Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

200 Led Light on 4 AA batteries.

Status
Not open for further replies.

RMB93

Newbie level 4
Joined
Jun 3, 2011
Messages
5
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,323
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.
 

hexreader

Advanced Member level 2
Joined
Apr 7, 2011
Messages
537
Helped
194
Reputation
392
Reaction score
196
Trophy points
1,323
Location
England
Activity points
4,766
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!
 
  • Like
Reactions: RMB93

    RMB93

    Points: 2
    Helpful Answer Positive Rating

RMB93

Newbie level 4
Joined
Jun 3, 2011
Messages
5
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,323
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

Administrator
Joined
Mar 16, 2008
Messages
11,895
Helped
2,021
Reputation
4,158
Reaction score
2,031
Trophy points
1,393
Location
Greece
Activity points
64,377
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
Joined
Jun 3, 2011
Messages
5
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,323
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.
42_1307128270.jpg


Hopefully you guys can help me out.
 

RMB93

Newbie level 4
Joined
Jun 3, 2011
Messages
5
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,323
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.
 

KJ6EAD

Advanced Member level 3
Joined
Oct 6, 2010
Messages
709
Helped
196
Reputation
392
Reaction score
194
Trophy points
1,323
Location
Earth
Activity points
5,092
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
Joined
Jun 3, 2011
Messages
5
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,323
Well maybe I'll just have to give up on batteries and use a 12V 4A power adapter instead
 

campus189

Member level 5
Joined
May 7, 2011
Messages
84
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,286
Location
Tennessee,USA
Activity points
1,940
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
 
Last edited:

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top