I have had the following motor kit for quite a few years now.
https://simplemotor.com/shop/motor-kits/kit-6/
I modded it to use an actual shaft, bearings and early on I learned the magnets tended to fly off the rotor at real high speeds so I used some neodymium magnets and epoxied them in place to where the epoxy is flush with the ends of the rotor.
Was a pain to properly balance the rotor so that it doesn't vibrate when running fast.
I used two 12 volt coils instead of the single coil and I used a 7805 to regulate the voltage to the hall effect sensor.
Here's the schematic.
Here's the motor.
The motor will increase speed until about 23Vdc and above that the waveform at the coil starts to have a higher duty cycle which tends to not allow any real speed increase.
Torque is not that great either, but it's fun to experiment with.
Currently I need to replace the hall sensor and transistor for it to operate. I could simply replace the parts with like parts, but there might be parts better suited for this application.
Getting a little side tracked for a brief moment.
Two things that I've been kicking around in my mind.
1. Get another rotor and build it the exact same and put two on one shaft with one clocked so the magnets are 45 degrees offset from the other rotor's magnets then use another separate transistor, sensor and coils. That would increase torque while likely keeping the higher speed,
2. Get a larger pipe so that I can use more magnets and possibly more coils. That will increase torque, but lower speed. Only reason I don't do that is I am not good at making stuff like that and I'd likely wind up with a rotor that is not balanced at all. What I'd need is a small pipe or other plastic thing that already has 8 or more flat sides on it. I've even thought of making a really large rotor maybe 5" and fill it with equally spaced magnets.
Now if I really wanted to get adventurous I could build a larger rotor and locate coils and sensors 120 degrees apart from each other. I'd then have a three phase brushless DC motor.
That said back on the topic at hand.
Four things I have questions about.
1. Is there a better hall effect sensor than the 21E for this application?
2. Is there a better transistor than the TIP-107 for this application? Perhaps a power MOSFET?
3. Is the 12 volt coil ok or would a 6 volt coil be better and would the coil type I used be best or is there a better type?
4. Is it better to have the coils in series or parallel?
https://simplemotor.com/shop/motor-kits/kit-6/
I modded it to use an actual shaft, bearings and early on I learned the magnets tended to fly off the rotor at real high speeds so I used some neodymium magnets and epoxied them in place to where the epoxy is flush with the ends of the rotor.
Was a pain to properly balance the rotor so that it doesn't vibrate when running fast.
I used two 12 volt coils instead of the single coil and I used a 7805 to regulate the voltage to the hall effect sensor.
Here's the schematic.
Here's the motor.
The motor will increase speed until about 23Vdc and above that the waveform at the coil starts to have a higher duty cycle which tends to not allow any real speed increase.
Torque is not that great either, but it's fun to experiment with.
Currently I need to replace the hall sensor and transistor for it to operate. I could simply replace the parts with like parts, but there might be parts better suited for this application.
Getting a little side tracked for a brief moment.
Two things that I've been kicking around in my mind.
1. Get another rotor and build it the exact same and put two on one shaft with one clocked so the magnets are 45 degrees offset from the other rotor's magnets then use another separate transistor, sensor and coils. That would increase torque while likely keeping the higher speed,
2. Get a larger pipe so that I can use more magnets and possibly more coils. That will increase torque, but lower speed. Only reason I don't do that is I am not good at making stuff like that and I'd likely wind up with a rotor that is not balanced at all. What I'd need is a small pipe or other plastic thing that already has 8 or more flat sides on it. I've even thought of making a really large rotor maybe 5" and fill it with equally spaced magnets.
Now if I really wanted to get adventurous I could build a larger rotor and locate coils and sensors 120 degrees apart from each other. I'd then have a three phase brushless DC motor.
That said back on the topic at hand.
Four things I have questions about.
