LED Dimmer controller design - Electronics engineering pulse width modulation
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Date: 2023-11-17
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Comments and reviews: 30
Stu
Hi All,
I'm looking for a simple circuit to dim a LED dash. It's for a project I'm helping a friend with. He is building a factory 5 cobra.
The new style dash they offer is a full LED backlight and clearly won't dim on a standard rheostat. The limitation I'm working to is that he wants to keep the dash looking original, so he will use the Lucas-style bakelite knobs.
The options are as I see it:
1, Use a potentiometer (modify it to take the Lucas knob); this clearly is not the most efficient circuit. But given its light use, it should be OK.
2, Use a 555 timer to build a PWM circuit.
The question I have is, can I control a 555 timer with a rheostat rather than a potentiometer? Using the original Lucas rheostat will mean I don't have to modify the dash and the overly brittle bakelite knob.
thanks, Stu
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Hi All,
I'm looking for a simple circuit to dim a LED dash. It's for a project I'm helping a friend with. He is building a factory 5 cobra.
The new style dash they offer is a full LED backlight and clearly won't dim on a standard rheostat. The limitation I'm working to is that he wants to keep the dash looking original, so he will use the Lucas-style bakelite knobs.
The options are as I see it:
1, Use a potentiometer (modify it to take the Lucas knob); this clearly is not the most efficient circuit. But given its light use, it should be OK.
2, Use a 555 timer to build a PWM circuit.
The question I have is, can I control a 555 timer with a rheostat rather than a potentiometer? Using the original Lucas rheostat will mean I don't have to modify the dash and the overly brittle bakelite knob.
thanks, Stu
reply
threeMetreJim
Amazing, really, that a 50 year old IC is still in production. I will probably shed a tear i(f it is ever replaced by a microcontroller.
Just be careful with these LED strips, they are pretty innefficient when used in large amounts as a fair bit of heat is produced by the dropper resistors. Also when the manufacturer says 12V, they mean it - running from a 12V vehicle battery (around 13. 8V) will seriously shorten their life. I attempted to make a light for a mobile home with these, and the strips got so hot they softened the glue and sagged (too many in a small space, stuck onto a non-metallic surface and running from 13. 8V. In the end I had to scrap it and make one using individual high power LED's running from a current limited supply (a bit more complex, but still running every night for 4 years now.
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Amazing, really, that a 50 year old IC is still in production. I will probably shed a tear i(f it is ever replaced by a microcontroller.
Just be careful with these LED strips, they are pretty innefficient when used in large amounts as a fair bit of heat is produced by the dropper resistors. Also when the manufacturer says 12V, they mean it - running from a 12V vehicle battery (around 13. 8V) will seriously shorten their life. I attempted to make a light for a mobile home with these, and the strips got so hot they softened the glue and sagged (too many in a small space, stuck onto a non-metallic surface and running from 13. 8V. In the end I had to scrap it and make one using individual high power LED's running from a current limited supply (a bit more complex, but still running every night for 4 years now.
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Pavol
HI, I want to ADD PWM dimming feature to my ESP32 Internet / WiFi mp3 radio / mp3 / flac / wav player. But I want it easy and simple. PWM is from EPS32 4 pins, PWM 5 - 24 kHz, I plan to use IR2104 or 2184 driver + synchronus buck for each from 4 LEDs. LEDs can be replaced with isolated/nonisolated DC/DC converters, so can be used as 8 AMPS BMS for 4S LFP or NMC battery pack. ESPs will communicate with ESP-NOW and at one point is gateway do MQTT / WIFI / BT / BLE. Also I want to send emails through SMTP, if some ESP detects TEMPS with AGM8833 array. Is there easy and simple way to control leds / BUKC with ESP32s PWMs with minimum parts, like R, C, L, FETs and drivers?
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HI, I want to ADD PWM dimming feature to my ESP32 Internet / WiFi mp3 radio / mp3 / flac / wav player. But I want it easy and simple. PWM is from EPS32 4 pins, PWM 5 - 24 kHz, I plan to use IR2104 or 2184 driver + synchronus buck for each from 4 LEDs. LEDs can be replaced with isolated/nonisolated DC/DC converters, so can be used as 8 AMPS BMS for 4S LFP or NMC battery pack. ESPs will communicate with ESP-NOW and at one point is gateway do MQTT / WIFI / BT / BLE. Also I want to send emails through SMTP, if some ESP detects TEMPS with AGM8833 array. Is there easy and simple way to control leds / BUKC with ESP32s PWMs with minimum parts, like R, C, L, FETs and drivers?
