12v regulated supplies

[Tusses]

Is there a range of 12v regulated supplies ?

 

it seems to come up on here quite often - 12v equipment and LED lighting etc.

 

is there a gap in the market ? (kerching:) )

or are the suitable solutions on the market already.

 

I am thinking along the lines of , for instance, a fuse board type box that takes the raw 12v (upto 15v ish (17v? on desulphation ?) ) and limits any over voltage situation on the output (fused) side.

[chris w]

I would guess that the reason they're not seen is that the market for them is not big enough. Most of the "12v" stuff on a boat will happily run at 12-15v so no problem. The few items that might be affected by 15v will almost always have internal 12v regulators in them anyway. For the remainder there are DC-DC converters or their own 240/12v power packs.

 

Having said that, rigging up a 12v regulator circuit on one of the fuses at the panel would be very easy though, electronically-speaking.

 

Chris

[Tusses]

Having said that, rigging up a 12v regulator circuit on one of the fuses at the panel would be very easy though, electronically-speaking.

 

Chris

 

 

Thats why I was wondering why no one does it . Sounds like a niche market for a sole trader perhaps ?

Not popular enough for the big boys to get involved, so leaves an opportunity for a one man band setup

[Chris Pink]

Thats why I was wondering why no one does it . Sounds like a niche market for a sole trader perhaps ?

Not popular enough for the big boys to get involved, so leaves an opportunity for a one man band setup

 

 

substitute 7812 for 7805, cheap as chips. Up to 1A continuous.

 

if you need more than 1 amp then the smart way is to use the above circuit to switch a power transistor.

 

http://www.ortodoxism.ro/datasheets/motorola/MC7809.pdf has more detail.

Edited March 31, 2008 by Chris Pink

[Tusses]

 

substitute 7812 for 7805, cheap as chips. Up to 1A continuous.

 

if you need more than 1 amp then the smart way is to use the above circuit to switch a power transistor.

 

http://www.ortodoxism.ro/datasheets/motorola/MC7809.pdf has more detail.

I was thinking of a much higher output - and if you are using power trannies - then a zenner would be my 1st thought ?

[Chris Pink]

I was thinking of a much higher output - and if you are using power trannies - then a zenner would be my 1st thought ?

 

 

My feeling is that a zener diode would do the job of protecting a sensitive piece of equipment but if used to permanently regulate then the excess power is being wasted by being dissipated as heat by the diode. If you are thinking of making a unit to sell then it is worth a bit of R&D to develop a properly regulated power transistor solution which, because it works by switching, will not waste so much power. And of course you will need to build-in various protections, reverse polarity eg.

[Gibbo]

substitute 7812 for 7805, cheap as chips. Up to 1A continuous.if you need more than 1 amp then the smart way is to use the above circuit to switch a power transistor.http://www.ortodoxism.ro/datasheets/motorola/MC7809.pdf has more detail.

This is another one that comes up often. As is this often shown "solution".The above circuit will NOT work. The 78xx regulators need an input voltage at least 2.5 volts higher than the output. So a 12 volt one will not work until the input voltage is above 14.5 volts. With an input voltage of (say) 12 volts they simply do not work. They produce an output of a few volts.The problem requires a switch mode solution so that the output can be above OR below the input voltage.It isn't such a simple problem to crack.Gibbo

Having said that, rigging up a 12v regulator circuit on one of the fuses at the panel would be very easy though, electronically-speaking.Chris

Go on then..... Gizza circuit diagram.:)Gibbo

[Chris Pink]

This is another one that comes up often. As is this often shown "solution".The above circuit will NOT work. The 78xx regulators need an input voltage at least 2.5 volts higher than the output. So a 12 volt one will not work until the input voltage is above 14.5 volts. With an input voltage of (say) 12 volts they simply do not work. They produce an output of a few volts.The problem requires a switch mode solution so that the output can be above OR below the input voltage.It isn't such a simple problem to crack.GibboGo on then..... Gizza circuit diagram.:)Gibbo

 

I hadn't though of that, it is true, I have used 78 series regulators for 9V (well 8 actually) and 5V which fit that spec, 12V units on my boat just have to like what they get. If they blow up it is the electronic version of natural selection.

[Tusses]

My feeling is that a zener diode would do the job of protecting a sensitive piece of equipment but if used to permanently regulate then the excess power is being wasted by being dissipated as heat by the diode. If you are thinking of making a unit to sell then it is worth a bit of R&D to develop a properly regulated power transistor solution which, because it works by switching, will not waste so much power. And of course you will need to build-in various protections, reverse polarity eg.

 

I was thinking as using the zener as a voltage reference for a power transistor when the voltage goes high.

 

there will still be power dissipated by the transistor - but this would only be during the charging stage - where a few watt's lost are less important.

[Keeping Up]

I was thinking as using the zener as a voltage reference for a power transistor when the voltage goes high.

 

there will still be power dissipated by the transistor - but this would only be during the charging stage - where a few watt's lost are less important.

