Introduction: Automatic Lighting Box With a Timer on Battery

I propose a simple lighting scheme of the kitchen drawer to turn off the timer. The backlight is switched on for 15 seconds. (that's enough for me)

Step 1: You See a Box With Light and Without

Hi

I propose a simple lighting scheme of the kitchen drawer to turn off the timer. The backlight is switched on for 15 seconds. (that's enough for me)

Step 2: We Need:

  • Magnetic contact 3 pins
  • Magnet D15H4
  • Transistor IRF840 (It can be any n-MOS transistor)
  • Resistor 500 Ohm
  • Resistor 300 Ohm (you can not put)
  • Resistor 20 Ohm (to reduce current LED strip - you can not put)
  • The capacitor 16c 22mkf
  • 25cm LED strip
  • 8pcs AA batteries (rechargeable batteries can not be used - high self-discharge)
  • 1 m double wire.

Step 3: The Scheme Is Very Simple

Step 4: How Does the Magnetic Contact

As I approached a magnet contact switches

Step 5: Solder the Resistor to the Transistor

Step 6: Solder the Remaining Parts of the Scheme

Step 7: Solder the Wires to the LED Strip and Connect to the Timer

Step 8: Assemble Battery Pack

Step 9: Test Duration and Current

Step 10: Set in Place and Glue LED Strip

Step 11: And Put a Magnet in Front of the Magnetic Contacts

Step 12: You Can See the Result.

With and without illumination.

More details you can see on the video.

Thank you for attention.

Comments

author
AlexanderS56 (author)2016-07-21

I think, reed with 2 normally open contacts will be simpler. There is no need to disconnect 500k resistor when 300 ohm is connected. So it's enough to connect capacitor and R1 constantly and only to connect R2 via just simple normally open reed.

author
rafununu (author)2016-07-04

Ilya, most of reed contacts are able to switch more than 0.5A. You don't need all that stuff, the reed and the magnet is enough !

author
wobbler (author)rafununu2016-07-04

The reed switch isn't being used to control the leds current, it's being used as a sensor. When the draw is closed the magnet makes the reed switch connect the capacitor to the resistor, which charges the capacitor up. VT1 is switched off so the leds do not light. When the drawer is opened, the magnet goes off the reed switch which then changes over and the capacitor is then connected to VT1. This causes VT1 to switch on until R1 discharges the capacitor and VT1 switches off again, so the leds then go out. The values of C1 and R1 control the time, the bigger C1 or the bigger R1 the longer the time and vice versa.

The design is good and simple, but I think it's a little bit of overkill on the leds. I would just use a couple of high efficiency leds and a current limiting resistor in parallel. This would be bright enough and would need a smaller voltage and therefore less batteries. You could then get away with 3 batteries and less leds. You could possibly even get away with one led using a diffuser.

author
hugof224 (author)wobbler2016-07-04

wobbler... If Ilyanov's chosen C1 & R1 combo for this circuit yields a 15sec. 'on'-cycle... how would one calculate the necessary values of C1 & R1 (in a similar circuit / application) to yield an "on" time of, say, 1-min., for example? Or, 2-minutes... etc.? Is it as simple as raising the "values" by a factor of 4, or 8... to achieve those time-lengths? I'm a complete novice... but, very interested in these sorts of timing circuits.

author
ILYANOV (author)hugof2242016-07-04

Oh sure. You think correctly.

Increase Capacity Capacitors proportionally - time is proportional to the increase.

