I developed a .VI that is successfully controlling the temperature of up to 8 components on a device I have built but the solution feels messy and I'm looking for feedback. Equipment I am using USB-TC DAQ board for temperature input and relay control (using digital out). - Link Type K thermocouples Crydom solid state relays to switch power. - Link 120 V Cartridge Heater I have included a .VI of an example of a single input. I start by configuring one of the USB-TCs output bits so that I can control the SSR. Then, once every ten loops I sample a DAQ board channel for a temperature. I do this because I'm using a second DAQ board for non-temperature measurements and that board reads in this time. The sampled temperature goes to the process variable of the PID .vi. The output range of the PID .vi is from 0 to 100 % because I want a duty cycle output. This is where it gets really "messy". I use the PID output to generate a waveform, then convert that to a digital waveform, and then convert the digital waveform into a boolean array. I found the [1,1] index of that array works and I use this to turn the digital output channel either high or low. I have this output wired to the SSR which when high allows current to flow to the cartridge heater. I feel like there is a cleaner way to do this. Thanks for all input. Hunter

Sorry, I didn't look carefully enough at your VI the first time through to fully understand what you did. Is this the sort of simplification you're looking for? If you don't want to track the time input yourself, you could use the similar "Square Wave.vi" (instead of the Point-by-Point version I used here).

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PID control of heating element feedback

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Re: PID control of heating element feedback

alican

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‎03-18-2011 03:05 PM

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thanks, i had it.

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