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Help with Water Pump

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

  1. salty joe

    salty joe Active Member

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  2. alec_t

    alec_t Well-Known Member Most Helpful Member

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  3. salty joe

    salty joe Active Member

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  4. dave

    Dave New Member

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  5. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Sure. The pumps are running from 24V at say 1.5A. Allowing for higher current at switch-on and a good voltage margin, I'd try to source an NMOS FET with a voltage rating of 40V or more and an R_on rating less than 30mOhm or so. Because the FET is only switched occasionally (not at kHz rates!) the gate charge spec isn't critical.
     
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  6. salty joe

    salty joe Active Member

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  7. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Post deleted.
     
    Last edited: Jan 21, 2012
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  8. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Rd = 8 Ohms?? I'm not familiar with Rd. The IRF3205 spec has R_on = 8 milliOhms. At 1.3A that means the FET will be dissipating <20mW continuously so a heatsink won't be needed. So, yes it will be fine. Bear in mind that the mounting tag of the FET package is also the drain connection!
     
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  9. salty joe

    salty joe Active Member

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    I meant to put this. Rds (On): 8m OHM It is from the linked IRF3205. I thought it might be a slightly different way to write R_on rating less than 30mOhm or so. I need to be more careful when I copy something.

    Anyway, I'm not at all familiar with this stuff. I very much appreciate you helping me get the right parts. Right now, my main concern is collecting everything to build this controller.

    When you say drain connection , is that ground?
     
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  10. alec_t

    alec_t Well-Known Member Most Helpful Member

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    No. A FET has a gate, a drain and a source. For an NMOS FET (e.g. your IRF3205) the source connects to ground (it's the source of electrons!), the drain connects to the load (pump), and the gate is the control input which must always be at a voltage >= ground.

    BTW, Salty, whereabouts in the world are you?
     
    Last edited: Jan 22, 2012
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  11. salty joe

    salty joe Active Member

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    I hate to admit it but this is still somewhat cunfusing. I'm hoping that when I start assembly it becomes a little more clear. I am aware that a lot of these parts must be only connected a certain way and I will take enough time to get it right. I have everything ordered except for the transformer, I'm still looking for that.

    I am in Medina, Ohio, USA-cold winters and hot summers.
     
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  12. ()blivion

    ()blivion Active Member

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    The first post has his real name and location.

    We know, we're here to help. On that note, I think it would be better if some one made you a "project layout" or "construction diagram" rather than a schematic. It would basically be a picture of the front and back of the board with parts on it detailing where to put the connections and such. There is a program out there for making stripboard layouts if I'm remembering correctly. Don't know whats it's called though, or if it's even freeware. Maybe when I'm not busy (Lazy) I'll Google it and try to make you something. You want all four-six "Pump channels" on the one single board right? Or did we decide that you were driving the pumps in pairs? Also what board did you finally decide on getting?

    Anyway, I'm only saying that I *COULD* do this if you want it. So don't get your hopes up that I *WILL*, cuz I'm pretty freaking busy (lazy). Then again, some one else might do it for you instead. But if you really want it, I will definitely think about doing it myself.

    Lastly, and this is entirely optional. Making a BIG post here detailing how you want the project built in it's entirety for the whole class would be golden. Like the schematic you like, the parts you have, the parts you don't have, points you need the most help with, what your idea for a box is, your powersupply, ect ect. This will help keep every one on the same page and we won't have to keep rereading this entire thread with a decoder ring putting together the pieces to figure out what you decided to do and how best to help you. Then again, this would just be helpful in my opinion.

    Does anyone disagree?
     
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  13. salty joe

    salty joe Active Member

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    I am working from the schematic in post 99. I am looking to control four pumps independantly.

    Today I ordered all the parts on the schematic plus a handful of 10 ohm resistors. " it would be advisable to connect a respective 10 Ohm resistor (not shown) close to the gate terminal of each FET to damp any unwanted oscillation. I.e. each 10 Ohm is connected in series from its inverter to its FET gate."(quote from Alec)

    1N5822 was substituted for MBRS340 and IRF3205 was substituted for IRFH5207.

    14 pin DIL sockets are on the way.

    This is the prototyping board I ordered. Some of the boards were listed as stripboards. This was not listed as a stripboard so I'm assuming I will have to make every connection manually. Hopefully, that's the way it is.

    http://www.ebay.com/itm/2-x-Prototy...914?pt=LH_DefaultDomain_0&hash=item3a6a0dc6c2

    I don't have a power supply yet. Still digging for that.

    I was going to deal with a metal box after I see what size the controller ends up being.
     
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  14. salty joe

    salty joe Active Member

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  15. salty joe

    salty joe Active Member

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  16. ()blivion

    ()blivion Active Member

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    Those both look a good fit for this project. They are almost identical to each other, so you will likely be able to work with either one just fine. The one that is "buy it now" is the one I would get personally. Both basically start at the same price but the one is just a hair more powerful. But considering they are so close to each other, the difference in part tolerance makes them basically the same. So it doesn't really matter.

