Connect with us

Push Button H2O - Reversing Polarity

Discussion in 'General Electronics Discussion' started by mcasey, Jul 9, 2016.

Scroll to continue with content
  1. mcasey

    mcasey

    64
    2
    Jul 9, 2016

    no. i have to touch red to positive and black to negative to open the valve, then i have to touch the red to negative and black to positive to close it. I only have to touch it momentarily because it is a latching valve. Using the same polarity twice does not change the state of the valve.
     
  2. mcasey

    mcasey

    64
    2
    Jul 9, 2016
    i have a tx/rx. i tried using it to supply power to the valve remotely, but i can only send the valve into one state. i would need to reverse the polarity to change the state.
     
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,482
    2,830
    Jan 21, 2010
    You could use an H bridge to enable power to be applied in either direction. Presumably the receiver will only apply a momentary pulse.
     
  4. Kiwi

    Kiwi

    360
    89
    Jan 28, 2013
    Like Bob, I would be rather annoyed if I had purchased that solenoid valve and found that it only works by changing polarity.
    That is not how the description reads to me.
    I would also not have expected a polarity reversing valve to have a red and black wires.

    Another thought.
    The valve is rated at 6v.
    Is your 9V battery capable of supplying sufficient current at 6V to operate the valve correctly?
    It may be that by reversing the polarity from your 9V battery the valve will change state.
    I would suggest that you try it on a 6V power source that is able to supply a few amps without the voltage dropping, eg SLA battery.
     
  5. mcasey

    mcasey

    64
    2
    Jul 9, 2016
    I've been researching H bridge. The only circuits i find still require two switches. How would i wire in the receiver? Would I need two channels, both momentary, in order to activate either side of the bridge?
     
  6. Kiwi

    Kiwi

    360
    89
    Jan 28, 2013
    Looks like Bob and I have been led astray by the ambiguous information given by the supplier of your valve.
    As you have discovered, your valve probably works by changing polarity.
    The wire colours indicate which way to connect power to get a particular operation.

    Just found this on another manufacturer's website;
    • Valve opens with quick positive pulse (red wire to "+" & black wire to "-")
    • Valve closes with quick reverse pulse (red wire to "-" & black wire to "+")
    • Valve stays in position with no additional power being applied
    Not sure how you can easily get remote operation with a single input.
    Possibly you could try a magnetically latching changeover relay?
     
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,482
    2,830
    Jan 21, 2010
    That would be simplest. It would also guarantee you know the state after you press the button. If not, all you know is that it has changed.
     
    BobK likes this.
  8. Bluejets

    Bluejets

    4,664
    984
    Oct 5, 2014
    Easy...if he uses the r/c tx and rx with a servo, traverse to one end closes one of a pair of micro switches, traverse to the other closes the other micro switch. In the centre, neither is operated.

    Micro switches set up exactly the same as for reversing a dc motor.
     
  9. mcasey

    mcasey

    64
    2
    Jul 9, 2016
    Where could i buy one of these?
     
  10. Bluejets

    Bluejets

    4,664
    984
    Oct 5, 2014

    Attached Files:

    Gryd3 likes this.
  11. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    I agree with Steve. One of my pet peeves is remotes that have a "power" button. When operating more than one device they will eventually get out of sync and you will turn some on and others off. If they had an "on" button and an "off" button, this would never happen.

    Do you have some way of knowing which state the valve is in when you choose to switch it? If not, you will certainly be better off with an "on" button and and "off" button.

    Bob
     
  12. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,482
    2,830
    Jan 21, 2010
    With more smarts at each end you could encode a single channel to send a start or a stop signal, but effectively boils down to the same thing.
     
  13. mcasey

    mcasey

    64
    2
    Jul 9, 2016
    I finally created the circuit to do exactly what I wanted with the exception of one thing, rapid battery drain. I am using a standard 9 volt battery to power the following circuit, and it works great. The problem is, the battery dies after about 24 hours. The L293DNE IC requires 5 volt internal logic. I'm thinking this is the culprit. Can anyone offer a suggestion on how to prevent battery drain? I only use the remote on/off and push buttons on/off a couple times a day for a few seconds, which leads me to believe there's something wrong with the design.


    schematic1.png
     
    Last edited: Oct 6, 2016
  14. davenn

    davenn Moderator

    13,802
    1,941
    Sep 5, 2009

    Those small pp9 batteries have VERY small capability. you are going to need something with much more capability ... a rechargeable 12V 7.2 Ah gel cell etc
     
    Gryd3 likes this.
  15. Alec_t

    Alec_t

    2,940
    799
    Jul 7, 2015
    According to the datasheet the minimum supply current of the L293D is 10mA (with all outputs at high impedance).
    What is the standby current of the two voltage regulators?
     
    Gryd3 likes this.
  16. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    Check out the previous answers as well, but if you want longer battery life you need your circuit to me more efficient, or you simply buy a bigger batter or an AC-DC adapter.
    Do a quick search for battery capacity too for a cell you want to use.
    9V cells typically have 500mAh unless you use rechargeable cells. You can also pay extra for lithium.
    In any case, it would seem fair to estimate a constant 20mA draw from your device if it dies in 24 hours.
    Confirm the details asked above, and let's see how we can best solve this.
     
  17. mcasey

    mcasey

    64
    2
    Jul 9, 2016
    upload_2016-10-6_20-57-59.png

    upload_2016-10-6_20-58-44.png
     
  18. mcasey

    mcasey

    64
    2
    Jul 9, 2016
    I'm thinking I could add a relay to the L293DNE in order to disconnect pins 1, 8, and 16 until one of the switches is pressed. Thoughts on this?
    This still leaves the problem of current drain for the RF part of the circuit. Any way to drop the Receiver/Decoder to a ultra low current state until a button is pressed on the transmitter?
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-