# Arduino controlled light dimmer

1. ## Arduino controlled light dimmer

Working on an urgent project of a light dimmer that starts low and the gets brighter in 4 steps. 5% glow then 20% then 50% then 80% or even gradually still good.. I found the circuit below at this great website.
My question is, the light power I need is 3000 Watt. Can I simply replace the Triac with a bigger power like BTA41-600V ? or do I need to make other changes on the circuit ?

•

2. ## Re: Arduino controlled light dimmer

Hi,

Open both triac datasheets and compare the gate drive currents.

In case the new one's are much higher, then open the MOCxxxx datasheet, it tells you what to modify to get the desired gate currents.

Klaus

•

3. ## Re: Arduino controlled light dimmer

First decide the number of steps: if by 5%, 20% etc. etc., you mean power levels, then compute from a sine table the required phase angles to turn on the triac.

If the 3000W lamps are good old W-lamps, you are on safe ground. But if the lamps are discharge lamps or even LEDs you need to worry more.

W-lamps at 5% power will just appear red-hot (without much light)- you may wish to set your dimmer at 5%, 20% etc. etc. at perceived brightness (lux)- that will be more realistic.

The 30V diac will not allow to turn on the lamps at full brightness but that may be perhaps desirable???

•

4. ## Re: Arduino controlled light dimmer

Using a triac optocoupler with a diac seems confused. I don't have even a remote idea which purpose it should have.

5. ## Re: Arduino controlled light dimmer

Originally Posted by c_mitra
First decide the number of steps: if by 5%, 20% etc. etc., you mean power levels, then compute from a sine table the required phase angles to turn on the triac.

If the 3000W lamps are good old W-lamps, you are on safe ground. But if the lamps are discharge lamps or even LEDs you need to worry more.

W-lamps at 5% power will just appear red-hot (without much light)- you may wish to set your dimmer at 5%, 20% etc. etc. at perceived brightness (lux)- that will be more realistic.

The 30V diac will not allow to turn on the lamps at full brightness but that may be perhaps desirable???
it doesnt matter what % glow. the aim is to have the bulbs start at as low as 5 or 10% and then ascend within a few second(not critical) to full or almost full glow.Yes the are the good old w lamps. So if I follow Klaus advice, found a bigger capacity Triac with similar gate specs, the I should be OK right , maybe I will need to upgrade the other components in the circuit with higher wattage.

•

6. ## Re: Arduino controlled light dimmer

... and leave the diac out, it serves no purpose whatsoever and may limit the lower end of the light control.

Note that unless you are cycle stealing (very slow PWM) which will make the lamp flicker, you have to use phase control and therefore need a zero crossing detector to find a reference timing point.

Brian.

--[[ ]]--