Need advice on electric remote control of a tap

I need to operate a 1/4 inch bore ball valve type tap remotely. Needs to turn on when the system electrics are first powered off and turn off when the rest of the system is powered down. Shaft movement is 90° from on to off. Quite easy to turn so I imagine that one of the compact RC servos will be well up to the job.

First thoughts were to get a small servo and build the necessary pulse generator circuit with provision in the linkage for over-travel to ensure that tap is fully off or on without having to set movement exactly. Before I set to and build the electronics is it possible to get either a fixed 90° rotation servo or equivalent unit off the shelf. Or is there a better, equally inexpensive way. I have sufficient electronic components in stock to build a controller and RC servos seem to be very cheap these days.

Clive.

Clive, PM sent

Why not use a solonoid valve ?

Why not use a central heating/hot water diverter valve, they are a 90° motorised unit.

Phil

Or an auto washer inlet valve?

Which is a solenoid valve, apologies to Ian, missed your point!

Washing machine water inlet valve, free at your local recycling centre.

Thanks for the suggestions but its a 12 volt system so the easy, domestic appliance sourced, way is out. Apologies for providing inadequate information in the orignal post. Didn't even think about the omission, too close to the problem I guess.

Anyway the tap in question is already fitted. Was supposed to have a simple mechanical connection to an external lever but there is no practical route for control rod and a solid centre wire flexi cable as per old style car choke cable or heater controls don't reliably turn the thing fully off.

Clive

12V version of washing machine valve here **LINK**

Steven

Clive,

From your description; I get the impression that the valve is already in place, and so you may not find a commercial device that's a convenient 'drop-in' substitute.

If that is the case, then your RC Servo idea seems perfectly reasonable; but I would also consider using a stepper motor. ... Depending on the balance of your requirements, this might have a direct mechanical connection, or be geared-down, or use a toothed-belt.

MichaelG.

Note: There are some very cheap little geared stepper motors on ebay, which were, I believe, designed for controlling louvres on air-conditioning units. Inevitably there is quite a lot of backlash in the gear-train, but I doubt that would be a problem in your application.

Edit: one of many listings, here.

Edited By Michael Gilligan on 10/05/2015 08:20:06

Michael

Indeed the tap is in place, replacing an inline solenoid device which didn't last well and appeared lacking in flow capability. Forunately just enough slack in pipework to get it in as alterations would have needed major changes.

Interesting little stepper motors in your link but external microcomputer control seems a bit overkill here.

What I was hoping for was an actuator which moved through a presettable angle when things were turned on and went back when they were turned off. Either a complete unit or a driver for RC servos or stepper motors. Given the uquibity, relatively low cost, and power of RC servos I'm surprised that such a simple controller isn't available from one of the usual Asian suspects. Would seem to be a goodly number of uses for a simple mechanical open / close type drive that could be controlled by a simple on off switch. Sounds much easier to install than the common DC motor drive with limit switches and reversal forcing diodes.

Clive

I've had a solonoid valve feeding an external watering system controlled by a time clock twice a day for 30mins for getting on for 24 years now....spring and summer months only mind

Same valve same time clock full 1/2" 15mm flow rate

you must have been unlucky with your valve

If choosing the r/c servo route then instead of worrying about specific 90deg range I'd have thought mounting the servo such that a lever from it goes full range while the valve does it's 90deg (as opposed to spindle to spindle connection).

Modifying something like one of these to control it should be possible **LINK**

Hi Clive,
I would consider using the model servo but remove its internal electronics and connect directly to the motor. I would then use limit micro switches. Just power it with one polarity to close it and reverse the polarity to open it. You will need to put a diode across each micro switch so it only prevented travel in one direction. I have never had one of these servos apart so I do not know how difficult it would be.
If you decide to use an unmodified servo have a look here at how I have used a model servo to control the airflow to my furnace. There is also the schematic of how I control it.

Les.

Edited By Les Jones 1 on 10/05/2015 20:42:09

pgk pgk

Thanks for the link. Should be able to modify one of the testers easily enough and do a one stop shop for the servos too. Prices are staggeringly low.

Les

Removing the electronics from an RC servo as you suggest was about Plan G in trying to sort this. Given the amount of room I don't have fitting switches would be a tricky shoehorn job. Hence the interest in driving the servo properly.

Ian

Problem with the original valve was material incompatibility between diaphragm and fluid. Far as I can see valve was specified for diesel but is fitted to petrol system. Modern fuel just ate the internals. Big mistake in assuming that the guy who did te work on the vehicle in question knew what he was doing not the only mega hassle do-over by any means..

Clive

Deleted, post a ppeared twice!

Edited By Clive Foster on 10/05/2015 22:52:02

Just something to inspire you. Hitec metal geared servo driving 3/8 swagelok 1/4 turn valve mounted in a 3d printed frame. Not mine, sadly...built by Rocket moonlighting.

What about a car door lock actuator?

Bruce

Or what about a bowden cable and forget all the electrickery?

Neil

.

Neil, for info. ^^^

MichaelG.