Resistors for panel lights

[Brian Degulis]

I'm putting in some new instrumentation and want to wire the ilumination into the existing sytem which is 32V. The gauges have 12 bulbs anyone what resistor to use?

Brian

 

[SKYCHENEY]

Can you replace the bulb with a 32v that has the proper base?

Another question: Are you sure you have 32v insturment lights? My boat is a 1985 as well and all of the instrument lights are 12v. They run off of a converter under the each helm. Put a tester on them if you don't know for sure.

 

[TedZ]

Need to know the resistance of the bulb and the wattage. If it is were a 12 watt bulb it would be 1 amp, i.e. Watts divided by volts. The resistance is low but it is likely .16 ohms or something similar. As soon as you take a meter and know that, i'll do it or send you the link i've posted before which has plug ins and does the math for you.

Don't get nervous if the numbers get very small...just do the math.

Stupid me...i'll put it in here now.

http://ourworld.compuserve.com/homepages/Bill_Bowden/r2.htm

And ther are many more. Search for voltage dividers.

Ted

PS the resistor should be double the wattage of the bulb or greater.

 

[Brian Degulis]

Can you replace the bulb with a 32v that has the proper base?

Another question: Are you sure you have 32v insturment lights? My boat is a 1985 as well and all of the instrument lights are 12v. They run off of a converter under the each helm. Put a tester on them if you don't know for sure.

Yes Sky they are 32 V and so far I can't find anyone who has the bulbs unless I want to buy 100 Pcs. A resistor would be the easiest way.

Brian

 

[Boatsb]

Why not just step the whole panel down to 12Volts so there is no need for individual resistors?

 

[yachtsmanbill]

Why not just step the whole panel down to 12Volts so there is no need for individual resistors?

Thats what I did and so far so good... all those gage lites are only about 2 amps total. When I was playing under the helm last winter, I pinched the
22 ga. wire for the binnacle light and and instantly had a wheelhouse full of smoke and didnt blow the breaker either!
Not to rehash the old thred, but why on earth did bubba pick 32 vdc for everything? Even 36 for starting with a 12 volt tap for everything else wouldve made much more scent (?) ws

 

[Fanfare]

I think those were the engineers at Rockwell. It really would have been a better idea if anyone else had followed their lead. Instead it was a dead end. Still, I keep seeing references to higher voltage DC systems coming out of Detroit for automobiles. 48 volts? Well, we'll see.

I am pretty happy with my 12v systems, as Jack Hargrave and Hatteras originally laid out in 1965.

 

[yachtsmanbill]

For years that was the problem with the "JEEPS for $49" thing. The military stuff all had 24 volt lighting which is good for vision but bad for a crash. An expensive adventure to de-militarize it.
Ever see a military convoy coming from 2 miles away; thats 24 volt lighting.
48 volts outa Detroit seems like a jap snuck in there ;-(
Lets see; a 4 cam, 16 valve, 12000 rpm buzz box with magnesium paddle shifters (? whatever those are) in a 4 cylinder doosh wagon, and youve still got a 4 banger doosh wagon.
Sorry everyone! I mustve overdosed on the cold medicine... I'm feelin' kinda "anxious" but still lousy. ws

 

[Brian Degulis]

Thats what I did and so far so good... all those gage lites are only about 2 amps total. When I was playing under the helm last winter, I pinched the
22 ga. wire for the binnacle light and and instantly had a wheelhouse full of smoke and didnt blow the breaker either!
Not to rehash the old thred, but why on earth did bubba pick 32 vdc for everything? Even 36 for starting with a 12 volt tap for everything else wouldve made much more scent (?) ws

The Tapping 12V from a 32V bank doesn't work very well cause when the 12V is being drawn only some of the cells in the 32V bank are being discharged. That causes the voltage to drop on the bank and the 32V charger to kick in. So what ends up happening is the cells that where not discharged by the 12 V draw get over charged and the cells that were discharged by the 12V draw don't get charged enough.

My guages are all 12 V powered by a 32V to 12V power supply so I could change the lights to that also. But it would be easier to just find a resistor to bring down the voltage to the 4 new guages I'm adding.

