Newbie needs some help feeding the fish!

Discussion in 'The Projects Forum' started by james211, Jun 15, 2012.

  1. james211

    Thread Starter Member

    May 29, 2012
    210
    2
    I see there are a lot of postings about fish feeders on here, and once again here is another! I've had great luck on this forum and hopefully that will continue.

    I have a drawing that I have attached, and its by no means a schematic, but more or less a chicken scratch. Basically here's the story. I have a fish feeder that runs on batteries and runs on a timer. I don't want either. I want this fish feeder to run from an outlet and be controlled by my aquatic controller. So far here is what I have figured out. The unit has a small switch (internally) that has constant power. When I press the feed button, power is cut power from the switch and the motor makes one complete rotation. So, I soldered two wires directly to the motor of the feeder and supplied it with 3.2 volts of power. When I do this the motor runs constant. However, if I keep the batteries in the unit, and supply it with about 2-3 seconds of power directly to the motor, the motor turns far enough to open the switch and then allows for the batteries to take over and finish rotating the shaft far enough to close the switch and complete the rotation.

    So here is what I'm thinking. I have an aquatic controller that has a dry switch. I also have a power supply and converter to provide 3.2 volts of power. What I want to happen is, the power supply provides constant power to the motor, basically replacing the batteries. At the same time, I want to have another wire coming off that supply that is connected directly to the motor, to basically do what its currently doing (basically jump starting the motor for 1-2 seconds). For this second wire (connected directly to the motor), I was thinking some sort of relay (no sure that's the right option) that is controlled by the dry socket to complete the circuit thus providing power to the motor for just 2-3 seconds to jump start the motor and to then allow the constant power to take over and finish the rotation.

    Does this make sense at all? I apologize for the rant, but I wanted to make sure the whole scenario was very clear.

    I'll answer any questions, I just need help to make this happen.

    Thank you so much!

    Here is a picture of the feeder:
    http://www.marinedepot.com/fish_food_eheim_feed-air_digital_auto_feeder-ap.html

    Video of feeder in action:

    http://www.youtube.com/watch?v=TeLG4wmbRCE
     
  2. james211

    Thread Starter Member

    May 29, 2012
    210
    2
    Nevermind, I found out some further info that makes this not possible. Back to square 1!
     
  3. elec_mech

    Senior Member

    Nov 12, 2008
    1,513
    193
    So what is the end goal? You currently have the fish feeder shown in the video and want to:
    a) Replace the batteries with a constant power source
    b) Manually control the dispenser through electronics instead of using the timer

    The first one is easy, just find a wallwart with the same voltage and a decent current rating. It would be a good idea to measure the current draw of the motor first to make sure you select a big enough wallwart.

    I'm confused by your second request. What is it you plan to use to send a signal to the feeder to dispense? Are you trying to control the feeder over the Internet, with another clock, etc.? Are you trying to get it to dispense more food at a time by running it longer?

    Either could be done using a MOSFET with a 555 timer. The MOSFET goes in series with one of the motor/power leads and is controlled by a 555 configured as a monostable which allows you to a) set how long you want the motor to spin for and b) control it with another signal.

    Would this do what you want?
     
  4. james211

    Thread Starter Member

    May 29, 2012
    210
    2
    My goal is to be able to trigger the feeder with my controller. Currently it works fine with the combo of AA batteries and the jump starter power from the 3.2 volt converter. I was hoping to some how avoid having two power sources but I think that's the only option.

    My other question is, right now I have 3-5 seconds of 3.2 volts going directly to the motor, could doing that and having direct power going to the battery terminals be bad? The jump starter source is only on for 3-5 seconds just to rotate the shaft enough to open the internal switch.
     
  5. elec_mech

    Senior Member

    Nov 12, 2008
    1,513
    193
    Could you post a sketch of how you've wired this? Is the 3.2V supply feeding your controller as well?

    That is not good. You could be damaging your batteries, your supply, and/or the circuit in the feeder. In the video, the user presses a button to force the feeder to work. Can you do that with yours? If yes, then you could replace that button with a relay or similar (maybe go to the controller's relay contacts directly depending on whether they are N.O. or N.C.). Then you could just replace the batteries and put the 3.2V supply across the battery contacts.

    What are you using to turn on the 3.2V to the motor for 3-5 seconds? A sketch or schematic would help immensely.
     
