Using PWM to control. Newbie here.

Hello everyone!

I have spent some time lurking these forums, and haven't quite found what I needed. I'm working on a school project where we're modifying a 3D printer to be able to cut (or etch at least) using a laser. Basically improve on a design, and make this device multi-functioning (print plastic and etch).

Now, part of the electronics has areas where we can add in extensions. This uses pulse width modulation, which by my understanding, acts as a switch (opening and closing at a certain frequency). By adjusting the pulse width, we can adjust the power going to the laser, hence able to use different laser classes for this project.

Now, for DEMONSTRATION PURPOSES, we will be using a 5mW laser, and show that we can control this laser (when and where it turns on to etch). AFTERWARDS, we will switch the laser in with a higher class that can actually do some damage.

My problem, is I don't really know where to start. I'm new to lasers, and reading up in these forums and online kinda swamped me with all sorts of information, and confused me even more. I know I need a driver for the laser, but I don't really know why, or what it does.
My plan is to connect the driver in series with the PWM and power source.
Also another thing to consider is focal length (from what I understand). For the 5mW laser, I don't think this is too important since we're only demonstrating it to public. However, afterwards, in order to actually cut, I will have to calculate this. The cutting surface will probably around 5cm away. How can I figure this out?

Anyways, if anyone can point me in the right direction, I'd greatly appreciate it. I'll be checking up on these forums often. Thanks for your time!

Before you begin, first read up about how PWM works for something like motors, and why they use PWM rather than other methods. Also learn how to use microcontrollers because you'll need a programmatic way to control your signals.

For PWM-controlled laser current, you can use something like this. Program the max current using this information (that image in the first link is the one missing in the second).

For the PWM signal coming in, you can use something like a PWM-based LED driver connected to a microcontroller, because it is often easier to program the PWM into that rather than manually do it with a microcontroller using bitbanging or their low-resolution PWM outputs.

I'm forever trying to rep you, and forever being denied the opportunity due to the fact that I haven't "spread the love" enough.. You always provide very good answers when questions are asked!

Thank you for the links. I will read into them and post a reply in the next day or so.

ElektroFreak said:

I'm forever trying to rep you, and forever being denied the opportunity due to the fact that I haven't "spread the love" enough.. You always provide very good answers when questions are asked!

Click to expand...

Thanks! That compliment is better than any rep. I'm in the same boat for repping many people too.

Ok, so I took the time to read through it all. I understand whats going on, and I can follow along in the explanations (second link). Would I be able to use this circuit directly?

I should have a 12V, 1A source for this circuit. Now, if I wanted to change the output power (for example I want 5mW now, but later I will swap it for a more powerful laser), is it R1 I'm supposed to change? Or can I add some resistors on to the output side of the circuit.

Also, because I'm still new to the lasers, I don't know why drivers are used, or what their purpose is. Will I still need a driver if I use this circuit?

Thank you for helping me out.

Can anyone help me?

I can see by your question that you do not have the basic
electronics knowledge to pull this off at this time.

The circuit you refer to shows how to connect a Microcontroller
to a current regulated driver to allow different levels of PWM
output.

If you apply the max voltage to R1 you will get the Max output
to the load as referenced by the Current sensing resistor R3.

If on the other hand you apply ground to R1 the output will be
at the Minimum output to the Load.

I would suggest you buy the parts for that circuit and a Breadboard
and experiment with it to learn how it works and if you want to use
it for your application....


Jerry

Thank you very much. Yes, I don't know too much. I'm still a student.

Just break the knowledge you need down to individual parts
and learn about them individually by doing research on one part
at a time.....

Jerry

Will do!
I've studied how to use the components, and how they operate, etc. But put them all together in one circuit, and it will take me a while to figure things out. Thank you for your help once again, if I have any questions, can I message you?

ElectroTurk said:

Will do!
I've studied how to use the components, and how they operate, etc. But put them all together in one circuit, and it will take me a while to figure things out. Thank you for your help once again, if I have any questions, can I message you?

Click to expand...

Sure you can....
I won't spoon feed you but I can certainly help
to point you in the right direction...

Jerry

That is all I ask!
I need to learn something.

It will not be hard to find a PWM circuit, look for something used in other applications such as a lamp dimmer or motor/fan control circuit.

Thank you for the tips, I will keep that in mind.