LED | PartQuest™ Explore

Copy of LED Dimmer Circuit using 555 Timer - on Sun, 11/15/2020 - 18:48

vladimir.jug
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vladimir.jug

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Description

This LED Dimmer Circuit uses a 555 Timer to control the PWM duty cycle of the current drive. Rather than apply proportional but continuous current to the LED for dimming, which can cause color shifts, modulating the duty cycle allows the LED to operate at its nominal current during the “ON” portion of the cycle. Because the frequency response of human vision is limited, using a PWM frequency of 250 Hz avoids the perception of flicker for the observer.

The LED model has an internal monitor for the "perceived" light output (blue waveform), which is a low-pass filtered version of the instantaneous light output. The filter pole frequency is set to 15 Hz to represent the bandwidth of the human eye. The value of the dimmer setting (green waveform) is increased from 10% to 90% at time 100msec. The LED current pulses (red waveform) are shown before and after the duty-cycle transition.

Part of this design is based on a dimmer schematic found on-line:

<a href="http://www.555-timer-circuits.com/led-dimmer.html">http://www.555-timer-circuits.com/led-dimmer.html</a>

That original circuit is actually incorrect, one of the diodes connected to pin 7 on the 555-Timer needs to be reversed. There was a comment from a reader who said he built the circuit as shown and it didn’t work. This is a good example of the value of simulating circuits before building hardware!

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Copy of LED Dimmer Circuit using 555 Timer - on Sun, 11/15/2020 - 14:53

vladimir.jug
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vladimir.jug

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Description

This LED Dimmer Circuit uses a 555 Timer to control the PWM duty cycle of the current drive. Rather than apply proportional but continuous current to the LED for dimming, which can cause color shifts, modulating the duty cycle allows the LED to operate at its nominal current during the “ON” portion of the cycle. Because the frequency response of human vision is limited, using a PWM frequency of 250 Hz avoids the perception of flicker for the observer.

The LED model has an internal monitor for the "perceived" light output (blue waveform), which is a low-pass filtered version of the instantaneous light output. The filter pole frequency is set to 15 Hz to represent the bandwidth of the human eye. The value of the dimmer setting (green waveform) is increased from 10% to 90% at time 100msec. The LED current pulses (red waveform) are shown before and after the duty-cycle transition.

Part of this design is based on a dimmer schematic found on-line:

<a href="http://www.555-timer-circuits.com/led-dimmer.html">http://www.555-timer-circuits.com/led-dimmer.html</a>

That original circuit is actually incorrect, one of the diodes connected to pin 7 on the 555-Timer needs to be reversed. There was a comment from a reader who said he built the circuit as shown and it didn’t work. This is a good example of the value of simulating circuits before building hardware!

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COPYMONDAY

Byron
Designer226490

Byron

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Description

This LED spotlight example demonstrates the value of simulating both the electrical and thermal aspects of power dissipating circuits together, simultaneously.

In this design, a Vishay NTCLE100 Thermistor is used in a detection circuit to monitor the enclosure temperature. It is used for thermal shut-down protection, to keep the enclosure temperature well below the "Tg" (glass transition temperature) of the spotlight's Nylon 6 polymer lens. This is particularly helpful when operating at higher external ambient temperatures.

Thermal dynamics models were automatically generated from a full 3D-CFD analysis using FloTHERM. This includes a thermal netlist model for the spotlight board layout and enclosure, as well as a BCI ROM model for MOSFET QFN package thermals. The format of both models is IEEE Standard VHDL-AMS, so it can be directly imported into the SystemVision "1D" circuit and system simulation context. The ability to include an accurate model of the thermal environment is key to having "thermally-aware" circuit function design and board layout processes.

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SEMI-THERM 37 Isothermal MOSFET

Mike Donnelly
Designer19

Mike Donnelly

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11 years 2 months

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Member of the PartQuest Explore Development Team. Focused on modeling and simulation of analog, mixed-signal and multi-discipline systems covering a broad range of applications, including power electronics, controls and mechatronic systems.

Description

This LED spotlight example demonstrates the value of simulating both the electrical and thermal aspects of power dissipating circuits together, simultaneously.

In this design, a Vishay NTCLE100 Thermistor is used in a detection circuit to monitor the enclosure temperature. It is used for thermal shut-down protection, to keep the enclosure temperature well below the "Tg" (glass transition temperature) of the spotlight's Nylon 6 polymer lens. This is particularly helpful when operating at higher external ambient temperatures.

Thermal dynamics models were automatically generated from a full 3D-CFD analysis using FloTHERM. This includes a thermal netlist model for the spotlight board layout and enclosure, as well as a BCI ROM model for MOSFET QFN package thermals. The format of both models is IEEE Standard VHDL-AMS, so it can be directly imported into the SystemVision "1D" circuit and system simulation context. The ability to include an accurate model of the thermal environment is key to having "thermally-aware" circuit function design and board layout processes.

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SEMI-THERM 37 BCI ROM for LED Spotlight

Mike Donnelly
Designer19

Mike Donnelly

Member for

11 years 2 months

1,709

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Member of the PartQuest Explore Development Team. Focused on modeling and simulation of analog, mixed-signal and multi-discipline systems covering a broad range of applications, including power electronics, controls and mechatronic systems.

