Hi,
I have laser module containing 20 laser diodes, and laser driver with 20 separated channels that i can turn on/off, the laser's anode is seperated and cathode is common.
I want to be able to measure voltage drop on each laser using microcontroller.
-only one laser is active at a time-
-laser operating current is 0-100mA CW
-voltage drop will be max~3.5V (red laser)
For that my idea is to use two 16 channels CD74HC4067 multiplexer ic's, and one ADS1115 4 channels ADC that will read the voltage of the selected channel by the multiplexer, (differential reading - ADC Inputs 1&2 is for one anode from the multiplexer and common cathode, and 3&4 for the other)
First question if this approach is common and OK?
Second, there is a possibility that i will have 12V on the laser diode line in case the laser is bad, and it can damage the multiplexer/ADC inputs,
What will be the right way (and simplest to design on PCB from components quantity perspective as i need 20 channels) for limiting the voltage to 3.3V/5v?
Attached is some initial drawing i made using voltage dividers, (ADC chip and laser diodes are not there as it is a PCB that sits in between the driver and the lasers)
Thank you,
Nir.
I have laser module containing 20 laser diodes, and laser driver with 20 separated channels that i can turn on/off, the laser's anode is seperated and cathode is common.
I want to be able to measure voltage drop on each laser using microcontroller.
-only one laser is active at a time-
-laser operating current is 0-100mA CW
-voltage drop will be max~3.5V (red laser)
For that my idea is to use two 16 channels CD74HC4067 multiplexer ic's, and one ADS1115 4 channels ADC that will read the voltage of the selected channel by the multiplexer, (differential reading - ADC Inputs 1&2 is for one anode from the multiplexer and common cathode, and 3&4 for the other)
First question if this approach is common and OK?
Second, there is a possibility that i will have 12V on the laser diode line in case the laser is bad, and it can damage the multiplexer/ADC inputs,
What will be the right way (and simplest to design on PCB from components quantity perspective as i need 20 channels) for limiting the voltage to 3.3V/5v?
Attached is some initial drawing i made using voltage dividers, (ADC chip and laser diodes are not there as it is a PCB that sits in between the driver and the lasers)
Thank you,
Nir.
Attachments
-
178.7 KB Views: 21
Last edited: