HELP!!! Need an EE's advice quick! Lance, anyone?

Henning

Henning

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Gone West
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iHenning
Ok, here's the deal, we have all halogen lighting onboard this boat, several hundred, and want to change them out with LEDs. Not really a problem if you leave them at full strength, or even down a bit from that, when we hit the dimmer switch down further though, they flash. The dimmers work the AC input side of the circuit to the transformer. All the LED dimmers operate on the DC side of the circuit, but all I can find here in Australia is crappy POT dials. What I want to do, is find a DC supply regulator that uses the variable AC current as its controller. Anybody have a solution to my problem? Even if it's something I have to build multiple units of, that ok with me, or if there's something on the market (I'm told here there isn't, but there are only 3 brands of toothpaste and 2 brands of deodorant here so I'm not sure that they may be familiar with everything available. Aus even filters the internet like China) for me to get? If someone is really hip on this and can sell me the gear, excellent. I have to have the bulbs changed out within 10 days, but most of the bulbs are available here. It's the variable power supply that is causing the problem.

Thanks!
 
Re: HELP!!! bNeed an EE's advice quick! Lance, anyone?

Contact Lucas Electric... they're somewhere in the UK. They'll fix ya right up with a reliable system.:D

It seems to me that you want variable DC voltage based on variable AC current? That one sounds like a toughy, maybe microprocessor required? I'm thinkin' that's way past the Grainger catalog...
 
Re: HELP!!! bNeed an EE's advice quick! Lance, anyone?

Clark1961 said:
Contact Lucas Electric... they're somewhere in the UK. They'll fix ya right up with a reliable system.:D

It seems to me that you want variable DC voltage based on variable AC current? That one sounds like a toughy, maybe microprocessor required? I'm thinkin' that's way past the Grainger catalog...
Click to expand...

I think I can even do it mechanically with a volume controller driving a pot.
 
Re: HELP!!! bNeed an EE's advice quick! Lance, anyone?

Henning said:
Ok, here's the deal, we have all halogen lighting onboard this boat, several hundred, and want to change them out with LEDs. Not really a problem if you leave them at full strength, or even down a bit from that, when we hit the dimmer switch down further though, they flash. The dimmers work the AC input side of the circuit to the transformer. All the LED dimmers operate on the DC side of the circuit, but all I can find here in Australia is crappy POT dials. What I want to do, is find a DC supply regulator that uses the variable AC current as its controller. Anybody have a solution to my problem? Even if it's something I have to build multiple units of, that ok with me, or if there's something on the market (I'm told here there isn't, but there are only 3 brands of toothpaste and 2 brands of deodorant here so I'm not sure that they may be familiar with everything available. Aus even filters the internet like China) for me to get? If someone is really hip on this and can sell me the gear, excellent. I have to have the bulbs changed out within 10 days, but most of the bulbs are available here. It's the variable power supply that is causing the problem.
Click to expand...

Okay, you're confusing me here. First you say the dimmers are on the AC side, then the DC side. :dunno:

With the flickering, it sounds like there is still some AC component at the LED's. Note that this may simply be something upstream turning the DC on and off, not the same AC that's at the input.

Regardless of what's going on, there's probably a diode drop somewhere on the AC side or in the AC to DC conversion that's causing this. You probably need your dimmers to be on the DC side to fix it.

I know absolutely nothing about boats - What kind of power do you have, where is the AC/DC conversion occurring on its way to the LED's, and what sort of power do the LED's expect? Do you have a multimeter on board? Check the voltage across the LED module at full power, partial power, and off. Check both DC and AC, you may have a DC voltage with an AC component riding on top of it. Check different fixtures as well, the AC may be being induced by something outside of the system you're looking at.

Ain't electricity fun? :no:

Reminds me of when I was transportation manager for a touring musical group. One of our vehicles was an RV that ate alternators and batteries and other electrical components for lunch. Eventually I discovered that when the generator was running, it was inducing about an 18-volt AC wave on top of the 12-14 volt DC system, so if they were rolling down the road with the big roof AC unit (and thus the generator) on, system voltage could be swinging from about -4 to +32!
 
