I am 100% new to this and a little lost on where to start platform wise. I seen on another form real close to what i want. Pressure Sensor used as a switch. What would be a good board to start with? My goal is one of the boards with a wide dc voltage input 6 to 30. I only need on pressure sensor 0 to 5v, but more inputs would not be bad, i would like a lcd screen that shows input pressure, and set pressure, and to out put switches one for a low pressure threshold and one for a high pressure threshold. If is possible i would also like a toggle switch that could easily change the settings of when to activate the output switch?
I do not recall any such Arduino boards, can you please help by identifying them? As far as beginning, go with one of the many Arduino kits available and only then consider your new project.
Say instart with a Arduino® UNO R4 Minima, it can handle up to 24 vdc, which exceeds the true max i need, i will be using a 16 volt lithium battery to power my complete project. I belive it supports 0 to 5 v transducer, so I would next need to figure out how to code it to the pressure sensor to get proper readings, next i would like to have a lcd screen the showsbthe pressure reading. I believe in the code you can give it ouput commands, say when pressure exceeds 100 activate this 12v relay until pressure drops to 90, if pressure is below 80 activate this relay till pressure hits 90. I believe i would have to add a relay board to handle the load of the actual solenoids doing the work? Next i would like to add 2 toggle switchs, on to adjust the lower limit and one for the upper, they could be buttons or what ever, does it sound like i am going the right direction with parts i want? Next would be learning how to write the code but one step at abtime
Just about any simple board. Since you mention 0 to 5 volts I assume you want a pressure sensor having a range of measurement which corresponds to a 0 to 5 volt output proportional to the applied pressure. You make no mention of a pressure range. A good choice would be an Arduino Uno Rev 3. Actually even that is overkill but would do just fine. The Arduino Uno R3 has six analog input channels each is 0 to 5 volts and if you exceed that you need to add voltage dividers. After you mate the sensor and Arduino board it's a matter of writing some basic code to include your upper and lower limits you mention and what you want to happen at the limits. Yes, you can add buttons to increment or decrement your set point limits. Yes, you can add a digital display.
You are going to need to better describe your project in detail including links to your hardware you plan to buy.
Welcome to the forums.
Ron
Thank you Ron, you are correct, the it is a pressure transducer, it truly operates at .5 volts 0 psi 4.5 volts is 250 with a linear scale. I don't have any hardware yet. At least for the building of the arduino. Ultimately it will be controlling to solenoid valves, which is where the relays come into play, most likely ssr relays to reduce the load on the the control board but i could wire them separately, just need the 12v signal from the arduino to trigger them. The relays have a fairly low amp requirement 20ma to trigger.
Well alrighty. Yes, what you are looking to do is easy enough. Any uC (micro-controller) be it an Arduino or similar has an intense dislike for things like relay or solenoid coils or let's just say inductive loads so using a SSR is a good way to go and also sans a SSR using flyback diodes across the solenoid coils, not a problem. Yes, the 0.5 volt to 4.5 volt spans on sensors has become popular. Just depends on your choice of pressure sensor, some even offer I2C communication outputs. Details are worked out in the code and looking at what you want to do the code is not all that complex.
I will say this as to hardware selection. Should this be an industrial application don't skimp and cheap out. Buy once and cry once on your sensor. A good pressure sensor will be stable and have temperature compensation. Also choose your sensor based on the environment you expect it to perform in.
Yes, just as an example a typical Arduino Uno Rev3 can source 20 mA on a digital output pin. Not really good for driving solenoids or large relays directly so either a SSR or a Logic Level MOSFET is used to drive relays and solenoids. Would you have AC or DC solenoid valves? AC solenoids are best driven using a SSR having 0 crossover switching.
Start with a clean white sheet of paper and list all of your parameters, must have and nice to have. Draw a simple rough schematic. Make sure your drawing pencil has a large eraser. 
Ron
I did a lot of work with large high pressure auto-claves adding and dumping gas in the 3,000 PSI ranges.
Once again Ron, you are spot on in the direction I am trying to go, the solenoid are dc 20 or 30 amp, and are being used like dump valve, they won't have to cycle very often, about 5 to 10 seconds a couple times a day when in use. I have learned my lesson on the cheap pressure transducers with data logging equipment, you are completely correct, th 20 dollar one gets replaced way to often that the expensive one pays for itself. I bought some cheap digital pressure guages with adjustable switches off Amazon to test my project, but would like to go this route, to build everything in a neat little box. Only thing i am worried about the more I research is the sustained high voltage on the arduino, so I thinking of running a voltage regulator from the battery 16 volts to 7 to the board. Because I should be able get the 16 volts back wiring the batteries through the relays? Possibly some diods to prevent back feeding from the relays on trigger wires? But awesome insight from you!!
What pressure range are you interested in and what kind of accuracy?
900 psi 1% would be ideal, but i have a little room
So, you need an industrial type hydraulic pressure transducer. Have you selected or bought one? if so, which one (brand name & full part number)?
Sensata Technologies PTE7100-22DC-0B100BN i would use something comparable to this, if not this one
Why would you use a 1450PSI sensor to read 100PSI? will the sensor be exposed to 900PSI?
Probably because i added an extra zero to the BAR pressure when i was pulling it up, my fault lol
I said that wrong, 1450 PSI is overkill, but i need some safety room, i should never see over 1200 psi worst case
So, what is the max pressure the sensor will EVER be exposed to?
1200
Hmm, 80PSI is only 5.5% of that sensor's range, if the output at 1450 is 4.5V the voltage at 80 will only be about 0.22V not much resolution with the Arduino's 10 bit (0 ~ 1023) ADC.
I created that confusion withnmy original post, i dont have my actual pressure figured out yet all the way but I will definitely be working in the 800 to 1000 psi range, i was little to vague trying to basically explain my goal to find a starting point, i should never see more than 1200 psi, but i will never need more than 1000, trying to control c02 pressure, to dump access when it gets above a threshold, and allow more in if it drops during due high temperature fluctuations. My end goal would be to control it with in 10 psi if possible but I have more room to play if i can't get the tolerance that tight
I will continue to look for sensors with tight tolerance, i believe that one is .25% i believe well within my tolerance. I also understand that most sensors dont function optimally on the outer limits
JC thank you for mentioning the 10 bit adc, gave me something new to learn and understand. I was reading about the R4 board can handle up to 14 bit, i am thinking this combined with a sensor with a narrower range say i can find something that was 500-1500 psi or tighter, would help with accuracy?