Need advice before connecting TTL laser driver to prusa i3
Posted by Mister Fab
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Need advice before connecting TTL laser driver to prusa i3 April 08, 2016 01:05PM |
Registered: 10 years ago Posts: 49 |
Hi all,
I just received all I need to modify my prusa i3 into a laser cutter.
I bought a chinese laser on ebay to make my first tests, I will see next to buy a better one.
The laser is this the one on the attached photo
I tested my D9 output and it gives 12V. As the TTL input accepts 5V I built a regulator using a 7805 circuit as on the schematic attached.
Does everything seem ok? I wouln't like to burn the driver at first try.
Thanks in advance for your answers.
I just received all I need to modify my prusa i3 into a laser cutter.
I bought a chinese laser on ebay to make my first tests, I will see next to buy a better one.
The laser is this the one on the attached photo
I tested my D9 output and it gives 12V. As the TTL input accepts 5V I built a regulator using a 7805 circuit as on the schematic attached.
Does everything seem ok? I wouln't like to burn the driver at first try.
Thanks in advance for your answers.
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Re: Need advice before connecting TTL laser driver to prusa i3 April 08, 2016 02:51PM |
Registered: 10 years ago Posts: 31 |
I would not use the 12V mosfet-controlled outputs. They don't give a pulse between 12v and 0V
that can be used here. My understanding is that there is always +12V and the N-fet gives a path to GND.
This is a problem if your laser driver is already grounded.
Instead it is better to find an unused pin, such as one of the servo pins on the ramps.
Re-configure your software to have the fan use that pin.
I have that laser driver also and it works fine using PWM to the TTL port.
Fully adjustable between 0 and 255.
that can be used here. My understanding is that there is always +12V and the N-fet gives a path to GND.
This is a problem if your laser driver is already grounded.
Instead it is better to find an unused pin, such as one of the servo pins on the ramps.
Re-configure your software to have the fan use that pin.
I have that laser driver also and it works fine using PWM to the TTL port.
Fully adjustable between 0 and 255.
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Re: Need advice before connecting TTL laser driver to prusa i3 April 08, 2016 03:04PM |
Registered: 10 years ago Posts: 49 |
I'm surprised about your answer.
I tested the output with my oscilloscope, and I got these results using the M106 command from 0 to 255
I tested the output with my oscilloscope, and I got these results using the M106 command from 0 to 255
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Re: Need advice before connecting TTL laser driver to prusa i3 April 08, 2016 03:19PM |
Registered: 10 years ago Posts: 31 |
There is no common ground, what is common is the high side, +12V,
It is only when mosfet is "on" that there is a common ground.
This is no problem when connecting the 12V to a heater, a fan or any
other free device. But when connected to an other device that already
has a path to ground, that most of the electronic devices have,
the mosfet has no effect since there is already ground.
Admittedly this is at the edge of my comfort zone.
Had it been a P-fet than it would have been possible.
With the N-fet I advice against it. And most if not all breakout
cards like ramps use N-fet.
It is only when mosfet is "on" that there is a common ground.
This is no problem when connecting the 12V to a heater, a fan or any
other free device. But when connected to an other device that already
has a path to ground, that most of the electronic devices have,
the mosfet has no effect since there is already ground.
Admittedly this is at the edge of my comfort zone.
Had it been a P-fet than it would have been possible.
With the N-fet I advice against it. And most if not all breakout
cards like ramps use N-fet.
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Re: Need advice before connecting TTL laser driver to prusa i3 April 08, 2016 03:35PM |
Registered: 10 years ago Posts: 49 |
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Re: Need advice before connecting TTL laser driver to prusa i3 April 08, 2016 04:01PM |
Registered: 10 years ago Posts: 31 |
I think the easiest is to take one of the servo pins if you use RAMPS.
For example SERVO 4 uses D4. (Ref. [rigidtalk.com])
Connect signal and ground from SERVO 4/pin 4 to TTL on the laser driver.
Then you do M42 P4 S10 and the laser should give some light.
Switch off M42 P4 S0
You can use this in a program as well, but precede it with M400 like
M400
M42 P4 S230
If you want that M106 should control this pin 4, then you go into this file [github.com]
and search for FAN_PIN and set it to 4 for pin 4. Then M106 S123 control pins 4.
Sketchy, but should cover the important I hope.
Edited 5 time(s). Last edit at 04/08/2016 04:24PM by falwty99.
For example SERVO 4 uses D4. (Ref. [rigidtalk.com])
Connect signal and ground from SERVO 4/pin 4 to TTL on the laser driver.
