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anita1984
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Joined: 19 Nov 2008
Posts: 7
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 Posted: Wed Nov 19, 2008 3:38 pm Post subject: Laser Display home made |
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Hello Forum , i am new here and new to this domaine ( laser and laser displays ). I have a motor ( polygonal mirrors ) with facets , i can rotate this motor up to 32000 RPM , and i have a normal laser pointer, these 2 devices can be connected to a microcotroller to set the frequencies . As i know that x facets mirror can give a x scan lines.My question is how can i make from this 2 devices a projected laser line of N dots of laser ?is their a special formula between the frequency of the laser pointer and the rotation speed? Thank you in advance
Last edited by anita1984 on Thu Dec 04, 2008 5:47 pm; edited 3 times in total |
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Alan
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Joined: 29 Jan 2006
Posts: 1399
Location: Winnipeg, MB
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| Posted: Wed Nov 19, 2008 9:42 pm Post subject: Re: Laser Display home made |
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| anita1984 wrote: | | Hello Forum , i am new here and new to this domaine ( laser and laser displays ). I have a DC brushless motor ( polygonal mirrors ) with 6 facets , i can rotate this motor up to 35000 RPM , and i have a normal laser pointer, these 2 devices can be connected to a microcotroller to set the frequencies . As i know that 6 facets mirror can give a 6 scan lines.My question is how can i make from this 2 devices a projected laser line of 128 dots of laser ?is their a special formula between the frequency of the laser pointer and the rotation speed? Thank you in advance |
Welcome to the forum!
We can sure help you out. Have a look at this project, not the same as your idea but it is similar.
http://forum.hackedgadgets.com/viewtopic.php?t=42
You will need to power the motor from a stable supply, I would suggest using a voltage regulator. There will also need to be a way to detect rotation. This can be done by using a hall effect or infrared sensor.
As far as the 128 dots go, I would just time out a for loop that produces a dot (if needed) then times out a blank space etc. This is possible since you can fix the rotating speed by keeping a steady voltage. |
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anita1984
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Joined: 19 Nov 2008
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| Posted: Thu Nov 20, 2008 7:08 am Post subject: Laser display |
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There will also need to be a way to detect rotation.
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if i know the rotation of the motor , let's say 30 rps , one thing i can't understand it , how the blinking of the laser diode should be with reference to the mirror ( motor ) to make those dots ?[/quote] |
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Alan
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Joined: 29 Jan 2006
Posts: 1399
Location: Winnipeg, MB
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| Posted: Thu Nov 20, 2008 8:16 am Post subject: Re: Laser display |
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| anita1984 wrote: | | Quote: |
There will also need to be a way to detect rotation.
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if i know the rotation of the motor , let's say 30 rps , one thing i can't understand it , how the blinking of the laser diode should be with reference to the mirror ( motor ) to make those dots ? |
You will need something that sends a signal when the motor is at a certain position on every rotation. For this I would recommend using an infrared sensor (beam). Here is a picture of one.
http://www.alan-parekh.com/cgi-bin2/view_details.php?pic_location=/clock_pics/optical_sensor.gif&pic_desc=
This was used in my hard drive clock.
http://alan-parekh.com/projects/hard-drive-clock/
Last edited by Alan on Thu Nov 20, 2008 9:05 pm; edited 1 time in total |
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anita1984
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Joined: 19 Nov 2008
Posts: 7
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| Posted: Thu Nov 20, 2008 11:45 am Post subject: Laser display |
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| Thank you Alan for the important information,so you recommand me to add a infrared beam sensor , this detect the rotation per revolution and send a signal to the microcontroller which can detect the exact location of the rotating platter and the microcontroller drives the laser.As i understand that i shouldn't change the speed of the motor , the speed should be fix and controled by the microcontroller only for ON or OFF. Is this true what i thought? |
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Alan
Site Admin
Joined: 29 Jan 2006
Posts: 1399
Location: Winnipeg, MB
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| Posted: Thu Nov 20, 2008 12:12 pm Post subject: Re: Laser display |
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| anita1984 wrote: | | Thank you Alan for the important information,so you recommand me to add a infrared beam sensor , this detect the rotation per revolution and send a signal to the microcontroller which can detect the exact location of the rotating platter and the microcontroller drives the laser.As i understand that i shouldn't change the speed of the motor , the speed should be fix and controled by the microcontroller only for ON or OFF. Is this true what i thought? |
That is what I would do. Some motors have a rotational sensor built into them and you could try to tap into that but using your own sensor is probably the easiest way to go. Just install a small tab onto the motor that will rotate through the sensor. |
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Tekwiz
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Joined: 20 Oct 2008
Posts: 36
Location: Vancouver Island
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| Posted: Thu Nov 20, 2008 3:10 pm Post subject: |
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| You can likely use the beam itself as a position sensor. Arrange things so that the beam reflected from the mirror crosses a photo sensor at the beginning of it's line. The timing of these sensor pulses can then be used to determine the mirror speed & position, eliminating any need for connections to the motor drive circuitry or external position sensors. You don't want to be adding anything physical to the rotating motor or mirror, as this will seriously upset the balance & cause vibration or failure. |
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anita1984
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Joined: 19 Nov 2008
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| Posted: Thu Nov 20, 2008 3:18 pm Post subject: |
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Waaaaw i like the idea , thank you alot for the important information , waaw i have now 2 methods , thank you , realy nice forum  |
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Alan
Site Admin
Joined: 29 Jan 2006
Posts: 1399
Location: Winnipeg, MB
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| Posted: Thu Nov 20, 2008 9:08 pm Post subject: |
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| Tekwiz wrote: | | You can likely use the beam itself as a position sensor. Arrange things so that the beam reflected from the mirror crosses a photo sensor at the beginning of it's line. The timing of these sensor pulses can then be used to determine the mirror speed & position, eliminating any need for connections to the motor drive circuitry or external position sensors. You don't want to be adding anything physical to the rotating motor or mirror, as this will seriously upset the balance & cause vibration or failure. |
Great idea Tekwiz! I like it.  |
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Tekwiz
HG Contributor
Joined: 20 Oct 2008
Posts: 36
Location: Vancouver Island
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| Posted: Fri Nov 21, 2008 2:20 pm Post subject: |
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Sometimes the simplest solutions are the best.  |
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anita1984
Semi Newbie
Joined: 19 Nov 2008
Posts: 7
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| Posted: Sun Nov 30, 2008 12:19 pm Post subject: PhotoTransistor |
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Hello again,
I attach a laser and phototransistor to the upper side of the polygonal mirror ( the upper side is a metal reflect too ) and i put a black dot, it's a mix between these 2 methods ( thanks for Alan and Tekwiz ) . The circuit increase the output from high to low in response to a light input. Like this i can have a pulse per revolution from the Phototransistor.I can't imagine the mathematical equation to control the on/off of the main laser to make dots  , Do you have idea ? |
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