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Help with Water Pump

Discussion in 'General Electronics Chat' started by salty joe, Dec 30, 2011.

  1. colin55

    colin55 Well-Known Member

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    R3 will have to about 1k. Even though the FETs don't take any current, you don't want the voltage on the outputs to drop if both come on together.
    Chip takes less current when 1, 3, 11, 13 taken HIGH.
     
    Last edited: Jan 7, 2012
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  2. alec_t

    alec_t Well-Known Member Most Helpful Member

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    I take your point Colin, but simulation shows that the voltage drop is less with R3 = 3k3 than with R3 = 1k. That's because the 24V supply drop which occurs has less effect on the 12V supply with the higher resistance.
    Can you confirm that? Do you have some figures? I would agree if we were using TTL logic, or TTL-compatible logic (such as the 74HC chip in your circuit), but I was unaware there was any significant chip current difference in the case of CD4000 series logic (which is used here so that the FET gate voltage can be higher, to reduce switching time).
     
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  3. colin55

    colin55 Well-Known Member

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    With the 74C14 it doesn't matter if the inputs are HIGH or LOW. Just don't leave them floating. With some 4000 series the inputs need to be HIGH to take the least current.

    I take your point Colin, but simulation shows that the voltage drop is less with R3 = 3k3 than with R3 = 1k.

    That's faulty analysis.

    The impedance of the 24v line is much lower than the 12v line.
     
    Last edited: Jan 7, 2012
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  4. dave

    Dave New Member

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  5. ()blivion

    ()blivion Active Member

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    Salty Joe, Out of curiosity exactly what are you planing on using, or already are using to power these pumps? Is it going to be a power supply picked just for these pumps? Or is it something you have right now that just works for them? I'm particularly interested in the amperage rating, but the wattage will do fine. If you don't know just describe the type of power supply to us and anything it might say on it, should you already have one.

    Also... could the pumps possibly give you the power and flow you need if they are just run off 12v? Have you tried and tested this at all to see what happens? We could cut a few parts and reduce complexity of the circuit as a whole if we could design it to work off 12 volts from the start. 24 volts just barely exceeds the max voltage rating for a few of the parts and is the main reason the circuit needs a voltage regulator.

    Finally, (and this is a less than ideal proposal)... but could you possibly use two power supply's? Like a small 12v wall wart for the controller circuit and a beefy 24v supply for the pumps? This would eliminate the need for a regulator circuit in your controller but still give you the benefit of the full power out of your pumps.
     
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  6. salty joe

    salty joe Active Member

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    I don't have a power supply yet, anything that works, is durable and reasonably efficient is perfect in my book.

    I just ordered the pumps & they won't arrive for a couple weeks or so. These pumps come with a controller set up for 220, I have 110. Also, the controller that comes with this pump does not do what I need. I don't know what the pumps will do with 12V compared to 24V. If you think it would be worthwhile, I could run a 220 line and see. There's no way I want 220 anywhere the aquarium. BTW, there are two other choices for DC pumps that perform in a similar fashion that are set up for 110, but they cost in the range of $500 each!!! I need six pumps, I can't afford that.

    I'm up for hooking this thing up any way that works. I hope I have this right-I was going to get a 24V, minimum 6A wall wart/transformer.
     
    Last edited: Jan 8, 2012
  7. alec_t

    alec_t Well-Known Member Most Helpful Member

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    If each pump is rated 30W, that is likely be the continuous power and implies a steady current of ~1.3A. However, the start-up current will be considerably higher, perhaps 3A or more? So for 6 pumps you're looking at a supply which can handle say 18A briefly and 6 x 1.3 = ~8A continuously without being stressed. I doubt you'll find that in wall-wart form, but it should be readily obtainable.
     
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  8. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Can you link us to the pumps you ordered? so we can have a look.
     
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  9. ()blivion

    ()blivion Active Member

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    I agree 100% with all of this ^ ^ ^ ^.

    If you don't have a power supply picked out yet, there are some good, cheep, and easy to work with units on ebay. I just searched with the term "24v power supply", and organized it by "best match" to find good ones for this project.