It CAN be done but it is surprisingly difficult. The power transistor needs some voltage across it (C-E) to make it work, and its output (at E) is slightly lower than the zener voltage (on . Then in order to get enough current when the battery volts are close to the zener voltage, you need a very small value of dropper resistor - which means it takes a lot of current when the volts rise during charge (so the resistor and zener get hot as well as the transistor).

Edited March 31, 2008 by Keeping Up

[Tusses]

I admit to not thinking about it in detail ! - I just thought you could use battery power up to your pre difined point and then switch to voltage limited supply. I'll have a think on it when I get some time later and see what I come up with.

 

btw - it is cool the way peep's on this forum know electronics - i've been my own geek for years - now you can all join in

[Gibbo]

It's one of those things that is dead simple until you look into it properly. Then you realise it's actually a major design challenge.

 

As Allan said, the zener and transistor seems simple enough until you realise (in addition to what he also said) there's not enough gain. So you have to add another transistor. Then you've got two transistor drops so you're losing about 1.3 volts. No big deal, just use a higher voltage zener. But that only works with a high battery voltage. At 11 volts input you've only got 9.7 volts output. Plus your transistors are dissipating the current through them multiplied by the volts across them in Watts.

 

So you can turn the problem on its head and use a PNP transistor. That way you can (almost) avoid the voltage drop problem and get an output voltage that is very close to the input voltage. But the regulation becomes far more complicated. Plus it isn't fast enough to stop the voltage spikes.

 

It's a nightmare of a problem and the only solution is a switchmode power supply. And a switchmode supply that can provide an output voltage above AND below the input voltage is not a simple device.

 

Gibbo

[Tusses]

It's one of those things that is dead simple until you look into it properly. Then you realise it's actually a major design challenge.

 

Gibbo

 

I shall look at it properly..... until then .... bah to SMPS

[DHutch]

Dont know whats in it, but we have one of these to run out 12v radio and phone chargers of our 24v boat.

 

http://uk.farnell.com/1257748/electrical-c...TRONICS-GSR400V

 

For £70 its not an awfull price to pay.

 

 

 

Daniel

[smileypete]

It's a nightmare of a problem and the only solution is a switchmode power supply. And a switchmode supply that can provide an output voltage above AND below the input voltage is not a simple device.

 

For small loads I'd look at modifying something like this to output 12v:

 

 

With a bit of luck it will just need a resistor change. There are ones around that will take 15V/16V input too.

 

I'd expect the reason they only go down to 15v is that laptops need at least that much to charge thier batteries.

 

Not saying that it's the only way to go, just that sometimes it's possible to adapt something instead of building from scratch.

 

cheers,

Pete.

Edited March 31, 2008 by smileypete

[Gibbo]

For small loads I'd look at modifying something like this to output 12v:

 

 

With a bit of luck it will just need a resistor change. There are ones around that will take 15V/16V input too.

 

I'd expect the reason they only go down to 15v is that laptops need at least that much to charge thier batteries.

 

Not saying that it's the only way to go, just that sometimes it's possible to adapt something instead of building from scratch.

 

cheers,

Pete.

 

That won't provide an output voltage that is BELOW the input voltage. The output voltage will always be higher than or equal to the input. I'd also lay odds that the one with 15/16 volt input that you mentioned won't provide an output voltage ABOVE the input.

 

And this is exactly what is needed.

 

You won't be able to mod it with a resisitor change.

 

I'll try to say this again....

 

Whatever the solution, it needs to produce an output voltage that can be above AND below the input voltage. This dictates one of two possible switch mode solutions (there are several different types). Neither of which are simple devices.

 

A switch mode to produce a higher output voltage is a simple device. A switchmode to poduce a lower output voltage is a simple device. A switchmode that can do both is NOT a simple device.

 

Gibbo

 

Dont know whats in it, but we have one of these to run out 12v radio and phone chargers of our 24v boat.

 

.............

 

For £70 its not an awfull price to pay.

 

 

 

Daniel

 

That looks just the job!

 

Gibbo

[Tusses]

Whatever the solution, it needs to produce an output voltage that can be above AND below the input voltage.

 

I was more thinking of a voltage limiter rather than a stable voltage under all conditions. maybe a low voltage cut off - like an inverter.

 

under voltage can be managed by watching battery discharge state. Over voltage cant be avoided when charging and I would guess this is when most thinks go pop !

[smileypete]

That won't provide an output voltage that is BELOW the input voltage. The output voltage will always be higher than or equal to the input. I'd also lay odds that the one with 15/16 volt input that you mentioned won't provide an output voltage ABOVE the input.

 

And this is exactly what is needed.

 

You won't be able to mod it with a resisitor change.

 

I'll try to say this again....

 

Whatever the solution, it needs to produce an output voltage that can be above AND below the input voltage. This dictates one of two possible switch mode solutions (there are several different types). Neither of which are simple devices.

 

A switch mode to produce a higher output voltage is a simple device. A switchmode to poduce a lower output voltage is a simple device. A switchmode that can do both is NOT a simple device.

