Bayonet Base Bulbs

You have not explained your issue well enough. Please elaborate.

Just like a screw type bulb, the shell is typically neutral. And just like a screw type bulb, when connected in series, the shell of one bulb will be "hot". There are some types of bayonet bulbs available that have two base contacts, with a single filament. You will have to do a fair amount of research to find the.

If you wire any light bulbs in series only one contact can be at ground potential! Think about it.

I just recently had to replace a #47 lamp (6.3V 150mA, bayonet base with a single bottom contact). This was the standard pilot lamp for most transformer-powered radios and many other devices in the USA from the '40's or earlier to well into the '70's.

In my experience, the base was always the neutral (if there was a neutral), but most often there was no neutral, so it didn't matter which wire went where.

I don't remember ever seeing any connected in series, so the question almost becomes moot.

On the other hand, if there is a neutral, the contact that is most difficult to reach should be the 'hot', so the base should be neutral (or closer to neutral in the case of series-connected lamps).

While the OP didn't explicitly state it, his mention of "live" and "neutral" led me to assume that he was asking about GLS (General Lighting Service) lamps.

I agree; he presumably is. Thanks for defining your acronym! I would not have known what GLS meant.

What is strange to me regarding this thread, is that I've never seen a bayonet base GLS lamp. There are plenty of low voltage bayonet lamps, but the only line voltage bayonet base lamps I can remember seeing were in slide and movie projectors, optical comparators, and the like. Those specialized lamps are way too expensive to use in an incubator, unless perhaps the OP came across a supply of surplus lamps and sockets at a very attractive price.

UK GLS lamps used to be (i.e. up to about 20 years ago) mostly BC types, but ES and SES (Edison screw and Small Edison screw) types seem to be taking over.

Finally, the joker comes on stage...

USA and related persons may be interested to see a bayonet cap "BC" bulb that fits a standard UK home 230V light socket. I think its official bulb-world title is Ba22d - 22mm.

The power goes to the two contacts - the brass cap does not have to connect to anything. The standard socket is insulated, but usually has a brass collar to engage the radial pins for mechanical strength reasons.

67model

The implication of this answer is that to connect bulbs in series, should only use screw caps, which clearly mark live from neutral. Or am I wrong? Thank you.

Nonsense. The thread was about bayonet cap bulbs. See #5.

Alas! We have not yet progressed to that point here in the USA. In most cases the bayonet fixtures use the center contact for "hot" and the case/shell is the "neutral-ground". It does present a problem when connecting them in series although I have not had to do that for several years.

We here in the Grand Old US of A (the left side of the pond), have gone past the ages of many series lamps situations because Risk Assessments were done by our ancestors to rid us of the inherent problems that they bring along. Why use lamps is series when you can use others in a much safer parallel circuit? Need a special light? Have them make one just what you want if there isn't what you want in the thousands of types that are available. With incandescent, fluorescent. LED. halogen, Sodium, mercury vapor, and many others available why should you have to unsafely arrange the circuit in an unsafe arrangement?

Probably the only regularly used series arrangement of bulbs is in street lamps. This is happening slowly.

Good Luck, Old Salt

I don't know if they're still made, a three pin BC cap with two contacts for 25Vlamps on machine tools.

Only a single filament bayonet bulb. A dual filament bulb has a asymmetrical pins on the on opposing sides of the base and corresponding asymmetrical slots on the sides of the socket. This is done to prevent the wrong filament being able to be used.

example- brake lights and the running lights within a single lamp on a car, #1157 lamp. Single filament is #1156.

http://www.hotrodders.com/forum/1157-bulb-1156-socket-152966.html

http://www.motorcycleforums.net/forum/mechanics-corner/18590-difference-between-1156-1157-lamps.html

Good Luck, Old Salt

Have a look for LoVo machine tool lighting

Don has your answer http://www.donsbulbs.com/cgi-bin/r/t.pl

Don apparently has the bulbs and sockets, but I didn't find where he has an answer to the OP's question.

In the USA bayonet bulbs are usually not used for other than low voltage applications. Typical of this would be the bulbs on cars and smaller (under 100 ft) boats. Some places that they were used have been changed to other types of sockets with better characteristics.