    Make sure what ever you get is greater than 250 watts, or greater than 10 amps. I personally would aim for 20A or 480W myself. Units with fans built in are the best IMO. My only complaint with any of these units is that they are all way to open and exposed. This is needed for ventilation, but this also makes you more endanger of electrocution and fire should you accidentally dump your reef tanks *salt water* on it. Make sure your careful where you place your power supply and have all your stuff hooked up to safe outlets with the proper protections (GFCI outlets on their own 5~15 amp breaker). You also could and should spend the extra cash and get a waterproofed power supply for outdoor use. Your looking at spending more than $70 just for a power supply this way though. But your life and home is prolly worth more, am I right?

    Also, If you have to (If you use a smaller power supply) you can work around the high surge currents alec_t is talking about with a few fatty NTC resistors and maybe a tank capacitor. It's not ideal, but this can make the power supply not switch it's self off as soon as the pumps start. We can also come up with something else like an active soft start circuit if need be. But we will cross with that bridge when we come to it.
     
    Last edited: Jan 8, 2012
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  10. Reloadron

    Reloadron Well-Known Member Most Helpful Member

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    OK, my simple take, and correct me if I am off target is these are 30 Watt 24 Volt aquarium pumps. So we get about 1.25 amps per pump. Pumps of this type are more a circulating pump than a pump that does considerable work. If a tank sits several feet above the floor and the pumps on the floor, other than circulation the pumps do not do any real work, they simply move the salt water. I am guessing you are simulating a reef. So with 4 pumps running the current would be about maybe 5 amps. Allow a margine maybe a 7 amp power supply.

    I realize a 7 amp power supply does not take into consideration inrush current when the pumps start, however, I don't see it as a concern. Even if all 4 pumps were to start simultaneously, since they are circulatory pumps I don't see inrush current as an issue because of the type pumps they are. I don't see it as an issue that could not be solved using a capacitor at the power supply output beyond any internal capacitors to the power supply. Keeping in mind these pumps are not pushing a column of water uphill that is not being pushed downhill at start.

    As to the 120 / 240 volts. Without seeing what exactly comes in the box it becomes hard to call. If sans the actual pump power the controller mentioned draws little current then a simple small transformer might be a viable solution. Low power control transformers are inexpensive.

    Just about everything goes back to what's in the box. Colin & Alec have both posted really good timing circuits. A link to the actual this is what's ordered would be real nice about now.

    Just My Take
    Ron
     
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  11. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Can you link us to the pumps you ordered? so we can have a look.
     
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  12. ()blivion

    ()blivion Active Member

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    Any electric motor will have inrush current, even if it's shaft is not connected to any thing. So alec_t is right to at least consider it a potential factor. And I would say 3~5x the nominal current is a decent approximation.

    Now.... not that you were suggesting it or anything, but the issue is not whether the power supply will survive the momentary current surge, it's a matter of if it's going to be enough to trip any over current or under voltage protection the power supply might have. And as you and I stated, using an external cap would more than likely fix this issue. For the most extreme cases however, a few hefty NTC resistors or even an active soft start system may possibly be needed. Of course, using a transformer as you suggest would not have these necessity's by design.

    In any case, this problem as a whole is an easy one to fix with little effort.

    Next time the OP gets on I'm sure he will. Please be patient.
     
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  13. salty joe

    salty joe Active Member

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    http://www.ebay.com/itm/RESUN-WAVE-...316?pt=LH_DefaultDomain_0&hash=item5d31dd975c

    I will have 6 pumps total, but two of them will be seperate so I'll need a transformer hefty enough to drive four pumps and another transformer for the other two.

    ()blivion your points on safety are well taken. I ran three seperate circuits in the fish room and wired five GFIs in paralell per circuit. I had not considered a power source rated for outdoor use. I like that idea.

    Reloadron you are right about the pumps not lifting any water. Strictly circulation.

    Humidity will be an issue I have to deal with and sometimes it is bound to be high in the fish room. Is there something that can be applied to the circuit to protect against humidity? Would it be OK to pour epoxy over the circuit if the pots were not buried?
     
  14. ()blivion

    ()blivion Active Member

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    *************************************************************
    EDIT: Question removed do to it having been answered already.
    *************************************************************

    Maybe, I live in WA state, the humidity is over a billion % year round. It's rained pretty much every day since I joined this conversation. And I have plenty of exposed electronics, some even out in the rain. I would say just don't submerse it in water. From what I have seen light amounts of *Fresh water* is not a problem for most electronics. Things will eventually start to corrode from electrolysis though.

