555 Timer | PartQuest™ Explore

LED Dimmer Circuit using 555 Timer

Mike Donnelly
Designer19

Mike Donnelly

Member for

11 years 1 month

1,706

designs

10

groups

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 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

Copy of LED Driver with Auto-Dimming for Thermal Protection - on Tue, 12/10/2024 - 10:13

User-1733796425
Designer260185

User-1733796425

Member for

1 week 5 days

2

designs

1

groups

Welcome to the community!!

Description

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

In this application example, a Vishay NTCS0603 Thermistor provides feedback of the enclosure temperature. This feedback is used to control PWM dimming of the LEDs, thereby limiting the internal temperature when operating at high external ambient temperature conditions.

This is a "Live" design, the user can change key parameter values and then run new simulations to see the results. These parameters include "r_mirror", the resistance of the current mirror that controls the capacitor charging rate of the 555 timer, and thereby set the PWM frequency. The user can also change "r_offset" that controls the temperature level at which the dimming operation begins. Finally, the user can set "r_iLED_set", to control the ON-state operating current of the LEDs.

----------------

* To reduce the time needed to simulate the transition and settling at 6 different temperature levels, all thermal time constants were reduced by approximately 1000x. The actual thermal response time constant of the NTCS0603 is approximately 3 seconds (depends on mounting), not 3 msec! Also, the enclosure thermal capacitance value would more likely be 3 (J/degC) instead of 3 (mJ/degC), giving a thermal time constant for the enclosure of 10 (degC/Watt) * 3 (J/degC) = 30 seconds. This time scaling does not affect the static relationship between the outside temperature and PWM dimming.

About text formats

Copy of LED Dimmer Circuit using 555 Timer - on Mon, 11/11/2024 - 13:58

User-1731329623
Designer259586

User-1731329623

Member for

1 month 1 week

5

designs

1

groups

Welcome to the community!!

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

Copy of LED Dimmer Circuit using 555 Timer - on Sat, 10/05/2024 - 00:28

peachFuzzz
Designer258815

peachFuzzz

Member for

2 months 2 weeks

1

designs

1

groups

Welcome to the community!!

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

LED Dimmer Circuit using 555 Timer - on Thu, 09/26/2024 - 16:51

Dieter Feiger
Designer258679

Dieter Feiger

Member for

2 months 3 weeks

8

designs

2

groups

Welcome to the community!!

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

Copy of LED Dimmer Circuit using 555 Timer - on Sat, 09/21/2024 - 23:32

Designer0

Member for

4 years 11 months

0

designs

0

groups

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

Copy of LED Dimmer Circuit using 555 Timer - on Mon, 08/26/2024 - 15:48

User-1724682126
Designer258067

User-1724682126

Member for

3 months 3 weeks

1

designs

1

groups

Welcome to the community!!

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

LED Dimmer Circuit using TLC555 Timer

Mike Donnelly
Designer19

Mike Donnelly

Member for

11 years 1 month

1,706

designs

10

groups

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 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

Copy of LED Dimmer Circuit using 555 Timer - on Tue, 07/16/2024 - 22:14

Designer0

Member for

4 years 11 months

0

designs

0

groups

Description

Este circuito dimmer de LED usa um temporizador 555 para controlar o ciclo de trabalho PWM do acionamento atual. Em vez de aplicar corrente proporcional, mas contínua, ao LED para escurecimento, o que pode causar mudanças de cor, a modulação do ciclo de trabalho permite que o LED opere em sua corrente nominal durante a parte "ON" do ciclo. Como a resposta de frequência da visão humana é limitada, usar uma frequência PWM de 250 Hz evita a percepção de cintilação para o observador.

O modelo LED tem um monitor interno para a saída de luz "percebida" (forma de onda azul), que é uma versão filtrada passa-baixa da saída de luz instantânea. A frequência do polo do filtro é definida como 15 Hz para representar a largura de banda do olho humano. O valor da configuração do dimmer (forma de onda verde) é aumentado de 10% para 90% no tempo 100 mseg. Os pulsos de corrente do LED (forma de onda vermelha) são mostrados antes e depois da transição do ciclo de trabalho.

Parte deste projeto é baseado em um esquema de dimmer encontrado on-line:

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

Esse circuito original está realmente incorreto, um dos diodos conectados ao pino 7 no 555-Timer precisa ser invertido. Houve um comentário de um leitor que disse que construiu o circuito como mostrado e não funcionou. Este é um bom exemplo do valor de simular circuitos antes de construir hardware!

About text formats

Copy of One second 555 Timer - on Fri, 06/14/2024 - 22:35

Designer0

Member for

4 years 11 months

0

designs

0

groups

Description

Design example from the Webinar: “Creating New Components, Part 2: “Making VHDL-AMS Models”. View the archive presentation here:

http://www.systemvision.com/webinars

This 555 Timer application circuit is configured as an astable multivibrator with a frequency-modulated output. The two 10kOhm resistors and the 1uF capacitor on the left set the output duty cycle and the base oscillation frequency. The controlled variable resistor on the right (attached to the CTRL pin of the 555 Timer) adjusts that frequency by compressing the state transition threshold voltage levels on the TRIG and THR pins (see plot on the left).

The mixed-signal 555 Timer model was created using the IEEE Standard VHDL-AMS modeling language. You can right-click on the symbol and choose "View/Copy Model" to see the digital logic and analog equations that represent the main characteristics of the 555 Timer.

A companion design example, "Graphical Model Of 555 Timer" shows the equivalent application circuit, but the 555 Timer model itself is "assembled" from building-block models from the systemvision.com library, rather than a directly using VHDL-AMS.

About text formats

Terms of Use Cookie Notice Data Privacy Notice

Mike DonnellyDesigner19

Member for

User-1733796425Designer260185

Member for

User-1731329623Designer259586

Member for

peachFuzzzDesigner258815

Member for

Dieter FeigerDesigner258679

Member for

Designer0

Member for

User-1724682126Designer258067

Member for

Mike DonnellyDesigner19

Member for

Designer0

Member for

Designer0

Member for

Mike Donnelly
Designer19

User-1733796425
Designer260185

User-1731329623
Designer259586

peachFuzzz
Designer258815

Dieter Feiger
Designer258679

User-1724682126
Designer258067

Mike Donnelly
Designer19