1. Is there a better hall effect sensor than the 21E for this application?
2. Is there a better transistor than the TIP-107 for this application? Perhaps a power MOSFET?
3. Is the 12 volt coil ok or would a 6 volt coil be better and would the coil type I used be best or is there a better type?
4. Is it better to have the coils in series or parallel?
The most fundamental things need to come first. You do not seem to have a diode for clamping the turn-off flyback voltage which would repeatedly avalanche the poor transistor, leading to its premature demise ...
https://www.allaboutcircuits.com/textbook/semiconductors/chpt-3/inductor-commutating-circuits/
https://www.allaboutcircuits.com/textbook/semiconductors/chpt-3/inductor-commutating-circuits/
The TIP-107 has a built in diode.
https://www.mouser.com/datasheet/2/149/TIP107-197063.pdf
I do want to figure out something with the hall effect sensor that will allow me to adjust its position as its exact position in relation to the magnet affects the motor's speed for any fixed voltage value.
https://www.mouser.com/datasheet/2/149/TIP107-197063.pdf
I do want to figure out something with the hall effect sensor that will allow me to adjust its position as its exact position in relation to the magnet affects the motor's speed for any fixed voltage value.
Wrong place for the diode my dear friend !! The diode needs to shunt the inductive load.
I tried a diode across the coil, but it just slowed the motor down.
It's ran several years the way it currently is though.
At one point I tried a neon bulb across the coil thinking it would light up when the transistor turns off and it never did so I removed it. I suppose that's due to the diode in the transistor keeping the voltage from going real high when the transistor turns off.
It's ran several years the way it currently is though.
At one point I tried a neon bulb across the coil thinking it would light up when the transistor turns off and it never did so I removed it. I suppose that's due to the diode in the transistor keeping the voltage from going real high when the transistor turns off.
That is what is termed as 'avalanching' wherein a high blocking voltage (>VCEmax) causes a (commutation) collector current to flow ...
You may not see the neon bulb glow as the commutation would occur only for a short period of time ..
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Also using a scope to view the waveform at the transistor collector, I never saw a high voltage spike. Just saw a square wave which increased its duty cycle as the voltage to the motor increased and the motor started to run faster.
This circuit works similar to the horizontal output circuit in a CRT TV.
This circuit works similar to the horizontal output circuit in a CRT TV.
Are you suggesting that the two coils are coupled like in a flyback transformer ? Even so, the coupling can never be perfect and there has to be some leakage inductance and stored energy ...
Well then, all the best.. BTW, how many MHz is your scope ?
Why ? Did you place the diode with the wrong polarity ?
Well then, all the best.. BTW, how many MHz is your scope ?
The one I used was at least 100MHz.
I placed the diode in the right polarity across the coil.
Think it has to do with how the diode affects the magnetic field collapsing.
I figured if the neon bulb didn't light up when placed across the coil then there wasn't any high voltage spikes to worry about.
I referenced a flyback circuit because it too switches a coil on and off, however a closer match for the circuit type is a PC fan which has a brushless DC motor.
Might be best to stick with the TIP-107 and just use a larger heatsink.
I just need to find the hall effect sensor and figure a way to adjust its position to optimize the motor's speed based on the voltage supplied to the motor.
What's nice is the bearings I used came from a VCR video head motor so replacements would be very easy to find.
I placed the diode in the right polarity across the coil.
Think it has to do with how the diode affects the magnetic field collapsing.
I figured if the neon bulb didn't light up when placed across the coil then there wasn't any high voltage spikes to worry about.
I referenced a flyback circuit because it too switches a coil on and off, however a closer match for the circuit type is a PC fan which has a brushless DC motor.
Might be best to stick with the TIP-107 and just use a larger heatsink.
I just need to find the hall effect sensor and figure a way to adjust its position to optimize the motor's speed based on the voltage supplied to the motor.
What's nice is the bearings I used came from a VCR video head motor so replacements would be very easy to find.
