basic 12v question...

[yockman]

Hi guys,

Very basic question here - I'm replacing some lights in my boat, there'll be four on one switch/circuit. Of the two circuits below, which is the go? Or is there a better third way?

Cheers,
Yock

[JasonT]

Go the parallel method (2nd pic).
In the first pic, if one bulb fails all will be extinguished as there is no path for current to flow to through the remaining globes

In parallel, the ones that aren't blown will continue to glow!

JT

[PADDLES]

gents, you use a parallel circuit because it's a "current divider" circuit and not a "voltage divider" circuit like your first diagram. what the first one does is split your 12V across the 4 lamps so each lamp has a drop of 3V (if they're all the same size of lamp). a parallel circuit will split the current and still give you a full 12V across each lamp. jaso is correct too, if the circuit goes open from a blown lamp in system one you lose everything. :)

ps. don't forget to use a fuse, yock.

[yockman]

In the first pic, if one bulb fails all will be extinguished as there is no path for current to flow to through the remaining globes

D'oh, ::), I knew that from Christmas tree lights. Thanks for reminding me.

Much appreciated info there guys, and explanations simple enough for this numbnut to understand.

Paddles, it shall be fused ;)

Cheers,
Yock

[Y-Not]

Hey paddles, That all sounds to technical. :o Easier just to say fuse the parallel one and smile when 1 of the lamps blow and the rest stay lit ;D ;D

[StevenM]

the second pic

[PADDLES]

good one ynot ;D

[JasonT]

By the way, there is actually a third way!
That is by way of a 555 timer and a couple of 12 bit counters!
Basically, what you're doing with this circuit is very quickly flashing the lights on and off.
This on the surface may not seem to make sense, but think about this...
When a globe is connected to a DC voltage source, it is constantly drawing current. The 555 timer and counters can be connected in such a way that you are able to pulse a voltage on and off across the globe. Providing you do that approx 50 times a second the globes will appear to be lit constantly, much like the globes in our homes.
Pulsing a voltage across the globes means you don't have a constant current flow, rather it's on off on off... #This allows for significant savings on battery power usage depending upon the duty cycle (the amount of time on compared to amount of time off).
I have set up a similar circuit to control water flow through my live well.
It turns on for 30 secs every 2 mins. In this time it replaces about a quarter of the water. Have managed to keep herring alive for over 12 hours.

Jason

[finga64]

Jason, mate if your that worried about current draw just bung a fluro or some LED's in ;)
Great idea with the bait pump though :)
Can you put a schematic up with the timers??

[yockman]

This sounds a bit clever. :)

Coupla questions - if it's pulsing that often, will it actually save any battery, and could a mug like me put this together. Also, would you get parts from jaycar or similar?

Cheers,
Yock

[murf]

when you said about a 555 timer all I could think of was you are setting the boat up for Xmas ;D
Murf

[Chimo]

Hi Jason T

Can you advise where one can source the 555 timers and the 12 bit counters and I'm with Finga, can you put up schematics too?

Do you have to water proof the bits and pieces and if so can you suggest ways. Where in the circuit would these things be installed.

Sounds an interesting project, thanks

Cheers

Chimo

[JasonT]

Firstly, yes it does make a huge difference to battery drain..
I'll try to explain it without mathematical formulae - wish me luck!

If you use a straight DC supply, your duty cycle (the proportion of time during which a component, device, or system is operated.) is 100%. That is, current is continually drawn.
If you pulse it on for say 1ms and off for 3ms your duty cycle falls to approx 25% (Current is drawn for only 1ms out of every 4ms)
This means you use 75% less power than with a 100% duty cycle to perform the same amount of work.

In the above example the lights will turn on for 1ms every 3ms. this means it will complete one on off cycle every 4ms which is roughly 250 times per second - 5 times faster than they really need to be. (the human eye loses the ability to see the flashes occuring anywhere around the 50hz mark (ie 50 times per second))

You could fiddle so that the globes illuminate only 50 times a second by adjusting your on/off times.

The point is you don't need to continually supply current. As long as you supply it in pulses at a frequency of or greater than 50hz, the light will appear to be constantly on.

I have neglected to mention anything about switching times (of components) and similar things you will need to consider when choosing components to make this cct.

A similar idea is used in new electric outboards and is advertised as a "power saver" feature.
They do the same thing... Power the motor via a series of pulses rather than supply constant DC.

