Increasing PWM output voltage
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Posted by Dave, I can't do that on September 18, 2008, 10:03 am
Please log in for more thread options Hello, I need to boost a PWM signal at 5KHz and 450mV to 5V at 5KHz and 100mA max. Could someone please give me a list of the components I need and a schematic to do this. A suggested idea was this... http://www.cnczone.com/forums/showpost.php?p=501327&postcount=4 But as you can see the guy was unsure of N-channel or P-channel and he never got back to me. Thank you. Dave | ||||||||||||||||||||||||||||||||||||||||||||||
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Posted by Robert Monsen on September 18, 2008, 12:43 pm
Please log in for more thread options On Thu, 18 Sep 2008 07:03:55 -0700 (PDT), "Dave, I can't do that" Do you need to pull both up and down? What are you driving with the PWM signal? At 450mV, not many mosfets will work directly in any case. The easiest thing would be to use a comparator, and use the output to control a driver chip like an SN754410: http://focus.ti.com/lit/ds/symlink/sn754410.pdf Regards, Bob Monsen | ||||||||||||||||||||||||||||||||||||||||||||||
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Posted by Dave, I can't do that on September 18, 2008, 2:05 pm
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Hi Robert, thanks for the reply. > Do you need to pull both up and down? What are you driving with the
> PWM signal? I do not know what that means. I am trying to drive a 25W CO2 Laser marking machine's Laser intensity. I was given the dead Laser and installed one I bought surplus. I now have everything working except the intensity. It is supposed to put out 5v PWM at 5KHz but it is only putting out 450mV. There are no schematics available as it is such an old model and there are several EEPROMs on board and I have no idea what they are coded to do. The PWM is working just not at sufficient voltage to trigger the Laser. I want to use the existing 450mV PWM output to drive something that will output the 5v I need. I have been told that this Laser requires "Output Current, max 100mA through a 50 Ohm CMOS driver" and that's all I have to go on. If I can't do that then I will tear out the electronics and install a 2-axis CNC stepper driver board and run it under EMC2. Obviously getting it to work would be better since it is configured as a printer for Corel and a simple matter to "print" the part. If I go the CNC route I will have to add in two more programming stages for every project. Dave | ||||||||||||||||||||||||||||||||||||||||||||||
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Posted by John Fields on September 18, 2008, 6:47 pm
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On Thu, 18 Sep 2008 11:05:58 -0700 (PDT), "Dave, I can't do that" >
>Hi Robert, thanks for the reply. > >> Do you need to pull both up and down? What are you driving with the
>> PWM signal? >
>I do not know what that means. I am trying to drive a 25W CO2 Laser >marking machine's Laser intensity. > >I was given the dead Laser and installed one I bought surplus. I now >have everything working except the intensity. It is supposed to put >out 5v PWM at 5KHz but it is only putting out 450mV. There are no >schematics available as it is such an old model and there are several >EEPROMs on board and I have no idea what they are coded to do. > >The PWM is working just not at sufficient voltage to trigger the >Laser. I want to use the existing 450mV PWM output to drive something >that will output the 5v I need. > >I have been told that this Laser requires "Output Current, max 100mA >through a 50 Ohm CMOS driver" and that's all I have to go on. --- What rise time, minimum pulse width, and fall time do you need? JF | ||||||||||||||||||||||||||||||||||||||||||||||
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Posted by Jamie on September 18, 2008, 7:25 pm
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Dave, I can't do that wrote: >
> Hi Robert, thanks for the reply. > > >>Do you need to pull both up and down? What are you driving with the
>>PWM signal? >
> > I do not know what that means. I am trying to drive a 25W CO2 Laser > marking machine's Laser intensity. > > I was given the dead Laser and installed one I bought surplus. I now > have everything working except the intensity. It is supposed to put > out 5v PWM at 5KHz but it is only putting out 450mV. There are no > schematics available as it is such an old model and there are several > EEPROMs on board and I have no idea what they are coded to do. > > The PWM is working just not at sufficient voltage to trigger the > Laser. I want to use the existing 450mV PWM output to drive something > that will output the 5v I need. > > I have been told that this Laser requires "Output Current, max 100mA > through a 50 Ohm CMOS driver" and that's all I have to go on. Maybe what they were referring to is that it must be current regulated to not exceed the 100 ma or set point since a Laser current is critical. >
> Dave http://webpages.charter.net/jamie_5" | ||||||||||||||||||||||||||||||||||||||||||||||
>
>I need to boost a PWM signal at 5KHz and 450mV to 5V at 5KHz and 100mA
>max.
>
>Could someone please give me a list of the components I need and a
>schematic to do this.
>
>A suggested idea was this...
>http://www.cnczone.com/forums/showpost.php?p=501327&postcount=4
>
>But as you can see the guy was unsure of N-channel or P-channel and he
>never got back to me.
>
>Thank you.
>
>Dave