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Shuvam Agarwal
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I am doing a project where I need to control brightness of a led light. according to presence. the brightness can be controlled using pwm but I cannot find a way to do that for high voltage input signals.
Shuvam Agarwal said:I am doing a project where I need to control brightness of a led light. according to presence. the brightness can be controlled using pwm but I cannot find a way to do that for high voltage input signals.
Shuvam Agarwal said:I am doing a project where I need to control brightness of a led light. according to presence. the brightness can be controlled using pwm but I cannot find a way to do that for high voltage input signals.
CWatters said:Are you asking how to convert 0-35V into something like 0-5V ?
Google "Potential Divider"
There are many different types of LED lights. We need to know exactly what type(s) you are using.Shuvam Agarwal said:I need to control brightness of a led light. according to presence.
Baluncore said:There are many different types of LED lights. We need to know exactly what type(s) you are using.
We understand PWM.
What do you mean by “presence”? How is that signal received?
Shuvam Agarwal said:The driver circuit of the led light I am currently working on gives a dc output of 35V/0.35A. This goes to light the led's. I want to perform pulse width modulation in between these two steps. So I need some circuitry that can take an input of 35v/0.35A and perform PWM on it which then goes to light the led's at a lower brightness.
berkeman said:Welcome to the PF.
Can you link to the datasheet of the LED light fixture that you are wanting to use? What do you have for a power source that you want to use for the PWM circuit? Will you be doing a high-side drive or a low-side drive of the LED light with your PWM signal?
In addition to the other issues that folks are pointing out in their replies, you may not be able to just put a PWM switch between this power supply and your load. If this power supply is a switching power supply, then in general you cannot be switching its load on and off at high frequency. This can cause instabilities in the control loop of the switched mode power supply, which can cause it to go unstable and overvoltage its output.Shuvam Agarwal said:Hi,
The driver circuit of the led light I am currently working on gives a dc output of 35V/0.35A. This goes to light the led's. I want to perform pulse width modulation in between these two steps. So I need some circuitry that can take an input of 35v/0.35A and perform PWM on it which then goes to light the led's at a lower brightness. I can use another 5V as a power supply but I need pwm signal for the 35V signal. I have been stuck on this step for quite some time now. Can you suggest a way to do this?
The driver circuit is a constant current source.CWatters said:We need to know if the existing driver is a constant current source or a constant voltage source?
You imply constant voltage but are you sure because raw LEDs normally need constant current.
Nidum said:You have a 35 V DC supply and you want to use this to drive LED's .
Just using basic PWM will not solve this problem . Without additional circuitry the LED's could still see 35V peaks and fail rapidly .
Whatever you use has to drop the output voltage to a safe level for the LED's .
There are many ready made modules and many published circuits .
Yes I do get a linear power output from the driver circuit which already exists.berkeman said:In addition to the other issues that folks are pointing out in their replies, you may not be able to just put a PWM switch between this power supply and your load. If this power supply is a switching power supply, then in general you cannot be switching its load on and off at high frequency. This can cause instabilities in the control loop of the switched mode power supply, which can cause it to go unstable and overvoltage its output.
If the source power supply is a linear supply, then you would generally be able to put a PWM switch circuit between its output and the load.
The duty cycle for a PWM signal is calculated by dividing the pulse width (ON time) by the total period (ON time + OFF time). To determine the pulse width, you can use the formula: pulse width = (desired output voltage / input voltage) * period. In this case, the period would be 1/frequency of the PWM signal.
Yes, a microcontroller can be programmed to generate a PWM signal with the desired duty cycle and frequency. You would need to connect the microcontroller to a power source that can provide the necessary voltage and current for your load.
The maximum frequency for a PWM signal is limited by the capabilities of your power source and the load. It is recommended to keep the frequency below 20 kHz for most applications. However, you can use higher frequencies if your components can handle it.
Yes, a MOSFET (metal-oxide-semiconductor field-effect transistor) can be used to switch the PWM signal on and off. This allows for more precise control of the output voltage and current. Make sure to choose a MOSFET with suitable voltage and current ratings for your application.
You can protect your circuit by using appropriate components such as diodes and capacitors to filter out any unwanted spikes or oscillations. It is also important to use components with suitable voltage and current ratings to prevent them from being damaged. Additionally, you can use a current limiting circuit to prevent excessive current from flowing through your circuit.