low voltage DC voltage doubling

[Froneck]

A bit off topic but maybe someone can help. I have a Moore Jig Borer. It has a work light, usually 2 but mine has one missing. It uses a 6 volt auto bulb, The type used on older cars even 12V for tail light. Looks a lot like the dual filament type but is not. The two connection terminals on the base feed one filament and metal outer shell is not connected to anything. Local Auto store checked the number and I purchased a box (10 or 12 bulbs) Replaced the dead bulb and it worked great, but in a few weeks was bad again. Voltage was from a dual primary and single secondary transformer so that 240VAC or 480VAC can provide 6VAC out. Machine is only 240VAC having a 2 speed motor.
To make a long story longer In about a year all the 6V bulbs were used since they all burned out! Switch in the bulb base also failed so I purchase a 12V auto bulb base and a box of 12V similar bulbs. A DC bridge (current rating enough for 50+ bulbs), have a few 50VDC large capacitors I converted the supply to DC and getting the peak to peak voltage of 9VDC. Working great but 12V bulbs now at 9V, I'm thinking that a bulb for autos is 14 or 15V since when running the charger increase supply voltage to 14VDC to 15VDC.
My question, if I make a simple voltage doubler 2 diodes and 2 large capacitors can I make it less if I use 2 different size caps? There is no longer any switch on the bulb so when I power the machine the bulb comes on. End of the day when I shut the RPC down all 3 phase power is removed including the single phase used to create the 3 phase via the RPC. Transformer and all control circuitry is connected to only single phase not the created 3rd phase.

 

[TDegenhart]

Sounds like this is a golden opportunity to switch to LEDs.

Tom

 

[Mark Rand]

A 12V 3 pin voltage regulator on the output of the voltage doubler will probably do the trick perfectly well. Something like a Texas Instruments LM1085IT-12 will only bee a couple of dollars from digikey or mouser etc.

Another option might be to find a suitably bright LED torch bulb that will cope with the rectified voltage as it is. They tend to have regulators built in to them.

Running auto bulbs on 12V rather than 14V won't make that much difference to the brightness, but it will improve the lifetime by an enormous amount.

 

[Froneck]

Didn't plan on operating the 12V bulb on 14V, 12V is fine 9VDC is working pretty good. I'm thinking at 12V it will not burn out as often as the 6V ones did. I understand bulb life, I worked for Fire Alarm company, we used 32V bulbs on 24V so that lifetime increased.
I'm trying to keep it as simple as possible. I have a project to list my projects to determine how many projects I have! Problem is I don't have time because projects keep me busy!

 

[rons]

My question, if I make a simple voltage doubler 2 diodes and 2 large capacitors can I make it less if I use 2 different size caps?

Don' think so.

voltage doubler circuit - Google Search

 

[CalG]

Incandescent bulbs are known to last longer on AC than DC due to the momentary cooling during each cycle.

 

[JST]

Using a smaller capacitor on the input side can actually change the voltage. But it is not very stable, it will change with load, so if one bulb burned out, the voltage would go up.

Similar to adding a series resistor, more impedance in series will lower voltage at any particular load. I won;t say it's a good plan.

Voltage regulators work well. 5V regulators as well as adjustable ones are available, and the 5V can be adjusted with a few parts to 6V. Several amps are possible, depending on input voltage.

 

[Froneck]

Only have one bulb, Yes I would think that load would change voltage. Bulb type is one used for tail light application not stop light or blinker so 12VDC shouldn't shorten life too much since it's design is for constant on use. 6V bulbs were last ones supply house had. lots of 12V available for less than 6V version.

 

[rons]

If you want to make it simple then just double the voltage and then put a resistor load on the output or maybe a power indicator led.
The voltage will drop depending on how much current you will be wasting. Well, don't do it this way unless you are a brute.