  6. james211

    Thread Starter Member

    May 29, 2012
    210
    2
    Currently the 3.2V supply to the feeder is delivering 3-5 seconds of power and being switched on by this,
    http://www.neptunesys.com/index.php?option=com_content&task=view&id=45&Itemid=40

    While the batteries are in the feeder, I put a jumper across the feed button and it did trigger the feeder. So what your saying is put a jumper across the buttons with a relay in the middle that would essentially make the contacts as though someone was pushing the button, correct? What type of a relay would this be?

    If that's the case then here is how I see it happening.

    **1-3.2V power source that provides constant power to the device.
    **1-Power source (not sure what voltage) that is plugged into the energy bar and wired to a relay which will be wired to the feed button contacts. When the energy bar outlet is turned out by the controller, it will in essence push the button and trigger the feeder, correct? How do I know if the controller's relays contacts are N.O. or N.C.?

    What type of relay?
    What type of power source?

    Going to try and do a schematic, but forgive me if its completely wrong. I'll append to this post shortly.
     
    Last edited: Jun 15, 2012
  7. elec_mech

    Senior Member

    Nov 12, 2008
    1,513
    193
    Okay, that helps.

    There are two ways of doing this right off the bat and I've included an attachment. Option A is the simplest assuming the controller you send in the last link a) is settable for 3-5 seconds and b) powers the 5V->3V supply.

    Option B assumes the controller sends a pulse, like 0.5 or 1 second long (to simulate a button press) to a 12VDC supply which then activates a 12VDC relay. Please ignore the 3-5 second pulse note on option B. The relay is then hooked in parallel with the feed button to simulate a button press. This assumes the feed button is normally open (N.O.), not normally closed (N.C.). If the latter, then you'll need a different relay.

    Hope this helps.
     
  8. james211

    Thread Starter Member

    May 29, 2012
    210
    2
    That worked perfectly! Thank you!

    Two questions.
    1. Where can I find dummy batteries, I'd prefer to use those so I can still use batteries if need be for some reason. I figure I can wire the 3.2V supply to the dummy batteries rather than solder right to the terminals.

    2. I'd like to use cable similar to cat5 cable to run the power and wire from the relay to the feeder. Can I use cat5? It would be carrying 3.2V for the power, and the other would just be from the relay to the switch.

    **If I can't use cat5 cable, do you know where I can find a 4 conductor wire that is cased similar to cat5?

    3. Any thoughts on where I can find inexpensive wall warts?
     
    Last edited: Jun 18, 2012
  9. elec_mech

    Senior Member

    Nov 12, 2008
    1,513
    193
    Cheapest but will take 1-2 weeks to receive: http://www.dealextreme.com/p/translucent-aaa-to-aa-battery-converter-case-8-pack-3657. You can drill some holes and solder to the terminals on the inside - note I haven't done this before with these, so I can't guarantee it will be easy (or 100% possible). The batteries are likely connected in series, so you only need to solder your power supply to one of the dummy positive tips and one to a negative tip. You'll need to determine which ones.

    Do you have any room inside the case of the feeder? If so, I'd putting something like this in: http://www.radioshack.com/product/index.jsp?productId=2102491. It should contain a switch which you can wire inline with the battery so that when a plug is inserted, the batteries are disconnected (thus avoiding damage and shorts) and when a plug is removed, the batteries power the feeder. This is also fits the most common size plug found on most wallwarts. However, if you need the mate: http://www.radioshack.com/product/index.jsp?productId=2103614.

    Alternately, you could open up the feeder and solder a couple of wires to the back of the battery input terminals and route a connector on the outside (you may need to drill a small hole to let the wire get outside the feeder enclosure), such as this: http://www.radioshack.com/product/index.jsp?productId=2102490. If you go this route, be extremely careful to only use either batteries or an external power supply - never have both connected.

    Voltage isn't a problem. Current is the only concern. If the CAT5 has 24AWG wire, then you should be okay. If I remember correctly, the relay needs just under 200mA on the coil and the motor shouldn't need much more. I'd just doubling all connections, i.e., uses two wires each for + power, - power, and each side of the relay to be safe. I assume you're just planning to use the cable itself and not the connectors, correct? If you're planning on using connectors, it will be difficult to fit jacks into small enclosures as they are designed as part of covers that go onto electrical boxes.

    A few sources:
    http://www.mpja.com/Plug-Supplies/products/37/

    http://www.allelectronics.com/make-a-store/category/480/Power-Supplies/1.html

    You can also check eBay. For cheap 5VDC, see if any family or friends have old/unused cellphone chargers. Almost all use 5VDC these days.
     
  10. james211

    Thread Starter Member

    May 29, 2012
    210
    2
    Awesome! Thank you for your help.
     
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