Usb Lamp With Timer&dimmer (LED)

555 monostable circuit

Step 1: YOU'LL NEED:

You'll need:

555 timer IC

Resistors (10ohm, 200k, 1k)

Capacitors (0.6mF, 10nF)

Stripboard
Pushbutton
Slide switch

Diode

Potentiometers (500k, 10k)

Soldering iron & solder

Usb cable( cut off the head that goes to your mobile device, ignore the green and whit wire, what you need is the black and red wire for your power source)

Step 2: Schematic

the period depends on the values of C1 and R2; Rpot1 sets a minimum or maximum period

tmax= 1.1* C1*(R2+Rpot1)

tmin=1.1*C1*R2

Step 3: Soldering and Testing

Step 4: Building a Case/stand for Your Lamp

I cut out holes to which will give me access to the power source, pushbutton, potentiometer, led's and slide switch

after making sure everything was in place, i painted the box and then installed the circuit in the box

Comments

[rafununu]

Looking at the schematic I can insure you the dimmer doesn't work, there's at least one mistake somewhere !

[maria_AI]

it works on mine...but I'd like to know how to fix it :)
thank you

[Omnivent]

Hi,

It may work for you, but there are several issues.

You cannot rely on such large component values (600µF and 200..700kOhm) if you want even a modest amount of reliability - timing will depend very much on temperature and humidity. A circuit with a 4060 (oscillator and binary counter) would be able to give you the large times you want (even much longer) with a much better precision.

I'm not sure I understand what you're trying to do with Pot 2, perhaps dim a bit after the timeout?

Anyway pot 2 is too large to give you a useful range (only the ends of the travel will be useful). However, you should not make it a better value (50..100 Ohm), as you shouldn't feed the output any current from outside, when the power to the 555 is off (but the ground still connected). You really need R3 and R4 for when Pot 2 is at the ends of its travel, or you will get much too high a current into your LEDs.

Each LED should have their own resistor, when driven in parallel, as they'll have small differences in voltage drop and through use, this will build to a point where they'll be very different in tint.

If you tell me, the purpose of the switched arrangement and/or, what it is you want it to do, I can make you a schematic that won't kill neither the LEDs, nor the 555 (or alternatively with a 4060).

Have a nice day :)

[maria_AI]

In initial lamp (which was bought) the LED's were already positioned that way with just one 220 ohm resistor which is why I put just one resistor before the rpot2 which dims the brightness to a certain point, when it's at the highest level the LED's turn off (which is what I wanted) as for the 555 timer, I couldn't find the right values to get the exact timimg, I always ended up with very high value capacitors, in the end I settled for this
I am an electronics student (in Italy), we just studied monostable circuits so I decided to apply it on my broken lamp which I was about to fix

but thank you very much for the corrwcrions, I'd really like to see your corrected schematic :)

[Omnivent]

Hi,

I bet there was a sticker on the lamp saying "Made in China" ;)

Yes, if you want long timing periods, you need large R's and C's to get them with a 555. The 4060 I mentioned doesn't need long time periods, as it contains a 14 bit binary counter and can thus use an oscillator frequency of 2^14 times higher for the same end result.

I have kept the timing components of your choice and Pot2 as well, although I've made it to have the highest brightness when you turn the pot clockwise (just like you'd do with an amplifier for a louder sound - seems the most logical). That goes for both the timed and the constant mode.When in constant mode, no voltage will go into the 555.

The reason for Q1 and Q2 is that the 555 won't be able to go to 5V (when driven from 5V). This way there's only a saturated transistor drop - around 100mV, which means that both timed and constant mode will give pretty much the same current to the LEDs (via the 68 Ohm resisters).

If I misunderstood your use of Pot2, do tell, it's easy to change. Feel free to use it whole or in part(s) in your instructable :)

Keep up the studies, you have a long design tradition to live up to :D (My sister spent a couple of years, bolstering her education in fashion design in your beautiful country)

Have a nice day :)

[maria_AI]

wow! I've learnt a lot from you :D, thanks a lot, I'll modify the circuit as you suggested :)

[Omnivent]

You're most welcome :)

[oscardelben]

I'm really going to make one of this. This well help me since I can't sleep without a light and my sister next to me can't sleep with a light.

[maria_AI]

ok :D

rafununu pointed out that there are a few adjustments to make so i'd suggest you look at the remade schematic

[Ehlers_TV]

Cool !!!

[maria_AI]

thanks :)

[ALEX96_MF]

AWESOMELY MADE AMORE! <3 :)

[maria_AI]

THANK YOU AMORE <3