Reduce the resistor is also proportionally increase the time

author
wobbler (author)ILYANOV2016-07-05

The time is propionate to the size of the capacitor and the resistor. If you double the resistor it will double the time. If you double the capacitor it will double the time. You can also change both and it will be the multiple so e.g. if you double the capacitor and triple the resistor it will take 2x3=6 times as long. Similarly if you wanted a shorter time you would use a smaller capacitor or resistor and they would be proportional as well, so half the resistor, half the time.

author
hugof224 (author)wobbler2016-07-05

What about introducing a 'pot', so one could vary/regulate the 'on-time', at will? I'm not thinking of this particular application, but rather, a "blinking' circuit. How would you determine the 'limits' (min. & max. range of pot); since, I'm assuming that not all LEDs are equal regarding how much applied power they can accept... before they 'fail' or become non-functional. I wish someone would contribute a schematic, with full explanation of how to make it 'blink' randomly, as well as, at consistent intervals. Also, how about having it run on a 9v battery? I'd buy them 'lunch'.

author
wobbler (author)hugof2242016-07-16

A long, long time ago I made some Christmas tree led lights which blinked randomly. The way I did it was with TTL circuitry using a gated oscillator. The basic way it worked was I had an oscillator which was continuously running really fast (about 1Mhz) and I had a timer circuit which lasted a longer time. The two weren't synchronised, so the timer triggered a D type flip flop which recorded the state of the oscillator at that time. As a result, whenever the timer triggered the D type flip flop it ended up as either a 0 or a 1 so the leds were then either on or off. So, it was random in terms of on or off and the state even though the state changed at fixed intervals defined by the timer.

Hope this makes sense, contact me directly if you want a rough schematic. It's also probably possible by using a dual 555 timer chip or going hi-tec and using an Arduino.

author
wobbler (author)ILYANOV2016-07-05

Reducing the resistor will decrease the time as it will cause the capacitor to discharge quicker.

author
ILYANOV (author)wobbler2016-07-05

Oh yes of course.

I made a mistake. Of course you're right

author
WannaDuino (author)wobbler2016-07-15

again Wobbler,

Thank you. In a few words everybody understands,

Go on with your good job.

author
rafununu (author)wobbler2016-07-05

I know. I'm only telling that the switch could easily drive the LEDs and nothing else is needed.

author
ILYANOV (author)wobbler2016-07-04

Yes you are right.

I chose a strip that's why.

It is flat and thin, has an adhesive layer. (LEDs Diffusers will stick out and I can break off them)

The light from the strip is much more diffused. I like it more.

For individual LEDs need damping resistor (which is extra cables and connections that can break)

And on the strip everything is already there. It is only necessary to connect the two wires.

For low-voltage transistor logics needed (this will not work)

author
ILYANOV (author)rafununu2016-07-04

I agree with you

but

This unit is where inconvenient to connect the power.

If you do not put off the timer if someone forgets to close the battery drawer quickly discharged from the always-on strips.

author
rafununu (author)ILYANOV2016-07-05

Ok, well thought.

author
PierreD6 (author)2016-07-14

I have a similar setup in my bedroom closet except i use only a micro switch.

author
BurgersBytes (author)2016-07-14

The RC time constant is the time constant (in seconds) of an RCcircuit, is equal to the product of the circuit resistance (in ohms) and the circuit capacitance (in farads),

So .000022 Farads times 500000 Ohms = 11 seconds roughly. The special transistor drains little.

If the magnet is not placed correctly the light may come on when closing it too cutting battery longevity in half.

author
vlascoff (author)2016-07-14

forgive my noob comment since im not that great at circuits, but what would happen if R1 wasn't there? wouldn't the capacitor discharge either way?

author
ILYANOV (author)vlascoff2016-07-14

Sorry, I confused myself
I am not answered (there were a few questions from different people, and I'm confused)
R1 - MANDATORY resistor
Sets the backlight time

R2 - not necessarily from the reed switch contact arcing protection

R3 - resistor is not necessarily - to save battery power (the strip is very bright)

author
ILYANOV (author)vlascoff2016-07-14

Hello.
R1 is needed to eliminate spawned reed contacts.
You can not put.
I put it on just in case.
It seems to me as more correct.

author
vlascoff (author)ILYANOV2016-07-14

you said R2 and R3 are optional (can not put). R1 is also optional?

author
UncleEd (author)2016-07-14

R1 is controlling the rate at which the capacitor discharges. If R1
were not there, the capacitor would discharge instantly and the light
would go off, rather than waiting for 15 seconds or whatever time was
selected.