Then you do M42 P4 S10 and the laser should give some light.
Switch off M42 P4 S0
You can use this in a program as well, but precede it with M400 like
M400
M42 P4 S230
If you want that M106 should control this pin 4, then you go into this file [github.com]
and search for FAN_PIN and set it to 4 for pin 4. Then M106 S123 control pins 4.
Sketchy, but should cover the important I hope.
Edited 5 time(s). Last edit at 04/08/2016 04:24PM by falwty99.
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Re: Need advice before connecting TTL laser driver to prusa i3 April 08, 2016 04:25PM |
Registered: 10 years ago Posts: 49 |
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Re: Need advice before connecting TTL laser driver to prusa i3 April 08, 2016 05:08PM |
Registered: 10 years ago Posts: 31 |
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Re: Need advice before connecting TTL laser driver to prusa i3 April 09, 2016 02:00PM |
Registered: 11 years ago Posts: 1,049 |
See
[jtechphotonics.com]
not exactly your laser
but principles and electronic driver similar
wear your red goggles
you won't need a white cane
[jtechphotonics.com]
not exactly your laser
but principles and electronic driver similar
wear your red goggles
you won't need a white cane
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Re: Need advice before connecting TTL laser driver to prusa i3 April 10, 2016 09:02AM |
Registered: 10 years ago Posts: 49 |
Thank you cozmicray.
I already got information from this website, and that's why I wanted to use D9 as their driver uses that pin also.
I won't have much time to test during the weekend anyway, but I keep questioning myself about the differences between jtech driver and my chinese driver that couldn't use D9.
I already got information from this website, and that's why I wanted to use D9 as their driver uses that pin also.
I won't have much time to test during the weekend anyway, but I keep questioning myself about the differences between jtech driver and my chinese driver that couldn't use D9.
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Re: Need advice before connecting TTL laser driver to prusa i3 April 10, 2016 09:13AM |
Registered: 10 years ago Posts: 31 |
Hehe, well you can always try.
I am not always sure of electronics stuff, but I found this on the jtech description of their laser driver.
What you can do is to check if one of the TTL inputs on your laser driver are connected to ground.
If not, then it should work with D9.
Edited 1 time(s). Last edit at 04/10/2016 09:25AM by falwty99.
I am not always sure of electronics stuff, but I found this on the jtech description of their laser driver.
Optically isolated input = it's ok with a N-fet, no ground issues. I think they have realized the problem with D9.Quote
jtech
The input connection provides an optically isolated input for control of the laser diode. The connection and the jumper settings were described in the previous sections. The voltage required to turn on the opto-isolator is 2.8 volts. The input can handle up to 36 volts at no more than 50 ma. The input can be cycled with no degradation up to 5KHz.
What you can do is to check if one of the TTL inputs on your laser driver are connected to ground.
If not, then it should work with D9.
Edited 1 time(s). Last edit at 04/10/2016 09:25AM by falwty99.
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Re: Need advice before connecting TTL laser driver to prusa i3 April 10, 2016 04:28PM |
Registered: 10 years ago Posts: 49 |
Thank you for you precision falwty99.
I just try to understand everything. I don't really have an high electronics skills, you seem to understand much better than me the TTL stuff.
When you say to check if TTL inputs are connected to ground, am I right if I test the continuity between these wires and the minus of the 12V laser power input?
I just try to understand everything. I don't really have an high electronics skills, you seem to understand much better than me the TTL stuff.
When you say to check if TTL inputs are connected to ground, am I right if I test the continuity between these wires and the minus of the 12V laser power input?
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Re: Need advice before connecting TTL laser driver to prusa i3 April 10, 2016 06:12PM |
Registered: 10 years ago Posts: 371 |
I've looking for the same kind of answers: [forums.reprap.org] even same module
whats have you accomplished?
whats have you accomplished?
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Re: Need advice before connecting TTL laser driver to prusa i3 April 12, 2016 03:21PM |
Registered: 10 years ago Posts: 49 |
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Re: Need advice before connecting TTL laser driver to prusa i3 April 13, 2016 03:01AM |
Registered: 10 years ago Posts: 31 |
Check if there is zero resistance between the TTL negative pin on the laer driver and ground on the ramps board,
if so they have a common ground: don't use D9.
If the multimeter reads like megaohms between ramps board ground and the TTL negative pin,
then you can use D9, if voltage also is ok.
if so they have a common ground: don't use D9.
If the multimeter reads like megaohms between ramps board ground and the TTL negative pin,
then you can use D9, if voltage also is ok.
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