# 200 Led Light on 4 AA batteries.

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#### RMB93

##### Newbie level 4
I want to make a 200 LED camera light using 4 AA batteries. My plan was to connect 20 10 led strands in parallel with a 130 ohm resistor on each strand. I was then going to add a potentiometer in series to control the entire circuit. I am wondering what problems I will run into and how I would go about resolving them. I was also wondering what potentiometer I should use.

Here are the specs for the LEDs I plan to use--

Size: 5mm.
View Angle: 25 Degree.
Lens Color: Water Clear.
Drive(Forward) Voltage: 3.0~3.6V.
Drive(Forward) Current: 20~30mA.
WaveLength: 460~463~466nm.

10 times 3Volts is 30 Volts. 4 times 1.5 Volt battery is 6 Volts, so you are AT LEAST 24 Volts short of your target, probably more.

Can't be bothered working out the maths, but I suspect that your potentiometer will burn out. If you want to reduce brightness, moving the light further away is much simpler. Else turn off half of the LEDs for half brightness etc.

Why not use 'D' cell batteries? They will last longer and (may) work out cheaper.

First problem is the most fundamental. You just don't have enough volts!

RMB93

### RMB93

Points: 2

#### RMB93

##### Newbie level 4
Ok, thanks. I didn't think about that. I have just recently gained an interest in electronics so I am not very experienced. Anyways I am thinking I will use 6 AA batteries instead so I could make strings of 3 LEDs. If I did this I would not need resistors correct? Also I am using AA instead of D because I have rechargeable AAs and all those D batteries would hinder portability. If I can't use a potentiometer Ill just add 4 switches into the circuit which should give me enough control. The only reason I wanted the potentiometer is because simply turning of some of the lights would make it less bright but it would also leave me with a smaller more focused area of light in comparison to the whole thing being dimmed.

#### alexan_e

What kind of batteries do you have?
If they are NiMH you should expect about 6*1.2v=7.2v , you can't connect 3 leds in that voltage.
Assuming a current of about 20mA you will need 200+0.02A=4A so the best case scenario with batteries of about 2000Ah is half an hour.
It is very difficult to use leds using constant volatile, it it very difficult to control the led current that way, you will need to use a resistor but that means that you will loose energy on these resistors as heat.
I think you should consider going for a few power leds (1w or 3w) to make the wiring much easier and use constant current drivers with your batteries to get the maximum performance.
In that case you may need a diffuser of some kind to avoid the focused beam light.

Alex

#### RMB93

##### Newbie level 4
High power LED's would make things easier but also more expensive. I can get 200 LEDs for $10-15 dollars and I don't have to worry about a good diffuser. Is there no good way to set it up as I originally planned aside from having 10 LED strings? I have found some 1.5 - 2.5V, 20ma LED's so perhaps I could use those instead which would give me the possibility of using a resistor to control current. I think I will go with 1.5 v batteries because they are more available even though my rechargeables are 1.2V. I could buy a light for about$50 or so but what is the fun in that. Also being a student I have a pretty tight budget so the cheaper the better. Here is an example of what I want to make.

Hopefully you guys can help me out.

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RMB93

### RMB93

Points: 2

#### RMB93

##### Newbie level 4
So I can just use 8AA batteries then make as many 3LED strings as I want without issue correct? I could get a good 12v rechargeable battery or use a wall adapter and it should work.

With the right DC-DC boost converter(s), you might be able to run your 200 LEDs from 4 AA NiMH batteries for 20 minutes or so, but it would definitely violate your cheapness requirement and probably damage the batteries.

I would like to fly to the moon, stay for a week and stop over in Hawaii on the way home for $20.00. Tell me how. :twisted: #### RMB93 ##### Newbie level 4 Well maybe I'll just have to give up on batteries and use a 12V 4A power adapter instead #### campus189 ##### Member level 5 That light looks like it has 48 leds, am I wrong about that? Reason that I'm asking is, you could run 48 leds with 2 of the circuit boards i got from ebay with a little modding to the resistors for under$5.00 & Lights at $3.99 each X 3 for$12.00 for a total cost of \$17.00 minus resistors.

Check out the post I made here for more details..
Mine runs from 12 volt power source ( Battery )
Of course you would have to design a custom case for it.
These lights will blind you for sure if you look at them even 3 feet away.
I'm still working on testing the project to get final results.
I plan on running 8 of these on a 12 volt battery for a total of 192 leds.
That's a little under your target amount.
Just a thought

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