A bayonet bulb will have the sides of the base (the part with the pins) connected as the neutral. On DC applications this is almost always the negative. The "hot" wire, in this case, the positive, is connected to the center bottom contact of the bottom. If there are two filaments within the bulb, there will be two contacts on the bottom. Each one of these has the neutral of each filament connected to the side. This is a dual contact to the side. Each filament has the hot side connected to one of the contacts on the bottom of the bulb. Therefore: one bulb; two filaments; and three contacts.

Typical examples of these are the #1156 and #1157 bulbs used in cars. The #1156 has one filament (one contact on the bottom) and is used in applications where only one is necessary such as the back-up lights on the rear of the car. These are white and indicate when the car is in reverse. The #1157 has two filaments encased in the bulb, one being brighter than the other. Each has one wire connected to the side and one connected to one of the two contacts on the bottom. These are often used as a combination of the running light (sometimes called the parking light) for the dimmer of the two elements and the brighter one as the brake lights, lit when the brake is applied. There are other application for these but this is the most frequent.

The side of the #1157, two element, bulb has two pins located asymmetrically on the sides to hold the bulb with in the socket. This way the bulb can only be inserted one way thus preventing the elements from being reversed. The 3 wires are connected one to each bottom contact and one to the side.

On a screw based bulb the only force holding the bulb in is the tension created by the screw. On a bayonet base bulb there is a spring located within the socket to make a forced tension between the base and the bulb. These do not vibrate loose as the screw type often does.

If two single element bulbs of the same type are placed in series the lamps will light equally but at a reduced brilliance if the normal voltage is applied to them. Connecting the filaments of a two filament bulb in series will automatically reduce the brilliance of the bulb for the same lower voltage reason. Another possibility is to operate a two filament bulb like the normal residential 3-way bulb. Filament #1 only, low brightness; #2 only, medium brightness; #3, both filaments powered at the same time for high brightness. This is what happens when the running light on a car is on because of darkness and the brakes are applied.

Good Luck, Old Salt

Why would you want to connect bulbs in series?

produce maximum heat and minimum light for an incubator.

Then you presumably want to use line voltage lamps (120V in the USA), so the series can plug in directly without using a transformer. A dimmer controlling the circuit would allow you to adjust the temperature easily.

It does not matter what kind of base (thread, bayonet, pin, etc.) you use, except that there are more different sizes easily available in screw base. What does matter is the construction of those bases; they must have the shell and the wiring contacts covered by insulation so no one (or no animal) can accidentally touch any electrically hot point when there are bulbs in place. Since your objective is to create heat, that insulation should probably be ceramic, rather than plastic.

You obviously know that placing bulbs in series will make them produce less light. You also need to know that all the bulbs in the series must be the same wattage; if you place a low wattage bulb in series with one or more high wattage bulbs, most of the voltage will appear across the low wattage bulb and the high wattage bulb(s) will produce no light and very little heat.

Also, in a series circuit, if one lamp fails or is loosened, the full line voltage will then appear across the contacts of the disconnected lamp. This is the real reason why both sides of the bases of all the lamps must be insulated from touch.

If anyone's interested, I once did some experiments with a 24V 10W lamp (using DC). The resistance at 26V was ~72Ω, dropping to ~50Ω at 13V. If this scaled up to the 100W lamps of your example, the power of two in series would drop to about 72W.

As you pointed out, the actual drop would depend on the filament design.

If you want bulbs in series for heat for incubator, the following test results I got may help.

A 230V 150W bayonet cap 2 pin bulb (UK) 50 Hz AC

Volts, Current A, Watts, % rated W

230, 0.65, 150, 100

115, 0.42, 48, 32

97, 0.38, 37, 25

58, 0.28, 16, 11

B 24 volt 1.2 W LES ("Lilliput" edison screw) panel lamp, DC test

Volts, Current mA,colour, % watts

4, 18 Dull Red 6

9, 28 Yellow 21

12, 34 Bright Yellow 41

15, 38 Brilliant Yellow 48

17, 42 White 71

24, 52 Blinding White 100

As you can see, you need a lot of lamps in series if you do not want light, some light will show the heater is working though. At 1/2 volts, one lamp is ~30% watts, the other ~40%.

Another consideration is that motor car lamps have much thicker filaments and last a lot longer than mains voltage, the difference is 20,000 hours versus 750 - 1000 hours (12V not the 14V you get with car battery on-charge). They also have 100 years development for surviving shock/vibration.