Re: HELP!!! bNeed an EE's advice quick! Lance, anyone?

Can you give me some data on the LED lamps being used and the supply you attempted to use (the one that "flashed" when dimmed). The "flashing" has me a bit puzzled, what specifically do you mean by that? What's the period (time from one flash to the next) and duty cycle (percentage of time that the LEDs are on) and are these things consistent when dimmed. What happens to the period and duty cycle as you dim further?

I'd also like to know what you're using for a dimmer on the AC side. Is it something like a typical incandescent lamp dimmer used in a home? Most of those use what's called "phase angle control" which is a fancy way of saying that the dimming is accomplished by cutting off an adjustable portion of the AC sine wave, reducing the average voltage and power delivered to the load.

If all you really need is something that would put out a DC voltage that varies with the applied AC voltage, I think you're making this more complicated than necessary. A simple unregulated DC supply made from a transformer and a diode bridge will produce a DC voltage that's almost exactly proportional to the applied AC voltage. But that's not what I think you need due to the way that LED's operate. What I suspect you really want is something to pulse the LEDs at full current with a duty cycle that's proportional to the AC voltage from your "dimmer". It would be possible to design something that would do this but I'm not aware of anything commercially available. There is a good chance that the simple transformer/bridge supply mentioned above with no output filter capacitor powered by a standard phase angle dimmer would work pretty well driving LED lamps that were intended to operate from a constant voltage. The results wouldn't be exactly the same as running incandescent lamps from the same source but it would likely be good enough.

Some LED theory for those of you who are interested:

Individual LEDs normally have a forward conduction voltage (voltage applied with the polarity that makes them light up) between 1.5 and 3 volts. This voltage varies slightly with temperature and current but they don't behave like a resistor (or incancescent lamp) at all. Instead, at a few hundredths of a volt below the forward as you increase the voltage above the point where they begin to emit light there's almost no current at all and a tenth of a volt or two above that voltage the current goes through the roof (until the LED overheats and dies). Ignoring the small resistance of the LED leads, the output of any LED is directly proportional to the current flowing through it as long as the current remains below that which would damage the LED.

Because of this all LED lamps must have some means of limiting the current to a safe value that's fairly independent of the voltage. The simplest method is to put a resistor in series with one LED that has a large enough resistance that there's as much or more voltage drop across the resistor as the forward conduction voltage of the LED. With this setup the current through the LED and resistor can be adjusted over the useful range by varying the applied voltage. For example take an LED with a Fv of 2 volts with a max continuous current rating of 50 ma. Ohms law gives us 40 ohms for a resistor that drops 2 volts at 50 ma. If we apply 4 volts to that combination the diode will conduct approximately 50 ma and if we drop the applied voltage to 3 volts the voltage across the resistor will reduce to about 1 volt which means the current through the two will be cut in half. IOW with this setup a 25% drop in voltage produces a 50% drop in current and LED light output.

If we used a 400 ohm resistor and powered the combination with 22 volts we'd get the same 50 ma LED current but reducing the applied voltage by 25% in that setup would only reduce the current by 27.5%. The downside of this approach is that the large resistor is wasting most of the power which is not only inefficient but also will generate a lot of heat if much current is involved. For a few small LEDs the power wasted and heat generated is too small to worry about but if you're talking high power, high output LEDs as would be used for room lighting this problem would be huge. In that case (and whenever efficiency is important) LED lamps usuually involve several LEDs connected in series along with either a small resistor to limit the current or a current regulator to make the current independent of the applied voltage. And to dim such a string of LEDs one normally just switches the current on and off at a high rate with a varying duty cycle. This makes the LEDs produce their full output for
an adjustable portion of a short time which appears to us humans as a constant level because the photoreceptors in our eyes don't respond very quickly.
 