 

This sort of thing'll do, 12-24v in and 16v out:

 

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?Vie...em=200202745466

 

If not confident about modifying these converters, then it should be straightforward to have a 12v regulator on the output.

 

cheers,

Pete.

Edited March 31, 2008 by smileypete

[Gibbo]

This sort of thing'll do, 12-24v in and 16v out:

 

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?Vie...em=200202745466

 

If not confident about modifying these converters, then it should be straightforward to have a 12v regulator on the output.

 

cheers,

Pete.

 

Now that's a bargain if the specs are right (on which subject I have my doubts).

 

Gibbo

[Tusses]

Now that's a bargain if the specs are right (on which subject I have my doubts).

 

Gibbo

 

I'm guessing its customer reterned and its been plugged in to see if it lights up !

[smileypete]

I'm guessing its customer reterned and its been plugged in to see if it lights up !

 

Ever the optimist Gibbo

 

Edit: Oops, it was Tusses, sorry Gibbo!

 

Try:

 

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?Vie...em=160211447769

 

http://www.google.co.uk/search?q=S26391F194L200

 

cheers,

Pete.

Edited April 1, 2008 by smileypete

[Tusses]

[Ex- Member]

I've read this topic from the beginning, but you electrical boffins have lost me. I run all LED mr16 bulbs. The first lot i bought blew numerous led's in each bulb after a few months, bloody annoying at a fiver each

 

A couple of months ago I bought another 20 x 12V 3W HIGH POWER LED soft white single bulb led from e-bay been in the boat 6 months, but one blew last weekend, and i did have the engine running with lights on. Been on to another e-bayer who sells 30 led bulbs, the guy states that they can only run from a DC transformer, so I emaild him with regard to using them on the boat, the guy was very honest and gave this reply.

 

 

Hi Julian

Yes the bulbs are voltage sensitive they will cope with about 15 volts DC but anything above 12 volts DC will affect their life, the problem with boats ect. is if the regulator is not working properly you can have 18-24 volts while the engine is running, and if the lights are on during this time you will damage the bulbs, the only way to check this is to measure the voltage at the bulb when the engine is running, this is easy to check by using a volt meter across the supply at any bulb when the engine is running.

If you require any further assistance please contact us.

Best regrads

xxxx xxxxxxxx

Technical Director

 

Now if I cant regulate a steady 12 volts for the lights using the 12 volt system. Would it pay to use the inverter through a transformer to regulate a steady 12 volts to mollycoddle these 12 volt Led's Or is this wasteful. The lights i have now are great, give off ample light and look good also, the 30 single LED bulbs are cheap but a bit ugly. The energy saving from Led is such that sorting something out to run them efficiently would be brilliant.

 

Or any other options to solve this issue. Maybe a battery dedicated to led's not charged by the engine maybe.

[Tusses]

jumping upoto 240 then back down to 12 would be wastefull of precious power !

[chris w]

I've read this topic from the beginning, but you electrical boffins have lost me. I run all LED mr16 bulbs. The first lot i bought blew numerous led's in each bulb after a few months, bloody annoying at a fiver each

 

A couple of months ago I bought another 20 x 12V 3W HIGH POWER LED soft white single bulb led from e-bay been in the boat 6 months, but one blew last weekend, and i did have the engine running with lights on. Been on to another e-bayer who sells 30 led bulbs, the guy states that they can only run from a DC transformer, so I emaild him with regard to using them on the boat, the guy was very honest and gave this reply.

 

 

Hi Julian

Yes the bulbs are voltage sensitive they will cope with about 15 volts DC but anything above 12 volts DC will affect their life, the problem with boats ect. is if the regulator is not working properly you can have 18-24 volts while the engine is running, and if the lights are on during this time you will damage the bulbs, the only way to check this is to measure the voltage at the bulb when the engine is running, this is easy to check by using a volt meter across the supply at any bulb when the engine is running.

If you require any further assistance please contact us.

Best regrads

xxxx xxxxxxxx

Technical Director

 

Now if I cant regulate a steady 12 volts for the lights using the 12 volt system. Would it pay to use the inverter through a transformer to regulate a steady 12 volts to mollycoddle these 12 volt Led's Or is this wasteful. The lights i have now are great, give off ample light and look good also, the 30 single LED bulbs are cheap but a bit ugly. The energy saving from Led is such that sorting something out to run them efficiently would be brilliant.

 

Or any other options to solve this issue. Maybe a battery dedicated to led's not charged by the engine maybe.

 

The mains transformers sold with LEDs are 13VAC and that is over 18v peak so I don't think 15v is going to kill them. I don't understand what he means by his statement that, "the problem with boats etc. is if the regulator is not working properly you can have 18-24 volts while the engine is running".

 

I presume he means the alternator regulator. If the regulator goes faulty on a boat you could get anything from zero to 120v DC out of the alternator but there is no common failure mechanism that would necessarily give 18v-24v. If the alternator regulator fails, the lights would be your least concern!

 

Chris