Power cable diagram for valve and StopShot

Reference: Stopshot manual version 1.7, page 47.

Pretty simple, but one thing to watch... wire the RCA cable outer wire/braid to the power supply negative terminal as shown. Mark that end of that wire with tape to keep this straight.

The same cable would be used for a 12V or a 24V solenoid valve.

I used 18 gauge lamp cord, but smaller wire is fine too... 24 gauge wire will be sufficient size for this, if mechanically strong. I measure the Shako PU220AR solenoid at 212 ma (5 watts), and the 24V STC 2P 025 solenoid at 256 ma (6 watts). 12V coils should double that current for same power. The regulation of this power supply is excellent, voltage does not vary at all when the valve opens. But the voltage across the valve will be a few tenths less than the voltage at the power supply, due to a small drop across the Stopshot switch circuits, which is just the nature of semiconductor things. Both this valve and this power supply use a terminal connection, only needing the wire to be stripped about 1/4 inch. Insert wire in hole, and tighten a clamping screw on the side.

Any old AC power cable will work for input power, attached the same way (but clamp cables with a tie wrap - no stress on terminals - DON"T let the AC wires get loose). The valve has a green third wire ground connection terminal, but neither the power supply or Stopshot has one (so two wire AC and DC cables are all you can connect. Just leave any third green wire unconnected, but not touching the others). Picture shows power supply mounted on about 7 inches of the optional bar, under the homemade table used for this water drop purpose (which was a darkroom enlarger table in the old days).

Make sure the three ends are long enough to reach your power, timer, and valve. I used ten feet of cable, spliced at about four feet. If not adding a connector, make sure valve end can be lifted over the top of the support pipe (if you plan to lift it off). You need a connector, but the DIN option could be that connector. The DIN takes a screwdriver, but it just unplugs, very easy to remove, and the same DIN connector will fit several valve choices (see below).

The polarity of even DC solenoid wires doesn't matter, it magnetizes the same direction either way. The Shako valve is not marked +/-, terminals simply say 1 and 2. It does not matter to the solenoid which wire is which. However, if there is a LED inside the DIN connector, the LED will greatly care about DC polarity. STC adds this LED, Shako does not.

Electrical text books say that if we put a bar magnet (with a N & S pole) inside the coil, reversing polarity does reverse the direction that the bar magnet is pushed. But solenoids are not made that way. They have soft iron cores, becoming electromagnets when energized. So when we put a soft iron bar inside the coil, and current is reversed, BOTH the coil AND the soft iron reverses field, with no change in the direction of solenoid push. Solenoids can be designed as AC or DC.

To help convince you, here are a couple of references, from 2010 and 1917. Also a Google search.

Adding a suppression diode (across the solenoid terminals) is normal good practice on DC solenoids, but possibly may not be required here, because StopShot claims to protect itself from inductive loads. Their 12V valve does not add the diode, but my thinking was that this is 24V, and it can't hurt. If a diode is used, the polarity of such a diode definitely matters. The marked cathode bar MUST go to the positive wire. The power supply will shut down (to protect itself) if power is connected backwards to the diode. I used a 1N4003 diode from Radio Shack, directly at the valve terminals (simply inserted in same holes with wires).

Put the heat shrink tubing over the wire at the valve end FIRST (while you can, before you add something that makes it impossible). It should be just large enough that both cables will go into it... 1/4 inch diameter probably. Then at the splice connection, twist the wires, and solder them, and I wrapped some tape over them. Then pull the heat shrink over it. You heat it, and it shrinks tight. Home Depot has 4 inch lengths of heat shrink, sufficient. The link for the brass fittings (MSC Industrial) has a wide variety. A hair blower won't do it, it needs a heat gun, but low power is enough. Too hot and you make it hard and stiff, and you might set off your home smoke detectors then. If no heat gun, here are 8 ways to heat your tubing.

There is not much else to it.

BTW, the DIN option on the solenoid valve is a handy plugon connector using three spade lugs, held on with the long screw. This possibly could be your only connector needed. Here is a picture of the Shako DIN. DIN is universal, so it also fits the other valves. No wire comes with the Shako, I added the wire and another connector (faster to disconnect). I also added the suppression diode in here, since it is directly connected to the wire, the polarity is always the same, regardless of which valve it is plugged on. Just push the wires into a little hole, and tighten the little screw clamps (shown on top here). This inner plug rotates in the housing so the cable can face out either way. It is a neat hookup. The top inlet fitting for tubing must be wrapped with a couple of turns of teflon tape to seal it. All NPT threads need that, except in this case for water drops, not the bottom output nozzle - only finger tight is fine for it, and we likley swap it often.

Shako valve disassembly

And below is a photo of the STC 2P 025 solenoid valve (with DIN option), showing how things go together (it's very easy, but keep it rinsed promptly, and clean so you dont need to disassemble it to clean out the dried up milk). This is the 24V version of the new StopShot valve II. They certainly did need a fix, but clean drops from this 2mm orifice needs a lower pressure head height.

Two STC valves are disassembled on that page.

My very strong opinion is that the 1.5mm orifice Shako PU220AR solenoid valve is greatly better and easier for this purpose (via about 5 inches of connecting tubing - maybe 11 inches overall head, measured from bottom of Mariotte top vent tube), using a 3/32 inch ID nozzle (about 2.4 mm ID).

Copyright © 2010-2016 by Wayne Fulton - All rights are reserved.

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