I am using a 5V 40 mA (max current) output on an Arduino to turn on (5V) or off (0V) as laser driver. The laser driver requires a max voltage of 2V to turn it on and flips at 0.8V. How can I lower the 5V to 2V for the driver?
Thanks in advance!
Lower 5V output to 2V max
arduino
Related Solutions
opamp is one idea - there are plenty of tutorials in the internets, but it might be easier to connect GND of your galvo to +5V. If you don't have +5V, you can make it from your +10V.
No, do not invert the sender. That would leave the laser on during idle, something you probably want to avoid.
You can flip around the receiving circuit so that the photodiode is between the positive supply and the inverting opamp input:
When the diode produces current, the opamp output will go low.
You have to think carefully about what power voltage is used for what. In the above circuit, the opamp can be powered from the same voltage as at the top of the diode only if the opamp's common mode range extends all the way to its positive supply. Otherwise, you'll need a little higher voltage for the opamp positive supply.
If the opamp negative supply is ground, then you have to make sure its active output range gets low enough for the digital input to reliably interpret that voltage as a low.
A CMOS "rail to rail" opamp might be good enough to use common power for the diode and the opamp. However, you need to check the datasheet carefully to see what "rail to rail" really means.
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Best Answer
I think that you are reading the specification of the laser driver circuit incorrectly. It would help if you can either post the exact specifications of the driver or post a link to a web page that describes the driver. Please don't link to a PDF file - most people won't download a file to view it.
I strongly suspect that the laser driver circuit wants to see a TTL-compatible signal. I'm inferring that from the 0.8V 'flip' voltage that you mention as well as the '2V max to turn it on'. What that means is that the driver needs a voltage HIGHER than 2.0 Vdc to turn it ON and a voltage LESS than 0.8 Vdc to guarantee that it turns OFF.
If I am correct, you don't need to anything except connect the Arduino output pin directly to the control input pin on the laser driver circuit.
Be sure to also connect your Arduino ground to the laser power supply ground.