PWM voltage peaks

Hi;

I’ve recently bought a Makeblock XY plotter with the laser kit. After getting used to to the platform, i’ve ordered a more powerful laser to replace the stock one.

The old laser was a 500mW laser which ran at 6 volts. The new one is a 2.5w at 12 volts.

The motor output of the makeblock orion board (UNO based) spits out 12v PWM so in theory i should be able to connect the new laser to the motor output directly and control the ouput via software.

Only thing is when i hook the output to the scope i see some peaks on the signal like this: (i drew it from memory)

The Vpp is around 15 volts. the peaks is only momentarily but i’m a little concerned that it might damage the laser or its driver.

Is this an acceptable signal? Or should regulate or filter this to be safe?

Thanks.

Hi,
Confused.. Are you talking about connecting the actual motor and laser on the same output? Why would you do that? The spikes you see are from the motor inductance.

Hi;

It's just the way the outputs are named in the arduino variant:
http://learn.makeblock.com/wp-content/uploads/2016/01/start_0s.jpg

You can see at the bottom there are 2 outputs named M1 and M2.

I will connect the laser to M2 as the only load.

When i hooked the output to the scope there wasn't any load on it.

Sometimes there is ringing caused by the scope probe, or it could be capacitance/inductance somewhere else in the circuit. ...You rarely see a perfect pulse on a scope, and you rarely need a perfect pulse. But of course, there are cases where a "bad" pulse or a bad/noisy clock can cause trouble.

The motor output of the makeblock orion board (UNO based) spits out 12v PWM so in theory i should be able to connect the new laser to the motor output directly and control the ouput via software.

You can't normally dim/control a laser with PWM on the power supply.

DVDdoug:
Sometimes there is ringing caused by the scope probe, or it could be capacitance/inductance somewhere else in the circuit. ...You rarely see a perfect pulse on a scope, and you rarely need a perfect pulse. But of course, there are cases where a "bad" pulse or a bad/noisy clock can cause trouble.
You can't normally dim/control a laser with PWM on the power supply.

You are right, the power supply PWM didn't work. The laser either works at 100% or not at all.

Here's a picture of the driver board:

Do you think i can connect T+ and T- to the controller to drive the TTL with 5v pulses?

How about some spec.s on the new laser module. Spec sheet should reveal all.

well, as with most of the things from china things get a little complicated when it comes to detailed spec sheet or pdf.

Here's the link to the product:

At the bottom of the page there's a discussion regarding the TTL modulation which didn't conclude with a convincing response.

Did you figure out what the T+ and T- are for? I had a poke around but didn't have enough time to figure our if they do anything.

I want to control my laser via TTL really so the fan is running constantly (and PWM the 12v supply, while it works, is not a good solution in my opinion - the spikes you see are probably caused by the inductance of the fan)

smremde:
Did you figure out what the T+ and T- are for? I had a poke around but didn't have enough time to figure our if they do anything.

I want to control my laser via TTL really so the fan is running constantly (and PWM the 12v supply, while it works, is not a good solution in my opinion - the spikes you see are probably caused by the inductance of the fan)

i ended up ordering one of these: http://www.banggood.com/12V-TTL-200mW-To-3W-445nm-450nm-Laser-Diode-LD-Power-Supply-Driver-Board-p-984552.html

Haven't hooked it up yet. You provide TTL and 12V to the board and it does the modulation and fan control.