On Friday, May 19, 2017 at 10:48:44 AM UTC-7, default wrote:
...
> >I already breadboarded it. I put a 270 ohm resistor (calculated from V=
=3DIR, with I set to the max safe current the Arduino could put out... I fo=
rget exactly what it was, and V set to 5V) between an output PWM of the Ard=
uino to the gate of an IRLZ34NPbF mosfet, and put one of these pumps betwee=
n +18V and the drain:
> >
> >I rather doubt that 80 mA figure; I'll have to measure it one of these d=
ays.
> >
> >My Arduino program displays the current power setting (0-100%) and if I,=
for example, send a "6" followed by Enter to the serial port, the Arduino =
sets the PWM at 60% power. The C code is somewhat laughable but I can post=
it if you really want.
> >
> >It works fairly well, but I noticed I had to put a heatsink on the MOSFE=
T, which had me wondering why.
> >
> >Oh! I put an SB140 schottky in parallel with the motor.
> >
> >Michael
>=20
> I'd doubt the 80 mils too. They don't give the conditions, like speed
> and back-pressure. Peristaltic pumps aren't known for their
> free-spinning characteristics, they are better suited for intermittent
> use (especially when directly driven). If the tubing isn't silicon
> tubing I'd recommend a change because the energy used to pinch the
> tubing is waste. (and I don't ever remember seeing any peristaltic
> with a direct drive, they always used gearboxes, even the ones driven
> with stepper motors)
>=20
> Motor current would be worth checking.
>=20
> I worked in a pharmaceutical chemistry lab doing electronic and
> electromechanical design.
>=20
> I take it the Arduino is basically just chopping the power to the pump
> motor? No inductors or filter caps involved? What frequency are you
> chopping power at? Have you looked at the waveforms with a scope?
I think it's either around 400 or 900 Hz, and nope I have no scope.
=20
> As for current limiting to the gate drive, that may not be necessary
> or desirable. The gate is essentially a capacitor. (of 880 pico
> farads in this case) The current is just necessary for a brief time
> to charge and discharge the gate. Do you have any idea what the peak
> current the Arduino chip can sink and source? If you have 18 Volts to
> play with it may be better to just drive the gate with a higher
> voltage (but absolute max for that part is 16 volts...)
>=20
> A scope might tell you what is going on to cause it to heat...
> I designed a variable speed (large) fan for my last tower computer.
> The specs on the brushless fan said it was 500 MA at 12 V and the
> mosfet was toggling at 15 KHZ and ran cool, with no heat sink. But
> then I wasn't using straight pwm and driving a brushed motor either, I
> was using it as a switching mode power supply and sending pure DC to
> the fan motor, except on the highest setting, then it was just turning
> on the mosfet with no chopping.
>
> My drive circuit was a single ended npn transistor, but only because I
> started out using pwm and a BJT transistor. (it turned out that the
> fan didn't like that; pulses from the drive would alias with the
> pulses to the fan coils) When I changed the programming for smooth DC
> (added an inductor diode and filter cap) and switched to a mosfet I
> just left the transistor in the circuit. (too lazy to rewire the
> perf-board I was using, and 12V meant there was no need for a logic
> level device)
Brushless fan... there's a controller board in there too. Seems kind of str=
ange when you think about it, PWMing the power to a brushless fan which wil=
l also have its controller board, Hall sensors, etc. buried under the fan b=
lade hub. Ceramic iron magnets too... and how do I know this? I somehow m=
anaged to corrode one, and decided to take it apart :p
Michael
Reply by default●May 19, 20172017-05-19
On Fri, 19 May 2017 08:30:22 -0700 (PDT), mrdarrett@gmail.com wrote:
>On Friday, May 19, 2017 at 4:13:22 AM UTC-7, default wrote:
>> On Thu, 18 May 2017 09:36:07 -0500, amdx <nojunk@knology.net> wrote:
>>
>> >On 5/15/2017 10:33 AM, mrdarrett@gmail.com wrote:
>> >> Hello,
>> >>
>> >> I've discovered logic-level mosfets, and am using an Arduino to drive a small 12VDC (about an amp or so) pump motor with PWM, using an IRLZ34N as the power mosfet.
