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Post by lollygagger on Nov 29, 2019 9:08:56 GMT
Morning. Still messing with my heating... Tell me about PWM spped controllers for a 12v pump please. I see lots for sale, they are typically rated at 12-40v. Will that work same on lower voltage? Or do I need to find one that's max is 12-13v? Problem being (from a quick look) that the lower voltage ones are also low amp rated, typically 1A, will that be ok? The object is to slow the pump so it's more like convection speed i.e. vey slow (and quiet and low power consumption). Sorry for being so thick.
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Post by Telemachus on Nov 29, 2019 9:41:38 GMT
You need to provide information about the pump being used and the specific device you propose to use. If the pump is a brushless type it means the motor speed is controlled electronically. A chunk of electronics creates a rotating magnetic field at a certain speed, and the magnetic rotor follows this rotation. So it can be that reducing the voltage by means of PWM or whatever, simply reduces the magnetic field strength hence maximum torque, and may mean that the motor either runs or stalls, with not much in between.
Other designs of circuit take account of a varying input voltage and electronically slow the rotation of the magnetic field at lower voltages. so there is less torque required to run the motor. They may also be able to maintain the current in the rotating field magnets at a lower voltage to reduce the tendency to stall.
What this all means is that a brushless pump may or may not respond well to PWM, according to how it’s designed. This is why I suggested you use the Solarproject pump since it is known to work well with variable voltage /PWM. But IIRC you decided to get a different pump.
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Post by JohnV on Nov 29, 2019 9:43:25 GMT
in a nutshell
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Post by peterboat on Nov 29, 2019 9:44:26 GMT
I have a couple of PWM speed controllers, they are both voltage ranged one is 24-36 volts and the other is 48-72 volts. Ok these are big units but both work at the lower voltages ok, so as they only control the voltage that is coming in and send it out in little pulses growing to continues voltage I think all should be good, having said that both my motors are brushed motors, big ones of course for driving the boat
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Post by lollygagger on Nov 29, 2019 9:57:17 GMT
I got the particular pump on a recommendation in a thread somewhere. The writer stated he'd controlled it with a cheap maplin pwm controller and provided a link that's now dead. So I know it will work, but not the details of that pwm controller other than it was a tenner, rated at 10A and he had a 2A fuse.
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Post by Telemachus on Nov 29, 2019 10:16:35 GMT
I got the particular pump on a recommendation in a thread somewhere. The writer stated he'd controlled it with a cheap maplin pwm controller and provided a link that's now dead. So I know it will work, but not the details of that pwm controller other than it was a tenner, rated at 10A and he had a 2A fuse. So which PWM controller are you now thinking of getting? What is the power or current rating of the pump?
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Post by Deleted on Nov 29, 2019 10:27:22 GMT
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Post by lollygagger on Nov 29, 2019 10:55:43 GMT
I got the particular pump on a recommendation in a thread somewhere. The writer stated he'd controlled it with a cheap maplin pwm controller and provided a link that's now dead. So I know it will work, but not the details of that pwm controller other than it was a tenner, rated at 10A and he had a 2A fuse. So which PWM controller are you now thinking of getting? What is the power or current rating of the pump? I don't know which controller, that's what the thread is for. Current rating at full chat is about 2-3A IIRC.
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Post by lollygagger on Nov 29, 2019 10:57:14 GMT
I have a couple of PWM speed controllers, they are both voltage ranged one is 24-36 volts and the other is 48-72 volts. Ok these are big units but both work at the lower voltages ok, so as they only control the voltage that is coming in and send it out in little pulses growing to continues voltage I think all should be good, having said that both my motors are brushed motors, big ones of course for driving the boat Thanks for answering the voltage rating question. Sounds like a 10A 12-48v for example would work.
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Post by Deleted on Nov 29, 2019 12:07:33 GMT
So which PWM controller are you now thinking of getting? What is the power or current rating of the pump? I don't know which controller, that's what the thread is for. Current rating at full chat is about 2-3A IIRC. That's a hell of a lot of power for a heating pump to draw.
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Post by lollygagger on Nov 29, 2019 14:04:30 GMT
I don't know which controller, that's what the thread is for. Current rating at full chat is about 2-3A IIRC. That's a hell of a lot of power for a heating pump to draw. I'm only guessing and it's 25l/min full on which is at least 3-4x fast as I need so in reality fingers crossed it'll be under 1a and definitely less than the webasto pump.
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Post by lollygagger on Nov 29, 2019 14:15:31 GMT
I don't know which controller, that's what the thread is for. Current rating at full chat is about 2-3A IIRC. That's a hell of a lot of power for a heating pump to draw. I over egged it, max current 1.3a
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Post by Deleted on Nov 29, 2019 18:27:10 GMT
I think I still have in my spares/junk box a device that uses a 555timer to slow a pump to half speed by pulsing the 12v. I have no use for it so for postage you can have it.
It is boxed and has a bypass switch when you need full power just sits in the feed to the pump.
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Post by lollygagger on Nov 30, 2019 8:11:51 GMT
I think I still have in my spares/junk box a device that uses a 555timer to slow a pump to half speed by pulsing the 12v. I have no use for it so for postage you can have it. It is boxed and has a bypass switch when you need full power just sits in the feed to the pump. Very kind of you, but I think I need something more variable.
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Post by Deleted on Nov 30, 2019 18:41:13 GMT
I think I still have in my spares/junk box a device that uses a 555timer to slow a pump to half speed by pulsing the 12v. I have no use for it so for postage you can have it. It is boxed and has a bypass switch when you need full power just sits in the feed to the pump. Very kind of you, but I think I need something more variable. Ok it was designed by a clever old friend of mine to reduce noise overnight on the pumped system on his boat, worked so well I asked for one but never got round to fitting it as I changed my boat.
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