HID Lamp Dimmer

[raki]

Hello Gurus!!

I'm a new joinee in this forum....and i'm very bad at circuits

I Have two questions::
1)
I want to design a Dimmer for HID Lamps which are used in outdoor lighting
The Dimmer is digitally controlled through a Microcontroller.
But, I'm not sure what all it takes to create this device.
Can some one bless me with Ideas
2)
I hooked up the traditional lamp dimmer for incandescent bulbs unsing MOC3021 & a triac and and it works with an external Pot.
But, I want this existing circuit to be controlled used the Microcontroller's PWM Output. what should i do for achieveing this????

Thanks for your patience in reading my queries.
And many more thanks for answering them

Raki

 

[mvs sarma]

Welcome to Electro-Tech-Online,

I feel PWM is the solution.

You may perhaps implement on PICs like 16F628 with isolated final stages for power drive.

 

[raki]

Sir,

Can you please help me with some resources...? u know i'm zero @ electronic design.

Please do help me with some resources/links so that i can get started with my design

Regards
Raki

 

[justDIY]

what kind of HID bulb are we talking about here?

your average metal halide or sodium bulb is not going to like being PWM'd. They do make dimmable metal halide ballasts, and they require special bulbs which support dimming.

General Electric had a press release a few years back regarding a new ballast designed for industrial / commercial applications, designed to save money - a warehouse could have its lights dimmed during off-peak hours when minimal staff was present or a grocery store was closed, while still providing sufficient light for cleaning crews and security personnel.

If you're talking cold cathode fluorescent, then PWM is a good solution.

 

[raki]

It is a high wattage (250-500w)metal halide lamp which is used as flood light or for illuminating the billboards

 

[justDIY]

i don't know about 500w (that's not a standard wattage), but 400w dimmable ballasts are around $200, if you can find someone that will sell you a small quantity. Usually the ballast has either a 10v DC control input allowing you to provide a 0 to 10v linear voltage for dimming, or they operate on some sort of digital interface. There are also some that use 100mV control, and some that accept a PWM input where the duty cycle indicates the dimming amount.

here is something to read:

https://news.thomasnet.com/companystory/536716

 

[mvs sarma]

It is a high wattage (250-500w)metal halide lamp which is used as flood light or for illuminating the billboards

Please see this article and gives some info and you may continue.

https://www.electro-tech-online.com/custompdfs/2008/01/702PET20.pdf

 

[raki]

but actually i want to make one ...but not buy the readily availbe ones from market

 

[justDIY]

read up on building SMPS - switch mode power supplies. That is what a modern ballast is.

They used to be hulking huge linear monsters with massive and expensive transformers, but now most ballast are svelte electronic gizmos. The bulbs used to run at 25/30 pps (50/60hz), but now run at 20000 pps+ thanks to the digital electronics in the switching power supply.

it's not going to be an easy weekend project