>> >>
>> >> Would a mosfet-driver be recommended to switch that mosfet on and off more quickly? Or is a logic-level mosfet already designed to efficiently turn on and off with the weak logic level signal?
>> >>
>> >> Thanks,
>> >>
>> >> Michael
>> >>
>> > This doesn't sound like a very critical application.
>> >So it might be overkill, have you looked at the TC4420 series of
>> >FET drivers.
>> >> http://www.learn-c.com/tc4429.pdf
>> >
>> > Mikek
>>
>> That's what I'm thinking too. He needs to breadboard something, or
>> simulate it and see what the actual problems are, rather than try to
>> over-kill it in the ruminating stage of design...
>>
>> The arduino outputs 5 volts, or 3.3V, and if he only has that to work
>> with, it may not be enough to fully turn on a so-called logic level
>> mosfet. But it is so easy to use the Arduino to run a flea power
>> boost converter so that shouldn't be a problem to just step up voltage
>> with an inductor and switching transistor.
>>
>> And then too, the Arduino is over-kill for most projects.
>
>
>I already breadboarded it. I put a 270 ohm resistor (calculated from V=IR, with I set to the max safe current the Arduino could put out... I forget exactly what it was, and V set to 5V) between an output PWM of the Arduino to the gate of an IRLZ34NPbF mosfet, and put one of these pumps between +18V and the drain:
>
>https://www.amazon.com/ZJchao-Dosing-Peristaltic-Aquarium-Analytic/dp/B00F9MXFFQ/ref=sr_1_4?ie=UTF8&qid=1495207608&sr=8-4&keywords=peristaltic+pump
>
>I rather doubt that 80 mA figure; I'll have to measure it one of these days.
>
>My Arduino program displays the current power setting (0-100%) and if I, for example, send a "6" followed by Enter to the serial port, the Arduino sets the PWM at 60% power. The C code is somewhat laughable but I can post it if you really want.
>
>It works fairly well, but I noticed I had to put a heatsink on the MOSFET, which had me wondering why.
>
>Oh! I put an SB140 schottky in parallel with the motor.
>
>Michael
I'd doubt the 80 mils too. They don't give the conditions, like speed
and back-pressure. Peristaltic pumps aren't known for their
free-spinning characteristics, they are better suited for intermittent
use (especially when directly driven). If the tubing isn't silicon
tubing I'd recommend a change because the energy used to pinch the
tubing is waste. (and I don't ever remember seeing any peristaltic
with a direct drive, they always used gearboxes, even the ones driven
with stepper motors)
Motor current would be worth checking.
I worked in a pharmaceutical chemistry lab doing electronic and
electromechanical design.
I take it the Arduino is basically just chopping the power to the pump
motor? No inductors or filter caps involved? What frequency are you
chopping power at? Have you looked at the waveforms with a scope?
As for current limiting to the gate drive, that may not be necessary
or desirable. The gate is essentially a capacitor. (of 880 pico
farads in this case) The current is just necessary for a brief time
to charge and discharge the gate. Do you have any idea what the peak
current the Arduino chip can sink and source? If you have 18 Volts to
play with it may be better to just drive the gate with a higher
voltage (but absolute max for that part is 16 volts...)
A scope might tell you what is going on to cause it to heat...
I designed a variable speed (large) fan for my last tower computer.
The specs on the brushless fan said it was 500 MA at 12 V and the
mosfet was toggling at 15 KHZ and ran cool, with no heat sink. But
then I wasn't using straight pwm and driving a brushed motor either, I
was using it as a switching mode power supply and sending pure DC to
the fan motor, except on the highest setting, then it was just turning
on the mosfet with no chopping.
My drive circuit was a single ended npn transistor, but only because I
started out using pwm and a BJT transistor. (it turned out that the
fan didn't like that; pulses from the drive would alias with the
pulses to the fan coils) When I changed the programming for smooth DC
(added an inductor diode and filter cap) and switched to a mosfet I
just left the transistor in the circuit. (too lazy to rewire the
perf-board I was using, and 12V meant there was no need for a logic
level device)
Reply by ●May 19, 20172017-05-19
On Friday, May 19, 2017 at 4:13:22 AM UTC-7, default wrote:
> On Thu, 18 May 2017 09:36:07 -0500, amdx <nojunk@knology.net> wrote:
>=20
> >On 5/15/2017 10:33 AM, mrdarrett@gmail.com wrote:
> >> Hello,
> >>
> >> I've discovered logic-level mosfets, and am using an Arduino to drive =
a small 12VDC (about an amp or so) pump motor with PWM, using an IRLZ34N as=
the power mosfet.
