I have managed to control an RGB LED Strip with an Arduino Uno R3 successfully. I would now like to switch and dim 12v LED Down lights. I am unsure of how to do this the Transformers I have are dimmable and have 10 watt dimmable LEDS. Would anyone be able to provide information on how to wire them while still being able to dim them manually. Also I have an assortment of electronics bits such as mosfets, transistors etc.
Arduino 12v LED Downlights
12varduinoled
Related Solutions
I have this strand of LEDs/Controllers and I've made it work with the LPD6803-RGB-Pixels library.
To connect the strip correctly:
- Di (Blue Wire) = VCC -> Connect pin: Vin on Arduino.
- Ci (Green Wire) = Data -> Connect to pin: 2 on Arduino.
- St (Red Wire) = Clock -> Connect to pin: 3 on Arduino.
- Li (Black Wire) = GND -> Connect to pin: GND on Arduino.
Once the Arduino is programmed, unplug USB cable, and only use the 12V supply.
Hope this helps.
Perhaps the dimmer circuit won't work without a resistive load. Some thyristor dimmer circuits might not see enough holding current from a rectifier-capacitor load to stay on for the half cycle. You may be able to wire a fat resistor in parallel with the LED lamps and have it work, however it may require some experimentation to determine an appropriate value.
Here's a typical small triac datasheet. The holding current is specified as maximum 10mA or 20mA, depending on type. If a phase-control trigger circuit provides a short pulse, the MT2 current must reach the holding current during the trigger pulse or the triac will not stay on for the remainder of the cycle. (bottom line below).
Here (from Wikipedia) is what the output of a typical phase control looks like. The gate trigger pulse would take where the vertical red chevrons are located. (a) is the power waveform. (b) is the output with triggering near the beginning of the cycle (bright) and (c) is the output with triggering near the end of the cycle (dim).
I would try about a 150 ohm 2W resistor -- if you get a few you can parallel several and go up in ~1W increments. You may find that too high a resistance causes half-wave triggering (intermediate brightness), since triacs have different holding currents in the positive and negative directions.
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Best Answer
The output of the "transformer" you refer to is 12VDC - ie it has rectification included so the LEDs are driven by DC.
So "dimmable LEDs" probably just means "accepts variable voltage DC". If so you should be able to use your existing circuit (which you should add to your post or provide a link to) with the "transformer" DC output, where V+ is now the +ve feed from the 'tranformer' and the LED downlights connect where the LED strip is now. The circuit that Emmanuel posted in his now deleted answer should also work and is likely to be functionally the same as your one. .
With the above arrangement, when you provide full on drive from the Arduino the LEDs will be dimmable manually, and when you provide full brightness with the manual dimmer the LEDs will be dimmable using the Arduino. Dim them both at once and they will interact - but it should do no harm.