Group Actions
Engagement
  • Author Author: sasquatch84
  • Date Created: Date Created
  • Views 1157 views
  • Likes 3 likes
  • Comments 7 comments
Related
Recommended

Let's try this again

sasquatch84

image

Ok, so I grabbed another Nano and got it all wired up like the last one.  I soldered a diode directly onto the solenoid valve contacts.  Maybe I should have just put it on the circuit board?  Anyone think I should?  Let me know. 

Also, I tried my hand at making a schematic.  Let me know if this makes sense.

image

I'm not plugging anything in until I get at least a little feedback on here. (gulp!)

Parents

  • Continuing: The diode soldered to the solenoid is actually a good idea as it deals with the counter EMF right where is occurs. Here is an example of part of your schematic. My schematic assumes that the output of the Arduino can handle the current demands of the relay (it probably can't) and that the Arduino will output a HIGH to energize the relay. I remember that you have a relay board which probably will take care of drawing a very small current from the Arduino and use the main power to the relay board to actually energize the relay coil. I have also shown a diode for the relay coil but the relay board that you have is a commercial product and they would have built in diodes to protect their own design so you probably do not need to worry about this. You can use the diode on the solenoid as it is soldered just switch the polarity of your hookup wires so that the plus wire goes to the banded end of the diode. To enlarge my schematic or any picture in these postings just click on it.

     

    image

     

    John

Comment

  • Continuing: The diode soldered to the solenoid is actually a good idea as it deals with the counter EMF right where is occurs. Here is an example of part of your schematic. My schematic assumes that the output of the Arduino can handle the current demands of the relay (it probably can't) and that the Arduino will output a HIGH to energize the relay. I remember that you have a relay board which probably will take care of drawing a very small current from the Arduino and use the main power to the relay board to actually energize the relay coil. I have also shown a diode for the relay coil but the relay board that you have is a commercial product and they would have built in diodes to protect their own design so you probably do not need to worry about this. You can use the diode on the solenoid as it is soldered just switch the polarity of your hookup wires so that the plus wire goes to the banded end of the diode. To enlarge my schematic or any picture in these postings just click on it.

     

    image

     

    John

Children
  • in reply to jw0752

    Awesome!  Yeah, I wasn't sure which way was which when making the schematic, but in reality I knew the striped side of the diode was supposed to go in the positive side to make it reversed like you said to.  I looked into all that stuff today and I really learned a lot.  Thanks for all the help so far.

    I never tried the solenoid valve yet, but when I plugged in the arduino to my computer it was really heating up A LOT so I decided to go with one of my very first ideas and put in a 7805 circuit to run the vcc for the relay and attach it to the 5v pin on the Nano.  I just hate heat. 

    Does this seem right or should I just use the 7805 to power the relay and then just use the regular 12volt for the Nano?

    Also, I have the negative side for the Solenoid valve running through the relay, not the positive side.  Does this matter at all?

  • in reply to jw0752

    Perhaps one downside to soldering the diode directly to the solenoid though is that if someone (especially a third party) has to replace the valve at a later point in time, then they may not realise that they have to add the diode to the new replacement solenoid.

  • in reply to sasquatch84

    Hi Clinton,

    Arduino over-heating is due to the power dissipated by the internal voltage regulator. Some of the heat comes from stepping down from 12v to 5v and the rest from excessive current requested by the Arduino board itself and for driving its output pins (powering the relay from the 5V pin, for instance). In addition, if you have appreciable ripple on your 12V power supply, the excess voltage would put even more strain on the Arduino internal regulator. Considering you have quite an inductive load attached to this supply (your solenoid and the relay), even with the flyback diodes, I would too decouple Arduino from the 12V line. Your choice of using a 7805 to step down the 12V line and power both the Arduino 5V pin and the relay is fine, as the 7805 can provide enough current to satisfy the needs of both. But if you got another spare 7805 lying around, and want to be a little overzealous in eliminating risk (like I am image), you could go a step further and use it to power the relay using a separate line coming from the 12V supply rather than using the 5V pin of the Nano. For the solenoid connection to the relay, it doesn't really matter as they are connected in series (just make sure the rest of the connections follow the choice you made).

  • in reply to sasquatch84

    Thank you to for stepping in with some great advice. I am 2 hours later that Clinton and I got tired and went to bed before we could finish last night. If you really don't like heat get one of these to use in place of the 7805.

     

    http://www.newark.com/recom-power/r-78e5-0-1-0/dc-dc-converter-5w-5v-1a-sip/dp/83X9336?ost=R-78E5.0-1.0&scope=partnumberlookahead&exaMfpn=true&searchref=searchlookahead&searchView=table&iscrfnonsku=false&ddkey=http%3Aen-US%2FElement14_US%2Fw%2Fsearch

     

    It is a little DC to DC converter that has about 90% efficiency (almost no heat) and doesn't waste power like the 7805 does. It is about the same size as the 7805 and has the same pin out compatibility with the 7805. They are more expensive but in my opinion worth the extra cost.

     

    I would keep the diode on the solenoid since you have already installed it. Electronically it is the best place for it but has also made a good point about someone other than you not knowing that a diode needs to be installed on a replacement. Personally I would use the same power supply for the Nano and the Relay board. There is no reason they will not work fine on the same supply as they have been engineered to work together. If the relay board runs on 5 volts though, I would not draw its power from the Nano's 5 volt supply as I doubt that the little regulator on the Nano is designed to support much more than the Nano itself.

     

    Whether you put the relay contacts for the solenoid on the supply side or the ground side of the circuit is strictly your preference. I usually put the switches on the supply side but that comes from working with mains power where I did not want the load to have lethal voltage applied when the load was supposedly turned off. Since you are dealing with 12 volts DC that is floating with respect to any earth ground this is not a issue for you.

     

    John

  • in reply to jw0752

    As always, your input is invaluable.  Bit since I need this thing working today before I go to work in camp for an indeterminate period of time, the 7805 will have to do.  My strawberries need water!  I'll be posting a video of this thing working shortly. Hopefully...:/