I attached an image on generally what I am trying to accomplish. Im trying to make device to sense when the object is there, and then to spray it with a chemical for a very brief amount of time.
I can use my arduino with an LDR to sense when there is presence of an object. I can also use an light level sensing circuit to detect the presence of an object. The electronic gate is my problem. What is there that I can use arduino with to switch on and off that air pressure when the object is detected? If i use light level sensing circuit (which i prefer) Im not sure what to use to control the air pressure for a certain amount of time.
One problem with your design is that the fluid will run out the spray head under the force of gravity. An alternative would be something like a garden sprayer where the fluid is under constant air pressure to force it through a tube to the nozzle and a valve in the tube is used to start and stop the flow. Perhaps an automatic sprinkler valve would do the job of controlling the flow of fluid.
The thing is i readily have air pressure available. There are air connections everywhere in the factory so that's why the design is trying to use the air. The object would be fairly close to the spray head maybe a few inches away.
@johnwasser good call I missed that. I attached image of a more feasible design. I really like the sound of your idea, I did not think of automatic garden sprayer. My only concern is if it can handle chemicals, specifically ethanol or alcohol.
I will research these thanks for the idea.
"For the first one an electromagnetic valve on the hose would do the trick."
Why is infrared or ultrasonic sensor superior to a LDR ?
hedstr0ng:
"For the first one an electromagnetic valve on the hose would do the trick."
Why is infrared or ultrasonic sensor superior to a LDR ?
The LDR will likely give you false readings, because it also detects light changes due to environment conditions.
An infrared distance sensor consists of an ir-led which sends pulsed light and an ir-ldr which only detects the pulsed light. If anything is near the sensor the infrared light will bounce off of it and will be detected by the ir-ldr.
Thats way more save to light fluctuations.
fluid will run out the spray head under the force of gravity.
Right, also there is a risk of fluid flowing into the air-hose. You need a non-return valve to prevent this.
Or you design it like this:
The air is pressed in the container and pushes the water out.
(the non-return valve is unnecessary here)
I thank you. I think you have the mechanics proper, which was my trouble. I researched solenoid valve and it should work! I see what you mean by IR superior for environment change, I agree. Now I try to make this work cheaply but not compromising durability as it needs to spray about 3,000 times per day.
You can buy agricultural spray nozzles that include a diaphragm that stop them from dripping. Here's an example that clamps onto PVC pipe; you just need a nozzle cap and spray tip to go with it, and of course there are kajillions of styles of spray tips so you can assuredly find one that fits your purposes.
The problem with spraying using only an air valve to pressurize a vessel is the the time it takes to pressurize the vessel will vary depending on how much fluid is left in the vessel. Time will increase as the fluid is used up. Also, without a separate vent valve, the vessel will STAY PRESSURIZED even when no more air is being added. The sprayer will keep spraying long after the air valve is closed. You MUST use a fluid valve to control the spray if you want any degree of control. If you have a fluid valve you don't need the air valve at all: just keep the vessel pressurized all the time.
I think a windshield-washer pump would do the spraying with more control and can certainly deal with alcohols. No need to pressurize the vessel so it will be much easier to re-fill. No need for a fluid valve. You'd need a 12v supply and a transistor or MOSFET for power switching but you'd probably need something like that for a solenoid valve anyway.
