| Author |
Message |
Luis (Sundancer) (67.120.233.20)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, August 08, 2004 - 9:11 pm: | |
Ok so my lovely wants those pretty little lights they sell all over the place. They plug into an ac outlet, which then steps the 120 AC voltage down to 12vac. Is there any reason why I can't just cut off the transformer and wire straight into my 12vdc system? I know the light won't care if its ac or dc. (cause I tried it). But is there some scientific reason, like the filament is different for ac versus dc and thus won't last as long. Maybe it'll actually last longer? Any comments? |
George Myers (12.74.75.114)
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Votes: 0 (Vote!) | | Posted on Sunday, August 08, 2004 - 9:27 pm: | |
When the engine is running or the battery charger is charging, the 12 VDC in the coach is more like 13.5 or 14 VDC. This could shorten bulb life. The plus side is that they will be brighter and more efficient, for a while. You might want to put a resister in series to drop the voltage to 12 VDC. This will have to be a trial and error thing unless you have good numbers to calculate what it should be. My suggestion would be to add resistance until it is the same brightness as one using the power supply that came with it. It is hard to say how much the life will be shortened, It may not be worth the effort to add the resistance. |
Abajaba (12.217.192.62)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, August 08, 2004 - 10:18 pm: | |
Hi there:
There is a phenomenon called DC notching that happens to incandescent filaments. It does shorten the life of the filaments but I don't think it is something that you should have to worry about. The overvoltage that you are seeing when the engine is running and the battery is being charged would be more detrimental to the life of the lamps. You would notice a shorter life span if the engine was charging the battery all the time that the lamps are on. But for the most part it will only be on at the camp site and the battery will be at the resting voltage
What one could do is use a DC to DC converter that stabilizes the power on the output of the device. I have seen some of these in industry that would allow input voltages from 30 Volts DC to 8 volts DC and give a stable output voltage of 12.0 volts. They work good and most of them were purpose built for the place they were used.
I think I would just hook it up and try it for a while. Like a couple of years. It might be less expensive to replace the lights than to put in the extra components that might fail and leave you in the dark. |
BrianMCI96A3 (69.34.170.243)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, August 08, 2004 - 10:19 pm: | |
Luis, are you certain that the transformer drops the voltage down to 12v ac and not 12v dc?
I'm not sure if it makes a difference, but you could always cut the wires to the transformer, and try it on a 12V battery and if it works...GREAT!
If it doesn't, you could simply reconnect the wires back to the transformer.
Brian |
CoryDane RTSII (66.155.188.248)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, August 08, 2004 - 11:28 pm: | |
I am using some of those track lights with the trasformer inside and when I took them apart, what did I find but a diode bridge and other AC to DC changing electronics.
I thought they were only transformers but for some reason the AC is changed over to DC. I didn't test the voltage but when I have it on the battery it works just fine.
The GMC motorhomers are using this fix for some of their lighting replacements as the lenses are becoming obsolete to them.
Feel comfortable with using the DC.
If you wanted to really get fancy.....
put the transformer on a dimmer, or a timer dimmer.
run the transformer low voltage to a double pole, double throw switch, connect to the normally closed contacts.
Run the DC from batt to the switch, to the normally open contacts.
The lamp will be connected to the switch blades.
When off, the light will respond to the timer dimmer/dimmer and if you do not have AC power, using the switch powers the bulb with 12vDC.
Thank you, Thank you, its the little things, you know
"Imagine"
cd |
Gary McFarland (Gearheadgary) (12.176.227.136)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, August 09, 2004 - 1:17 am: | |
"Is there any reason why I can't just cut off the transformer and wire straight into my 12vdc system?"
Nope, I have one, works great, planning for more.
As far as I know, resistive loads don't care about AC or DC.
Gary |
DrivingMissLazy (66.168.175.51)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, August 09, 2004 - 8:25 am: | |
The first thing I would do is find out exactly what the output voltage is. With 120 volts AC applied (and is it really 120 volts or maybe 115 volts) then check the output voltage with an accurate voltmeter. It may be anywhere from 11 to 15 volts, AC or DC.
In general, the voltage tolerence is fairly wide, so I do not think 13.5 volts will make any significant difference in bulb life.
