Chips & Chips
Junior Member level 3
I am designing a control circuit that uses 24VAC for the controls, ultimately switching 115VAC On and Off. In adding the bells and whistles, I want a couple of LEDs that indicate the ON condition and a safety condition. Both would be illuminated by the presence of that 24VAC control Voltage. I know I need to rectify the AC to DC and perhaps filter it, but that part is easy with diodes and capacitors. What I would like is to use a switching IC driver to give me the constant current needed for the LEDs instead of using resistors. The LEDs only draw 25mA, but even at that current level, the resistors calculate to 1.2K Ohms and 0.77W. So I need a 1W or two 1/2W resistors per LED and I will be wasting 1.5 or 2.25 Watts of energy when the LEDs are lit.
What I would like is a simple switching style IC driver where the current can be programmed with a single resistor or two. That would waste a lot less power so it appeals to my conservative side. Oh, and it should be cheap, of course. If it could handle 50mA that would be better as I may want to use two LEDs for the power on light. I am imagining a three or four pin device, preferably with accessible pins for soldering. I do not need any fancy things like dimming, just ON and OFF. I estimate the input Voltage, after rectification and filtering, to be around 33 VDC.
I searched before posting this so I hope I am not being redundant. I tried to search on Digi-Key but got tens of thousands of returns. It would take me forever to go through them. Any suggested ICs would be appreciated.
What I would like is a simple switching style IC driver where the current can be programmed with a single resistor or two. That would waste a lot less power so it appeals to my conservative side. Oh, and it should be cheap, of course. If it could handle 50mA that would be better as I may want to use two LEDs for the power on light. I am imagining a three or four pin device, preferably with accessible pins for soldering. I do not need any fancy things like dimming, just ON and OFF. I estimate the input Voltage, after rectification and filtering, to be around 33 VDC.
I searched before posting this so I hope I am not being redundant. I tried to search on Digi-Key but got tens of thousands of returns. It would take me forever to go through them. Any suggested ICs would be appreciated.
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