The final note is that theatre stage lights have to be pre-heated gently to avoid quick failure, something about tungsten being more brittle at some temperatures, I think, so there may be a voltage range to avoid.

I do not have any info. on hand about life increase vs voltage under-running bulb but it is considerable.

Sorry tables did not come out well.

67model

Perhaps a dimmer is too expensive?

yes. also wish to try out theory.

Be practical and install an IP68 heater element in this incubator instead. Then one wouldn't have to worry about light and about bayonet caps at all.

Yes correct and changing the wires at the switch makes it go backwards.

Please do not touch live wires!

Thanks!

As is commonly the case, the perspective on answering the original question varies significantly depending on where the questioner lives (I have been assuming the USA, but could well be mistaken) and where the person answering lives.

I guess in my various trips to Europe, I've never had occasion to change or even pay any attention to light bulbs. I was not aware that bayonet bases were common for mains voltage lamps there. As I indicated in a previous post, the only line voltage bayonet base bulbs I recall having seen were special-purpose bulbs, which are far too expensive to use as incubator heaters...

You should listen to Andy and Redfred and Solar Eagle: If you put tungsten bulbs (or anything else electrical) in series it will change the resulting power consumption, and if the bulbs (for example) present enough resistance, you basically have a low wattage resistor present. Not only that, but you will also have voltage present where there should be a neutral - along with considerable if not lethal shock hazard. Do not try this at home (or in an incubator). Why not just resort to the usual incubator tools?

Then I should simply use ES with a neutral.

NOOOOOO! Clearly you have not understood fully the implications for your safety. If you can get bayonet lamps in your mains voltage then use those. WHY? Because the base has two connections for the mains current. One is active and the other is neutral. The receptacle is earthed. The receptacle is the bit with the two slots for the bayonet pins. It doesn't matter which of the two connectors you make live, so wiring is easy. It IS important that you connect an earth.

Jim

For the sake of safety and simplicity the multi-bulb configuration can easily be changed to eliminate the inherent shock/electrocution hazard of the wiring between the two bulbs in series. Run the system with more 120v bulbs in parallel, to eliminate the shock hazard, increase the heat given off and reduce the light from the lamps. This is easily done by using higher voltage lamps, in the range of 115vac to 240vac, bayonet base lamps. With a dimmer ($5.49 brand new at the orange box) you can reduce the light as each additional one is placed in the circuit and/or heat given off. Determine the number of bulbs in parallel needed by a little experimentation. The use of low voltage lamps can also be done by using a transformer between the dimmer and the bulbs. If the circuitry is at line voltage a line voltage thermostat can be installed to regulate the heat.

If low voltage bulbs are to be used place a transformer between the dimmer and the bulbs. For low voltage DC operation, install a full wave rectifier between the transformer and the bulbs or use a DC voltage regulator , such as an LM317HV circuit, between the rectifier and the lamps. Connect this to a thermistor and you have a thermostat controlled power source.

To eliminate hot spots and provide more even heating, place a small computer fan in the enclosure to circulate the heated air. This will use the heat generated more efficiently. These are easily available in 12vdc or 120vac.

All this eliminates the dual hot voltage shock hazard, keeps light emitted low, provides more efficient heat and keeps the heat within the container more even.

Good Luck, Old Salt

Australia was exclusively bayonet type except for exotic equipment. With cheap light fittings coming from China and being made for the US market we are seeing more ES bases. In recent decades ALL light fittings have to be fitted with an earth and so the pins and the metal ring they are mounted in, are earthed. As a previous poster indicated the lamp can be put in the receptacle 180 deg from the first way you put it in so it doesn't matter which of the two contacts are live.

There used to be xmas tree lights that had small globes in series. When one blew it was a pain in the right royal ask ya muther to find the blown globe.

For an incubator or cat cave i use a pilot light at 15w or 25w.

What country are you in?

Jim

I am from Hong Kong and use parts made in China.

Recently a helpful expert also from Australia but not from CR4 may have answered my question.

He said that screw bulbs need to be grounded because of the possible accident of the hand touching the threads of the neutral side.

Bayonet bulb base have no such problem as long as no wires are exposed. And since BB have no polarity, connecting 2 BB in series becomes very straightforward.

I may have made the matter more complicated.

"I may have made the matter more complicated ...." - indeed.