Which is better to control 12v/15a dc motor?

Between the two below,which is better to control 12v/15a dc motor?

  1. A dc motor speed controller (25khz freq) and use arduino as 0-5v signal
  2. A solid state relay and use arduino pwm function

No specification provided for the speed controller so any advice would be of dubious quality. That said i'd go for the speed control IF it contains an acceleration and load limiter to control the motor stall current or when starting from rest.
A motor rated at 15A full load may well require in excess of 100A to get started or stalled

The SSR provides no protection.

Could you further explain the protection part? This is a methanol/water pump. A lot of these motors running using a simple on/off hobbes switch. Mine has been running for a couple years on hobbes.

Also do these ebay controllers give out a starting voltage to start the motor before pwm?

Ebay stuff couldn't find any detailed info on the controller

100a! Maybe that's why so many $150 methanol pump controllers failed (not mine, on google).

Look at that picture of the motor controller - see that 8-pin IC? Dollars to donuts its a 555 timer running as an astable multivibrator to generate the PWM - you can find a ton of "motor controller" schematics online that show such a similar control scheme.

Find it's output pin (most likely pin 3) that goes to the base of MOSFET (maybe via a series resistor) that drives the motor (that should be -very- easy to do); cut the pin, and feed a PWM signal into it from the Arduino (remember to tie in the ground of the Arduino, too).

Want to change the direction? A DPDT (or a couple SPDT) relay(s) with high-current rated contacts is your solution (for instance, a couple BOSCH-style 12V 40A SPDT automotive relays would be perfect); control it with another MOSFET or transistor (tons of examples online of this). However - only switch the relay with PWM set to ZERO (that is, no PWM signal) - otherwise insane arcing and welding of the relay contacts will occur). Hook the motor outputs to the relay(s), and the motor to the switched outputs of the relay(s).

cr0sh:
Look at that picture of the motor controller - see that 8-pin IC? Dollars to donuts its a 555 timer running as an astable multivibrator to generate the PWM - you can find a ton of "motor controller" schematics online that show such a similar control scheme.

Find it's output pin (most likely pin 3) that goes to the base of MOSFET (maybe via a series resistor) that drives the motor (that should be -very- easy to do); cut the pin, and feed a PWM signal into it from the Arduino (remember to tie in the ground of the Arduino, too).

Wouldn't running it using 0-5v be easier? Don't need reverse either.

Most controllers for this pump runs around 30hz. Would it be ok to use a 220hz pwm?

The older style controllers were around 1khz.

Wouldn't running it using 0-5v be easier? Don't need reverse either.

Well, if you can figure out how to make the arduino output 0-5v. The arduino analog output is actually a pulsed 5v signal.

zoomkat:
Well, if you can figure out how to make the arduino output 0-5v. The arduino analog output is actually a pulsed 5v signal.

Ahh i didn't know that. Thanks for the info. Will use the linear 0-5v from my ecu instead. Preffered that arduino sent 0-5v instead in case something goes wrong ecu wont get damaged.

Between the two below,which is better to control 12v/15a dc motor?

You could use the arduino analog pin pulsed output to control a simple MOSFET like below.

zoomkat:
You could use the arduino analog pin pulsed output to control a simple MOSFET like below.

N-Channel MOSFET 60V 30A - COM-10213 - SparkFun Electronics

Thanks. Much better/reliable solution.

Some questions
1 does mega250 have overload protection?
2 is the wiring below fine or can i wire in a diode for some additional protection? Or will the diode reduce voltage enough to stop trigger of mosfet?
3 whats the purpose of the resistor on the pwm and ground?

  1. No. None at all.
  2. Diode? Where? To protect against what?
  3. Resistor keeps MOSFET off until sketch comes alive to control the gate.
    2nd resistor should be added betwee D3 and the gate to limit current into the input capacitance of the gate.
    (5V/.020A) = 250 ohm.

Ah, you're controlling a motor? Then Yes a diode across the motor - anode to MOSFET, cathode to Plus supply. Needs to handle as much current as is being drawn thru the motor.

CrossRoads:

  1. No. None at all.
  2. Diode? Where? To protect against what?
  3. Resistor keeps MOSFET off until sketch comes alive to control the gate.
    2nd resistor should be added betwee D3 and the gate to limit current into the input capacitance of the gate.
    (5V/.020A) = 250 ohm.

CrossRoads:
Ah, you're controlling a motor? Then Yes a diode across the motor - anode to MOSFET, cathode to Plus supply. Needs to handle as much current as is being drawn thru the motor.

