this. The batteries will be held in a battery holder(similar to this) on the underside of the light box. I have some stripboard to mount the circuit.

What info is required on the LEDs?
Im not sure if I have any more than I have already provided...they look exactly like the normal 5mm two legged ones...only difference is they change colour slowly.
hi,
Due to the fact that the power is 4 * 1.5V = 6V [ with fresh batteries] each 3.2Vdp LED will require its own series resistor.
Allow say 15mA/led from a 6V supply so, Rseries = [6V - 3.3V led]/0.015 = 180R.

Say 15mA/led, 10 * 0.015A = 150mA.

This means when using a CMOS 555 the 10 LEDs will need to be driven by a transistor, which in turn is controlled by the 555 timer.
A 2N2222 transistor would be OK.

Configure the 555 as a Monostable with a 20sec period.

Use the tilt switch to trigger the 555 input.

Position the tilt switch so that it is normally open in the 'resting' position.

#### rj_uk

##### New Member
Hi Eric,

A big thanks for helping with this, electronics are like a foreign language for me. The light box is to be a part of a presentation, intially I was just going to dismantle an LED torch and use the gubbings from that but then decided it would be better if I attempted the circuit myself and had it do what I wanted. Having no knowledge of electronics I bite off more than I can chew, Im willing to learn so your help is very much appreciated.

Due to the fact that the power is 4 * 1.5V = 6V [ with fresh batteries] each 3.2Vdp LED will require its own series resistor.
Allow say 15mA/led from a 6V supply so, Rseries = [6V - 3.3V led]/0.015 = 180R.

Say 15mA/led, 10 * 0.015A = 150mA
I will admit this bit has confused me, will I need a resistor for each LED or 1 resistor for each series of LEDs?

With regards to the math,am I correct in thinking that Rseries is the calculation for the resistor required = (power voltage - forward voltage) divided by the mA drawn. By your calculation this is 180R. Is R equal to ohms?
How do I decide what size resistor is required, 1/4w or 1/2w? Would this make any difference?

Configure the 555 as a Monostable with a 20sec period.
Ive seen a few schematics of these.

After some hunting I think this is the one I need, is this correct?

Am I correct in thinking Q1 is the transistor and C1 is a capicitor? How do I calculate the capicitor size, if need one?
I also dont understand how the time is controlled. What is the difference between a 20 second timer compared to a 10 second timer? How is it altered?

Finaly as a true display of my lack of knowledge where do the LEDs fit within the circuit if this circuit is indeed the correct one?

Many thanks

Ryan

#### ericgibbs

##### Well-Known Member
hi,
Have a look at this circuit.
To increase the timing period, increase the 470K to 1M0 or the 47uF to 100uF.

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#### flat5

##### Member
You beat me and very good job!

#### rj_uk

##### New Member
hi,
Have a look at this circuit.
Wow...thank you very much. you Sir are a Gent!

I can understand the circuit you've uploaded and feel capable of assembling it ... except for one little details; coming off the 1 & 2 leg is a capacitor labelled 2n2, what does this mean?

I was also thinking it would be a good idea to insert an on/off switch so the circuit can be disabled during transport, would it be acceptable to just put a switch coming off the battery terminal to break the circuit?

#### ericgibbs

##### Well-Known Member
Wow...thank you very much. you Sir are a Gent!

I can understand the circuit you've uploaded and feel capable of assembling it ... except for one little details; coming off the 1 & 2 leg is a capacitor labelled 2n2, what does this mean?

I was also thinking it would be a good idea to insert an on/off switch so the circuit can be disabled during transport, would it be acceptable to just put a switch coming off the battery terminal to break the circuit?

Fit an On/off switch in the +V line of the battery.

#### rj_uk

##### New Member
Thank you very much.

I'll get to the store at the beginning of next week and buy the extra pieces I need and should have the box constructed by next weekend, I'll post some pics.

You have been a great help

Side Note: Nice Avatar! ...... (Im Welsh)

#### ericgibbs

##### Well-Known Member
Thank you very much.

I'll get to the store at the beginning of next week and buy the extra pieces I need and should have the box constructed by next weekend, I'll post some pics.

You have been a great help

Side Note: Nice Avatar! ...... (Im Welsh)

Hi,
Look at the colour of the Dragon and the background colour of the flag.!!!

Isnt the Welsh flag a Red Dragon on a White background.?

Its an old English battle flag.

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#### charbel89

##### New Member
Thank you very much.

I'll get to the store at the beginning of next week and buy the extra pieces I need and should have the box constructed by next weekend, I'll post some pics.

You have been a great help

Side Note: Nice Avatar! ...... (Im Welsh)
Have a look at this site:

They appear to have what you are trying to do using a normal switch.

#### rj_uk

##### New Member
A big thanks to you all especially Eric.

I have now built the circuit and it works exactly how it is supposed to.

It is fanatactic and worth the effort(I may try my hand at some electronics in the future), thanks for the time you put into helping me with this project

Much Appreciated

Ryan

#### starhero

##### New Member
Multi colour LED

Hello Friends,

I am new in this forum. I am not much familiar with electronics.
I need circuit diagram for multi colour LED (3sec Flashing LED with inbuilt IC-red,green & Blue).

My objective is I have 10 LEDs. It should light one by one in one colour(say red) and after that next colour and so on.Is any circuit avilable for this? any reply in this regard will appreciated.

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