Controlling the brightness of the led using the PWM and optocoupler and 0 -10 volts led driver

[kunj_2308]

I am currently using the STM32F103C8 board, in this, I connect the OPTOCOUPLER  input to the PA6 PIN of stm32 which is the PWM pin, and at the output side I connect the optocoupler's output to the driver's 10v + pin and optocoupler's output with 10v - pin, and I also generate the PWM signal using timer 3 ,and in this i want to control the led brightness using the pwm dutycycle but this is not proper working . give me suggestions what should i do in this case?

this is the pwm initialization code

void PWM_Init(void) {

    // Initialization struct

    TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStruct;

    TIM_OCInitTypeDef TIM_OCInitStruct;

    GPIO_InitTypeDef GPIO_InitStruct;

    // Step 1: Initialize TIM3

    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);

    // Configure TIM3 base

    TIM_TimeBaseInitStruct.TIM_Prescaler = 144;

    TIM_TimeBaseInitStruct.TIM_Period = 499;

    TIM_TimeBaseInitStruct.TIM_ClockDivision = TIM_CKD_DIV1;

    TIM_TimeBaseInitStruct.TIM_CounterMode = TIM_CounterMode_Up;

    TIM_TimeBaseInit(TIM3, &TIM_TimeBaseInitStruct);

    TIM_Cmd(TIM3, ENABLE);

    // Step 2: Initialize PWM

    TIM_OCInitStruct.TIM_OCMode = TIM_OCMode_PWM1;

    TIM_OCInitStruct.TIM_OutputState = TIM_OutputState_Enable;

    TIM_OCInitStruct.TIM_OCPolarity = TIM_OCPolarity_Low;

    TIM_OCInitStruct.TIM_Pulse = 0;

    // Initialize OC1

    TIM_OC1Init(TIM3, &TIM_OCInitStruct);

    TIM_OC1PreloadConfig(TIM3, TIM_OCPreload_Enable);

    // Initialize OC2

    TIM_OCInitStruct.TIM_Pulse = 0;

    TIM_OC2Init(TIM3, &TIM_OCInitStruct);

    TIM_OC2PreloadConfig(TIM3, TIM_OCPreload_Enable);

    // Initialize OC3

    TIM_OCInitStruct.TIM_Pulse = 0;

    TIM_OC3Init(TIM3, &TIM_OCInitStruct);

    TIM_OC3PreloadConfig(TIM3, TIM_OCPreload_Enable);

// Initialize OC4

TIM_OCInitStruct.TIM_Pulse = 0;

    TIM_OC4Init(TIM3, &TIM_OCInitStruct);

    TIM_OC4PreloadConfig(TIM3, TIM_OCPreload_Enable);

    // Step 3: Initialize GPIOA (PA6, PA7) and GPIOB (PB0)

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_GPIOB | RCC_APB2Periph_AFIO, ENABLE);

    // Initialize PA6 as push-pull alternate function (PWM output) for LED

    GPIO_InitStruct.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7;

    GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF_PP;

    GPIO_InitStruct.GPIO_Speed = GPIO_Speed_2MHz;

    GPIO_Init(GPIOA, &GPIO_InitStruct);

    // Initialize PB0 as push-pull alternate function (PWM output) for LED

    GPIO_InitStruct.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1;

GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF_PP;

    GPIO_InitStruct.GPIO_Speed = GPIO_Speed_2MHz;

    GPIO_Init(GPIOB, &GPIO_InitStruct);

}

[Andrew Neil]

Please see the posting tips for how to properly post source code, etc:

https://community.st.com/t5/community-guidelines/how-to-write-your-question-to-maximize-your-chances-to-find-a/ta-p/575228

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@kunj_2308 wrote:

I am currently using the STM32F103C8 board

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What "STM32F103C8 board" ?

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@kunj_2308 wrote:

I connect the OPTOCOUPLER 

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What optocoupler?

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@kunj_2308 wrote:

 this is not proper working

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What, exactly, does that mean?

So what investigation / testing / debugging have you done to find out what's wrong?

[TDK]

If you initialize the pin as a GPIO output and toggle it, does it control the LED as expected? If not, there's a hardware issue.

> TIM_OCInitStruct.TIM_Pulse = 0;

This will not produce a PWM signal, but will produce a DC low signal (or high depending on settings).

[kunj_2308]

okay , thanks for your guidance

BLUEPILL board

optocoupler PC817  

i find that if i give the voltages according to that i am not getting the voltage difference of 10v

[kunj_2308]

yes it is toggled

[TDK]

Did you change the TIM_Pulse value to something nonzero? 100 for example.

[Andrew Neil]

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@kunj_2308 wrote:

okay , thanks for your guidance

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See point #3 - provide a schematic of your setup.

Some good, clear photos may also help ...

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@kunj_2308 wrote:

if i give the voltages according to that i am not getting the voltage difference of 10v

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Sorry, I don't understand that.

What voltages? Where? According to what? Difference relative to what?

Again, this would be a lot clearer on a schematic!

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@kunj_2308 wrote:

optocoupler PC817  

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This: https://global.sharp/products/device/lineup/data/pdf/datasheet/PC817XxNSZ1B_e.pdf ?

[mƎALLEm · Accepted solution]

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@kunj_2308 wrote:

BLUEPILL board

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Hello,

ST resources are only dedicated to supporting genuine ST products. We are not committed to ensuring that clones/fakes products work properly with the firmware we provide.

We suggest to purchase a genuine products and purchase them from known and trusted distributors.

Thank you for your understanding.