Brian

 

[chris piazza]

Brian,

Try this site, it will tell you at least what resistor you need . I just did this on my boat on the bridge for the five 24v lights for the pumps. Simple just soldered them in-line and dropped voltage from 32/24v.
http://www.kpsec.freeuk.com/components/resist.htm
Just be advised that Radio Shack don't carry crap any more, I had to go to an electronic parts specialist to get the wattage I needed.

Chris
Superior Nights 53C

 

[yachtsmanbill]

The PO did a really half-assed job of tapping off the 12vdc generator battery for electronics.
Aside from the electronics, both Atlantes heads and a potable water pump are now 12 vdc. I am still in the process of ripping out some of Bubbas handiwork, but most of the routing is done with new wire. Almost all helm stuff has been converted as the terminus blockus are right there. This all started because of the deck courtesy lights being 32 vdc "festoon" bulbs are like $20 each GMAFB !
I am going to leave the nav lites 32 vdc for higher visibility. As for now, the 12vdc battery is run on a charger only, but I do have a Delcotron alternator thats getting mounted to the starboard engine for charging while underway. ws

 

[REBrueckner]

Brian,
Your question involves several subtle issues.

First is that each 12 volt bulb with a different wattage requires a different size resistor inserted. Second, you can't measure the resistance of a cold bulb; it's much less than the rated (hot) resistance. Third, when you calculate the size of the resistor to insert, you need also determine its power consumption as you'll likely have to specify a POWER resistor or it may burn up.

The reference by Ted does the calculations...be sure you record also the power requirements calculated there. Likely a 10 watt (power) resistor will be big enough, but don't guess. I can do the calculations if you have the data posted here: All I really need is the rated wattage of each of your 12 volt illumination bulbs.

 

[SKYCHENEY]

You could just buy 100 of the 32v bulbs and post the other 99 here for sale. Just a thought.

 

[Brian Degulis]

Need to know the resistance of the bulb and the wattage. If it is were a 12 watt bulb it would be 1 amp, i.e. Watts divided by volts. The resistance is low but it is likely .16 ohms or something similar. As soon as you take a meter and know that, i'll do it or send you the link i've posted before which has plug ins and does the math for you.

Don't get nervous if the numbers get very small...just do the math.

Stupid me...i'll put it in here now.

http://ourworld.compuserve.com/homepages/Bill_Bowden/r2.htm

And ther are many more. Search for voltage dividers.

Ted
PS the resistor should be double the wattage of the bulb or greater.

I went to the sight and it apears to be showing 2 resistors one on the + side and 1 on the -. Why would this require 2 resistors or am I reading it wrong?

Brian

 

[TedZ]

The one on the plus side is the bulb...the other the resistor. If you want to supply 12 vdc to all of the gauges, wire them in series - you will do that anyway - and measure the resistance as a group and add up the wattage.

this is not cancer research. Buy a 100 resistor assortment from radio shack and come close to what the numbers show. If a resistor gets hot, parallel them with resistors 2x the rating of the one, as two resistors in parallel end up being 1/2 the total. The hot bulb phenomenon is correct but play and see if it gets dim...likely won't.

 

[Brian Degulis]

I'm only needing to power 4 12V bulbs with 32V I don't want to wire in series cause then one goes out and none work. The Bulbs are G3 or # 5 and there will be 4 being powered. What resistor to buy?

Brian

 

[yachtsmanbill]

How about one of those old Chrysler ignition resistors with the ceramic block.
General motors used a resistance wire for the same thing... X number of inches in length of SS wire dropped the volts to the coil from 12 to 9 for steady voltage when cranking. ws

 

[MikeP]

My helm/FB lights/gauges (1980 53 MY) is like Sky's - 12v provided by several 32v to 12v converters that are the oem Hatt setup in the helm/FB. Seems odd that your boat doesn't have them in a 32v configuration. Wonder if a PO removed them in a misguided moment?

 

[Brian Degulis]

It has them for the guages themselves but the lights are 32V looks OEM to me but can't be sure.

Brian

 

[krush]

X number of inches in length of SS wire dropped the volts to the coil from 12 to 9 for steady voltage when cranking. ws

Got it backwards 12v during cranking (notice the wire that comes off the starter solenoid to the positive side to the coil), 7-9volts during running to keep the points from burning. Don't let a young punk of the computer age show you up on points!