Automatic light dimmer using SCR as switch control

In summary: He is a very experienced PWM designer and should be able to help you with your project.In summary, an automatic light dimmer using SCRs would be suitable for controlling the power delivered to a 12V or 24V DC light bulb corresponding to the ambient light intensity. The dimmer could be implemented using a Picaxe IC to detect the ambient light level and deliver pulse width modulation to a switching transistor.
  • #1
lizxay
3
0
Hi guys, can u guys help me on this?? I want to design and construct an automatic light dimmer circuit that controls the energy delivered to a 12V or 24V DC light bulb corresponding to the ambient light intensity.
The control of energy will be established through switching action to improve efficiency and i will use SCR as means for switching.
I have no idea where should i start. any ideas guys? thank u very much and hope to hear from u guys soon =)
 
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  • #2
lizxay said:
Hi guys, can u guys help me on this?? I want to design and construct an automatic light dimmer circuit that controls the energy delivered to a 12V or 24V DC light bulb corresponding to the ambient light intensity.
The control of energy will be established through switching action to improve efficiency and i will use SCR as means for switching.
I have no idea where should i start. any ideas guys? thank u very much and hope to hear from u guys soon =)

I believe that SCRs (and the closely related triac) are usually used for AC power control, not DC. SCRs and triacs work by passing part of one AC cycle (or several cycles) in order to modulate power delivery; not by ballasting part of the voltage, or by chopping the DC, as you would need to do in order to modulate power delivery with DC.

I'm not sure if you can use Pulse Width Modulation with an incandescent (depending on the frequency you use, I'd think that it'd decrease the lifetime of the bulb), however you can do this with an LED (and that's how it's done all the time). You can probably begin here:
http://en.wikipedia.org/wiki/Pulse-width_modulation
 
  • #3
Easy, but not with a SCR. These do not switch pure DC easily as they stay on once turned on until the power is removed. If you had pulsing DC you could probably do it like that. Very messy process though.

I would do it with a Picaxe IC detecting the ambient light level and delivering pulse width modulation to a switching transistor. The Picaxe 8M has 3 A to D converters, I think, and it can produce PWM from one of its outputs. So, it would be ideal.

If you are in the USA look up P.H.Anderson on Google.
 

FAQ: Automatic light dimmer using SCR as switch control

How does an automatic light dimmer work?

An automatic light dimmer works by using a silicon-controlled rectifier (SCR) as a switch control. The SCR is connected in series with the light source and is triggered by a control circuit. When the control circuit senses a change in the ambient light level, it sends a signal to the SCR to turn on or off, adjusting the amount of voltage and current flowing to the light source and thereby controlling its brightness.

What are the advantages of using an SCR for light dimming?

Using an SCR as a switch control for light dimming has several advantages. First, it is a simple and cost-effective solution compared to other methods. It also allows for precise and smooth dimming without flickering or sudden changes in light intensity. Additionally, an SCR-based dimmer is more energy-efficient since it regulates the amount of current flowing to the light source.

Can an automatic light dimmer be used with any type of light bulb?

Yes, an SCR-based automatic light dimmer can be used with any type of light bulb, including incandescent, fluorescent, and LED bulbs. However, it is important to ensure that the dimmer is compatible with the specific type of light bulb being used in order to avoid damage to the bulb or the dimmer itself.

How is the sensitivity of an automatic light dimmer adjusted?

The sensitivity of an automatic light dimmer can be adjusted by using a potentiometer or a variable resistor in the control circuit. This allows for fine-tuning of the dimmer's response to changes in ambient light levels, ensuring that the light is dimmed to the desired level.

Is it possible to override the automatic dimming and manually control the light brightness?

Yes, it is possible to manually control the light brightness by incorporating a manual switch in parallel with the SCR in the dimmer circuit. This allows for the automatic dimming to be overridden and for the light to be controlled manually. However, it is important to ensure that the manual switch is properly wired and does not interfere with the operation of the dimmer.

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