Hello Vienna is calling for help to modulate a Laser on 38kz carrirerfreq.

wranox · Nov 30, 2018

Hello from Austria , and sorry for my english.
i search for help on a project.
I like to puls a 523 nm Laser to transmitt a ID ( one startbyte 3 times ID Byte and one Stopbyte )
A easy way by to use same protocol as a IR remote control . Carrier freq. 38hz

Switch on and off for differed timing is a 1 or 0 bit .
I am plan to using a Arduino Uno R3 to build the 38kz carrier and the 1 and 0 bit or bytes , but how can i switch the laser so fast and precise on and off or better what kind of laser or lasermodul ar the best for this. In case that i like to see the beam on daylight it soud by a 532nm green one.
Thanks for help.
PS: Hello Santaclaus, this ar my wishes for Christmas " Freedom on would and ideas for my project" LOL

diachi · Nov 30, 2018

Guessing you mean 38kHz... Anyway...

532nm is not a good choice for this as it does not modulate well, the rise and fall times are terrible, especially on cheap 532nm modules. Just a result of how the light is produced. 532nm is produced by "pumping" a set of crystals with an 808nm laser diode, which then gets converted in 532nm light.

If you want fast modulation go with a direct diode laser, such as a 520nm laser diode.

What's the purpose of your project?

wranox · Nov 30, 2018

diachi said:
Guessing you mean 38kHz... Anyway...

532nm is not a good choice for this as it does not modulate well, the rise and fall times are terrible, especially on cheap 532nm modules. Just a result of how the light is produced. 532nm is produced by "pumping" a set of crystals with an 808nm laser diode, which then gets converted in 532nm light.

If you want fast modulation go with a direct diode laser, such as a 520nm laser diode.

What's the purpose of your project?

O yes it is 38 khz . Thanks for the idee to use 520nm . I dinent now the differenziertes betwin 532 and 520. So a 520 mm diode drive whit a mosfet from a pin of the Arduino must by good for 38 kHz. Du have a idea whot diode i shut take ( not more or less then 5 mw output )It is not easy to explane the purpose in case of some patens but so far it is part of a game idea.

Immo1282 · Nov 30, 2018

wranox said:
O yes it is 38 khz . Thanks for the idee to use 520nm . I dinent now the differenziertes betwin 532 and 520. So a 520 mm diode drive whit a mosfet from a pin of the Arduino must by good for 38 kHz. Du have a idea whot diode i shut take ( not more or less then 5 mw output )It is not easy to explane the purpose in case of some patens but so far it is part of a game idea.

Correct me if I misunderstood you - but you CANNOT drive a laser diode from the pin of an arduino, and you certainly shouldn't drive such a device by using a microcontroller pin to switch a MOSFET on and off alone. Laser Diodes require careful current regulation - if you just stick one across the power rails (i.e. a constant voltage supply), it will draw far too much current and just die immediately.

Look for a laser diode driver that has TTL input for modulation - that way you can drive the TTL input of said driver with your arduino all day - and the driver circuitry will handle the proper current regulation for the laser diode. I'm not sure if such a driver exists but you have to be smarter about driving LDs, or you'll have a neat pile of dead ones.

Encap · Nov 30, 2018

You are not going to see the beam in daylight. Forget about that aspect of you imagined device.

paul1598419 · Dec 1, 2018

I have driven a 532nm DPSS laser driver's TTL with KHz frequencies, but have not tried it at 38 KHz. I know that it can be done, however. Why are you limiting the optical power to 5 mW? It certainly isn't necessary unless your project needs such a low power for a reason I don't know. You can get a direct diode lab laser ~505nm at 60 mW for around $65.00. This might also be a good laser to chose for your project.

wranox · Dec 1, 2018

Immo1282 said:
Correct me if I misunderstood you - but you CANNOT drive a laser diode from the pin of an arduino, and you certainly shouldn't drive such a device by using a microcontroller pin to switch a MOSFET on and off alone. Laser Diodes require careful current regulation - if you just stick one across the power rails (i.e. a constant voltage supply), it will draw far too much current and just die immediately.

