Super Noob. How to I route diff voltages from one battery source

[echo]

I am a big idiot with electricity, so your help is greatly appreciated.

I was trying to read the recommended readings, and I am confused, since there is a very fundamental lack of understanding.

I am trying to create a lighting system for my bike. What I need to do is pull power from a battery which can output as much as 19V DC and route it to headlights and taillights of different voltages, as low as 6w/3v.

What I've found in searches is that I need a voltage regulator?, but do I need one for every different voltage I have? It seems to me there has to be another way to manage the voltage... What am I missing?

Thanks very much in advance for taking the time to help me. Even just pointing me to some previous threads would be a great help.

 

[Jaguarjoe]

I would try real hard to commonize all of your lamps to a standard voltage value, like 12 volts. Then you will only need one regulator to step down from Batt voltage to 12 volts. Make sure that the minimum voltage of the battery is at least 2 volts more than your common lamp voltage (hopefully 12 volts).
If you can't come up with common lamp voltages, you can put lamps of the same voltage and wattage in series to get to a common value but this only works with equal voltage/equal wattage lamps. The problem with doing it this way is that if one lamp in the string burns out, all the lamps in that string will go out too.
If you still can't commonize your voltages, read up on SMPS or switching power supplies to learn about efficient regulators.

 

[birdman0_o]

Read about the basics of Series Connections.
Each bulb will drop a certain amount of voltage.

Example: 18V source and 6W/3V bulbs.

P = IV => 6W = I*3V => I = 2A

Now, lets make a series interconnection.

+ --- Bulb ---- Bulb ---- Bulb--- Bulb ---- Bulb ---- Bulb---- gnd. Since each bulb is dropping 3V we have 6*3V = 18V.

18V - 18V = 0V ( gnd ) so our circuit is correct. In series, the current is the same so it will be 2A.

Then the total power draw of this circuit is 2A * 18V = 36W.

This will get you started lets move on from here after.

p.s. if you were a big idiot you wouldn't be asking for help

 

[BrownOut]

What I've found in searches is that I need a voltage regulator?, but do I need one for every different voltage I have? It seems to me there has to be another way to manage the voltage... What am I missing?

There are different ways. The best way will depend on exactly what you're trying to power. For example, you might use a voltage regulator to get 9V from your system, then use a resistive divider to get 3v for a low power device. But we would need to know exactly what you are doing before we could recommend the components.

 

[echo]

Thanks so much for the responses. I appreciate the help.

Actually, since you mention commonizing things - and after looking at my options with that in mind, I guess I can use 12V for everything.

But then, I still need resistors to keep the amps at the right levels for each appliance right?

Thanks,

 

[KeepItSimpleStupid]

Are these LED lamps?

 

[echo]

The taillights would be, yes, but the headlights would be standard bulbs.

 

[BrownOut]

Thanks so much for the responses. I appreciate the help.

Actually, since you mention commonizing things - and after looking at my options with that in mind, I guess I can use 12V for everything.

But then, I still need resistors to keep the amps at the right levels for each appliance right?

Thanks,

I don't think that's what JJ really meant. He is suggesting that you change all of your appliances so that they all operate on a common voltage, say 12V. What you're talking about is possible, but may not be practical. Incadescent lamps, for example, have resistance that changes over time as they warm up, so a simple resistor might not do. We would probably need to look at each appliance you're operating.

 

[echo]

OK, thanks for going through it with me,

So I bought this:
44W Variable input and output battery pack
Portable lithium ion battery pack Battery Power Station weighs only 1 pound, portable battery system, USB external battery

I will recharge it as I ride with this (albeit slowly, just to extend time between charges):
Shimano Hub Dynamo generating 6w/3v output
Universal Cycles -- Shimano Nexus Sport Dynamo Hub

I want to power these lights (or something similar with different specs if, I am not married to these):
Maybe something like this for headlights
**broken link removed**

Something like this for a horn
12V Horn for Motorbike Motorcycle Mini Chopper Scooter: 004616-137 Virtual Village USA

Don't know yet what I would use for tail lights.

Thanks!

 

[echo]

I posted a reply with links to the items, but it's in moderation.

Just letting you know that I am responding.

Thanks!

 

[KeepItSimpleStupid]

The reason why I'm asking about the LED's is LED's are CURRENT devices with a specific voltage drop. In other words you have to supply a current to the LED and limit it with an active limiter or resistor. If the LED voltage was Vfd = 2.1 V and you wanted to operate it at 20 mA, then the resistor required would be <= (12-2.1)/20e-3 ohms.

You can buy LED replacements for some standard automotive bulbs.

 

[carbonzit]

So, to simplify a bit, perhaps:

• For incandescent bulbs, you don't need resistors for current limiting. You might need resistors if you're going to divide down voltage, but of course you should realize that you'll be wasting energy as heat (in the resistor) then.
  
• If you use LEDs, you definitely need current-limiting resistors. Value of resistors depends on LEDs, voltage and current. Some LEDs contain internal resistors.

 

[KeepItSimpleStupid]

Switching regulators can convert voltages higher or lower with 80-90* % efficiency which is another option.

 

[echo]

Don't know when my post with links will leave moderation, but I have to just get you the list of the parts I will use.

I don't know yet which I will use, but it will be something along these lines:

Battery pack can output in various voltages up to 19v, 44w.
Portable lithium ion battery pack Battery Power Station weighs only 1 pound, portable battery system, USB external battery
I bought that already.

Lights are variable, but would be something like this, specs-wise
**broken link removed**

Taillights could be any standard LED taillight strip, here is an example:
**broken link removed**


Horn would be something simple like this:
Chris Products 2 1/2 in. 12V Horn - DennisKirk.com

Switches would be like this:
**broken link removed**

Then I would add turn signals too, all LED of course.

Thoughts?