Description

This LED spotlight example demonstrates the value of simulating both the electrical and thermal aspects of power dissipating circuits together, simultaneously.

In this design, a Vishay NTCLE100 Thermistor is used in a detection circuit to monitor the enclosure temperature. It is used for thermal shut-down protection, to keep the enclosure temperature well below the "Tg" (glass transition temperature) of the spotlight's Nylon 6 polymer lens. This is particularly helpful when operating at higher external ambient temperatures.

Thermal dynamics models were automatically generated from a full 3D-CFD analysis using FloTHERM. This includes a thermal netlist model for the spotlight board layout and enclosure, as well as a BCI ROM model for MOSFET QFN package thermals. The format of both models is IEEE Standard VHDL-AMS, so it can be directly imported into the SystemVision "1D" circuit and system simulation context. The ability to include an accurate model of the thermal environment is key to having "thermally-aware" circuit function design and board layout processes.

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Copy of LED Blinker updated - on Tue, 11/03/2020 - 20:32

angie301d
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angie301d

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Copy of LED Dimmer Circuit using 555 Timer - on Sun, 11/01/2020 - 19:59

dmaues
Designer236219

dmaues

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Description

This LED Dimmer Circuit uses a 555 Timer to control the PWM duty cycle of the current drive. Rather than apply proportional but continuous current to the LED for dimming, which can cause color shifts, modulating the duty cycle allows the LED to operate at its nominal current during the “ON” portion of the cycle. Because the frequency response of human vision is limited, using a PWM frequency of 250 Hz avoids the perception of flicker for the observer.

The LED model has an internal monitor for the "perceived" light output (blue waveform), which is a low-pass filtered version of the instantaneous light output. The filter pole frequency is set to 15 Hz to represent the bandwidth of the human eye. The value of the dimmer setting (green waveform) is increased from 10% to 90% at time 100msec. The LED current pulses (red waveform) are shown before and after the duty-cycle transition.

Part of this design is based on a dimmer schematic found on-line:

<a href="http://www.555-timer-circuits.com/led-dimmer.html">http://www.555-timer-circuits.com/led-dimmer.html</a>

That original circuit is actually incorrect, one of the diodes connected to pin 7 on the 555-Timer needs to be reversed. There was a comment from a reader who said he built the circuit as shown and it didn’t work. This is a good example of the value of simulating circuits before building hardware!

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Copy of LED Dimmer Circuit using 555 Timer - on Mon, 10/19/2020 - 19:02

mawie2u
Designer235937

mawie2u

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4 years 2 months

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Description

This LED Dimmer Circuit uses a 555 Timer to control the PWM duty cycle of the current drive. Rather than apply proportional but continuous current to the LED for dimming, which can cause color shifts, modulating the duty cycle allows the LED to operate at its nominal current during the “ON” portion of the cycle. Because the frequency response of human vision is limited, using a PWM frequency of 250 Hz avoids the perception of flicker for the observer.

The LED model has an internal monitor for the "perceived" light output (blue waveform), which is a low-pass filtered version of the instantaneous light output. The filter pole frequency is set to 15 Hz to represent the bandwidth of the human eye. The value of the dimmer setting (green waveform) is increased from 10% to 90% at time 100msec. The LED current pulses (red waveform) are shown before and after the duty-cycle transition.

Part of this design is based on a dimmer schematic found on-line:

<a href="http://www.555-timer-circuits.com/led-dimmer.html">http://www.555-timer-circuits.com/led-dimmer.html</a>

That original circuit is actually incorrect, one of the diodes connected to pin 7 on the 555-Timer needs to be reversed. There was a comment from a reader who said he built the circuit as shown and it didn’t work. This is a good example of the value of simulating circuits before building hardware!

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Copy of LED Dimmer Circuit using 555 Timer - on Mon, 10/12/2020 - 14:04

jmendez
Designer235788

jmendez

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4 years 2 months

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I have been with UEI for 27+ years in various roles.

Description

This LED Dimmer Circuit uses a 555 Timer to control the PWM duty cycle of the current drive. Rather than apply proportional but continuous current to the LED for dimming, which can cause color shifts, modulating the duty cycle allows the LED to operate at its nominal current during the “ON” portion of the cycle. Because the frequency response of human vision is limited, using a PWM frequency of 250 Hz avoids the perception of flicker for the observer.

The LED model has an internal monitor for the "perceived" light output (blue waveform), which is a low-pass filtered version of the instantaneous light output. The filter pole frequency is set to 15 Hz to represent the bandwidth of the human eye. The value of the dimmer setting (green waveform) is increased from 10% to 90% at time 100msec. The LED current pulses (red waveform) are shown before and after the duty-cycle transition.

Part of this design is based on a dimmer schematic found on-line:

<a href="http://www.555-timer-circuits.com/led-dimmer.html">http://www.555-timer-circuits.com/led-dimmer.html</a>

That original circuit is actually incorrect, one of the diodes connected to pin 7 on the 555-Timer needs to be reversed. There was a comment from a reader who said he built the circuit as shown and it didn’t work. This is a good example of the value of simulating circuits before building hardware!

About text formats

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vladimir.jug
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vladimir.jug
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Byron
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Mike Donnelly
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Mike Donnelly
Designer19

angie301d
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dmaues
Designer236219

mawie2u
Designer235937

jmendez
Designer235788