120v led lamp

Electronic Ballasts: The electronic ballasts use semiconductors to limit power to a fluorescent lamp. First the ballast rectifies the AC power, then it chops it to make a high frequency for improved efficiency. The ballast can more precisely control power than a magnetic ballast but does have a number of problems.

That is the circuit you have there.

You can use a simpler diode- resistor combo to cut the voltage down for the led's, but its not efficient, and in my opinion dangerous, Because of the fact that it would be direct mains connection. I don't like this type of setup, i like isolation between any of my circuitry, and the mains, but that's just me.

I would look to PMW to drive the led's, but that may be too much for your project.

If you want a simple diagram, here is one using a Transformer, it may need some customizing for your led's, but it should be a starter.

The transformer in the diagram isolates the mains for me in this circuit.

Let me know exactly what your looking for.

Someone else may be able to chime in if your looking for a switching power supply.As I am not too familiar with them.

If you can maybe calculate the led stats, so we could know the Amperes, and voltage limitations for your circuit.

That would be helpful.

Electronic Ballasts: The electronic ballasts use semiconductors to limit power to a fluorescent lamp. First the ballast rectifies the AC power, then it chops it to make a high frequency for improved efficiency. The ballast can more precisely control power than a magnetic ballast but does have a number of problems.

That is the circuit you have there.

You can use a simpler diode- resistor combo to cut the voltage down for the led's, but its not efficient, and in my opinion dangerous, Because of the fact that it would be direct mains connection. I don't like this type of setup, i like isolation between any of my circuitry, and the mains, but that's just me.

I would look to PMW to drive the led's, but that may be too much for your project.

If you want a simple diagram, here is one using a Transformer, it may need some customizing for your led's, but it should be a starter.

The transformer in the diagram isolates the mains for me in this circuit.

Let me know exactly what your looking for.

Someone else may be able to chime in if your looking for a switching power supply.As I am not too familiar with them.

If you can maybe calculate the led stats, so we could know the Amperes, and voltage limitations for your circuit.

That would be helpful.

Ok thanks, that helps a lot. in that case i wont be using the ballast!

for the leds, the forward voltage is  3.4v and they use 20mA. I think i could have 10 rows of 3 in parallel at 12v with 90ohm resistance. so around 200mA Total. Maybe ill throw more led in, they are rated a 3.7cd each.

For the power supply, is it cheaper to build on like you showed there? Would a transformer like that would do?

http://canada.newark.com/myrra/44087/transformer-12v-1-5va/dp/50P9099

btw i might use PWM for this project, but is there any other advantage other than setting better range on the potentiometer?

Looks OK, but, in my circuit, the transformer wont work for 12v.

You see you will loose some in the rectifier bridge, and the 7812 will not be able to hold the 12v output.

1. You can drop the 7812 down to 9v version, supplying 9v to the led's.
2. Or find a transformer around 14+ volts.

As for the PWM, I think it is more efficient. Less loss on the supply

Everything else looks good.

NOTE: you can buy a "wall wart" type power supply ready made, that should work, than u just need to do the PWM. But there would be no fun in that.

I like building stuff myself, but it is an option.

Ok cool, I really like the idea of building my own circuit for this project and im catching up on the knowledge as we speak, but for PWM, i know how it work on a microcontroller, but what you're talking about is a chip like this ?
UC3845BNG ON SEMICONDUCTOR PWM Controllers | 88H5157 | Newark element14 Canada

This particular one seem to have a well written datasheet that ill read during the weekend, but the example don't seem to apply to what im doing. Would you have an idea or a little example? Thanks!

Here's the pins

1 Compensation

2 Voltage Feedback

3 Current Sense

4 RT/CT

5 Vref

6 VCC

7 Output

8 GND

You can use that chip, i have used a "mic502yn" before.

There is the 555 timer, you can use, or i prefer going old school, and using an op amp.

Or, rather four.

But your space is limited so mabe a mic502ym with a transistor or fet would be fine

I have a schematic of the op-amp PWM circuit if you would like.

Thanks but opAmps seem pretty advanced for me for that project.  Seem like the 555 timer could be a simple/cheap solution. With that a i should be able to make the final design.

Ok, well, breadboard this, and see what you think.

it should get you on track.

Hi Lupe,

Not sure that circuit will work, unless there is something I don't understand about the 555 (quite likely).

Anyway, there is a great resource here, with plenty of 555 circuits - including PWM ones. Just hit Ctrl-F

and type PWM to find them there.

That particular website has good circuits in general - some websites have poor or faulty circuits.

For known working 555 circuits, I would consult that website first.

Hi Shabaz, What a great site and recommendation. I always find some good sound ideas and advice in your posts.

John

Hi John,

Thanks! That site also has links off to 100 transistor circuits, and another 100 more. They seem to be pretty good!!

Hi Shabaz, Yes I noticed all the goodies on the site. It was a litttle like opening a treasure chest for me.

John