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Gregg
Your videos are fantastic. Even a layman like myself can understand.
I have what I hope isnt a dumb question. When the transistor drains the capacitor it looks like it does so by just connecting the drain on the potentiometer to the ground. The diode ensures current only flows one way. That makes sense. But isnt the positive terminal of the battery still connected to the same circuit too at 12v less the voltage reduction of the potentiometer resistance and that resistor before the diode? I dont see anything that would somehow tell the potentiometer to switch from the input to the drain circuit, but maybe Im not understanding how the drain works.
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Your videos are fantastic. Even a layman like myself can understand.
I have what I hope isnt a dumb question. When the transistor drains the capacitor it looks like it does so by just connecting the drain on the potentiometer to the ground. The diode ensures current only flows one way. That makes sense. But isnt the positive terminal of the battery still connected to the same circuit too at 12v less the voltage reduction of the potentiometer resistance and that resistor before the diode? I dont see anything that would somehow tell the potentiometer to switch from the input to the drain circuit, but maybe Im not understanding how the drain works.
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Julian
Small correction to anything from 3: 20:
The MOSFET actually doesn't change its resistance meaningfully after you applied more than its gate Threshold Voltage (in this case around 3V. That also means that the MOSFET isn't doing the averaging over the PWM Signal by putting out an average resistance. It actually switches with the same frequency the PWM Signal does and so do the LEDs. The perceived change in brightness is done by the human eye: )
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Small correction to anything from 3: 20:
The MOSFET actually doesn't change its resistance meaningfully after you applied more than its gate Threshold Voltage (in this case around 3V. That also means that the MOSFET isn't doing the averaging over the PWM Signal by putting out an average resistance. It actually switches with the same frequency the PWM Signal does and so do the LEDs. The perceived change in brightness is done by the human eye: )
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ElectricAvian
The divider on the gate is unnecessary imo. The 555 can sink and source current, so it can both charge and discharge the gate. Not to mention added resistance creates a low pass filter out of the gate, which limits the operating frequency. Too high and you'll get waveform distortion at the gate, not a clean on/off, and it will start heating up more. Just drive it directly from the gate. It can take 12V no problem.
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The divider on the gate is unnecessary imo. The 555 can sink and source current, so it can both charge and discharge the gate. Not to mention added resistance creates a low pass filter out of the gate, which limits the operating frequency. Too high and you'll get waveform distortion at the gate, not a clean on/off, and it will start heating up more. Just drive it directly from the gate. It can take 12V no problem.
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Ktown
Hi, my microscope led is this exact model. I burnt out the original circuit board because I plugged a 12 V wall charger instead of the recommend 5 V. So my question is can I use this led with a buck converter to allow a normal generic 12v to power it? Also need a dimmer switch attached to control brightness. Does anyone know how to go about this?
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Hi, my microscope led is this exact model. I burnt out the original circuit board because I plugged a 12 V wall charger instead of the recommend 5 V. So my question is can I use this led with a buck converter to allow a normal generic 12v to power it? Also need a dimmer switch attached to control brightness. Does anyone know how to go about this?
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Caffeinated
Bigclive showed an interesting design for an rgd led dimmer. Instead of using the 555 as a pwm driver, it was used there as a triangle wave generator and the mofsets were actually driver by a comparator. Potentiometer wiper to the + pin and the triangle ramp waveform to the - pin. This is the circuit in a nutshell
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Bigclive showed an interesting design for an rgd led dimmer. Instead of using the 555 as a pwm driver, it was used there as a triangle wave generator and the mofsets were actually driver by a comparator. Potentiometer wiper to the + pin and the triangle ramp waveform to the - pin. This is the circuit in a nutshell
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Alexander
Could this circuit be scaled to power higher powered LED's? Say a 100 watt CREE led running PWM frequency of about 100KHz? I would imagine that the main factor for this would be to select a proper MOSFET/FET for the switching and properly heatsinking it. In addition protecting the 555 timer from gate current.
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Could this circuit be scaled to power higher powered LED's? Say a 100 watt CREE led running PWM frequency of about 100KHz? I would imagine that the main factor for this would be to select a proper MOSFET/FET for the switching and properly heatsinking it. In addition protecting the 555 timer from gate current.
