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Convert LR44-powered to AC

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horc00

New Member
Hi everyone,

Sorry, electrical noob here. I know I can probably spend some time googling to piece together a solution (I've tried but haven't yet gotten all the answers I need yet), but I'm eager to do up a lighting display for my kid's room, hence hoping you guys can help me out here.

I have 8 lighting displays that each uses 3x LR44 batteries (1.5V, 150mAH each) in series. I would like to wire them all up to a single AC adaptor. I have a few questions:
  1. Option 1: Using an adaptor with 9V DC output, can I just wire the lights into 4 paralleled series of 2 lights each? i.e. 2 lights in each parallel circuit (2 x 3 x 1.5V = 9V)
  2. Option 2: Using an adaptor with 5V DC output, can I just wire the lights into 8 paralleled series of 1 light each? i.e. (3 x 1.5V = 4.5V) in each parallel circuit
  3. Which option is preferable?
  4. Do I need any other components such as a voltage regulator or can I just wire the adaptor directly to the lights?
  5. What is the minimum output amperage that I would need?
Appreciate any help I can get.

Here's an example of the light.
 

dknguyen

Well-Known Member
Most Helpful Member
Hi everyone,

Sorry, electrical noob here. I know I can probably spend some time googling to piece together a solution (I've tried but haven't yet gotten all the answers I need yet), but I'm eager to do up a lighting display for my kid's room, hence hoping you guys can help me out here.

I have 8 lighting displays that each uses 3x LR44 batteries (1.5V, 150mAH each) in series. I would like to wire them all up to a single AC adaptor. I have a few questions:
  1. Option 1: Using an adaptor with 9V DC output, can I just wire the lights into 4 paralleled series of 2 lights each? i.e. 2 lights in each parallel circuit (2 x 3 x 1.5V = 9V) This is fine.
  2. Option 2: Using an adaptor with 5V DC output, can I just wire the lights into 8 paralleled series of 1 light each? i.e. (3 x 1.5V = 4.5V) in each parallel circuit This is also fine.
  3. Which option is preferable? It doesn't matter really. I'd choose base on availability of wall warts and the wall wart that has the max power output.
  4. Do I need any other components such as a voltage regulator or can I just wire the adaptor directly to the lights? As long as it's a regulated AC-DC wall wart you should be fine without anything else since it is already regulated.
  5. What is the minimum output amperage that I would need? I wouldn't worry about it tbh since any wall wart you choose should be more than enough if they are LR44 bbatteries. I'd try and go for a wall-wart of at least 1A though.
Or you could use an AC-DC brick adapter similar to what you might find for a laptop charger if you really need more current.
See quotes post. Series and parallel mean opposite things. So do not say "parallel series" since it is somewhat ambiguous if we can't trust that the person saying it knows what they are trying to say, even though I get what you mean in this case.

Just use more words. Like "four parallel groups where each group is 2 lights in series with each other".
 
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Pommie

Well-Known Member
Most Helpful Member
You can work out the amperage from how long the batteries last - if they last 3 hours then each light takes 150/3 =50mA So, 4 paralleled will take 200mA - add 50% for safety and get a supply that can supply 300mA or more.

Mike.
 

horc00

New Member
See quotes post. Series and parallel mean opposite things. So do not say "parallel series" since it is somewhat ambiguous if we can't trust that the person saying it knows what they are trying to say, even though I get what you mean in this case.

Just use more words. Like "four parallel groups where each group is 2 lights in series with each other".
You can work out the amperage from how long the batteries last - if they last 3 hours then each light takes 150/3 =50mA So, 4 paralleled will take 200mA - add 50% for safety and get a supply that can supply 300mA or more.

Mike.
Thanks for the input guys! Appreciate it.

I will wire them in 8 paralleled groups of 1 light each so it's easy to troubleshoot if anyone breaks down in the future. I think I've got a 5V or 4.9V mobile phone adaptor somewhere I can use.
 

audioguru

Well-Known Member
Most Helpful Member
The LR44 button battery cell is so small that it has a fairly high resistance that limits the current.
We do not know if the lights use additional resistors inside to limit the current.
If no additional resistors are used then connecting a light to more powerful 4.5V or connecting two lights in series to 10V will instantly burn them out.

Are the LEDs white and connected in parallel with no additional resistor?
Are the LEDs very dim and do you want them to be brighter?
Do the LR44 cells power the lights for longer than 1 hour? How long?
Do the LEDs blink on and off?
Does each letter have 5 LEDs?

The Energizer datasheet for an LR44 cell shows a resistance when new of from 5 ohms to 15 ohms.
Then if the LEDs do not blink and are 3V white ones and the cells each have 5 ohms, the battery current is (4.5V - 3V)/15 ohms= 100mA then each LED in the 5 LEDs light get 20mA and will be bright with a new battery but the battery will last for only 2 hours while slowly dimming.
If the 3V LEDs are powered from three 15 ohm battery cells then the battery current is (4.5V - 3V)/45 ohms= 33.3mA and each LED gets 6.7mA and will be dim but the battery will last for 6 hours while slowly dimming.

Do you know how to measure the polarity of a DC power supply? Then try using a 5VDC /1A power supply with a 39 ohm resistor in series to power one light with the battery removed. The 5VDC power supply can be one that produces more than 1A.
 
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