How to wire a LED

[Mats]

Hi guys!

I´ve got a product that I want to start manufacturing where I need to wire a 12v model rail way light to a 9 volt battery.

Now I´m a complete noob when it comes to wiring but so far I´ve understood that I need to include some sort of resistance(?) in order to keep the battery from draining within minutes.

I´ll much appreciate any help on this.


Best Regards

Mats

 

[BobK]

If the light is a single LED with a resistor designed to work from 12V it will probably work as is from 9V but at a lower brightness. To bring it up to full brightness, you would lower the value of the series resistor that is already there. A 9V battery will be able to drive a single 20ma Led for about 24 hours.

Bob

 

[cjdelphi]

that's a little incan bulb, replacing it would be easy enough with an LED.... (try to finder an LED which is on the warmer side, or you'll not get the street lamp feel (high/low pressure sodium lamps) ...

basically, what LED are you using?

 

[(*steve*)]

A really important benefit of using LEDs is that they have the same colour at all brightness levels.

A small surface mount LED would probably work well in this case, maybe covered with a small blob of clear epoxy to simulate the glass.

 

[Mats]

Thank you.

Thanks guys! these replies came a lot quicker than I had hoped.

If the light is a single LED with a resistor designed to work from 12V it will probably work as is from 9V but at a lower brightness. To bring it up to full brightness, you would lower the value of the series resistor that is already there. A 9V battery will be able to drive a single 20ma Led for about 24 hours.

Bob

I don´t think the lamppost has a resistor built in, are you saying that the battery should last 24 hours without a resistor?

that's a little incan bulb, replacing it would be easy enough with an LED.... (try to finder an LED which is on the warmer side, or you'll not get the street lamp feel (high/low pressure sodium lamps) ...

basically, what LED are you using?

If it is a normal bulb I prefer leaving it as is, but when I connect it to a battery it still only glows for about 10 mins.

A really important benefit of using LEDs is that they have the same colour at all brightness levels.

A small surface mount LED would probably work well in this case, maybe covered with a small blob of clear epoxy to simulate the glass.

Thats a good idea, but I´m planning to produce quite a few of these objects, and I need to omit anything time consuming in the process of making them.

Thanks to all of you.


Mats

 

[(*steve*)]

What sort of battery are you using?

 

[Mats]

What sort of battery are you using?

One of these

 

[(*steve*)]

With a battery that small it's not unexpected that it will have a short life driving a bulb. However 10 minutes does seem short.

Can you measure the current it draws? (Or give us the exact specs of the bulb)

 

[Mats]

With a battery that small it's not unexpected that it will have a short life driving a bulb. However 10 minutes does seem short.

Can you measure the current it draws? (Or give us the exact specs of the bulb)

Hi.

This is the information I´ve got on the bulb:

• Brand: Everest.
• Size: Approx. 75mm(H) or 2.95''(H) Inch.
• Scale: 1:76~1:100,Suitable for OO scale or HO scale etc....
• Color: Gray.
• Operating Voltage: 12V, AC or DC Compatible.
  [*] Operating Current: 70mA.
• Material:Coppery Column Model Lampposts.
• Package Included: 10 complete lamps.

Cheers


Mats

 

[BobK]

At 70ma you should be getting something like 6 hours out of a 9V battery.

Bob

 

[Mats]

At 70ma you should be getting something like 6 hours out of a 9V battery.

Bob

Hi. I still only get like 10-15 mins and all the while the buld becomes dimmer and dimmer and then finally goes out completely. If I switch it off and wait half an hour and then turn it back on it lights up again and repeats the former.


Mats

 

[BobK]

Does it do this with a fresh new battery?

Bob

 

[Mats]

Yes.

With cheap batteries and brand batteries alike


Mats

 

[(*steve*)]

Are you running 1 of these lights or 10?

Do you have a multimeter?

I'd like to know what the current actually is when the bulb finally goes out, and the voltage across the bulbs.

My suspicion is that the bulb (a 12V bulb) requires a relatively high voltage to appear lit, and the 9V battery quite rapidly falls below this.

Have you done a comparative "tongue test" on a new and an old battery?

 

[Mats]

Hi

I´m only running one with each 9volt battery.

I don´t have a multimeter.

I´ve done tongue test now, and there is definitively juice to begin with..


Cheers.