I don't know if your transformer is a simple step down or it is something special for the Halogen lights. If the output of the transformer is AC then you might be able to use this LED driver, it's in NZ.

http://www.surplustronics.co.nz/shop/product-LA0915.html

I also don't know if the output of this LED driver is dimmable. They also have a 3 watt version, that one is 1 watt.

By the way, here are some LED replacements lights with different types of connectors and input voltages.

http://www.lightingfx.com/cat--LED-Bulbs--ledbulbs

greg
 
This is going back quit a few years to that damn theory of semiconductor class where we spent the entire year developing the ideal diode equation. But if I recall correctly LEDs do not dim like light bulbs. That is to say that just reducing the voltage across them will not cause a significant change in their output luminosity. To change the output i.e. dim them you vary the amount of time they are actually on or change some of the current.

The varying current approach wastes a lot of power is a resistive load device. This approach is used in backlighting application a lot. For higher output lights like the ones I think you are using it would not be a good approach as the current deviersion device would have to handle very high loads and would get really hot. I think for room lighting you would want to use the duty cycle approach.

To do that you have to be pulsing the LEDs on an off fast enough that your eye is tricked into thinking that they are on all the time, then reduce the amount of time they are on for one cycle and your eye thinks that the light has decreased as the average luminescence over the time period has been reduced.

You might want to see if there are any COTS solutions instead of trying to design this yourself.
 
Ok, here's the deal, we have all halogen lighting onboard this boat, several hundred, and want to change them out with LEDs. Not really a problem if you leave them at full strength, or even down a bit from that, when we hit the dimmer switch down further though, they flash.

So does this mean you've put some of the LED lamps in the holes meant for the Halogen lamps? If so, what is the voltage of the halogens, 12, 24, 120 ac?

The dimmers work the AC input side of the circuit to the transformer. All the LED dimmers operate on the DC side of the circuit, but all I can find here in Australia is crappy POT dials.

At this point, my guess is the dimmer you have is using triacs to chop the sine wave and give you the dimming effect. The transformer is not smoothing this out enough and the LED's are flashing. Another possibility is the electronics in the LED lamps don't like the reduced RMS voltage they are seeing.

What I want to do, is find a DC supply regulator that uses the variable AC current as its controller. Anybody have a solution to my problem? Even if it's something I have to build multiple units of, that ok with me, or if there's something on the market (I'm told here there isn't, but there are only 3 brands of toothpaste and 2 brands of deodorant here so I'm not sure that they may be familiar with everything available. Aus even filters the internet like China) for me to get? If someone is really hip on this and can sell me the gear, excellent. I have to have the bulbs changed out within 10 days, but most of the bulbs are available here. It's the variable power supply that is causing the problem.

Tell me about the bulbs and I think we can fix your problem.
 
gismo said:
I suspect these would solve Henning's problem, but they're rather pricey plus they put out about about half the light as the incandescents they replace.
Click to expand...


Money is not an issue, they're only $34 a piece at case pricing and I need 214 of them. In the grand scheme of a $25MM program all in the name of safety when he could have achieved the same end result for <$500k but didn't because the operations were "dodgy", saving $7500 on something that is responsible for a large percentage of fires on yachts would be a bit silly. Heat is the primary issue, the owner doesn't want the halogens, and I don't blame him. Halogens are a hazard on boats because you cant properly ventilate them. They had already replaced all the 20 watt bulbs with 10 watt to reduce the heat, and it was still too hot. The obvious solution is LEDs, especially since they're available in a standard MR-16 sizing that will fit in or fixtures. He says his bright ones put out the equivalent of a 40-50 watt halogen and the dim ones about a 15-20 watt Halogen Since we have all 10 watt bulbs onboard at the moment, we shouldn't have an issue.
 
