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Request: Convert UNder-car neon tubes to household plug-in Answered

I have neon tubes that I use to use under my car. I want to find a way to use them around my desk, or to add more ambient lighting to my room or something. I tried to find something to do with this, but had no luck. I am a complete noob,so if someone could point me in the right direction that would be awesome.



10 years ago

Even easier - just buy a 12V "wall wart" and hook it up to that. Somewhere on the neon tubes (or on the package, if you still have it), it presumably says how much current they need, or how much power/wattage (divide by 12V to get current in Ampere). Make sure the wall wart can supply at least that much.

. Since a car uses DC, the wall wart output probably needs to be DC also. Maybe not, but keep it in mind.

a car uses dc. however, the inverter for the neon lamps contains this (see picture) which produces pulsed dc at high voltages. and a wall wart would work, but were is the challenge in that. plus, there is no bragging right. or opportunity to experiment. plus, a lot of those wall warts are not full wave rectified. this is a huge problem for something like car neons, because a batterie is a PERFECT 12 volts. no ripple.

iroda solderpro 35.jpg

I'm not sure how "perfect" that 12V will be when the car is driving though, with the load from the spark plugs and AC, and the recharge from the alternator.... Either way, nothing an extra capacitor and/or a zener diode couldn't solve - same as on your circuit. Except this solution will be much easier for a "complete noob" who needs help reading a circuit diagram, and probably doesn't even own a soldering iron. Just being practical here... ;-)

the ac is powered by a belt from the crankshaft. the alternator is called that because it generates AC. unlike dc, wich required high rpm to generate, ac can even be produced when the car is at idle. so the 12 volts would be pretty perfect. and there would almost certainly be no ripple. an extra capacitor would remouve ripple, and would be needed if you used a wall wart. if you do use the wall-wart, the zener diode IS A MUST!! most wall-warts produce more than 12 volts, so that, under full load, it still gives 12 volts. do not use a voltage regulator. it will be more expensive, complicated, and will require a heat sink to work properly.

Well... the car battery is charged by the alternator, which is probably poorly rectified as well. And the AC (Air Conditioner) and the ignition coil are presumably highly inductive loads that create their own voltage spikes. Not to mention the starter engine, which will definitely have an impact on the battery voltage.

I've never looked at a car's voltage on an oscilloscope while it was going full tilt, but I would bet that a running car is not exactly the cleanest of electrical environments. These lights have to hold up even under the worst-case conditions, not just when the car is parked. ;-)

Still, as you say, a capacitor and zener should work fine to condition the power supply.

its probably rectified with a full wave rectifier. the ac runs the compressor of a belt from the crakshaft, not an independant electrical motor. although the ignition coil is a large load, i highly doubt it causes serious fluctuations in the power supply.

It doesn't, becasue the alternator has been built to match/ surpass the usage from the coils, the car's battery would die slowly from driving about otherwise, the battery makes a good rectifier by being a battery though... so there aren't any real spikes because the output of the battery under normal usage is less the the input charge from the alternator, this mean smooth voltage.

The vast majority of wall warts are DC, but good point nonetheless.

sure. sw1 is an on off switch f1 is a fuse, and protects from line surges (buy a regular kind, NOT A FAST BLOW) T1 is a transformer, and reduces voltage from 110v to 16 volts (i know the diagram says 12) br1 is a full wave rectifier, and changes the ac into dc C1 is a capacitor, and remouves ripple from the circuit d1 is a zener diode with a turnover voltage of 12 volts. its a voltage regulator. finally, you simply connect the lead marqued 12V to you inverter.

your going to have to dumb it down a bit for me

try this: