I use a 1" stir bar as well. I set my mixture in a bowl of hot water for about ten minutes then put it on the stir plate, worked just fine. The only other alternative I can see is using a bigger 24v fan that spins at higher RPM....
Need Help With DIY Stir Plate
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I use a 1" stir bar as well. I set my mixture in a bowl of hot water for about ten minutes then put it on the stir plate, worked just fine. The only other alternative I can see is using a bigger 24v fan that spins at higher RPM....
I can stir 30ml 80% vg mix with a 1 inch bar like a champ. Maybe your magnet is too far away?
My magnets are only millimeters away from the roof of the box. I'm sure mine would do just fine in 30 mL, but 100 mL wasn't so great.
It sounds like a motor power issue. ( don't confuse voltage with power here ) When using current to vary motor speed you are reducing the power the motor can use. Best to use voltage to vary the speed. PWM.
Edit:
I will try to explain more clearly about pwm. In both your setup with current limiting and with a pwm setup, the voltage is the same at the motor at any instant power is supplied. However, with current limiting the power is reduced to the motor (amps available). With pwm (on-off-on-off-on-off) the amps are not reduced at the motor when the voltage is present. It will supply all the amps that the motor can eat. Just on-off-on-off ... With current limiting the motor can only use what that resistor will let it use, like pushing something with the brakes on. PWM is like pushing something with everything you got, intermittantly, you still have maximum power, just not all the time. It is a 'fake' voltage over time. 12 volts 50% of the time will read 6 volts on a volt meter. Its still 12 volts at max amps, but the motor thinks its getting a lower voltage and thus will run slower, but at full power.
To confuse further - just to see what happens in a current limiting system by the numbers ...
Here's a formula that some guy named Ohm came up with. As far as electricity goes, he's the law.
V=IR Voltage = current x resistance
Another one from a guy named Watt. A watt is a unit of power.
VI=W Voltage x current = watts
Lets plug some numbers in. I will use the ratings off a 4" fan motor I have. It is rated at 600 milliamps, or, .6 amps. Thats the current the motor uses with no load.
12 = .6 x R or
R = 12/.6
R = 20 ohms ... the resistance of the motor
Lets see what happens to that current (.6 amps) when we add a resistor in series with the motor, lets use 1000 ohms just for the heck of it ...
I=V/R
I=12/1020
I=.0117 amps or 11.7 milliamps ... certainly not the 600 milliamps the motor wants to run properly
Relating that to power
W=VI
W=12 x .6
W= 7.2 ... 7.2 watts with no added resistance. The motor has 7.2 watts of power.
Adding in the current limiting resistor ...
W=VI
W=12 x .0117
W=.1404 ... .1404 watts, not anywhere near 7.2 watts. The motor may not even have enough power to get out of its own way.
Conclusion ... By adding resistance you reduce the power.
PWM - no added resistance, no reduction in power.
Edit:
I will try to explain more clearly about pwm. In both your setup with current limiting and with a pwm setup, the voltage is the same at the motor at any instant power is supplied. However, with current limiting the power is reduced to the motor (amps available). With pwm (on-off-on-off-on-off) the amps are not reduced at the motor when the voltage is present. It will supply all the amps that the motor can eat. Just on-off-on-off ... With current limiting the motor can only use what that resistor will let it use, like pushing something with the brakes on. PWM is like pushing something with everything you got, intermittantly, you still have maximum power, just not all the time. It is a 'fake' voltage over time. 12 volts 50% of the time will read 6 volts on a volt meter. Its still 12 volts at max amps, but the motor thinks its getting a lower voltage and thus will run slower, but at full power.
To confuse further - just to see what happens in a current limiting system by the numbers ...
Here's a formula that some guy named Ohm came up with. As far as electricity goes, he's the law.
V=IR Voltage = current x resistance
Another one from a guy named Watt. A watt is a unit of power.
VI=W Voltage x current = watts
Lets plug some numbers in. I will use the ratings off a 4" fan motor I have. It is rated at 600 milliamps, or, .6 amps. Thats the current the motor uses with no load.
12 = .6 x R or
R = 12/.6
R = 20 ohms ... the resistance of the motor
Lets see what happens to that current (.6 amps) when we add a resistor in series with the motor, lets use 1000 ohms just for the heck of it ...
I=V/R
I=12/1020
I=.0117 amps or 11.7 milliamps ... certainly not the 600 milliamps the motor wants to run properly
Relating that to power
W=VI
W=12 x .6
W= 7.2 ... 7.2 watts with no added resistance. The motor has 7.2 watts of power.
Adding in the current limiting resistor ...
W=VI
W=12 x .0117
W=.1404 ... .1404 watts, not anywhere near 7.2 watts. The motor may not even have enough power to get out of its own way.
Conclusion ... By adding resistance you reduce the power.
PWM - no added resistance, no reduction in power.
Last edited:
Anyone know what those little crimper things are called that you use to attach a wire to a terminal or another wire so you don't have to solder them on? Where can I find them?
Ta dad! It's done and it works great. If I ever do anything else to it it'll be adding a stronger motor so I can have a higher range of RPM.
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