Finga,
Your idea of flouros and Leds is spot on mate. They will draw less current than a conventional globe.
That's why I use them! Combined with the above circuit I can pretty much power my whole boat for days on end without needing to charge the battery, which is handy as my outboard does not have a rectifier/regulator cct! YET!


All parts are avalable from DSE or Jaycar, but you will need #some electronics knowledge to successfully put the circuit together.

Watch the Io(max) #(max output current) figure on your output transistor if you use one..Personally I used a relay instead as the particular 555 timer I used could drive it, and relays are a bit hardier than transistors!

Be particularly careful if you use CMOS components as they are ESD (static electricity) sensitive and can be rendered inoperative simply by touching the pins with a finger. It's important to make sure you, your soldering iron, and the component are correctly earthed to prevent ESD occuring.

You will need to waterproof it of course and this can be done using a flowable silicone. place the cct in a suitable box and run your wiring through drilled holes. Place tape over the wires and holes on the outside of the box and fill the box to above the cct board with flowable silicon.
This will protect it from rust/water etc but does make it hard to carry out repairs should something break!

I'm happy to help anyone who decides to give this a go.. Post here or preferably PM me with any questions!

You can get a cct diagram from googling "555 timer circuit" on the web, but it will need to be modified to suit your purpose.


Jason

[JasonT]

One thing guys...(and gals!) :)

This circuit should NOT be used to run sounders, gps's or any other electronic device like radios etc as it may adversely affect them. (they are designed to operate with a constant 12V supply.)

Things like lights and DC motors are fine...
Applications include Winches, bait pumps, lights etc.
If you're not sure, play it safe and don't connect a pulsed supply to the device.
Feel free to PM me with questions or post them here.

Jason

[Roughasguts]

Jason, sounds good and worth a shot at it as long as the set up doesn't cost much.

But thinking for reliability of service should a bi-pass switch, a simple loop and, a toggle switch be made before and after the 555 setup, just in case it fails.

Think I would tackle it this way electronics, and the marine enviroment aren't that favourable for long service.

[Noelm]

not too sure about the 50hz thing, in electronics there is an old saying "you get nothing for nothing" so in effect, to run this "miracle" 555 timer will require power, in fact probably more power than you save by 'switching" off the lights 50 times a second, if you could get "something for nothing" you could just hook up an alternater to a 12volt motor, give it a spin and then the alternater supplies power to run the motor than runs the alternator, get the idea?? perpetual motion has facinated scientists and inventors for centuries!

[JasonT]

Excellent point Roughasguts and the very reason I have both a total bypass and redundancy throughout the whole system.
If a relay fails, I can easily piggyback another as the relays are rated much higher than the current actually being passed through them.

I have given alot of consideration to it, and designed mine with safety, ease of use and repair in mind.
the only tricky part for me is all the PCB covered with silicone. if this board fails, I have to use the bypass and wait to repair it at a later date.

If you're going to use LED lighting and a have a bypass, make sure you have a current limiting resistor in series with the led's as you may blow them depending on the LED itself. I suggest a resistor on the positive supply prior to the bypass switch.

Jason

[JasonT]

not too sure about the 50hz thing, in electronics there is an old saying "you get nothing for nothing" so in effect, to run this "miracle" 555 timer will require power, in fact probably more power than you save by 'switching" off the lights 50 times a second, if you could get "something for nothing" you could just hook up an alternater to a 12volt motor, give it a spin and then the alternater supplies power to run the motor than runs the alternator, get the idea?? perpetual motion has facinated scientists and inventors for centuries!

Noel.. at 5V this "miracle" 555 draws a maximum current of 6milli amps.. That's 6 thousandths of an amp. MAXIMUM. It typically draws 3mA 3 thousandths of an amp.
At 15V these figures increase to between 10 and 15mA
That's way better tna a globe!


You're not getting something for nothing with this circuit. And any similarity between this and a perpetual motion machine is entirely in your imagination.

All you are doing is usng the battery power in a much more efficient manner.

Happy to supply you a #block diagram


Jason

[quigley595]

Jason,
I would love to give this one a shot.
Would it be possible for you to supply a diag and simple instructions, parts list etc??? I am no electronics expert, but I am competent with electrics generally.

How much do the components cost??

regards
Mike

[Dirtysanchez]

Actually I have a customer who almost perfected perpetual motion using rhe back EMF from an electric scooter motor to charge the battery.
Very ponderous, then a large oil company came along with a piece of paper with many zero's on it so he would go away

True story, he was going to make a fully renewable system to power a wheel man (look up wheel man on the net)