    Here is another unit that's exactly the same but for a little bit less money + free shipping.
    http://www.ebay.com/itm/DC-24V-15A-...045?pt=LH_DefaultDomain_0&hash=item2314c0154d

    The prototyping boards you ordered are good, and the fact that you got two is prolly a good move in case you make a mistake. However I just realized if anyone makes you a layout with any average Veroboard software it's not really going to work for these boards. So I guess I'll have to make a layout for you after all. No worries, I'll take care of it.
     
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  17. ()blivion

    ()blivion Active Member

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    Question to Salty joe:

    The IRFH5207 ????... Isn't that a surface mount part? I can't find it in through hole anyway. If it is surface mount "B" package, then your guna have a REAL HARD TIME putting that on this kind of a board, or any prototyping board for that mater. It's not impossible though... just not advised. If the pads line up with the board dots perfectly, you can put them on the copper side easy enough. It's guna be trick to solder for a newbie though. You'll have to use improper etiquette and tin/plate both joints first, then reheat and press things together. It will work but the solder Nazis's will prolly hang you.
     
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  18. alec_t

    alec_t Well-Known Member Most Helpful Member

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    @()blivion
    The OP has opted for the IRF3205 FET. It's a T0220 part.

    @SaltyJoe
    As stated above, those power supplies seem fine.
    Can't tell from the pic if the protoboard is stripboard or point-to-point; but either will do. If it's stripboard then a 3mm twist-drill hand held can be used to remove copper track where necessary. Simple.
     
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  19. ()blivion

    ()blivion Active Member

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    Ah... good to hear, The schematic on post 99 and his recent posts suggested otherwise. I'm making the layout based on TO-220 parts. Do you know what other parts hes getting? Specifically all the parts packaging that isn't obvious is the information I'm after. That would be useful information to make the layout more accurate for him. Otherwise I'm just guna guess and wing it the best I can. I can change it as time goes on.
     
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  20. salty joe

    salty joe Active Member

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    Here is a copy of what I ordered yesterday. Thanks all.

    15 x 1N5822 5822 3A 40V SCHOTTKY DIODE (250481310203)

    Paid on Jan-22-12
    Price: $1.50, Qty: 1 $1.50
    Estimated delivery: February 07 - February 21, 2012 Standard Shipping $2.00



    50 x Resistors 10 Ohms OHM 1/4W 5% Carbon Film (250840202018)

    Paid on Jan-22-12
    Price: $0.99, Qty: 1 $0.99
    Estimated delivery: 12-21 business days* Economy Shipping from outside US FREE



    50 x 1N4148 Switching Signal Diode - Free Shipping (250857538753)

    Paid on Jan-22-12
    Price: $1.49, Qty: 1 $1.49
    Estimated delivery: 12-21 business days* Shipped with item above --



    10 x 10uF 25V 105C Radial Electrolytic Capacitor 5x11 (250861566468)

    Paid on Jan-22-12
    Price: $0.99, Qty: 1 $0.99
    Estimated delivery: 12-21 business days* Shipped with item above --



    5 x 14 pin DIP IC Sockets Adaptor Solder Type (250863160325)

    Paid on Jan-22-12
    Price: $0.99, Qty: 1 $0.99
    Estimated delivery: 12-21 business days* Shipped with item above --



    10 x CD40106 CD40106BE 40106 HEX SCHMITT TRIGGER IC (250865624498)

    Paid on Jan-22-12
    Price: $3.99, Qty: 1 $3.99
    Estimated delivery: 12-21 business days* Shipped with item above --



    5 x L7812CV LM7812 L7812 Voltage Regulator IC + 12V (250879158263)

    Paid on Jan-22-12
    Price: $1.49, Qty: 1 $1.49
    Estimated delivery: 12-21 business days* Shipped with item above --



    2 x Prototyping PCB Circuit Board 142x74mm (250887390914)

    Paid on Jan-22-12
    Price: $2.79, Qty: 1 $2.79
    Estimated delivery: 12-21 business days* Shipped with item above --



    500K OHM Logarithmic Taper Potentiometer Pot A500K (260803628248)

    Paid on Jan-22-12
    Price: $0.99, Qty: 4 $3.96
    Estimated delivery: 12-21 business days* Shipped with item above --



    10 x 100uF 50V 105C Radial Electrolytic Capacitor 8x11 (260807171978)

    Paid on Jan-22-12
    Price: $0.99, Qty: 1 $0.99
    Estimated delivery: 12-21 business days* Shipped with item above --



    5 x IRF3205 MOSFET N-CHANNEL 55V 110A - Free Shipping (260829032036)

    Paid on Jan-22-12
    Price: $4.59, Qty: 1 $4.59
    Estimated delivery: 12-21 business days* Shipped with item above --



    10 x 0.1uF 100V 5% Polyester Film Box Type Capacitor (260841764609)

    Paid on Jan-22-12
    Price: $1.89, Qty: 1 $1.89
    Estimated delivery: 12-21 business days* Shipped with item above --



    2 x 1M OHM Linear Taper Potentiometer Pot B1M 1MB FREE SHIPPING (280779248369)

    Paid on Jan-22-12
    Price: $1.89, Qty: 2 $3.78
    Estimated delivery: 12-21 business days* Shipped with item above --
     
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  21. salty joe

    salty joe Active Member

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    I thought all the parts would copy as links. If you want links, let me know.

    I just ordered that power supply you linked ()blivion. Thank you!
     
    Last edited: Jan 23, 2012
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