A simple battery operated emergency light

[adam2]

In case of power failure one may wish to light up a room for safe movement etc.
There are numerous types of lantern and torch on the market, but most are not ideal for longer term use.
They suffer from limited light output or short run times.
Anything with an incandesent bulb is now very last year.
Flourescent and LED lanterns are fairly good, but if hung from the ceiling, dont give much light verticly downwards.

Most types go dim as the battery voltage drops.

Home made may therefore be better,

I have made a couple recently that are far superior to those on sale.
They consist of a good qaulity multi voltage LED torch bulb on the end of a length of flex and powered from 6 D cells in a battery holder.
A switch may be fitted next to the battery holder, or an in line switch can be fitted part way along the flex.

The light output is very impressive, and is virtually constant as the batteries run down.
The lamp and lamp holder are of neglible weight and may be hung from existing light fittings without concerns, unlike a lantern containing heavy batteries.
The switch may be placed wherever convienient, unlike a lantern with a built in switch.
With 6 alkaline D cells the run time should be at least 100 hours, that would cost about 10 pence an hour.
If the batteries leak, only a cheap and easily replaced battery holder will be damaged, not a costly lantern.

6 cells will be about 8 volts on load, declining as they age.
Full light output will be achieved down to about 3 or 4 volts, thus extracting almost all the energy from the cells.

Battery holders, flex, MES lampholders, and switches are available from Maplin.
The LED bulbs can be found on ebay, they are used in Petzl head torches and advertised as such.
The more common PR base LED torch bulbs are not suitable as holders for these are not readily available.

Perhaps worth considering.

Much of the above is now out of date, please view later posts for more up to date information.

[Blue Peter]

Adam,

Would it be possible to go into slightly more detail for those of us who are electrically challenged e.g. which battery holder, flex, MES lampholder (whatever it may be), and switch?


Peter.

[adam2]

Adam,

Would it be possible to go into slightly more detail for those of us who are electrically challenged e.g. which battery holder, flex, MES lampholder (whatever it may be), and switch?


Peter.

A suitable battery holder may be obtained from Maplin
Get one that takes 6 D cells

Any common type of twin flex may be used, nothing special is required, suggest at least 0.5mm so as to avoid excessive voltage drop, and no more than 1.0mm as that would be excessively bulky, heavy and expensive.
Most people probably have something suitable lying around, but if you need to buy it Maplin part number BA41U would serve.
That is a 10M length of single core white wire at about �2.
Cut it in half and twist the 2 pieces together to give 5M of twin wire.

Maplin also have an MES bulbholder, part number RX86T.

Any common type of in line switch may be used, as would be used for say a table lamp.
Maplin part number VJ83E or similar.

The positive wire must be connected to the center contact of the lamp holder.
If wired otherwise it wont work, but no harm will be done, simply swap over the two wires at the bulb holder.

The LED bulb may be purchased from ebay

Edited to add, much of the above information is now outdated, please see following posts for more detail.

[adam2]

Time to update this old thread I think.

Maplin are no longer in business, but all parts are available elsewhere.

Battery holders for 6 D cells are now less common than in the past. If you cant find one, use a pair of holders that each take 3 D cells mounted back to back and connected in series.

Any common type of twin flex may used, at least 0.5mm and up to 1.0mm.
If you don't have anything suitable, buy some twin speaker flex of at least 0.5mm.
Avoid semi rigid bell wire or very thin flex. Single core is fine, simply twist two pieces together.

An in line switch as used for a table lamp is needed, these are cheaply available from many places.

The bulb holder must be an MES type, sometimes called E10 or miniature screw base. Available from fleabay, suggested search term is "E10 bulb holder" these come with either screw terminals or short ready attached wires, either type is fine.
Avoid the bare or exposed style, insulated bulb holder needed to avoid short circuits.

It is important to use a good quality bulb of 1 watt rating and with an E10/MES base. needs to work over the range of 2 volts to 9 volts, at least.
"the torch site" are my favoured supplier, but others exist.