Electronics help

Mark M

Mark M

Mark M

Soldato
Joined
6 Jan 2006
Posts
3,423
Location
Newcastle upon Tyne
Ive been tasked with coming up with a solution to make some led cocktail tables on the cheap for my mates barn where he has the occasional party. The price of the units new are apparently around the £500 mark so theres no way he can afford that and probably doesnt need anything as professional.

Given we are going for a budget alternative I would be happy not having them colour changing and just a single colour so should make things slightly cheaper.

Ideally the units need to run off batteries as cables and drunk people dont mix. Can you get suitable batteries to drive LEDs? I know you can get LED xmas lights so I think the answer to that must be yes but any info would be appreciated.

My only other alternative would be to go with cables and use cable protectors taped down? This way I could use LED Par cans and could even hook them up via DMX so they could change colour at the same time.

Any other thoughts fire away

Mark
 
Also, let's say you wanted to run 3 LEDs on each table - one for each colour maybe (R, G, B), they will pull about 60mA altogether.

If you use 2*AA batteries at 1.5V each to make up your 3V, you should have about 4000mAh to play with (assuming you can just add up battery capacities like that, I'd assume you can) - which I think leaves you with 66.6r hours of light in one pair of batteries.

If you want to be clever then you should be able to get colours phasing with a bit of electromatrickery - but I haven't looked in depth to see what kind of voltage is needed and current pulled by the logic chip: http://www.instructables.com/id/RGB-LED-Color-Sequencer-without-a-Microprocessor/
 
sara said:
I haven't looked in depth to see what kind of voltage is needed and current pulled by the logic chip
Click to expand...

Microchips use next to nothing in terms of power compared to the LEDs. You will need some sort of LED driver circuit if you are going to be using them with a microchip though such as a transistor or FET.

This is a PIC based project for a RGB LED mood light, I built one for a Halloween lantern last year. http://picprojects.org.uk/projects/rgb/
 
As Sara is saying, If he just wants to light a table up using LEDs in one colour, then all you need is a battery, a number of LED's and a resistor (to limit the current)..


Here's a page that lets you calculate the resistor required for single/series and parallel LED's, to make it even easier.

http://ledz.com/?p=zz.led.resistor.calculator


You can use larger value resistors to reduce the brightness if required..
 
sara said:
Also, let's say you wanted to run 3 LEDs on each table - one for each colour maybe (R, G, B), they will pull about 60mA altogether.

If you use 2*AA batteries at 1.5V each to make up your 3V, you should have about 4000mAh to play with (assuming you can just add up battery capacities like that, I'd assume you can) - which I think leaves you with 66.6r hours of light in one pair of batteries.

If you want to be clever then you should be able to get colours phasing with a bit of electromatrickery - but I haven't looked in depth to see what kind of voltage is needed and current pulled by the logic chip: http://www.instructables.com/id/RGB-LED-Color-Sequencer-without-a-Microprocessor/
Click to expand...

batteries in series add their voltage, their overall capacity stays the same.
batteries in parallel add their capacities and their voltage stays the same.

An of two pairs of AA's in series in parallel would give you the 3v and 4000mAh you want.

of course, you could just use D cells which have a capacity of about 15,000mAh
 
Thanks for the input guys, a lot of it is going over my head but Im sure a bit of reading will get me up to speed.

Anyone know where I can get a battery pack that I can connect to a PCB or just wire it straight from it perhaps?
 
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