hi everyone i'm new to this forum and found it as i'm just designing a lamp for my final year on a furniture and product design course.
i have several questions concerning the electronics involved in this project but first i explain what i'm trying to create:
it's a lamp with a main base which has 6-10 other smaller light objects attached through jack-plugs (headphone plugs) that the user is supposed to take away when he/she need light for reading or as atmospheric light.
all the small objects are charging on the main light base.
each of the small objects have a metal plug-socked which i want to use as a touch switch.....
what do i have to do to create a touch switch that is connected to the plug socket at a low voltage of 3.6v
another problem i have is the charging as i have always different amounts of charging objects on the main base.....is that a problem or is there a charger that can charge various different amounts of batteries?
is it possible to have the light being very low when charging and brightening up when taken away from the main charging base?

i appreciate any comment or advise on this as i am very new to the field of electronics and do not have the knowledge yet that it takes for realisation.
thanx
moinmoin

 

White LEDs generally have a 3V to 3.5V forward voltage drop, so powering them from a 3.6V source isn't very practicle They'll work but the brightness won't be very consistant. Use a higher voltage like 4V minimum and there shouldn't be a problem.

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There are many touch switch designs available, for example see http://www.discovercircuits.com/C/capacitance-sw.htm. If you see one that appears to meet your needs, I, or someone else in the forum, can likely help you with the details.

The charging circuit depends upon the recharable batteries you will use and the desired recharge time. NiMH can be trickle charged so a simple resistor in each object may suffice if you can tolerate a long (say 15 hours) charge. If you use Lithium ion batteries or want a faster charge you will likely need a charging regulator in each object. Several manufacturers make ICs that perform that function.

 

thanks a lot to hero999 and crutschow .....i will come back asking more specific questions when i've worked out what you are proposing and directing me to...
thanx again

 

the objects i want to light up from the inside are made from opaque plastic and they are about the size of a general purpose light bulb....as i want the whole surface of the object to shine, the battery and led's as well as the electronics for the light touch switch have to fit in there. i know of the 12v led strips which have tiny 2 by 2 mm leds on it that give out quite a good amount of light but through the plastic are still quite low ....also 12v means a farely big battery pack....so do you have any suggestion which kind of led's to use that are bright and small but do not give out too much heat for a closed object
the maximum size of the battery pack is about a 9v block battery

any suggestions welcome

 

Most LEDs don't produce much light. They have a narrow angle for the beam.
Very bright LEDs are made and are fairly wide-angle.
But they use a power supply, not a battery that won't last long.

A little 9V alkaline battery will power one or two very bright wide-angle LEDs for about 15 minutes. It will power one or two ordinary little narrow angle LEDs for about 16 hours.

A little rechargeable Ni-MH 9V battery doesn't have enough power for very bright LEDs and will power one or two ordinary little narrow-angle LEDs for about 5 hours.

If your plastic objects are opaque then light will not shine from inside them. They must be transparent or translucent.

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Uncle $crooge

 

I've seen a listing for a lithium 9V recharageable with 500mAH capacity which is about twice the 9V Ni-MH capacities.

 

Energizer has a disposeable lithium 9V battery that will blow up and catch on fire if you try to charge it. Its capacity is 1200mAh at a current of only 9mA and you allow the voltage to drop down to 5.4V.
So it will light one or two ordinary little LEDs rather dimly for 130 hours (less than 6 days.

At a current of only 120mA it might activate a safety mechanism which can permanently affect performance.

It is very expensive.

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Uncle $crooge

 

thank you guys for the replies.....it is much appreciated !!!!!

....what i meant with opaque was a milky translucency ....i probably used the wrong word....
what about phone batteries ..are they any good for such applications??
or batteries from photo and video cameras they are also pretty small...do they have enough power?????
...because the problem is they have to recharge otherwise the my project won't work.
thanks
moinmoin

 

The capacity of the battery has a lot to do with its size; you can't get away from that. Some technologies are better than others; various lithium rechargeables are some of the best, but charging circuits aren't as easy as NiMH.

But, to the project: First define how bright it needs to be (including the diffuser). Then, choose an LED. Try to find the most efficient that you can. Define operating time. From all this you can calculate how much energy the battery needs to hold. (volts x amps, x hours). From there, choose a battery, and then a driving circuit (if you have a 3V LED but a 1.25V battery seems to be the best fit, there are booster circuits.)

 

thank you!
this definitely helps.....i will try some things and come back when more questions arise..... i'm sure there will-.
thanx
moinmoin

 

hey
are there electronic shops or internet sellers out there who sell touch dimmer for an led project that uses a 9v battery??????

 

Nobody makes an LED light with a tiny 9V battery that lasts only 15 minutes.

I have some "flashlights" that blink an LED 5 times very brightly in half a second then a pause for half a second. The 9V battery lasts 24 hours.

My Ultra-bright LED Chaser projects use two AA alkaline cells for red LEDs and four for blue or white LEDs. They blink each LED brightly but for only a moment. They chase around in a circle (mounted on a CD) a few times then a pause before chasing again. They use PWM for dimming and have a speed control. Their battery lasts a long time.

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