Buzby
Senior Member
The circuit is very simple. It's basically as per the datasheet.
There is a built-in load resistor in the S6986 ( other devices are open-collector ), so I just added a simple resistor and NPN transistor to drive the indication LED. There was also a diode to provide a 'diode-OR' function, as the device was 'paralled' with other identical circuits to make a multi-beam gate.
The laser was wired direct to the S6986, exactly where the datasheet expects an IR LED. The S6986 has a constant current drive ( ~ 35mA ), whereas the other devices have an open-collector drive.
The duty cycle of the device is about 1:8, so a 35mA current equates to just over 4mA continuous, well within the laser's limits.
The S6986 can work upto 16v, so I drove the whole circuit at 12v, to ensure I could drive both 3v and 5v lasers. The constant-current drive supplies the same current no matter what the supply voltage.
This might sound complicated, but these devices are so easy to use.
There is a built-in load resistor in the S6986 ( other devices are open-collector ), so I just added a simple resistor and NPN transistor to drive the indication LED. There was also a diode to provide a 'diode-OR' function, as the device was 'paralled' with other identical circuits to make a multi-beam gate.
The laser was wired direct to the S6986, exactly where the datasheet expects an IR LED. The S6986 has a constant current drive ( ~ 35mA ), whereas the other devices have an open-collector drive.
The duty cycle of the device is about 1:8, so a 35mA current equates to just over 4mA continuous, well within the laser's limits.
The S6986 can work upto 16v, so I drove the whole circuit at 12v, to ensure I could drive both 3v and 5v lasers. The constant-current drive supplies the same current no matter what the supply voltage.
This might sound complicated, but these devices are so easy to use.