I enjoy projects like this, because they remind me that
good, useful, and effective things do not have to be complex. When I
saw what was being designed, I thought of a 555 timer and a Hall-effect
transistor. How embarrassing! At least, I didn't think of doing it
with an Arduino.

Well done!

author
vlascoff (author)UncleEd2016-07-14

wouldn't the transistor gate throttle that discharge somewhat?

author
ILYANOV (author)vlascoff2016-07-14

I'm sorry I did not understand your question.

author
ILYANOV (author)UncleEd2016-07-14

Many thanks!!!!

author
DonSteve (author)2016-07-14

That's a great idea and instructable.

author
ILYANOV (author)DonSteve2016-07-14

Thank you

author
Eh Lie Us! (author)2016-07-14

Right on. The light makes a big different. My kitchen drawers are places where seldomly used utensils go to die.

author
ILYANOV (author)2016-07-06

Hey.

For example.

http://www.ebay.com/itm/10pcs-Reed-Switch-MagSwitc...

Look at their stores. It is not uncommon

author
TomášK2 (author)ILYANOV2016-07-08

Thank you.

author
TomášK2 (author)2016-07-06

Hi, where to buy magnetic contacts with three pins?

I found only two contacts.

Thank you.

author
bklyn_40 (author)2016-07-04

For those who know, I apologize for my ignorance, but what does "you cannot put" mean in step 2 for the 300 & 20 ohm Resistor?

author
hugof224 (author)bklyn_402016-07-04

bklyn 40... He is 'suggesting' that you can omit, or "NOT use" the resistors.

author
bklyn_40 (author)hugof2242016-07-05

Ah! Thanks. Much appreciated.

author
ILYANOV (author)bklyn_402016-07-04

Hey.

Resistor 300 ohm need to contact the magnetic switch is not a spark (they vrodeby not spark but better) You can not put

Resists 20 ohm current limiting strips. bright strip - to reduce the brightness and really save battery power.

author
AnnabellaMarie (author)2016-07-05

Nice! You worked hard figuring this out and I appreciate you taking the time to share it.

author
ILYANOV (author)AnnabellaMarie2016-07-05

Thank you.

author
silvialockers (author)2016-07-04

Wow you are complete genius and welding expert i would never weld with my bare hands

author
gm280 (author)2016-07-03

While I really do like your idea and concept, your circuit assembly leaves a lot to be desired. The basic idea is good, but I would most certainly have to design some quality PC boards for the circuit(s). And I would have used a line voltage reduction power supply and then never have to deal with the batteries ever again. Reed switches are a great way to turn on and off the drawer lights. I use them all the time in storage areas. Thumbs up on the basic idea.

author
ILYANOV (author)gm2802016-07-04

Thank you.

My homemade calculated as of the same non-professionals like me. The difficulty in the form of fees deter many.

And in the circuit board need not because such a small number of elements.

Thank you for your opinion.

author
stef4n (author)2016-07-03

16 months will do fine! Thnx

author
stef4n (author)2016-07-03

How long will the battery pack last? Days or weeks?

author
ILYANOV (author)stef4n2016-07-03

I have been working for half a year.

The calculation is as follows:

Capacity AA cell 2000ma / h

2000 mA / 100 mA = 20 hours of continuous operation

For 1 hour = 60 minutes * 60 seconds / 15 seconds (work) = 240 inclusions

20 hours * 240 starts per hour = 4800 inclusions

if 10 inclusions in the day, it turns out

4800/10 = 480 days = 16 months

author
DIY Hacks and How Tos (author)2016-07-02

Nice lighting arrangement. That makes it much easier to find things in the dark.

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