> >>
> >> Would a mosfet-driver be recommended to switch that mosfet on and off =
more quickly? Or is a logic-level mosfet already designed to efficiently t=
urn on and off with the weak logic level signal?
> >>
> >> Thanks,
> >>
> >> Michael
> >>
> > This doesn't sound like a very critical application.
> >So it might be overkill, have you looked at the TC4420 series of
> >FET drivers.
> >> http://www.learn-c.com/tc4429.pdf
> >
> > Mikek
>=20
> That's what I'm thinking too. He needs to breadboard something, or
> simulate it and see what the actual problems are, rather than try to
> over-kill it in the ruminating stage of design...
>=20
> The arduino outputs 5 volts, or 3.3V, and if he only has that to work
> with, it may not be enough to fully turn on a so-called logic level
> mosfet. But it is so easy to use the Arduino to run a flea power
> boost converter so that shouldn't be a problem to just step up voltage
> with an inductor and switching transistor.
>=20
> And then too, the Arduino is over-kill for most projects.
I already breadboarded it. I put a 270 ohm resistor (calculated from V=3DI=
R, with I set to the max safe current the Arduino could put out... I forget=
exactly what it was, and V set to 5V) between an output PWM of the Arduino=
to the gate of an IRLZ34NPbF mosfet, and put one of these pumps between +1=
8V and the drain:
https://www.amazon.com/ZJchao-Dosing-Peristaltic-Aquarium-Analytic/dp/B00F9=
MXFFQ/ref=3Dsr_1_4?ie=3DUTF8&qid=3D1495207608&sr=3D8-4&keywords=3Dperistalt=
ic+pump
I rather doubt that 80 mA figure; I'll have to measure it one of these days=
.
My Arduino program displays the current power setting (0-100%) and if I, fo=
r example, send a "6" followed by Enter to the serial port, the Arduino set=
s the PWM at 60% power. The C code is somewhat laughable but I can post it=
if you really want.
It works fairly well, but I noticed I had to put a heatsink on the MOSFET, =
which had me wondering why.
Oh! I put an SB140 schottky in parallel with the motor.
Michael
Reply by default●May 19, 20172017-05-19
On Thu, 18 May 2017 09:36:07 -0500, amdx <nojunk@knology.net> wrote:
>On 5/15/2017 10:33 AM, mrdarrett@gmail.com wrote:
>> Hello,
>>
>> I've discovered logic-level mosfets, and am using an Arduino to drive a small 12VDC (about an amp or so) pump motor with PWM, using an IRLZ34N as the power mosfet.
>>
>> Would a mosfet-driver be recommended to switch that mosfet on and off more quickly? Or is a logic-level mosfet already designed to efficiently turn on and off with the weak logic level signal?
>>
>> Thanks,
>>
>> Michael
>>
> This doesn't sound like a very critical application.
>So it might be overkill, have you looked at the TC4420 series of
>FET drivers.
>> http://www.learn-c.com/tc4429.pdf
>
> Mikek
That's what I'm thinking too. He needs to breadboard something, or
simulate it and see what the actual problems are, rather than try to
over-kill it in the ruminating stage of design...
The arduino outputs 5 volts, or 3.3V, and if he only has that to work
with, it may not be enough to fully turn on a so-called logic level
mosfet. But it is so easy to use the Arduino to run a flea power
boost converter so that shouldn't be a problem to just step up voltage
with an inductor and switching transistor.
And then too, the Arduino is over-kill for most projects.
Reply by amdx●May 18, 20172017-05-18
On 5/15/2017 10:33 AM, mrdarrett@gmail.com wrote:
> Hello,
>
> I've discovered logic-level mosfets, and am using an Arduino to drive a small 12VDC (about an amp or so) pump motor with PWM, using an IRLZ34N as the power mosfet.
>
> Would a mosfet-driver be recommended to switch that mosfet on and off more quickly? Or is a logic-level mosfet already designed to efficiently turn on and off with the weak logic level signal?