Look for a laser diode driver that has TTL input for modulation - that way you can drive the TTL input of said driver with your arduino all day - and the driver circuitry will handle the proper current regulation for the laser diode. I'm not sure if such a driver exists but you have to be smarter about driving LDs, or you'll have a neat pile of dead ones.

Thanks ,you ar right i need a driver board to ttl the laserdiode. Du you now some driverboars for 532 or 520 nm diods max 5 mw and powert by 5 V . in case it is a mobil Applikation and i like to use akkus from mobilphones or Rc models so small as possible.

wranox · Dec 1, 2018

paul1598419 said:
I have driven a 532nm DPSS laser driver's TTL with KHz frequencies, but have not tried it at 38 KHz. I know that it can be done, however. Why are you limiting the optical power to 5 mW? It certainly isn't necessary unless your project needs such a low power for a reason I don't know. You can get a direct diode lab laser ~505nm at 60 mW for around $65.00. This might also be a good laser to chose for your project.

Hello thanks for reply . How fast du you puls your 532nm diode . Some papers that i found

paul1598419 said:
I have driven a 532nm DPSS laser driver's TTL with KHz frequencies, but have not tried it at 38 KHz. I know that it can be done, however. Why are you limiting the optical power to 5 mW? It certainly isn't necessary unless your project needs such a low power for a reason I don't know. You can get a direct diode lab laser ~505nm at 60 mW for around $65.00. This might also be a good laser to chose for your project.

hello . Thanks for reply. How fast puls your 532 nm diode . Diachi tell me ,532 nm Diode ar not so fast in case the have some cristalls inside the pump . 520nm ar straight .

wranox · Dec 1, 2018

Encap said:
You are not going to see the beam in daylight. Forget about that aspect of you imagined device.

Hello , thanks for reply .yes i cant see the beam self . I need only see the dot on a taget. And on daylight gren is better for this.

Immo1282 · Dec 1, 2018

Wranox - do try to avoid double/triple posts - you can reply to multiple people in one comment and it'll get exactly the same visibility on the forum.

It's been said before - but why do you specify <5mw? Is the application something that could pose an eye-hazard?

paul1598419 · Dec 1, 2018

I have driven the TTL of a 532nm laser at ~5 KHz. I know it's not close to 38 KHz, but I had no problems at that frequency. I no longer have a frequency generator or I'd try to run one at 38 KHz for you. Sorry.

Singlemode Laser · Dec 1, 2018

I modulate laser diodes with frequencies up to the GHz range without any problems. If your current driver doesn't have a wideband modulation port, use can use a simple bias-tee to couple your AC signal in.

Singlemode

Benm · Dec 2, 2018

The problem is using DPSS here. These things do have a lag in both turning off and on between electrical input and optical output.

This already gives notable issues when scanning at 20 kHz or so, but you can compensate for that in software by delaying the movement of the galvo's and power up times of the non-dpss lasers in a system making it look pretty good in the end.

Just use a direct laser diode if you need speed, without the dpss process you can modulate them in the MHz to GHz regime if your drivers are up for that.

paul1598419 · Dec 2, 2018

Since the OP isn't using this in a projector the fact that there is some amount of lag in the solid state laser shouldn't matter. I don't know specifically what this project is, but it seems to be for communication as the OP is using it to send a binary code.

Singlemode Laser · Dec 2, 2018

The OP don't gave us more information about his project and not a lot other informations either. If lag is important (active feedback scheme o s.e.) than other laser types than dpss are a suitable choice. If not, every led will do the job, kHz modulation was perfected decades ago.

Singlemode

Benm · Dec 3, 2018

It's not lag as such. These DPSS lasers average out rapidly changing power levels of 808 nm light going into then, and the actual solid state laser makes them too slow to transmist 38 kHz signals.

Any LED or direct lasser diode would have no problem with this, probably you can modulate those into the gigahertz range as they do in fibre optics for internet connections

Hello Vienna is calling for help to modulate a Laser on 38kz carrirerfreq.

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