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Nisal
Sir, I need to Build this same circuit using SMD components, (For LED Video Light Project. Is there any special method to convert those components into SMD? Is there any simulation software or, Is there any special procedure to follow? Could you please give me a help to solve this matter. highly Appreciated
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Sir, I need to Build this same circuit using SMD components, (For LED Video Light Project. Is there any special method to convert those components into SMD? Is there any simulation software or, Is there any special procedure to follow? Could you please give me a help to solve this matter. highly Appreciated
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Light
I am looking to expand my knowledge. My degree is not in electrical engineering and I am well beyond typical student age, other than a lifelong student.
Any suggestions for material or a focus to start with?
I am looking for more complex led, battery and power management type things.
Thanks!
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I am looking to expand my knowledge. My degree is not in electrical engineering and I am well beyond typical student age, other than a lifelong student.
Any suggestions for material or a focus to start with?
I am looking for more complex led, battery and power management type things.
Thanks!
reply
Prime
This is simple but poorly designed circuit. The output pin of a 555 timer can provide 200mA at best, with current limiting resistors as shown above it is not enough for the fastest gate charging. The transistor will be extremely hot and energy wasteful. This circuit requires a proper transistor driver.
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This is simple but poorly designed circuit. The output pin of a 555 timer can provide 200mA at best, with current limiting resistors as shown above it is not enough for the fastest gate charging. The transistor will be extremely hot and energy wasteful. This circuit requires a proper transistor driver.
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Tim
Okay, I'm not an electrical engineer, but why build this circuit instead of just putting a variable resistor in series with the power wire?
I'm sure there must be a reason. Can someone explain it to me, please?
I have LED lights and just put a variable resistor in line and it works like a charm.
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Okay, I'm not an electrical engineer, but why build this circuit instead of just putting a variable resistor in series with the power wire?
I'm sure there must be a reason. Can someone explain it to me, please?
I have LED lights and just put a variable resistor in line and it works like a charm.
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InnocentBastard
Hi Paul, when discharging the mosfet, youve connected a 10kOhm resistor to ground but youve used a 1kOhm resistor to protect pin 3 of the 555.
Will the electrons not follow the path of least resistance and flow back to pin 3? Or am I missing something, which is likely the case.
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Hi Paul, when discharging the mosfet, youve connected a 10kOhm resistor to ground but youve used a 1kOhm resistor to protect pin 3 of the 555.
Will the electrons not follow the path of least resistance and flow back to pin 3? Or am I missing something, which is likely the case.
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Michael
I ordered the pcbs. The problem is there is not schematic with the actual components. R1 r2 r3 which ones are which? Which capacitor goes where on the board? I'm having to watch this video and assemble it by your description. Pain in the butt. Thank you for the design and tutorial though.
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I ordered the pcbs. The problem is there is not schematic with the actual components. R1 r2 r3 which ones are which? Which capacitor goes where on the board? I'm having to watch this video and assemble it by your description. Pain in the butt. Thank you for the design and tutorial though.
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Groonworld
Just built this, and it works fine. One funny thing that happens though is that the LEDs flicker brightly if/when I turn the poti too fast. Could this be due to my using a normal 555 timer rather than the CN version? I don't really understand what the difference between the two is.
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Just built this, and it works fine. One funny thing that happens though is that the LEDs flicker brightly if/when I turn the poti too fast. Could this be due to my using a normal 555 timer rather than the CN version? I don't really understand what the difference between the two is.
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John
This video is amazing, but I'm a bit confusing: at 6: 40, you said that when input one (positive) voltage equals to input two (negative) voltage, output signal is low. However, at 8: 05, when both inputs are at 8 volts, the output signal is high. Is that a typo? (I could be wrong)
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This video is amazing, but I'm a bit confusing: at 6: 40, you said that when input one (positive) voltage equals to input two (negative) voltage, output signal is low. However, at 8: 05, when both inputs are at 8 volts, the output signal is high. Is that a typo? (I could be wrong)
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mike
I know I don't understand this fully and I probably need to be corrected but if the output is to just control the light intensity why don't he just use the potentiometer to control the voltage and not need to create such a complexity, can someone please explain what am I missing?