>
> Thanks,
>
> Michael
>
This doesn't sound like a very critical application.
So it might be overkill, have you looked at the TC4420 series of
FET drivers.
On 2017-05-16, Tim Wescott <seemywebsite@myfooter.really> wrote:
> On Tue, 16 May 2017 05:01:34 -0400, default wrote:
>
>> On Mon, 15 May 2017 12:02:39 -0700 (PDT), mrdarrett@gmail.com wrote:
>>
>> https://en.wikipedia.org/wiki/Baker_clamp
>
> That's not at all what I was referring to. Zetex (or somebody) figured
> out that you could go ahead and let the transistor saturate, but still
> get significantly faster turn-off if you actively drew the carriers out
> of the base.
maybe just stick the right capacitor in parallel with the base or with
most of the base resistance.
--
This email has not been checked by half-arsed antivirus software
Reply by rickman●May 17, 20172017-05-17
On 5/17/2017 2:56 PM, John Larkin wrote:
> On Wed, 17 May 2017 11:41:42 -0700 (PDT), mrdarrett@gmail.com wrote:
>
>> On Wednesday, May 17, 2017 at 11:33:56 AM UTC-7, Tim Wescott wrote:
>>> On Wed, 17 May 2017 13:53:05 -0400, rickman wrote:
>>>
>>>> On 5/16/2017 1:59 PM, Tim Wescott wrote:
>>>>> On Tue, 16 May 2017 09:22:59 -0700, mrdarrett wrote:
>>>>>
>>>>>
>>>>>> You might have to write another book! I took a peek at your Controls
>>>>>> book and I had no idea Scilab was free. A free Matlab clone, huh?
>>>>>>
>>>>>> Michael
>>>>>
>>>>> BETTER than Matlab. For a certain meaning of "better" (it's not
>>>>> compatible), but I like it.
>>>>>
>>>>> People keep trying to tell me to use Python for scientific computation,
>>>>> and I keep stabbing at learning it, only to gag at learning yet another
>>>>> interpreted language (and, I'm sorry, indentation should NOT tell the
>>>>> compiler what the program structure is -- that's simply nuts).
>>>>
>>>> I know a variation of Forth that uses color for syntax. There are modes
>>>> of execution of the code. Some code is executed by the editor, some by
>>>> the compiler and some is run time. They are all distinguished by color
>>>> (along with some other categories like comments).
>>>>
>>>> Oddly enough it is called... ColorForth (written with "color" in red
>>>> and "Forth" in green).
>>>
>>> Eeew.
>>>
>>> --
>>>
>>> Tim Wescott
>>> Wescott Design Services
>>> http://www.wescottdesign.com
>>
>>
>> It would be a nightmare for those of us who are moderately color blind :)
>
> Forth is a nightmare no matter what your vision.
From someone who doesn't program. Forth is easy to learn, but you have
to learn it. Funny though. Programming in Forth requires you to start
with the basics (it doesn't have arrays built in for example, but they
are easy to create, very easy) but can be very powerful opening the full
potential of the system you are running on. That strikes me as
analogous to the way JL does analog. I guess when it comes to things he
doesn't understand he expects it all to have been done for him.
--
Rick C
Reply by rickman●May 17, 20172017-05-17
On 5/17/2017 2:41 PM, mrdarrett@gmail.com wrote:
> On Wednesday, May 17, 2017 at 11:33:56 AM UTC-7, Tim Wescott wrote:
>> On Wed, 17 May 2017 13:53:05 -0400, rickman wrote:
>>
>>> On 5/16/2017 1:59 PM, Tim Wescott wrote:
>>>> On Tue, 16 May 2017 09:22:59 -0700, mrdarrett wrote:
>>>>
>>>>
>>>>> You might have to write another book! I took a peek at your Controls
>>>>> book and I had no idea Scilab was free. A free Matlab clone, huh?
>>>>>
>>>>> Michael
>>>>
>>>> BETTER than Matlab. For a certain meaning of "better" (it's not
>>>> compatible), but I like it.
>>>>
>>>> People keep trying to tell me to use Python for scientific computation,
>>>> and I keep stabbing at learning it, only to gag at learning yet another
>>>> interpreted language (and, I'm sorry, indentation should NOT tell the
>>>> compiler what the program structure is -- that's simply nuts).
