A while back I bought on e-bay a 2W Laser to be added to my Makeblock XY plotter. The laser I bought had TTL PWM control. But the Motor (M2) output cannot be connected directly to the TTL input on the laser. The voltages of the Motor output do not match the required input voltages for the laser module. I needed to add some additional electronics to make it work. According to the specifications the input for the TTL PWM on the Laser Module was 0 – 5V. 0V being Laser Off, 5V being Laser Off. An easy experiment learned me that the module I was using demonstrated the following behaviour:
- When Input was open (nothing attached), the laser would be on.
- When the input was shortened, the laser was off.
So a pull down to ground would work. Also I wanted to make sure the Laser Module was isolated from the Orion Board (I do not want to blow up anything). So I wanted to use a Opto Coupler as well.
Below the final schematic which I build:
I have added also a rectifier to the schematic. With the mDraw software the M2+ is really the plus and the M2- is really the minus. But strangely the BenBox software sends a negative signal swapping the plus and minus. Anyway this schematic works for either software package.
On the right side (the Laser Module side), you see a +5V, this can also be a lower voltage. I connected a Li-Ion battery. If you cannot find a TIL111 opto coupler, I believe any generic opto coupler should also work. You may need to change R1 when using a different opto coupler.
The laser module is working very well and I am happy with the result.
Some more pictures of the end result: