I have an application which needs to determine various states of ambient light from daytime to night. An LDR is well suited as it has a linear working range. A LDR I tested required roughly a 3k high side resistor to give a good voltage divider. Two problems however have me looking at photodiodes, with which I have no experience, 1. LDR's are not SMT and 2. I need to add switch in capacitance to smooth light transients over a good few seconds. With a 3k resistor these capacitances are too large for the application design.
I hit LtSpice and came up with the attached circuit. I'm basing the light output and the sensitivity on R2, which is a complete guess. I don't know at what light point a photo diode typically hits it's turn on region.
The switch in capacitance in real life but be via an MCU with open drain pins.
Any thoughts/suggestions/improvements?
I hit LtSpice and came up with the attached circuit. I'm basing the light output and the sensitivity on R2, which is a complete guess. I don't know at what light point a photo diode typically hits it's turn on region.
The switch in capacitance in real life but be via an MCU with open drain pins.
Any thoughts/suggestions/improvements?