Thanks for the info.

Yes.
Diode looks correct, with cathode to 60V.

TIP120 may heat up more than a low Rds MOSFET tho. How much current is expected?
https://www.fairchildsemi.com/datasheets/TI/TIP122.pdf
With Ic = 5A, Ib = 20mA, Vce will be up to 4V.
Power dissipated is P=IV, so 5A * 4V = 20W - pretty hot! Also motor sees less voltage.

With low Rds MOSFET, say 8.4 mOhm,
P = IIR = 5A * 5A * .0084 ohm = 0.210W - barely warm. Motor sees nearly all the voltage:
V=IR: 5A * .0084ohm = .042V across the MOSFET.

CrossRoads:
Yes.
Diode looks correct, with cathode to 60V.

TIP120 may heat up more than a low Rds MOSFET tho. How much current is expected?
Intelligent Power and Sensing Technologies | onsemi
With Ic = 5A, Ib = 20mA, Vce will be up to 4V.
Power dissipated is P=IV, so 5A * 4V = 20W - pretty hot! Also motor sees less voltage.

With low Rds MOSFET, say 8.4 mOhm,
P = IIR = 5A * 5A * .0084 ohm = 0.210W - barely warm. Motor sees nearly all the voltage:
V=IR: 5A * .0084ohm = .042V across the MOSFET.
http://www.digikey.com/product-detail/en/IRFB7787PBF/IRFB7787PBF-ND/4807808

Motor is around 10-15amps. So 180w at 12v?

P=IV. 15A (Ic) x 4V (Vce) = 60W. Gonna smoke the TIP120. Definitely want to go MOSFET.

MOSFET:
15A * 15A * .0084 ohm = 1.89W. Add a small heatsink.

Or a lower Rds part: 4.5mOhm
http://www.digikey.com/product-detail/en/TK72A08N1,S4X(S/TK72A08N1S4X(S-ND/2071361
1515.0045 = 1W

Will need to drive the gate to higher voltage, 10V vs 5V, extra transistor to do that will be worth it.
Check other for other Logic Level gate parts, Vgs <=4.5V, see what’s available with really low Rds and Vds >=75V.
Surface mount
http://www.digikey.com/product-search/en?pv959=5&pv607=31&pv69=3&FV=fff40015%2Cfff8007d&k=n-channel+mosfet&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25
Thru hole
http://www.digikey.com/product-search/en?pv959=5&pv607=31&pv69=80&FV=fff40015%2Cfff8007d&k=n-channel+mosfet&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25

To perhaps keep things simpler and help dissipate heat, several logic level MOSFETs might be paralleled.

CrossRoads:
P=IV. 15A (Ic) x 4V (Vce) = 60W. Gonna smoke the TIP120. Definitely want to go MOSFET.

MOSFET:
15A * 15A * .0084 ohm = 1.89W. Add a small heatsink.

Or a lower Rds part: 4.5mOhm
http://www.digikey.com/product-detail/en/TK72A08N1,S4X(S/TK72A08N1S4X(S-ND/2071361
1515.0045 = 1W

Will need to drive the gate to higher voltage, 10V vs 5V, extra transistor to do that will be worth it.
Check other for other Logic Level gate parts, Vgs <=4.5V, see what’s available with really low Rds and Vds >=75V.
Surface mount

This would work without transistor?

Drain to Source Voltage (Vdss) 75V
Current - Continuous Drain (Id) @ 25°C 75A (Tc)
Rds On (Max) @ Id, Vgs 5.5 mOhm @ 25A, 10V
Vgs(th) (Max) @ Id 2V @ 1mA
Gate Charge (Qg) @ Vgs 95nC @ 5V
Input Capacitance (Ciss) @ Vds 11693pF @ 25V
Power - Max

http://www.digikey.com/product-detail/en/BUK9506-75B,127/568-6632-5-ND/1163584

zoomkat:
To perhaps keep things simpler and help dissipate heat, several logic level MOSFETs might be paralleled.

Thanks for the tip. This would also have the protection of redundancy correct? (one mosfet burns up, motor will still run)

This would also have the protection of redundancy correct? (one mosfet burns up, motor will still run)

Well it would be redundant in that if one MOSFET burned up, the other MOSFETs would probably also burn up.

Hi Ricekikr

Had the same problem you where facing. Thanks to @cr0sh 'cut the output' I made this tutorial.

Kind regards
Kleinejan