Richard |
Gary Stadler (Boogiethecat) (68.7.217.217)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, August 09, 2004 - 11:26 am: | |
Rated incandescent lamp life goes down some crazy number like 50% per VOLT of overvoltage. But that's the only problem you'll run into.
If you are worried about 13.5 volts vs 12, just figure out how many amps your string of lights use and get yourself two rectifier diodes rated at slightly more amperage (double is nice for fudge factor), and put them in series with your lamp string. Polarity of the diodes must be correct or it won't light up. You could use resistors but creating the correct resistance is messy with higher-current loads. Diodes have a no-brainer built in drop of .5 -to.7 volts per, so two in series will drop just enough to give you your 12 volts...
I also use this trick for my drinking water pump- it used to pump so fast that it cycled when I was using the tap. Annoying. So four diodes in series with it slowed it down just enough that it stays on now and doesn't cycle...
Cheers
gary |
Gary Carter (68.25.98.192)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, August 09, 2004 - 12:13 pm: | |
When we did our 4106 back in 1990 I used mosty hologen (sp) lighting. Removed the transformers and ran them on staight battery power (12vdc or whatever). In the 12 years we owned the bus we never burned out a bulb.
So simply put it will work just fine. Pull the transformer and enjoy the light. |
Gary Carter (68.25.98.192)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, August 09, 2004 - 12:15 pm: | |
And in addition for you folks stuck with 24vdc, JC Whitney has a nice 24/48vdc to 12vdc convertor in their invertor section |
Jim-Bob (12.46.52.74)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, August 09, 2004 - 1:37 pm: | |
I too am using the halogen "puck" lights Gary mentions. I cut off the transformer & run right off 12 volts.
The next ones I do will keep the transformer, and install a 120V relay so that the lights run from 120 when it's present but switch automatically to 12 volts when 120 isn't there. The relay will have a 120vac coil, but will switch the light string from transformer to 12 volt when the coil is not energized. That way no power is used. |
Luis (Sundancer) (67.120.233.20)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, August 09, 2004 - 9:27 pm: | |
You people are good. Thanks for all your comments. Brian,the transformer says its putting out 12 vac from an input of 120 vac so that is all I have to go on. But now I am intriqued so I will test it to see. If its like CoryDane says, then this thingy is a rectifier as well as a step down transformer. I think I'll do as Gary did 12 years ago and hope they last me as long or longer. Thanks to all for your advise. Luis |
cjm (63.158.201.85)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, August 09, 2004 - 10:33 pm: | |
You can just buy 24 volt bulbs and put them in the fixture. Try xenon or LED instead of halogen. They burn much cooler. They also make the bulbs in 120 volt models. John |
Jayjay (152.163.252.199)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, August 10, 2004 - 10:17 pm: | |
Hey Luis, I'll betcha' a bottle of straight malt to an old flat Budweiser, that if you use a good digital voltmeter to check the 12V AC transformer, that it is putting out around 18 volts.!!! DC notching should not be an issue at this low of a voltage, perhaps above 48V, and usually only with heavily loaded circuits. Take a reading and let us know what it is. Cheers...JJ |
DaveD (142.46.199.30)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, August 11, 2004 - 8:38 am: | |
I installed a set of three 12V halogen lights in a valance panel over the vanity in the bathroom in our coach and they are working fine after three seasons of use. I'm running them from a nominal 12V dc source (battery when on the road, 12v dc regulated output from a converter when connected to shore power). Even mains ac voltages fluctuate. I wouldn't be too concerned about the charging voltage being a problem.
FWIW
Dave Dulmage
(MC-8) |
pete lanthorn (165.247.86.139)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, September 03, 2004 - 11:01 pm: | |
luis--go to ledmuseum.com and chk out ever-brite led string lites--we use them all the nites dry camping and they last forever and do not use any enrgy at ll--much pete lanthorn mci8 |
S.M. Heath (66.82.52.28)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, September 04, 2004 - 8:26 pm: | |
Pete has the best soultion. But, you alredy have the lights (I think). Has anyone tried a seprate inexpensive inverter?... seems that wold do OK. For 24V. just wire pair's (Of bulbs) in sreies (for direct conecting to 24V. DC) S.M.H. |