Hi All,
I'm attempting to make a microcontroller that controls the brightness of a halogen globe while also pulsing said globe at 50 or 100hz depending on the position of a switch. This brightness & frequency, through a separate unit, is recorded as pulses & intensity via 4-20mA which I am logging. Everything is working as intended except for the final brightness step. I am unable to get the brightness up to a sufficient value to record a high enough value of pulses & intensity. Currently I have relays that select a resistor from a bank to limit current to the globe to control brightness & then the negative leg of the globe is pulsed by a tip41A transistor (through a PWM pin of the Arduino to the Base) to control the frequency. Through this current setup, my current to the globe is limited by the transistor (i've played with different values for the base resistor to no avail) which stifles the max brightness. My question is, is there any solution to this? Am i limited because of the max current output of the Arduino? is the pulsing at 50 & 100hz combined with the PWM frequency not allowing the transistor to saturate?
Also, I'm possible looking at changing the transistor to a MOSFET so that its voltage driven instead of current as i thought this may rectify the issue.
Any help would be greatly appreciated, thanks.
If i recall correctly, halogen bulb light is based on the temperature of the bulb, NOT the current. At maximum current, wait for 1 to 2 seconds and see if the rated light is emitted.
There is this thing called the halogen cycle. In light bulbs tungsten is heated until it emits light. Doing this tungsten is boiled off the filament and is deposited on the cooler surface the glass bulb. This deposit is what causes bulbs to change color. In the halogen atmosphere the tungsten still boils off but is redeposited on the filament extending its life. If you are not hot enough for the halogen cycle it will die a tungsten bulbs death.
This link will give you a good explanation. https://sciencestruck.com/halogen-cycle-explained
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