Hi,
I am thinking of making a project where a motor will constantly need to run.
Ideally I want something where the battery does not run out, so something like constant supply of power is ideal.
It is possible to keep the device connected to a wall power source, so AC to DC conversion is possible.
The motor will need 9V power supply to keep running.
Since my knowledge of power is very poor, i am looking for some guidance.
1 option I thought was to buy 9V DC power adapter and directly connect it to motor, but I guess I will only get about <1A current.
On the other hand, Lipo battery are small and more powerful, but they will run out of juice shortly and I have not figured out if I can constantly keep then charging them while they are being used.
My question may sound stupid but I am looking forward to doing some learning here
It is possible to keep the device connected to a wall power source, so AC to DC conversion is possible.
The motor will need 9V power supply to keep running.
You need to specify the current the motor needs.
1 option I thought was to buy 9V DC power adapter and directly connect it to motor, but I guess I will only get about <1A current.
You will get whatever current the power supply is designed for. You need to buy a PSU with sufficient output current for the motor.
If you also want a battery to keep the motor running when the mains fails then as long as space and weight are not an issue then lead acid batteries are robust, cheap and easy to use in the situation you describe, as long as space and weight are not important. You would need a 6 cell, nominally 12V battery of sufficient capacity for your needs. As you have not stated how much current the motor draws I cannot advise you there. You need a power supply that will provide 13.2V to 13.8V and a buck converter to convert the battery voltage to 9V. The 13.2V supply must have sufficient current rating to supply the motor and charge the battery.
You connect the 13.2V supply across the battery, you connect the buck converter across the battery and the motor to the 9V output of the converter.
Note on battery capacities. People make the mistake of calculating a battery capacity and buying a battery of that capacity. The problem is that any battery of any chemistry loses capacity over its life, so what starts out as a battery with sufficient capacity quickly becomes a battery with insufficient capacity for the job. My recommendation is buy a battery of twice whatever capacity you calculate.
Thanks a lot for your advice.
I would say weight is a concern. Currently I have a 6 cell battery that I use to test, but eventually I plan to make this compact so that it can be shipped.
Basically is a tiny pottery wheel that I want to make.
The reason I want constant current is that if I have to wait for battery to charge, the clay can dry.
I'm not clear what's wrong with a mains power supply. You haven't said what current you need at 9V but you can get one for any power you need 3A, 4A, 5A or a lot more. A search on EBay will find hundreds.
The reason I want constant current is that if I have to wait for battery to charge, the clay can dry.
There are 2 reasons to use a battery: If there is no mains available or if you want to be sure the device continues to operate when the mains fails. If neither of these applies then you don't need a battery.
The setup in the photo does not look very practical. I would expect the motor to rotate much too fast and not have enough torque.
ssdesign:
eventually I plan to make this compact so that it can be shipped.
If you are thinking of making a product for sale that ships with LiPo cells then I suggest you give up the idea very quickly. The most likely outcome is that you will set fire to someone's home.
LiPo cells must be charged with a specialised charger.
Lead acid is totally unsuitable for something that's not used regularly - in storage they degrade to a useless state in a matter of months. As vehicle batteries they work well, only because vehicles are used regularly so the batteries are recharged. Normally NiMH, LiPo or LiFePO4 would be chosen for rechargable pack. You need
to understand the limitations of any battery chemistry you do choose as they each have limits regarding
over-charging, over-discharge and so forth. A BMS is basically needed for demanding applications.
You'll definitely need a gearmotor, not a plain motor, as you need very low speed and high torque. Small
motors run at 4000rpm to 20000rpm, you want a few tens of rpm...
Electric motors do not like moisture of any kind, you'll need to find a way to prevent any water ingress. I recommend housing the motor with the shaft coming out of the bottom of a housing and using belt-drive
to the load, as belts can survive getting wet. You'll still have the issue of condensation on the motor to
worry about. Sealed motors are available, not cheap.
