The objective of this project is to remotely control the opening/closing of actuated solenoid valves through an Android phone. I have attached circuit diagrams - breadboard and schematic versions. I have little to no electrical engineering background at all so excuse me for any glaring flaws or epic fails.
It would be greatly appreciated if any of you can point out any possible flaws in my system. Some concerns and questions I have:
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Solenoid valves must be rated to ~100 psi. What is better: high AC voltage valve (120V AC) or low DC voltage valve (12V DC) for this system? The relay module should be able to accommodate either option.
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I have a separate 5V power supply for the relay module (as suggested by some research I did). I am also unsure of the circuitry.
I did NOT carefully study/analyze your design.
What is better: high AC voltage valve (120V AC) or low DC voltage valve (12V DC) for this system?
12V is less dangerous (to you or anyone who might touch the wiring). 
But, with 120V you don't need a power supply. If you go with 12V, make sure your power supply can provide the current (Amps) required by the solenoids.
The relay module should be able to accommodate either option.
Correct. NOTE: Your solenoids are wired to the relays incorrectly... There is no power... The relay contacts must be in-series with the solenoid power so that closed contacts turn the solenoid on, and open contacts turn it off.
Also if you use 12V solenoids, add reversed diodes to suppress the high-voltage [u]Back-EMF[/u] spike when the solenoid is switched-off. (The relay board probably has a diodes for the relay coils.) Do NOT use diodes with AC solenoids!
- I have a separate 5V power supply for the relay module (as suggested by some research I did). I am also unsure of the circuitry.
That's generally a good idea, but not always necessary. Sometimes you'll get a problem and separate power supplies turns-out to be the solution... There are two issues - The relay coils draw a bit of current, and if you use the Arduino's on-board regulator for the 5V you may over-stress that regulator. If you are powering the Arduino with a "big" 5V power supply and bypassing that regulator, current draw is not an issue.
The 2nd issue is that back-EMF spike, that while "suppressed", can still potentially cause electrical noise on the power supply line, causing the Arduino to "glitch".
In your case you're showing a 9V power supply, so a separate 5V regulator for the relays would help to isolate the noise. (But, a regular 9V "smoke alarm" battery might not supply enough current and it won't last long in any case).
What is the application for this? What are you trying to accomplish? It makes a HUGE difference
I'm trying to inject gas and water into a porous medium and monitor fluid flow using a machine, however once the machine is in use we cannot manipulate the setup anymore. Hence, we need the wireless Bluetooth functionality.
And thank you for the detailed suggestions DVDdoug. I have attached an updated schematic with the incorrectly wiring between the solenoid and relay fixed.
9434260:
And thank you for the detailed suggestions DVDdoug. I have attached an updated schematic with the incorrectly wiring between the solenoid and relay fixed.
The solenoid/relay still doesn't look right.
By the way, many AC solenoids will get pretty hot without water/air cooling when energized. Be sure there is fluid moving to remove the heat.
Paul
Yes I just realized there is no power feeding into the COM. Like I said, I'm quite an amateur lol. In the other projects I have seen, they have been using a power cord in series with whatever is connected to the port of the relay (in my case, a solenoid).
However, since I mentioned this system must be standalone, what would be the best way to supply power to the solenoid (most likely 12V DC) without using a power cord?
Solenoids can be power hungry, so what you need (power wise) would be based upon the solenoid and how long you plan on keeping it energized.
How much flow is required? Have you thought about using automotive injector? That would make metering easier and they can handle the pressure. Many car injectors are 12v, while some bigger ones like mine are 120V.
tinman13kup:
How much flow is required?
Low flow rate. We'll probably be injecting not much fluid (<1L) over a long period of time (~1hr)
Do you think a 12V 7 Amp Rechargeable Lead Acid Battery (link below) would be sufficient to power at least 2 and maybe more solenoid 12V DC valves?
https://www.amazon.com/ExpertPower-EXP1270-Rechargeable-Lead-Battery/dp/B003S1RQ2S/
DVDdoug:
Also if you use 12V solenoids, add reversed diodes to suppress the high-voltage [u]Back-EMF[/u] spike when the solenoid is switched-off. (The relay board probably has a diodes for the relay coils.)
Also, how would I go about hooking up multiple solenoid valves to a single power source all the while using these reversed diodes as suggested?
All the solenoids would be hooked in parallel, withe the diode in parallel with each solenoid. Typically, one end of the solenoid is hooked straight to ground, and the other to the control voltage. The diode would be hooked up so the cathode end (band side) is to the control voltage side of the solenoid and the anode lead is hooked to the ground side of the solenoid. All solenoids would be hooked up the same way. The ground end would be common to all solenoids, but the control end would go to their respective relays, which then get connected to the positive battery .
I have attached the updated schematics. The solenoids I am interested in using are 12V DC and 3 amps. I expect 3 of these solenoids to be running simultaneously. To accommodate for the high amperage requirement, I am considering using a 12V 9 Amp Rechargeable Lead Acid Battery (link below):
Thanks for all the feedback and please let me know if there are any other errors. I will continue doing research on what sort of reversed diodes I plan on using.
Also, I read something about solder-less breadboards not being able to handle more than 1 amp, so I believe my fritzing diagram, which shows a second breadboard being used for the solenoid part, is wrong. If I can't use a breadboard for this section, would I have to wire everything by hand?
Not an error, but 36 watts per solenoid for an hour or so will be a lot of heat in a small area. Better hope the liquid will be moving through the valve to carry off the heat.
Paul
