You might think I am one of those guys who registers for a forum, asks a million questions in his first ever post, and then never returns. Not the case with me; I am engineer working on a prototype for a project/invention, and am looking for some feedback on the feasibility of using Arduino components as one the pieces to my puzzle. If Arduino technology is what I need and use, I will continually update the forum on the progress of my project in hopes of teaching someone in return. Thank you in advance for any insight or feedback - it is greatly appreciated!
Objective: Control and monitor the air pressure in a vessel with a wireless system which will activate electro-pneumatic solenoids that allow air in or out of the vessel. In other words; I want to use a small battery powered remote control to set the vessel air pressure, while receiving real time pressure readings from the battery powered air management unit.
Equipment: I found an all-in-one air pressure controller that will adjust the pressure in the vessel by comparing the input signal with the signal from the internal pressure sensor, for example; if the input setting is 1.5 VoltsDC and the pressure sensor is reading 1 VoltDC, the intake solenoid is open and letting air from the source into the vessel until voltages are equalized.
The user interface for the remote control needs to have 3 programmable buttons and a digital screen showing the pressure reading obtained from the pressure controller.
Parameters:
-SMALL
-Low battery consumption
-Operation under harsh conditions: -20 to 120 deg F, constant vibration and movement
-Signal range: 10'
-Output pressure setting signal: 0-5 VDC
-Input pressure monitor signal: 0-5 VDC
-Pressure Controller Unit current requirements: < 400mA
Sounds like a very interesting project but not sure about your question.
If you are asking if Arduino can do it, certainly.
I would be concerned about the environment thou...
Are your prototyping or a production item.
Can you add a heat source to keep Arduino nice and toasty?
I would build a structure to dampen the vibration.
Enclusre necessary to keep on the dirt?
Use Wireless (XBee)?
Maybe a relay for the solenoids? Maybe not?
4 line LCD, some buttons and how about LEDs to indicated when the valve is open and for how long.
Gauge to measure air pressure in the vessell
Gauge to measure supply pressure. If the supply pressure is lower than the vessel pressure then the valve will not open.
Perhaps an indicator to make sure the solenoids have power...maybe not?
I can use Arduino, super.
This is simply a prototype for a little invention I have been pondering lately, if it makes it to a production line...fine with me!
Environment: I am concerned too. Space is limited and weight is an issue. All components will be contained in a durable waterproof housing of some sort. I like the idea of vibration dampening, I will work on that. As for the heat: I want both units (Unit 1 - air controller & Unit 2 - remote controller/monitor) to be battery powered, able to last long periods of time (100 hours) without battery replacement or charge, and lightweight...a heat source would be tough to integrate unless someone knows of a TINY turbine enerator that could actually charge Unit 1 as air is passing through it?! (maybe prototype #2) Pretty Cool>http://www.ecogeek.org/wind-power/539
I am reading up on XBee right now, this is exactly what I need for this project.
I wont need a relay for the solenoids because the Pressure Controller will do that itself. Once I send a signal that correlates to the air pressure I want to maintain, the Pressure Controller will open and close the valves as is needs. This is the controller I have in my sights for now: http://www.parker.com/literature/Literature%20Files/Precision%20Fluidics%20Division/UpdatedFiles/OEM%20Data%20Sheet.pdf
LED's: I would like a power on LED, and a battery low LED. I don't need to know when the solenoids are open and closed because I will be able to watch the air pressure fluctuate on my screen, but I might need it to monitor the air consumption. The air source will be a refillable air cartridge, and the only way I can think to keep track of what I have left in the cartridge is by knowing how long the solenoid was open for. I could use a mathematical equation written into the code that would calculate how much air was required to go from this psi to that psi. Going from 61-65 PSI would the same amount of air to go from 71-75 psi - this is proven by the ideal gas law equation - so I would have to do some homework on that one.
The gauge to measure the air pressure in the vessel is in the Air Controller. It is an electronic sensor that the controller uses to detect if the pressure matches the voltage setting that I have set, the Air Controller sends a signal 15 times a seconds with the voltage reading which I would convert to psi within the code then display on my screen.
4 line LCD would be nice, as long as the energy consumption inst huge.
Questions:
What hardware do you suggest I use for this project?
Is it difficult to integrate recharging capabilities?
I'm working on a few projects which I enjoy, just getting the time to complete them. I like practical project the best. Projects that solve a problem or provides a solution.
I like your ideas. I have some suggestions which you can kick around. There are many ways to do things as I'm sure you already know.
A few hardware suggestions.
Arduino Mega
XBee, I think it is the ZB model. Lots of documentation. Go with the chip anttenna if they are close to each other.
You will need a xbee shield
xBee regulator
LCD screen...there is all kinds, sizes and colors. There are a few with buttons on it.
Recharging, I'm not sure. I have never done it so it would take some investigating.
Can you use the weight of the air cylinder to indicate if it is empty?