How to power a h7 bulb from 110v?

[MolaKule]

Originally Posted by mk378
Since there are 12 volt halogen household bulbs, there exists a device specifically for the OP's application.
https://www.amazon.com/gp/product/B07V1PM3KS/ref=ox_sc_act_title_1?smid=A25WFPRHTKYO28&psc=1
These power supplies put out high frequency AC which is only suitable for filament light bulbs. But they are also designed to supply the surge of current needed to initially light a halogen bulb.


Wow! I would like to hear the theory behind the need for high frequency AC in a H7 incandescent bulb.

The product above appears to be a simple 120 VA, 120V AC to 12Vac AC stepdown transformer with a current capability of 8.3 Amps.

 

[mk378]

These ballasts are a switching power supply but since it isn't necessary to have DC output, there is no rectifier or filter on the secondary side. The bulb is connected directly to the transformer, thus it gets AC at the switching frequency. That frequency was chosen for transformer efficiency, not anything to do with the bulb.

The unit is much smaller and lighter than a conventional 60 Hz transformer of comparable rating.

 

[Alfred_B]

It's eye damage or house fire waiting to happen. Find a low voltage LED cluster and stuff it in there.

 

[JimPghPA]

Be careful that the metal case of that light does not end up being tied to one side of the AC line. Some switchers do not isolate the incoming AC from the output DC. You could end up with a lethal shock hazard.

 

[redbone3]

Originally Posted by mk378
These ballasts are a switching power supply but since it isn't necessary to have DC output, there is no rectifier or filter on the secondary side. The bulb is connected directly to the transformer, thus it gets AC at the switching frequency. That frequency was chosen for transformer efficiency, not anything to do with the bulb.

The unit is much smaller and lighter than a conventional 60 Hz transformer of comparable rating.


Well said. The higher the frequency the smaller the transformer can be. Plus, if rectified to a DC voltage a smaller capacitor will do. Same reason aircraft use 400 HZ.

 

[PandaBear]

Old ATX power supply that you wire the power control together to keep it on.

Seriously, do you really need that much light? Or just a science project? An LED may be more efficient for stationary source.