12v dc pump circuit

I have a 12vdc 110W pump that I’m attempting to turn on and off. My original plan has me using a MOSFET4 board, which is already rated to run up to 25amp and has diodes in place to prevent voltage leaking. when I go to turn on the pump, the pump motor is making noise, but not getting the power needed to fully engage.

I’ve thought about using an SSR for this instead, but I can only find SSR’s that are activate with ac power, not dc. I’ve heard of using voltage interrupters, but I know nothing about circuit design at this point and while I’m learning, this is above my ability to understand at the moment.

can someone point me in the right direction for powering this pump.

midiean:
I have a 12vdc 110W pump that I'm attempting to turn on and off. My original plan has me using a MOSFET4 board, which is already rated to run up to 25amp and has diodes in place to prevent voltage leaking. when I go to turn on the pump, the pump motor is making noise, but not getting the power needed to fully engage.

I've thought about using an SSR for this instead, but I can only find SSR's that are activate with ac power, not dc. I've heard of using voltage interrupters, but I know nothing about circuit design at this point and while I'm learning, this is above my ability to understand at the moment.

can someone point me in the right direction for powering this pump.

Well, it would be nice if you supplied a link to the "MOSFET4 board" so we're sure to be on the same page. And, a diagram of how you hooked everything up would also help. As it is, it's very hard to diagnose, since there are so many unknowns. :wink:

You can just do a drawing on paper, of your setup (make it as clear as you possibly can) then photograph it, or scan it, etc -- then post the photo. Unless, of course, you have some sort of CAD software [i.e. "Schematic Capture"]. Try to avoid Fritzing, though. You might try:

Hi,

A 110W DC pump will draw ~ 2.5 time the running current on startup. Is your supply capable of such a current?

Just for your information, DC SSRs do exist. I have one in a box of real AC SSRs. The DC SSR is just an opto-isolator and a transistor to switch on-off. All were pulled from a piece of commercial equipment.

Paul

would an opto-isolator need a heat sinc? there's a significant amp draw during operation... I accidentally melted a mosfet in my initial testing lol

I really am noobish at this. Reading as I can to try and make sense of what it is I'm doing.

An opto-isolator does not need a heat sink any more than a single LED needs a heat sink if it is being low powered. the pass transistor that the opto-isolator turns on-off may REQUIRE an heat sink.

Paul

midiean:
would an opto-isolator need a heat sinc? there's a significant amp draw during operation... I accidentally melted a mosfet in my initial testing lol

I really am noobish at this. Reading as I can to try and make sense of what it is I'm doing.

Opto-isolators are, usually, not meant to serve as "drivers". Their purpose is to isolate. Then, if needed, the opto feeds into a driver of some sort. So, no. An opto rarely needs a heatsink, if properly used.

I've melted a few myself :wink: The smoke smells like wet leather, to me.
Did you want help with your MOSFET issue? If so, particular's please.

I don’t currently have it hooked up. using the lights to test timing code which functions properly. power is supplied from a 12v deep cycle battery for powered wheelchairs

https://www.google.ca/search?q=car+starter+relay&tbm=isch&tbs=rimg:CQ879_1rBfY-sIjix1XJanbAGEvxm_1h8nsrrVC2YVsUiGdClWgmnGRvM8Qu83wl2urZd91rY_1zbGQ2JASWk7ovxlhXCoSCbHVclqdsAYSEY1QcWCzJ4vEKhIJ_1Gb-HyeyutURPscKG0YhmqsqEgkLZhWxSIZ0KRHQHuhfuGZ2iCoSCVaCacZG8zxCEdp_1BhKusk45KhIJ7zfCXa6tl30RUzBH7a2C5ZQqEgnWtj_1NsZDYkBFL7Lj7efCYxyoSCRJaTui_1GWFcEV_15Ze5Er7ea&tbo=u&sa=X&ved=2ahUKEwiQi6D25uzaAhXhzIMKHRYLB9QQ9C96BAgBEBs&biw=1440&bih=787&dpr=1

?

Ted, is that module capable of switching using a low voltage signal? those terminals look a little big for arduino to provide the power to engage the switching mechanism. Just going on visual representation. those look like their ready for 16aug wire.

Here's one of many, can't attest to quality but I would buy one of the add on heat sinks and thermal paste.
https://www.amazon.com/SODIAL-Solid-State-3-32VDC-5-60VDC/dp/B00IIDYHTG/ref=sr_1_8?ie=UTF8&qid=1525470266&sr=8-8&keywords=DC+ssr

that's what I need!!

OP should have mentioned in post#0 that this thread is a continuation from this one.

Leo..

I seriously doubt that Amazon SSR would withstand the starting current inrush, I always derate Chinese parts by 50% which gives you a relay that will probably fail on the first motor start.

The real problem with these inexpensive components is that there are no specifications. Sure, it says says 25 amps but for how long? With or without a heatsink? A basic spec like the voltage drop across the part at 10 amps and 20 amps of current would allow you to calculate how much heat will be generated - but no, you’re left to guess because the specs are probably so bad that people that understand the importance of those missing specifications would never buy the stuff.

The usual Mosfet 4 boards like this:

Newegg mosfet4

Cannot handle any current. They use IRF540 or other devices that do not fully turn on with 5 volts input. They are not logic level mosfets. Big problem.

The relay that Ted posted is certainly a possibility but only you are just turning the pump on and off, no speed control. So, is it on-off only? How may times per minute? Per hour? Per day? That matters a lot with a mechanical relay.

Speed control with PWM will require a proper logic level mosfet.

midiean:
Ted, is that module capable of switching using a low voltage signal? those terminals look a little big for arduino to provide the power to engage the switching mechanism. Just going on visual representation. those look like their ready for 16aug wire.

Add mosfet to control relay

avr_fred:
They use IRF540 or other devices that do not fully turn on with 5 volts input. They are not logic level mosfets. Big problem.

Not a problem.
That board uses optocouplers between Arduino and mosfets.
The mosfets gates are driven by the (12volt) supply on the mosfet/load side.

Only thing is the not_so_low Rds(on) of those mosfets.
Leo..

Wawa:
Not a problem.
That board uses optocouplers between Arduino and mosfets.
The mosfets gates are driven by the (12volt) supply on the mosfet/load side.

Only thing is the not_so_low Rds(on) of those mosfets.
Leo..

Right you are, thank you for the education. I had only used the single device boards that have no opto’s and I did not see the single dip package opto for what it really was. With some more investigation, I see that there are other 4 channel boards with individual optos which makes it obvious.

Low Rds(on), supply quality and wire/pc trace resistance in general at 12 amps can be problematic. OP has not stated what the measured voltage across the motor is in operation.

Leo, it's related in that it's part of the same project, but that was a coding issue that has since been resolved and evolved into better code. I also blew out the mosfet on channel 1... ooops

voltage across the motor is 12v. The pump will turn on every 2 minutes for 30 seconds. There is currently a 2x3" aluminum heat sync on the mosfets.

Thank ya'll so much for your help with this project

Hi,

I also blew out the mosfet on channel 1... ooops

Place a fuse in the battery power line, before you set fire to your self and your project.

Use a lamp as your load until you get it right, and fit a fuse size fitting the lamp.

Tom.... :slight_smile:

TomGeorge:
Place a fuse in the battery power line, before you set fire to your self and your project.

aw come on.. where's your sense of adventure lol

thank you for the tip, Tom. It is definitely a good idea, considering the whole thing about water and electricity not generally getting along..