Henning said:
Money is not an issue, they're only $34 a piece at case pricing and I need 214 of them. In the grand scheme of a $25MM program all in the name of safety when he could have achieved the same end result for <$500k but didn't because the operations were "dodgy", saving $7500 on something that is responsible for a large percentage of fires on yachts would be a bit silly. Heat is the primary issue, the owner doesn't want the halogens, and I don't blame him. Halogens are a hazard on boats because you cant properly ventilate them. They had already replaced all the 20 watt bulbs with 10 watt to reduce the heat, and it was still too hot. The obvious solution is LEDs, especially since they're available in a standard MR-16 sizing that will fit in or fixtures. He says his bright ones put out the equivalent of a 40-50 watt halogen and the dim ones about a 15-20 watt Halogen Since we have all 10 watt bulbs onboard at the moment, we shouldn't have an issue.
Click to expand...

Sounds like a good solution then. One thing I would do is check to see how much heat the LED lamps put out over the range of dimming. Unlike incandescents, it's quite possible they might run hotter when partially dimmed. Not likely to be a problem but possible. Even then I'm pretty certain they will be a lot cooler than Halogens.
 
instead of dimming them, just split the circuits so you can turn 25% of them off at a switch - would at least give you 4 levels of light from OFF to 100% on...
 
Henning said:
Thanks for the lead,:smilewinkgrin:he says he has what I need, shipping tomorrow...
Click to expand...

Your welcome, I hope they work the way you want them to.

If you need help installing them I just need a round trip ticket from LAX and I'm there. :D

greg
 
gismo said:
Sounds like a good solution then. One thing I would do is check to see how much heat the LED lamps put out over the range of dimming. Unlike incandescents, it's quite possible they might run hotter when partially dimmed. Not likely to be a problem but possible. Even then I'm pretty certain they will be a lot cooler than Halogens.
Click to expand...


Thanks, I have a heat sensor gun and should be getting the first lot on Monday, I'll check that out, but yeah, I'm reasonably confident it won't be an issue since at full power they are barely over room temp, but it is a good thing to check.
 
gkainz said:
instead of dimming them, just split the circuits so you can turn 25% of them off at a switch - would at least give you 4 levels of light from OFF to 100% on...
Click to expand...

I'd have more switches than Carter has little liver pills....:rolleyes: :smile: Not to mention all the extra wire I'd have to drag, we're trying to leave in a week...
 
yeah, there is that ... I thought of the extra wires as I remembered I need to run 2 new circuits at home tomorrow; 1 for my new shed/workshop and putting in an RV plugin outside the garage.
 
gkainz said:
yeah, there is that ... I thought of the extra wires as I remembered I need to run 2 new circuits at home tomorrow; 1 :yesnod:or my new shed/workshop and putting in an RV plugin outside the garage.
Click to expand...

You have to run 2... I have 47 zones I'd have to split into 4....:yikes::yikes::yikes: I'm really hoping the new bulbs work out
 
Henning said:
I'm really hoping the new bulbs work out
Click to expand...

Well, you shouldn't have to buy new bulbs for a while; did you buy any spares while you were at it? What's their return policy if they don't work (or will you just be selling them on eBay?)?
 
TangoWhiskey said:
Well, you shouldn't have to buy new bulbs for a while; did you buy any spares while you were at it? What's their return policy if they don't work (or will you just be selling them on eBay?)?
Click to expand...

They'll take them back less the shipping, and yes, I ordered a few spares (10%) figuring an infant failure rate.
 
Henning said:
You have to run 2... I have 47 zones I'd have to split into 4....:yikes::yikes::yikes: I'm really hoping the new bulbs work out
Click to expand...

yeah but .... one run entails digging 60' of trench without destroying my sprinkler system that currently occupies the same space.
 
gkainz said:
yeah but .... one run entails digging 60' of trench without destroying my sprinkler system that currently occupies the same space.
Click to expand...

Uhhhhh...I take it you've never worked in the overhead of a boat....:eek: Wire runs often require "hot work"...:frown2::frown2::frown2:
 
nope ... I was an Navy aviation electronics technician ... the blackshoes wouldn't let us brownshoes touch their wiring on their boats ... but I did grow up as a lineman and worked plenty of hot 14.4 and 28kVA lines for the REA. (Never standing in a steel bucket surrounded by salt water, tho ...)
 
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