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I know I don't understand this fully and I probably need to be corrected but if the output is to just control the light intensity why don't he just use the potentiometer to control the voltage and not need to create such a complexity, can someone please explain what am I missing?
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BlueDog42
Great Project, I did have one question? On review of the video at time stamp 10: 11 I see that the Wiper output is connected to the CW to Diode trace. and was wondering if this is incorrect? getting ready to do a breadboard example, and will try. Thanks
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Great Project, I did have one question? On review of the video at time stamp 10: 11 I see that the Wiper output is connected to the CW to Diode trace. and was wondering if this is incorrect? getting ready to do a breadboard example, and will try. Thanks
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Ktown
Man for the life of me I can't figure it out. I want to power a 3 watt star LED replacement for my microscope on a dimmer switch. I want to use a regular 12 volt input, not the 5 volt original. Can I buy something to achieve this?
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Man for the life of me I can't figure it out. I want to power a 3 watt star LED replacement for my microscope on a dimmer switch. I want to use a regular 12 volt input, not the 5 volt original. Can I buy something to achieve this?
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Southern
Hi Paul, I love and enjoy your tutorials. Do you have or can you create PCB for LED sequencer?
I would like to build sequential turn signal for my car. it would be nice to run 14 or 28 Chanels.
Thank you in advance.
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Hi Paul, I love and enjoy your tutorials. Do you have or can you create PCB for LED sequencer?
I would like to build sequential turn signal for my car. it would be nice to run 14 or 28 Chanels.
Thank you in advance.
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Mohammad
Hi there. Thank you for this video. I build the circuite but LEDs does not turn off completely. I tried different hacks and finaly i solved the issue by adding a 47nf cap between the gate and the GND.
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Hi there. Thank you for this video. I build the circuite but LEDs does not turn off completely. I tried different hacks and finaly i solved the issue by adding a 47nf cap between the gate and the GND.
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George
i did it. it works on the breadboard. but i have a question if i want to limit the output for only 9 led what alteration should i do to the plan if the power supplied is a 12v 280 amp capacity
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i did it. it works on the breadboard. but i have a question if i want to limit the output for only 9 led what alteration should i do to the plan if the power supplied is a 12v 280 amp capacity
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David
You stated using a 555 timer simplifies the circuit. But using a different 8-pin DIP (say, an ATtiny25) would be MUCH simpler, with many fewer components, and more easily modifiable as well.
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You stated using a 555 timer simplifies the circuit. But using a different 8-pin DIP (say, an ATtiny25) would be MUCH simpler, with many fewer components, and more easily modifiable as well.
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Mariusz
Great tutorial, however, the controller is useless if one wants to use the dimmer for video light applications. The flicker is visible (as horizontal bands) whenever dimming is in effect.
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Great tutorial, however, the controller is useless if one wants to use the dimmer for video light applications. The flicker is visible (as horizontal bands) whenever dimming is in effect.
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Arsenic
You should be fine to use the smallest track size JLCPCB accepts and have no issues up to 500mA of draw. Idk why everyones always trying to make their tracks wide af for a tiny current.
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You should be fine to use the smallest track size JLCPCB accepts and have no issues up to 500mA of draw. Idk why everyones always trying to make their tracks wide af for a tiny current.
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Nafyad
Hey sir, you explained the function of pin 3 very well (you chiseled it in my mind, but I don't see any reason why increasing/decreasing the frequency controls the dimness of the light.
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Hey sir, you explained the function of pin 3 very well (you chiseled it in my mind, but I don't see any reason why increasing/decreasing the frequency controls the dimness of the light.
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Professional
Will this design work for 5V supplied 114 LED display?
As all the cathodes in the display will be connected together can it be connected there to regulate their brightness?
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Will this design work for 5V supplied 114 LED display?
As all the cathodes in the display will be connected together can it be connected there to regulate their brightness?
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Kyosho
Just got the PCB's I ordered for this project, can't wait to build it. Thank you Paul for taking the time to make this video and for sharing, I love it! Thank you Sir: D
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Just got the PCB's I ordered for this project, can't wait to build it. Thank you Paul for taking the time to make this video and for sharing, I love it! Thank you Sir: D
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afak
I ordered this board and completed its assembly. But I can't get voltage from the output when there is voltage on the on-off button, please someone who knows help me
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I ordered this board and completed its assembly. But I can't get voltage from the output when there is voltage on the on-off button, please someone who knows help me
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