Sunday, 20 June 2010

More solenoid valve tests

I manufactured a custom nozzle to fit directly onto my 1/4" solenoid valve and decided to photo document the nozzle manufacture procedure.

I started with some 20mm Delrin bar

I then turned this down at one end to allow me to tap it to 1/4" BSP at 19 turns per inch with is a standard pneumatic fitting in the UK.

I then applied a thread to it with a die that my Grandfather left me.
I held the die by hand with the work piece in the lathe chuck. I turned the chuck with the chuck key.

Ironically, I was applying a British Standard Pipe thread with a die that was made in the USA.

I then put a chamfer on the thread to ease starting the thread

The next stage was to drill a 2.5mm hole through the nozzle

And added a taper to reduce the internal diameter from 1/4" to 2.5mm

I then added an external taper using the lathe cross slide at an angle

Here is the finished nozzle

Here is a video of the solenoid valve in use

The trigger is very responsive but as I experienced last time, the range is greatly reduced. I got about 28 geet out of this test. The problem is that the solenoid valve has a restricted inlet port and this is where the problem lies.

I've decided to give up on solenoid valves. They are OK with air but water is too viscous. Ball valves are the way to go, but automating them could be a pain.

However, I do have some experience with pneumatics, and I have a tank full of compressed air on my back.......Watch this space.

Monday, 14 June 2010

Rapid Fire

I tried controlling the water flow with a solenoid valve this weekend with mixed results. I wired it to a 12V battery pack via a push button switch I had lying around.

The valve has 1/4 inch BSP inlet and outlet fittings, yet my pipe and nozzle are 3/8 inch BSP. I had to get some adapters to reduce for then expand from the valve. They can be seen as the silver fittings on each side of the solenoid valve.

The valve worked perfectly. I was able to rapidly turn the flow on and off. But due to the restriction from 3/8 to 1/4 at the valve inlet, and expansion from 1/4 to 3/8 at the outlet, plus flow resistance from the valve innards there was too much pressure reduction and the range was reduced to about 28ft.

I'm going to try a new nozzle turned to fit directly onto the 1/4 inch valve outlet next. Hopefully this will reduce the pressure drop.

Wednesday, 9 June 2010

Printed Circuit Board

My adventures with Kicad continue. I was going to make the solenoid control circuit on a piece of veroboard but decided to use Kicad to design a PCB instead. I've recently moved from Windows XP to Windows 7 and my old electronics design software will not run without tweaking. As a result, this has become an exercise in PCB CAD package education as well as the water gun itself.

Here is the single sided PCB I've designed:

I'm not going to make it though until I have tested the water gun with the solenoid valve I have to see if it is suited to pulsed operation.

Monday, 7 June 2010

Water Control

I still need to do some more experiments with nozzles, but in the meantime I have started on the design of a controller for a solenoid. The ball valve is somewhat unwieldy to use in practice, a trigger mechanism would be much better.

As I do not have access to a push button operated valve that is high pressure rated I'm going to use a 12V solenoid valve I got from ebay.

It is rated at 130PSI and so is OK for the pressures in my system.

I'm going to control it with a small micro controller so I can operate it in one of several modes:

Single Shot,
Three Shots Rapid,
Continuous Pulse,
Continuous Stream.

The trigger will be a push button switch and the mode changed with a seconds push button. The controller will indicate the new mode with audio feedback from a buzzer.

I'm using a Microchip PIC for this design as I am familiar with them and I already have all the development tools.

Here is the schematic drawn with the fantastic Kicad.

The power for the circuit will be supplied by 8 x AA batteries.