Using LABVIEW To Read and generate pressure for fuel injection

[jamran]

SHALL I USE THE LABVIEW piD TOOLKIT TO MAKE THE Pid cONTROLLER? IM NOT QUITE SURE. DO I NEED TO MAKE A CIRCUIT?

[TechWiz]

You can use the PID VIs that come with the PID tookkit.

However, you must know that once you generate the TTL pulse train, you have to use a driver circuit like an H-bridge to control the PCV/VCV. The output of the NI DAQ cards is limited and cannot provide the currents required to operate the PCV and VCV.

Cheers!!

[jamran]

ok thanks!

So what would your recommend? How would you advise me to do the PID controller? at the moment it seems to me the PID cont. is something virtual and not a controller which is an object? im not sure. please could you ecxplain to how to make one and what to use. thanks very much for your help

[jamran]

hi mani

ive found a PID controller which i think will be suitable to use on the pump. could you please verify if these are ok to use? thanks

http://uk.farnell.com/jsp/search/productdetail.jsp?sku=3080080
http://uk.farnell.com/jsp/search/productdetail.jsp?sku=9795260

[jamran]

also initially you mentioned the following:

"The PCV and VCV are solenoid actuated valves and the operating voltage is 0-5 Volts DC usually. 0 volts usually means minimum opening of the valves but I have seen and used pump which reverse this and make 5V as the minimum opening so you need to know the specs of your system. The pressure sensors also usually provide a 0-5V DC signal."

but recently you told me that you posted this

"

The PCV and the VCV are pulse width (or duty cycle) modulated controls where the duty cycle of the pulse train determines the opening of the valve.

The frequency of the digital pulse train will depend on the manufacturer but a freqency of 200 to 300Hz for the VCV and about 1 to 1.2 kHz for the PCV. So you generate a TTL compatible pulsetrain (0 to 5 V typically) and use the duty cycle to adjust the opening.

The operation can still be performed as I said in the earlier post. Keep a fixed opening of the VCV (20 to 30%) and then change the CV to adjust the pressure.

You cannot use a DC Voltage directly."

so which 1 is correct mate?

thanks for your help

 

[TechWiz]

I had mentioned in the PWM (duty cycle) post to disregard the voltage control message.

The PCV/VCV are controlled with a PWM signal and are NOT directly voltage controlled.

As for the PID controller, i'll look at it once I have some time.

Cheers!

Message Edited by Mani's World on 03-25-2009 08:56 AM

[jamran]

thanks. as well as this, we wanted to check if the Injector opens as we havent got the power drive yet. so we made up a circuit wich would genearte around 150V dc. we connected it to the injector to see if it opens while we simple put oil thru a syringe into the inlet valve. however, the solennoid vibrated for a couple of seconds but then 'blew' up i think as the smell of burning was sensed. what oi gathered was that is it the same as the pump in that it also uses PWM and we ca nnot give it DC voltage directly?

[TechWiz]

Its not that simple. The opening current is much higher than the holding current since you want a fast opening. That is why you need an expensive power drive that can accurately control the current profile during the injector opening event.

Once you applied the 150V, did you regulate the current or do you know how much current flowed through the solenoid coils. The coil can burn pretty fast if a lot of current flows and my guess would be that is what happened

Cheers!!

Message Edited by Mani's World on 03-26-2009 01:03 PM

[jamran]

yes i thinku r right, thats exactly what happened. ive read around

n am i right in saying its also PWM signals? my work is due tomorrow so i have wrap it up. basically prof. said to just make it a foundation for someone else to come in and make the program.

thanks

[TechWiz]

Yes, the injector control signal is also a PWM signal. Its a neat way of regulating the power that you apply to any device.

Good luck with your report !