    Your salt water exposed environment changes the equation quite a bit though. Back when I had one the table that my fish tank was on keep getting wet in one spot, we thought we had a leek. Turned out that the bubbles from the air supply were causing enough spray to exit the tank and pool up on the table, yet was almost impossible to see with the naked eye. I fixed it with a better lid. If something like this happens in your salt water environment though you may have problems. The stupidest things can cause your electronics exposure to the salts.

    If your worried about it you can encase the whole thing in epoxy like you said. Or you could spray the guts of the whole project down with several coats of $1 acrylic clear coat spray paint. This is probably the cheapest conformal coating you can get. I have found as long as it's fresh, projects are still quite solderable even after sprayed with this stuff. Acetone takes it off really quick after it's dried too.
     
    Last edited: Jan 9, 2012
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  15. Reloadron

    Reloadron Well-Known Member Most Helpful Member

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    Wow, it's true. Pictures are worth a thousand words. Now I "get it". :)

    I was expecting little pumps and what we have are small motors with impeller propellers.

    OK, while the motors are clearly labeled 30 watts (1.3 amp) the individual wall warts are labeled In: 220 volts with an output that looks to be 24 VDC @ 1000 mA, so they only can deliver an amp max from the way I read them. That what others are seeing?

    The problem being things were designed for 220 VAC 50 Hz mains. Which, you mentioned early on. So we need a 120 VAC / 24 VDC supply capable of supplying four pumps. Let me look around today in my odds and ends buckets. I'll get back to the thread.

    As to a little weather proofing? I agree it should not be a big problem. There are ways to address that.

    Ron
     
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  16. alec_t

    alec_t Well-Known Member Most Helpful Member

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    If adjusting the timing of the pumps is a one-off set-and-forget operation then the pots can be trimmers mounted on the circuit board and once set can be waterproofed with a conformal coating as mentioned above. But if adjustment is likely to be done regularly the pots need to be mounted off-board and connected using screened cable. The pots then should be sealed types.
     
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  17. ()blivion

    ()blivion Active Member

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    :facepalm: I totally forgot that he had said this before... I need to pay more attention. I'll edit my post.
     
  18. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    salty, Sorry but I have to ask. Why dont you use the timers that come with the pumps and just change the transformers to 110VAC input ones? or just run 220VAC ones off 220 volts? You will have the same amount of safty thru the transformers ether way.
     
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  19. salty joe

    salty joe Active Member

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    I don't want to run the supplied controllers for a few reasons. They don't have the kind of control I am interested in. I'm looking for the pumps to either run wide open or not at all and to be able to adjust the on time as well as the off time. Plus I am leary of running a 220 line anywhere near an aquarium. I've never seen a GFI for 220, there probably is such a thing, but what do they cost?
     
  20. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    It would have to be a GFI circuit breaker in your box. Cost would be a little more than a regular breaker, well maybe a lot more.
    You could put them well away from the aquarium and just run the 24 volt lines to the aquarium.
    They may be slightly more energy efficient running of 220 volts.
    Its all up to you just seems a wast to not use the stuff that came with them.
    If it was me I would use the 220 volt transformers and modify the timer that comes with it.
     
  21. ()blivion

    ()blivion Active Member

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    Chances are the provided power supply's are SMPS bricks rather than just transformers. So modifying them for 110 is probably not impractical. Most universal SMPS's usually just use a simple voltage doubler for doing 110 volts anyway. I'd just assume go with the flow of the OP though when I try and help. Other wise I would have suggested doing it with MCU's as that's what I would do. Or modify the units that came with it to fit my needs assuming I didn't just use them the way they were from the start. But then again, I don't really have a problem with people doing things "the hard way". Gives me something to do.

    As for running it off 220... I agree that metric voltage is not the big bad scary monster that us Americans think it is. But then whats wrong with 110? Both will kill you dead if your not careful and well protected. And yes, they do make GFCI for 220 outlets and breakers, and no... they are not really cheep.

    Anyway... Ima go make a sandwich now.....
     
    Last edited: Jan 9, 2012

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