| General > General Technical Chat |
| What is the purpose of the IC in this SLR lightmeter circuit? |
| (1/1) |
| julian1:
Schematic is the light-meter for a circa 1998/2000 slr camera. What is the function of the 10 pin IC within J100. Is it analog switch?, level adjust, switchable comparator?, analog sample-and-hold? Is it likely a custom part? - SOUT (pin 5) connects to what appears to be a light dependent resistor. - The analog signal is connected to the microcontroller ADC (AN0). - SEL1, SEL2, SEL3 are uncertain select/switch functions driven by MCU gpio. |
| Zero999:
Please post the complete circuit. It appears to be a sample and hold circuit. Q1 is a FET, probably low power MOSFET, but I couldn't find a sane data sheet. |
| julian1:
The complete analog section is shown. I believe Q1 (pchannel fet connected to body/rail VDD) just allows the microcontroller to power on/off the analog section as a whole. Eg. by pulling AVDDCNT and the mosfet gate low to turn on. Edit. I think there is some kind of integration/negative feedback with AOUT,AIN,SOUT around what looks like a light dependent resistor. Edit 2. I now suspect the 10 pin IC is just level shifter - to bridge the digital voltage levels of the GPIO select pins to the analog circuit. eg. pull SOUT high - to get a LDR reading at the ADC. pull the AOUT or AIN high to get reference voltage levels at the ADC. |
| Navigation |
| Message Index |