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Author Topic: 12V Halogen Array Display  (Read 1362 times)
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I am starting a project to build a light array with 12v Halogen globes. 6x8 array
This would be to make shapes and Display letters for a stage prop.

The Halogen lights will be connected in an array as displayed in Diagram  on
http://www.nuxie1.com/images/stories/gallery/albums/LED_Matrix/LEDM88G_Circuit.GIF

Each line will be triggered with a mosfet via the PWM ports of a arduino.
They will be powered by a 12v Transformer.
http://uk.farnell.com/pro-lite/pro60va/transformer-12v-60va/dp/1299795
http://uk.farnell.com/pro-lite/pro60va/transformer-12v-60va/dp/1299795

Would this work electrically or do I need to change my plan?
Any advice would be appreciated
Thanks




 
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Halogen bulbs, unlike LEDs, allow power to flow in both directions.  You will need to add a diode in series with each bulb to keep the power from flowing through the other bulbs.  You will probably have to boost the voltage to get the same brightness as a lamp without a diode.   If they are driven in a matrix (one row at a time) you will also need to boost the voltage to get the average brightness back up.  I don't know what voltage you will end up needing.

What bulbs are you using?  Halogen bulbs tend to draw a lot of power.  Typically 20 Watts which is 1.66 Amps at 12v.  If you are lighting them a row at a time you will need 10 Amps for 9 rows of 6 or 15 Amps for 6 rows of 9.   The transformer you specify seems to be rated for about 1/4 Amp.

If you are using a matrix to drive them, like the diagram you provide, you will need high-powered high-side drivers and high-powered low-side drivers.  The MOSFETs can be the low-side drivers.  I'm not sure what you would use to source 10 or 15 amps for the row drivers.
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Will halogen bulbs react the same was as LEDs to multiplexing - will you get the POV experience, or will you just get bulbs that are 1/6th the brightness?
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Will halogen bulbs react the same was as LEDs to multiplexing - will you get the POV experience, or will you just get bulbs that are 1/6th the brightness?

The halogen bulbs won't have to rely on Persistence Of Vision as much because they won't have time to cool down in very short time between refreshes.  LED's go on and off nearly instantly.
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True, the thermal inertia will cover up the refreshes ("Thermal inertia" awesome phrase. If I just made that up, it's mine; back off)

Another thought - with each row being cycled through as part of the refresh, won't the non-linearity of colour temperature to brightness be shown up - you'll end up with a dimmer array (due to the refreshing) and it will be more orange in colour too?

Pol.
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with each row being cycled through as part of the refresh, won't the non-linearity of colour temperature to brightness be shown up?

I would expect that boosting the voltage to get the same RMS voltage as the nominal 12v would get the same color temperature as at the nominal 12v.
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You have to change a plan.
Electronics Transformer (ET) shown on a link outputs AC, and  mosfet's wouldn't like it at all.
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OP could use triacs to switch the AC but then the current can then still flow through many paths consisting of 3 other bulbs because of no blocking diodes.  So best bet is probably to switch to a DC power supply.
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Quote
Would this work electrically or do I need to change my plan?
You haven't got a plan. You have a schematic of an LED matrix and a link to a transformer, there is no plan, any you are a long way off anything that would work.
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