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AnsweredHot!MOSFET as Switch to turn on Laser Using PIC32

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m_snaeem@hotmail.com
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2020/10/23 00:43:14 (permalink)
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MOSFET as Switch to turn on Laser Using PIC32

Hello, 
I am trying to Switch On/Off a laser that requires 2.7-3.3V to turn on. I have tried using BSH114,215 NMos. I have applied 3.3 Volts at the laser positive side and the negative side of the laser is connected to the drain of NMOS. and I am using 3.3V input from the controller to turn it on and off but it does not work. I have also applied 5V to the laser side also but it did not work.
Though It switches LED with 3.3V on the Laser side but does not power on Laser. As I am increasing voltages on the Laser side Vds increase but the voltage across Laser remains constant around 2.3V where it requires 3V to switch on.
I did LT-spice simulation (use resistor at the place of laser ) so it worked but with laser, it does not work.
Kindly give suggestions on how can I turn on the laser with a microcontroller using Mosfet with 3.3V to 5 volts power supply???
#1
GeeWhizz
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Re: MOSFET as Switch to turn on Laser Using PIC32 2020/10/23 01:17:56 (permalink)
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According to the datasheet for the BSH114, even if you heat the device to 150'C (!!), it will barely start to turn on with 3.3V on the gate (assuming that the PIC output is a perfect switch).  At room temperature (25'C), it starts to turn on at about 3.8V.  You need to use a MOSFET driver of some sort or a pretty rare MOSFET.
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m_snaeem@hotmail.com
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Re: MOSFET as Switch to turn on Laser Using PIC32 2020/10/23 01:35:34 (permalink)
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Laser need 100 mA maximum according to data sheet but upon power on using power supply it take maximum about 15mA.
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m_snaeem@hotmail.com
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Re: MOSFET as Switch to turn on Laser Using PIC32 2020/10/23 01:41:16 (permalink)
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Rds On of BSH114215 is 0.5 ohm which is low as compared to FDV301 which has 5 ohm.
So BSH114215 should work.
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m_snaeem@hotmail.com
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Re: MOSFET as Switch to turn on Laser Using PIC32 2020/10/23 06:39:50 (permalink)
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Ok thanks i"ll try FDV303N;
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Denge
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Re: MOSFET as Switch to turn on Laser Using PIC32 2020/10/23 13:51:25 (permalink)
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Maybe have a look at the IChause.de website. They have quite nice laser drivers. BTW what laser are you using, a diode laser? Than Vexorg is right you can't use a resistor as simulation.
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m_snaeem@hotmail.com
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Re: MOSFET as Switch to turn on Laser Using PIC32 2020/10/26 06:58:44 (permalink)
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Yes it is a laser diode
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m_snaeem@hotmail.com
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Re: MOSFET as Switch to turn on Laser Using PIC32 2020/10/26 07:38:50 (permalink)
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It worked using FDV303N. Thanks vexorg and Denge for your help.
post edited by m_snaeem@hotmail.com - 2020/10/26 07:43:52
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