richie81

Hi Shaun, It was definitely financial reasons that I chose the 12v dc pump (I bought it on ebay for 20euro:P)! Otherwise I probably would have tried to get a 3 phase or something like that. Anyways, as it turns out I'm finished - I had my project presentation Wedsnesday afternoon. It went very well - I got the PID & PWM working, thanks to the help of my project supervisor during the presentation (it was a pretty informal affair!). I wasn't far off, thanks to all the information from you and this site but it was just putting it all together in labview where I fell down. We ended up using a simulate signal block for the PWM. We installed this 1st into my basic program with just the input driving the output, and put a control on the duty cycle to set our pulses, and also set the samples per second, offset, frequency. We then managed to wire in the simple PID subvi, and it was just a matter of trial and error with the PID values. In the end, when a setpoint was entered it held very well going by the double needle meter, and the PID response was quite good. This could have probably been bettered but I was happy enough to get as far as I did with this. You probably think that I have a softie for a supervisor;) but I think he saw that I had all the pieces of the puzzle, just not in the right order!! Thanks again anyways Shaun - I have posted the working vi just in case you were intrigued how I got on. I'm sure it's pretty simple to you:worshippy:. P.s - Taking a break from Labview for a while. My results are out Monday. That will be level 7 complete(pass degree or diploma), but I will probably be back to this site when I attempt level 8 of the course... Take it easy, Rich RichProject2010-Basic Program.vi simplepid.vi

Hi Shaun, I'm sorry, my submission deadline is soon enough, so I've been a bit naive with this expecting everything to fall into place in a short space of time... That's not going happen... My pump is just on-off, 12v dc. An analogue controlled pump would probably have been a sounder option, at least when working with labview. I realize that now... I have the PID toolkit, so I'll have a look at the 'PID simulator' and the other examples like you said. I have attached the main program & sub vi's. I've also attached the basic program that I started off with(minus PID & PWM) & a manual PWM program that I was also trying to use... Thanks for all the help and I apologize if you thought that I'm trying to get you to do my project for me!! I'm just hoping to pass it when it comes down to the crunch... Thanks again, Rich LavaG.zip

Hi Shaun, Thanks a mil for all the help - I'd be lost without it:worshippy:! I've attached my vi with the PID & PWM subvi's added in. I'm sure that it'll be wrong somewhere but I'm going to try and tune the PID controller tomorrow and see can I get some sort of response... When it comes to the PID tuning, I spoke to my project supervisor from the college & he said that I would need to work out my values by the 'plant response' method...? Leaving Ki & Kd at zero, he said to 1st get; Kc = % change in voltage shift of my output % change in voltage shift of my input He said that I then calculate the rise time of the slope Kr and the lag Kl. These values are then used in the ziegler nicolls formula to calculate my P, I & D... It sounds like an awfully complicated way of calculating the gains to me, but then again so does most associated with PID...! The 0-500 values on my front panel is just the range of response I got from my cistern arm(pot) from empty to full... Thanks again, Richie PID-RichLevelControl.vi

Thanks everybody for all the help and advise:rolleyes:! I'm going to focus on trying to make my process work with one of two programs; 1 - My initial program with the on-off controller added in(cheers anon), 2 - An edited version of the FPGA PID PWM program(thanks for pointing that out Shaun). I've run into a bit of a snag with wiring my DAQ assistant Ai/p and Do/p into the FPGA program... My analog input subbed in nicely into the PID loop, but in the PWM generation loop there are 2 terminals to wire into my digital output(direction bit & PWM output), where as I only have one digital output to generate on my DAQ assistant. Also, when I did try to wire up the DAQ assistant to one of the terminals it gives the error; '2 terminals connected of different types. Type of source is boolean(T or F). Type of sink is 1-D array of boolean(T or F)'. I understad that one is a scaler type and one is array type, but even by clearing the error I can't be sure that I'd wire it up correctly... Am I on the right track? I've attached the FPGA program. Thanks again guys, Richie (Labview & PID rookie)!! FPGA PID PWM Control.vi

Hi, I am wondering does anyone know the best way to work out my P, I and D values for my level control project? Basically I am using a subvi called simplePID which I found on the NI website. I have two DAQ assistants in my program - one configured as an analog input (this input is from a cistern arm turning a pot which will determine the level of my test tank), and the other is configured as a digital output driving a pump. I havnt tried to use this program with my hardware yet due to my lack of understanding of PID and tuning the controller. I have read up a bit on manual tuning and the Ziegler-Nichols method, but I have been reluctant to try these without a bit of advise 1st. If this works will I need to incorporate pulse-width modulation to ensure more accuracy on reaching my setpoint (my pumps flow rate is 13L/Min but I have installed a manual valve to restrict the flow as necessary)? I have attached the vi below. Thanks for your time, Rich PID-RichLevelControl.vi

Hi, I'm looking for a bit of help with code for a Level Control project using a USB 6008. Basically my project consists of a reservoir and test tank. The test tank has a cistern arm turning a pot for my analog input. I have a 24vDc pump which is to be controlled by a Pulse Width Modulated Digital output. I'm not that familar with PID control or labview code for that matter, but ideally if I could achieve some form of PID that would be great!! As of now, I have a program for my cistern arm, where I configured a DAQ assistant as an analog input. This VI basically simulates where the arm is at in the tank through a meter,tank,etc in the graphics. I also have a PWM program which I sourced off the net(this site I think) which has a DAQ assistant configured as a digital output. The PWM program has 'duty cycle' & 'milliseconds to wait' numeric controls on the front panel which can be adjusted manually during execution. I have managed to get both programs working with my hardware(digital output was tricky because of the current limitations of the 6008), but my main problem is trying to link these 2 programs... Maybe I'm going the wrong way about this though... I understand also that there is a PID block in the labview code. It would be great to use this... I just find that any time I try to wire up say a DAQ assistant configured as an analog input to my Digital o/p DAQ assistant in PWM program, that trying every way possible I can't get it written without generating errors!! I would greatly appreciate if someone could help me or point me in the right direction with this. I have attached the analog input VI, and the PWM program. Thanks for your time, Richie MyProject2010.vi NBMyProjectPWMProgram.vi