laser diode circuit problem.....
I am using laser diode of 650nm (http://www.farnell.com/datasheets/43664.pdf)and 630 nm.(http://www.farnell.com/datasheets/43652.pdf).
for testing of laser diode, i made the driver circuit (http://www.rog8811.com/laserdriver.htm).
now, the thing is that, though i am giving maximum acceptable voltage and current to 650nm, it gives very low output even i can directly see by my eyes. but if i am giving max. to 630nm, it brights high for 2 to 3 minutes and than it dims.
so i don't understand that why laser diode output is not high even though i am giving high voltage and current...
Did you check batteries, replace it, or check power source and voltage regulator.
Use voltmeter and ampermeter and monitor instruments.
You have probably blown up the lasers. That circuit is not the way to drive lasers with built in monitor photodiodes. You need a closed loop, optical power monitoring circuit and you need to set the optical output power, not the operating current.
Keith
---------- Post added at 04:28 ---------- Previous post was at 04:23 ----------
By the way, you will see that there is no absolute maximum laser current in the data but there IS a maximum laser optical output power. That is because it is optical output power that is critical and must be controlled, not current.
hi tpetar...
I am using power source is from ac to dc conversion and voltage regulator. I am using multimeter for checking current and voltage...
---------- Post added at 05:08 ---------- Previous post was at 04:39 ----------
Thaks for your reply keith....
How can i design optical power monitoring circuit ? How can I set optical power ?
There are probably some decent discrete circuits on the web for controlling laser power, but the easiest way is probably to use an IC designed for the job such as the ones made by ic-haus. You also need an optical power meter - there is no way round that. The lasers are rated for optical power, not laser current. They are actually damaged by excess optical power.
A proper control circuit will maintain constant optical power as the laser warms up - the threshold current varies significantly.
Keith
thanks keith... I will do on that direction. If i will find any problem than get back here...