Hi everyone

I'm planning to start this project.A circuit that sens the light intensity and decide the pulse width (pwm) to increase or decrease the light of light bulb.

my question : Is is correct to use SSR relay? I mean I want to connect the pwm signal to input of ssr , and connect the output of it to light bulb.

is this device (ssr) valuable to use in this project?

 

is there any idea if using SSR is correct or not ??

 

Does the light bulb needs AC or DC power?
How about the voltage/current of light bulb?

light bulb type.

 

the light bulb uses 220V AC power. and its current is about 0.5 amps. a 100 watt

sth like this :

 

Nice photo of a bulb.

 

Hi everyone

I'm planning to start this project.A circuit that sens the light intensity and decide the pulse width (pwm) to increase or decrease the light of light bulb.

my question : Is is correct to use SSR relay? I mean I want to connect the pwm signal to input of ssr , and connect the output of it to light bulb.

is this device (ssr) valuable to use in this project?

+1 terrific photo..

Yes, You can use an AC SSR for dimming the lamp. The trick is to synchronize the control signal to the actual AC wave. You want to trigger the lamp at the same point in every AC cycle.

Earlier is brighter, later is dimmer.

 

+1 teriffic photo..

Yes, You can use a SSR for dimming an AC operated lamp. The trick is to synchronize the control signal to the actual AC wave. You want to trigger the lamp at the same point in every AC cycle.

Earlier is brighter, later is dimmer.

thanks for your response , but I didn't get the reason of your trick :-??

I just want to connect the pwm signal (for example with 3Khz fr.) to the input of the ssr , and when the pwm is in high state the light is on, and when its in low state the lamp is off ( its fast enough that human eye cannot recognize it )

am I right ??

and what about the working frequency of ssr ? is it fast enough to handle with a 3Khz signal ?

 

Why 3KHz?

The SSR can switch at 3KHz but it will not turn off at that rate because of the AC line frequency, 50 or 60Hz.

The SSR will only turn off when the current reduces to zero and this will happen when the AC power crosses zero. Light dimmer circuits work by controlling the phase angle at which the SSR is turned on, not by PWM.

 

Why 3KHz?

The SSR can switch at 3KHz but it will not turn off at that rate because of the AC line frequency, 50 or 60Hz.

The SSR will only turn off when the current reduces to zero and this will happen when the AC power crosses zero. Light dimmer circuits work by controlling the phase angle at which the SSR is turned on, not by PWM.

thanks , so if I want to control the light by pwm signal, whats your suggestion ?

 

Eric_s88,

Please don't get stuck on the idea of using PWM for this particular situation. PWM IS the thing when controlling voltage/power for many applications, but not necessary in this case.

Google "How light dimmers work"

Do you already have the PWM signal and must use it? Because, yes, it can be done using that signal with a bit more circuitry

 

hi tubeguy

yes you are right, but this is the thing I have to do.. I have a project with this definition: close-loop pwm control in order to control ambient lighting .. so any idea ?

 

Eric_s88,

Do you already have the PWM signal and must use it? Because, yes, it can be done using that signal with a bit more circuitry

exactly , this is what, I must do. so do you have any idea to use pwm to control an ac load like a light bulb ?

 

I'm not sure why you using 3Khz, but if only adjust the light brightness then I always using triac and diac to control the light.

The circuit as below.
Simplified AC Power Control Circuit using a Triac.

 

I'm not sure why you using 3Khz, but if only adjust the light brightness then I always using triac and diac to control the light.

The circuit as below.
Simplified AC Power Control Circuit using a Triac.

thank you

3KHz was just an example

can I use uC and its pwm signal in the circuit you have posted the link ??

 

You can use the PWM signal to control a photocoupler that drives the diac or triac.
I have made my own photocoupler using an LED and an LDR.

 

I can't do a schematic for a while. Only a minute.

One Idea - just the basic's:

First, you need an isolated sync signal from the AC line. An AC optocopler or AC transformer with diodes for example. Make a ramp signal from this. Feed that in to a comparator.
Feed the pwn signal through a low pass filter to convert it to a variable DC voltage, then into the other input of the comparator.
This should make a voltage controlled trigger signal synchronized to the AC line. Then use this signal to trigger the AC SSR.

 

thank you

3KHz was just an example

can I use uC and its pwm signal in the circuit you have posted the link ??

Examples 1.

Examples 2.

6-Pin DIP Random-Phase Optoisolators Triac Driver Output.

 

If you want to use PWM rather than phase angle then the simplest way is to full-wave rectify the mains without smoothing and feed the lamp pulsey dc. Not smoothing is important as that would increase the rms voltage the lamp sees.

You can then switch the lamp at kHz with a single n-channel mosfet in the negative side. Note that the negative side is not at earth potential but instead bounces between 0 and -340V relative to earth. This means that you should provide optical or transformer isolation between your PWM source and the mosfet. The only exception is if you treat the whole circuit as live and insulate apropriately, only chose this approach if you really know what you're doing.

An alternative is to put only the mosfet inside the bridge so that the load still sees a.c. For a filament lamp it doesn't really matter which method you use.

 

You can use the PWM signal to control a photocoupler that drives the diac or triac.
I have made my own photocoupler using an LED and an LDR.

thank you all for your replies

@to MrChips: is this schematic correct for my work ? dear ScottWang posted this.

can I use it as a dimmer with for example 3Khz PWM signal ?

schematic

and another question, in this schematic if when pwm signal is low the lapm will be off ?? I mean in this circuit for the turning the TRIAC off, is it enough to turn off the optocoupler ? don't we need any zero-cross detection , right ?

confused

 

according to this link which dear ScottWang posted :
http://electronics.stackexchange.com/questions/45035/triac-dimmer-circuit-design-help-resistive-load

we have this :

Remember the operating behavior of a TRIAC when deciding to use it in this manner. It won't turn off until the AC voltage swings to the opposite polarity and crosses zero. This means you can't use PWM in the traditional sense as provided by the uC (since that's generally dozens of kilohertz), and will have to watch the zerocross yourself and count internally to trigger the triac. You may have simplified the diagram, but I didn't see anything to indicate that you are feeding the zero-cross signal into your uC.

so pwm is useless I'm really confused