12v Halogen with RGB lights

[EmmienLightFan]

Would it be OK to use  10watt 12vac fishtank waterproof light on DC with the CMB24D, which also has RGB floods and strips on it.

 

Also, which type of dimmer do I need to dim an inductive load?

[k6ccc]

Most likely yes. For your second question, what are you trying to dim?

[EmmienLightFan]

I am trying to dim the transformer for the halogen light, just incase it wouldn't work at 12v

[radioguy1007]

You cannot use a transformer with DC.  Transformers only work with AC.  Is the light an incandescent or LED?  A 12 volt light will work on either AC or DC - and dim correctly.  With LED's you have to make sure the DC polarity is correct.  But you cannot use an AC input with the CMB24D - it has transistor outputs (no triacs) that will not work with AC!

[pelikan]

No it would not work. AC rated lights needs AC source and DC rated lights needs DC source to work properly. You cannot interchange this. You could use a dimmer switch for an AC lights that are dimmable (e.g. incandescent) but not all AC lights are dimmable. DC lights can be dimmed with varying the input voltage or current. There are several ways to achieve this one is using a potentiometer in series with the load.

 

Regards,

Levent Pelikan

http://blog.7pcb.com

[EmmienLightFan]

The light is incandecant. I think it should work on DC.

[radioguy1007]

What I read is the original poster says he has a 12 volt halogen light - an incandescent light does not care if it is fed AC or DC.  The transformer part cannot be used with DC.  If it is a LED light, that is a different story.  I believe the CMB24D controls brightness by PWM (pulse width modulation) and not a linear function as there are no heat sinks attached to the power transistors.  The AC controllers do the same thing but they chop up the 60 cycle waveform for dimming.  The reason transformers do not work with AC dimming is that they do not like to have the current through them constantly changed - this is due to inductance of the coils.

 

An incandescent lamp does not care if it is AC or DC - the voltage rating is important.  If it is rated 12 VAC, that usually is an RMS (root mean square) value or effective voltage of an AC signal.  It will work fine at 12 VDC and be effectively just as bright.  Just take a bulb from your car and run it off a 12 VAC transformer.  The 12 volt halogen light would light just fine if connected across the car battery.

 

The issue with using an incandescent on DC is that the surge current at turn on needs to be considered.  A 10 watt lamp at 12 volts draws 0.83 amps.  It will be much higher the instant it is turned on to full or partial brightness due to the fact that a filament has much lower resistance when it is cold.  LED lights do not have this surge current at start (instant on).  So there is no way you want to pile on 4 of these 10W lamps on one channel of the CMD24D even though it is rated at 4 amps per channel.  I personally would keep it to one 10W lamp per output.

 

Mr. Pelikan's comment about all AC lights not being dimmable is correct for LED or fluorescent technologies.  For incandescent (filament) lamps that does not apply - no matter what voltage they are rated at.

[EmmienLightFan]

What I read is the original poster says he has a 12 volt halogen light - an incandescent light does not care if it is fed AC or DC.  The transformer part cannot be used with DC.  If it is a LED light, that is a different story.  I believe the CMB24D controls brightness by PWM (pulse width modulation) and not a linear function as there are no heat sinks attached to the power transistors.  The AC controllers do the same thing but they chop up the 60 cycle waveform for dimming.  The reason transformers do not work with AC dimming is that they do not like to have the current through them constantly changed - this is due to inductance of the coils.

 

An incandescent lamp does not care if it is AC or DC - the voltage rating is important.  If it is rated 12 VAC, that usually is an RMS (root mean square) value or effective voltage of an AC signal.  It will work fine at 12 VDC and be effectively just as bright.  Just take a bulb from your car and run it off a 12 VAC transformer.  The 12 volt halogen light would light just fine if connected across the car battery.

 

The issue with using an incandescent on DC is that the surge current at turn on needs to be considered.  A 10 watt lamp at 12 volts draws 0.83 amps.  It will be much higher the instant it is turned on to full or partial brightness due to the fact that a filament has much lower resistance when it is cold.  LED lights do not have this surge current at start (instant on).  So there is no way you want to pile on 4 of these 10W lamps on one channel of the CMD24D even though it is rated at 4 amps per channel.  I personally would keep it to one 10W lamp per output.

 

Mr. Pelikan's comment about all AC lights not being dimmable is correct for LED or fluorescent technologies.  For incandescent (filament) lamps that does not apply - no matter what voltage they are rated at.

Thank you very much. I understand now. I only have one. I was expecting it wouldn't work and I would have to buy a small LED flood or something, but now I don't have to spend money on that.

 

Another small question-Would the switch be waterproof? It has a switch about 30cm up the wire that looks just like a normal inline switch for a lamp or something, but as it is used around water I guess it too should be waterproof.

Edited July 22, 2015 by EmmienLightFan