>>>
>>> I know a variation of Forth that uses color for syntax. There are modes
>>> of execution of the code. Some code is executed by the editor, some by
>>> the compiler and some is run time. They are all distinguished by color
>>> (along with some other categories like comments).
>>>
>>> Oddly enough it is called... ColorForth (written with "color" in red
>>> and "Forth" in green).
>>
>> Eeew.
>>
>> --
>>
>> Tim Wescott
>> Wescott Design Services
>> http://www.wescottdesign.com
>
>
> It would be a nightmare for those of us who are moderately color blind :)
Yeah, there's supposed to be some way of getting around that, but I
don't recall. It was written by one person for himself, Chuck Moore.
--
Rick C
Reply by John Larkin●May 17, 20172017-05-17
On Wed, 17 May 2017 11:41:42 -0700 (PDT), mrdarrett@gmail.com wrote:
>On Wednesday, May 17, 2017 at 11:33:56 AM UTC-7, Tim Wescott wrote:
>> On Wed, 17 May 2017 13:53:05 -0400, rickman wrote:
>>
>> > On 5/16/2017 1:59 PM, Tim Wescott wrote:
>> >> On Tue, 16 May 2017 09:22:59 -0700, mrdarrett wrote:
>> >>
>> >>
>> >>> You might have to write another book! I took a peek at your Controls
>> >>> book and I had no idea Scilab was free. A free Matlab clone, huh?
>> >>>
>> >>> Michael
>> >>
>> >> BETTER than Matlab. For a certain meaning of "better" (it's not
>> >> compatible), but I like it.
>> >>
>> >> People keep trying to tell me to use Python for scientific computation,
>> >> and I keep stabbing at learning it, only to gag at learning yet another
>> >> interpreted language (and, I'm sorry, indentation should NOT tell the
>> >> compiler what the program structure is -- that's simply nuts).
>> >
>> > I know a variation of Forth that uses color for syntax. There are modes
>> > of execution of the code. Some code is executed by the editor, some by
>> > the compiler and some is run time. They are all distinguished by color
>> > (along with some other categories like comments).
>> >
>> > Oddly enough it is called... ColorForth (written with "color" in red
>> > and "Forth" in green).
>>
>> Eeew.
>>
>> --
>>
>> Tim Wescott
>> Wescott Design Services
>> http://www.wescottdesign.com
>
>
>It would be a nightmare for those of us who are moderately color blind :)
--
John Larkin Highland Technology, Inc
picosecond timing precision measurement
jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
Reply by ●May 17, 20172017-05-17
On Wednesday, May 17, 2017 at 11:37:22 AM UTC-7, John Larkin wrote:
*squish*
> >> That's kinda old. Actually, very old. There are some milliohm mosfets
> >> around now.
> >>
> >> https://www.digikey.com/product-detail/en/alpha-omega-semiconductor-inc/AO3416/785-1011-2-ND/1855783
> >>
> >>
> >>
> >> --
> >>
> >> John Larkin Highland Technology, Inc
> >>
> >> lunatic fringe electronics
> >
> >
> >Oh nice!
> >
> >From the datasheet, Vgs,th,max = 1.1V. This should work fine as a logic-level mosfet, then?
> >
> >http://aosmd.com/res/data_sheets/AO3416.pdf
>
> If you have 2.5V of gate drive, that makes <26 mohms ON resistance.
> 3.3 volts, even lower.
>
> If there is a possibility that your drive port could go hi-Z (like
> maybe a uP port that's not configured at powerup) a resistor from gate
> to ground, 10K or something, would be prudent.
>
> >
> >In general, for PWM at 1-2A, 12-18VDC, are mosfets preferred (lower resistance, cheaper) than BJTs?
> >
> >Thanks,
> >
> >Michael
>
> I sure prefer them. I rarely use bipolar transistors these days. Maybe
> exotica like emitter followers or cascodes or something. Bipolars do
> have lower capacitances, which sometimes matters. But for power
> switching, mosfets are great.
>
>
> --
>
> John Larkin Highland Technology, Inc
> picosecond timing precision measurement
>
> jlarkin att highlandtechnology dott com
> http://www.highlandtechnology.com