Powering Solenoid using PWM from Func. Gen

[Gorgon]

If you think PWM, you need to see the time stream as a sequence of 2.5ms periods, as the base for your duty cycle. This equal a 400Hz PWM period frequency.
The Pull-in has 100% for 8 periods =20ms, the next X periods have 0.875ms pulses of each 2.5ms. Making a duty cycle of 35%. This pulse train lasts until you want to release the solenoid, where the duty cycle falls to 0%, or OFF.
The X above is how many periods the solenoid is intended to open, Ts_open.
X=Ts_open/2.5ms. If you can find how fast the solenoid activates inside the 20ms, in the datasheet, you may subtract this time from the total.

You can't have more than 100% duty cycle, this equals continuous ON.
Since the frequency is 400Hz, the time accuracy will be -2.5 - 0ms, if you don't round it off.

 

[mazahyr]

If you think PWM, you need to see the time stream as a sequence of 2.5ms periods, as the base for your duty cycle. This equal a 400Hz PWM period frequency.
The Pull-in has 100% for 8 periods =20ms, the next X periods have 0.875ms pulses of each 2.5ms. Making a duty cycle of 35%. This pulse train lasts until you want to release the solenoid, where the duty cycle falls to 0%, or OFF.
The X above is how many periods the solenoid is intended to open, Ts_open.
X=Ts_open/2.5ms. If you can find how fast the solenoid activates inside the 20ms, in the datasheet, you may subtract this time from the total.


You can't have more than 100% duty cycle, this equals continuous ON.
Since the frequency is 400Hz, the time accuracy will be -2.5 - 0ms, if you don't round it off.

Cheers! Got it. Things are clearer and started making sense. Now coming back to the original query how to power/replicate these profile characteristics? What would be the best or atleast the closest method to test it?

I've got the Func. Gen mentioned in the very beginning got a capable enough power supply, can take upto 20A. What should be safe enough circuit logic?
Thanks.

 

[Gorgon]

To be honest, that sounds to me like shooting a flea with a cannon, an automatic cannon in this case. We still need a bit more information about what you want to use the solenoid for. You said this is to dose something.
The question is then, how do you control the dosage?
The sequence we have been through now is just one of a series of openings that will produce the dosage. How long is the dosage period, since this will be the second set of duty cycles in your system?
To know the timing you need to know the rate the chemical you want to dose, run through the pipe, and what dosage range you want to process?
And not least, how is this info presented to your system?

 

[mazahyr]

To be honest, that sounds to me like shooting a flea with a cannon, an automatic cannon in this case. We still need a bit more information about what you want to use the solenoid for. You said this is to dose something.
The question is then, how do you control the dosage?

The sequence we have been through now is just one of a series of openings that will produce the dosage. How long is the dosage period, since this will be the second set of duty cycles in your system?
To know the timing you need to know the rate the chemical you want to dose, run through the pipe, and what dosage range you want to process?
And not least, how is this info presented to your system?

I do understand the vagueness of my description, sorry about that. Just a quick question. You've seen the spec that I've shared above as well as the characteristic profile. What can you think of all this? What is the system doing?
To me its a solenoid with a valve getting turned on and off using PWM. The Frequency and Duty parameters are specified. What I'm thinking to do is simply run it using these set parameters and see how the solenoid behaves!

 

[mazahyr]

Any simple suggested circuit fellaws?

 

[FvM]

I understand the function generator concept so, that you'll replay a predefined PWM waveform.

Everything you need is a voltage source, a powerswitch (e.g. MOSFET) and a free-wheeling diode of sufficient current rating. The coil current waveform would be monitored (e.g. at a shunt resistor) and used to adjust the PWM waveform offline. What's your problem with this setup?

 

[mazahyr]

I understand the function generator concept so, that you'll replay a predefined PWM waveform.

Everything you need is a voltage source, a powerswitch (e.g. MOSFET) and a free-wheeling diode of sufficient current rating. The coil current waveform would be monitored (e.g. at a shunt resistor) and used to adjust the PWM waveform offline. What's your problem with this setup?

I've got the tools, was just looking for a nicely laid out schematic before I start blowing things up.