Convert PWM wave to VDC to operate a valve

[shooter]

A SSR MUST be fed with a PWM, you can not use an analog signal for this, as it means all rest energy must be taken by the transistor.

even a toy train uses PWM so a valve can do the same.
and the 12 Volt is no issue as you should put the transistor just above GND in the line.
or use a L298N

 

[kihtrak]

Hello there,
To update on this. We purchased a 4 channel relay from Sainsmart. From the specs, it seems that any voltage above 2.5v seems to trigger on the relay. But, when connected to our digital board, the relay doesn't turn on. I heard that PWM wave doesn't make a relay on. Is it so?
I also heard that we need to connect a transistor in between the board and the relay. Why should we have to do this? Can anyone please explain us how to proceed with this?

 

[shooter]

PWM does not work with relais as they have to be ON or OFF, however a valve sometimes can have a analog signal (or a PWM) so just find a transistor, put it with the base on the output, with the emitter on gnd and the collector to you rvalve, the other side to 12 Volt power.
type of transistor is NPN.
see arduino.cc for example of a simple motor control.

 

[kamenges]

kihtrak, the way your system is designed I really don't think you want to be dealing with PWM at all. In your present design you simply want the valve to be fully on or fully off. You have other methods in place to meter the flow. This type of control does not call for PWM control.

As mellis pointed out several posts ago, you can control the valve the way you want to by setting your PWM duty cycle to 100% to turn the valve on and to 0% to turn the valve off. You still need the SSR between the controller and the valve due to the voltage differences.

Keith

 

[kihtrak]

Thanks for the reply shooter. But, what we tried today is by testing the SSR by just connecting it to our main digital control board. We also hooked up a 5v power supply to the SSR. Without any transistor in between, the control board was able to open/close the valve by SSR. How could this happen? Am I overloading something?
As you told Keith, I've done the same thing. Kept the duty cycle to 100% (almost 100 ) and controlled the valve having SSR in between the two. Do I have to keep it to full 100%?