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So revisiting the circuit I redid it to show the typical way with B+ and ground.
Here's the way I think the circuit might be improved.
Here's the way I think the circuit might be improved.
After reading up on th hall sensor it pulls its output more negative.
So the previous modification won't work.
This is what I think will work. The schematic also shows the TIP-107 how it actually is.
Not sure what the resistor on the base should be though. The hall sensor has a built in regulator, but I am not sure what the output voltage is. I'll need to order the sensor then test it powered and hold a magnet to it just to see its output voltage. Once I find that I need to use a voltage divider calculator with the 10k base resistor, the sensor output voltage and the 1.4 volt base emitter drop to figure the necessary resistance for the base resistor.
Here's the sensor.
https://simplemotor.com/shop/parts/hall-effect-ic/
Here's the transistor.
https://simplemotor.com/shop/parts/transistor/
I may get this heatsink if I do not have a better one at home.
https://simplemotor.com/shop/parts/heat-sink/
So the previous modification won't work.
This is what I think will work. The schematic also shows the TIP-107 how it actually is.
Not sure what the resistor on the base should be though. The hall sensor has a built in regulator, but I am not sure what the output voltage is. I'll need to order the sensor then test it powered and hold a magnet to it just to see its output voltage. Once I find that I need to use a voltage divider calculator with the 10k base resistor, the sensor output voltage and the 1.4 volt base emitter drop to figure the necessary resistance for the base resistor.
Here's the sensor.
https://simplemotor.com/shop/parts/hall-effect-ic/
Here's the transistor.
https://simplemotor.com/shop/parts/transistor/
I may get this heatsink if I do not have a better one at home.
https://simplemotor.com/shop/parts/heat-sink/
Here's the motor with a larger heatsink.
I'll wire it up as it was originally so I can get the hall sensor in the best spot for optimum motor speed.
I'll then change it over to where the coils are in the collector and a resistor is in series with the base and see if that makes the motor work better.
I ordered two transistors and two hall sensors. That way if I mess one up I have a spare.
Now if I really wanted to make the motor better, I could maybe wire up an identical circuit only using one coil per circuit and offset the other coil and hall sensor by 45 degrees.
That would increase the torque some.
I'll wire it up as it was originally so I can get the hall sensor in the best spot for optimum motor speed.
I'll then change it over to where the coils are in the collector and a resistor is in series with the base and see if that makes the motor work better.
I ordered two transistors and two hall sensors. That way if I mess one up I have a spare.
Now if I really wanted to make the motor better, I could maybe wire up an identical circuit only using one coil per circuit and offset the other coil and hall sensor by 45 degrees.
That would increase the torque some.
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Got it all wired up. Decided to leave it as originally wired given it works good that way.
The position of the hall sensor in relation to the magnets determines how well the motor runs.
The way the hall sensor is placed the motor will run on as low as 3.2Vdc at about 50mA running at 546 RPM with the motor driving nothing.
At 30Vdc the motor is still wanting to go faster, but I am limited by the 412mA maximum current the power supply can do. The motor at 30Vdc runs at 18,210 RPM with the motor driving nothing.
The RPM measurements are based on the formula (Hz x 60 x 2) / number of poles = no-load RPM
The number of poles is 4 given there are 4 magnets.
The position of the hall sensor in relation to the magnets determines how well the motor runs.
The way the hall sensor is placed the motor will run on as low as 3.2Vdc at about 50mA running at 546 RPM with the motor driving nothing.
At 30Vdc the motor is still wanting to go faster, but I am limited by the 412mA maximum current the power supply can do. The motor at 30Vdc runs at 18,210 RPM with the motor driving nothing.
The RPM measurements are based on the formula (Hz x 60 x 2) / number of poles = no-load RPM
The number of poles is 4 given there are 4 magnets.
Here's a short video of the moor driving a fan blade running on 12Vdc. The blade has a very light pitch as the motor isn't very strong.