Lead acid is totally unsuitable for something that's not used regularly
Hi Mark,
I agree that lead acid batteries are not appropriate for this application; I made that suggestion based on the first post. Now I know more I am not convinced a battery is needed at all.
If a mains power supply is used then it should be kept well away from the motor with only low voltage cables to the motor so if water does get into the electrical parts there won't be any danger of electric shock. As an additional safety precaution it should be fed through an earth leakage protection device and all metal work associated with the work area bonded to earth.
Sorry for the dirty prototype. It was just to test if the system works, eventually the motor and circuit will be housed inside an enclosure and protected from water.
Based on the discussion, I am leaning more towards mains power supply using 5V adapter.
Here are the parts I intend to use eventually.
Let me know if I am making the right choices here:
I have never tried making pottery so in that sense I don't know what I'm talking about, however, that motor does not look to me like it would have anything like the torque needed to rotate a lump of clay while your hands are round it shaping it into a pot. I would think you'd need a more powerful motor. It does say the torque is 0.2kg/cm. So, at 1cm from the centre of the shaft it can supply a force of 200g, does that sound reasonable for a lump of clay with your hands round it? (I don't think so).
Use the higher current power supply for whatever Arduino you get, there is no reason (other than saving $2) for getting the lower current one. Again though, a 2A PSU implies a maximum motor power of 10W, disregarding the power taken by the Arduinio, that just doesn't seem enough. Why are you looking at motors powered from 5V anyway? I would have thought a higher power motor with a higher voltage would be more appropriate.
PerryBebbington:
that motor does not look to me like it would have anything like the torque needed to rotate a lump of clay while your hands are round it shaping it into a pot.
[....]
Why are you looking at motors powered from 5V anyway? I would have thought a higher power motor with a higher voltage would be more appropriate.
I suspect there is an illogical link between these in the sense that the OP hopes that a low voltage will give a low speed without appreciating that it also gives very low torque.
I also suspect that the OP does not appreciate that even the maximum torque from that little motor would be inadequate for a potter's wheel - and a direct drive motor would be virtually uncontrollable as it would accelerate to a ridiculously high speed as soon as the potter takes his/her hands off the work piece. Holding the motor to a very low speed also runs the risk of it overheating and destroying itself.
There needs to be a substantial gear reduction between the motor and the pottery wheel (perhaps with a belt drive as someone else suggested) so that the motor can run at high speed and optimum power and the pottery wheel can rotate at the slow speed needed by the potter.
Like you I have never tried pottery myself but I have seen it done and I would be surprised if it can be scaled down to the size of the thing in the OP's picture.
Hi,
About the pottery wheel and clay weight question, I suppose I was not clear that this is not a real size pottery wheel, but it's going to be used to make tiny pots on a 2 inch circular base. So the amount of clay we are talking here is a small lump the size of a marble.
ssdesign:
This image shows the relative size of the wheel.
I still think that considerable torque will be needed and it has to be possible to maintain a near-constant turntable speed even when the load changes - for example when the potter takes his fingers off the clay.
I don't think there is any point worrying about the power supply until you have a satisfactorily working prototype.
ssdesign:
Hi,
About the pottery wheel and clay weight question, I suppose I was not clear that this is not a real size pottery wheel, but it's going to be used to make tiny pots on a 2 inch circular base. So the amount of clay we are talking here is a small lump the size of a marble.
Thank you! You know that bit where I said I've never done pottery so I don't know what I'm talking about....
Robin2:
I doubt it. The table will spin at 2000 RPM and the mud will be spattered over the walls
...R
Any reason why you think the table will spin at 2000 RPM?
The motor I have linked above is just 300 RPM motor, and is high torque for the small load of clay we are talking.
So curious to know.
You might consider using a continuous rotation servo for the motor. You could attach a pot to the arduino and be able to control the rotation speed as well as the rotation direction.
