Linear actuator control - water valve

Discussion in 'The Projects Forum' started by liddells, Jan 14, 2018 at 12:25 AM.

  1. liddells

    Thread Starter New Member

    Sunday
    3
    0
    Hi all,
    I'm new to the forum and very new to the world of electronics but fascinated by the IOT and what is possible today. I have a project in mind I'd be keen to get some advice on. I've had a search through the forum but couldn't find anything specifically related to what I want to do.
    I have a house that is supplied by rainwater. The house is 200 km from where I live. The rainwater leg to the tank has a drain pipe on it with a flush valve to enable the roof and leg to be flushed so that the dirty water is not directed to the tank. The valve is a simple pull up domestic pvc water valve (approx 100mm stroke). I would like to be able to operate the valve remotely. My thinking is to use a linear actuator to open the valve with the actuation being activated by a phone call or sms. I would like the valve to operate in a cycle mode. That is, with the valve closed, receipt of sms starts opening. If no further sms is received, the valve opens to the open limit of the actuator. if a sms is received before this, the actuator stops in the current position. The next sms starts the actuator operating in the opposite direction (ie closing the valve). If no further sms is received, the actuator operates to its closed limit (valve closed). If an sms is received before this limit is reached, the actuator stops in current position etc. I have been looking at the concens actuators and control board (www.concens.com/) and cheap gsm units (http://www.imexbb.com/the-gsm-contr...control-swich-in-systemy-alarmow-11928505.htm) but I don't think this will manage the control I want. Perhaps it is an arduino project with the gsm shield to manage the sms.
    I will also need the ability to calibrate the open and close limits on the actuator.

    Any thoughts as to how I might achieve this would be gratefully received.

    Cheers
    Steve
     
  2. tranzz4md

    Member

    Apr 10, 2015
    276
    61
    Probably Arduino project w the GSM as you mentioned. That said, the timing of SMS messages is widely variable. If you actually, seriously think you may need or get substantial benefit from partial action as opposed to full on/off, you'll only get decent control by your SMS carrying a value or code to indicate a time or step value for the amount of action you want.
     
  3. liddells

    Thread Starter New Member

    Sunday
    3
    0
    Many thanks for the response. You are probably right that partial action is a nice to have and the simpler project is just to actuate to open limit on receipt of first sms and then to close limit when the next sms is received.

    Cheers
    Steve
     
  4. LesJones

    Active Member

    Jan 8, 2017
    887
    189
    As you are remote from the valve I don't see how you will know exactly when to tell the valve to stop moving. (Plus the fact that the message will take some time to get to the valve and this time will not always be the same.) Would it not be better to send a message to say for example move to the 75% position. I would think a resolution of 8 positions would be enough.

    Les.
     
  5. liddells

    Thread Starter New Member

    Sunday
    3
    0
    Thanks Les. I think you're correct and the interim positions aren't really important. I really just need to be able to calibrate the actuator to the valve open and closed positions so that when the sms is received, the actuator moves to the open limit and then to the closed limit when the next sms is received. I was hoping to use hall sensors to determine the position of the actuator.

    Steve
     
  6. LesJones

    Active Member

    Jan 8, 2017
    887
    189
    I think most linear actuators have built in limit swtches. If you can find one with adjustable limit switches that would be a good one to choose.

    Les.
     
  7. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    7,575
    1,645
    I don't think relying on time delays between sms messages to establish the open/close state is advisable, because of the message delay variability as already mentioned. The 'close' message might not be received in time to stop all the water being drained.
    The valve really needs an encoder on it which senses the degree of opening, so that feedback can be provided to a comparator which receives a sms command specifying the required position. It would be nice if the feedback signal or other confirmation of a completed action could also be relayed by sms back to the user.
     
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