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Help with problems running motor via usb plug... motor not getting enough power. Answered

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I'm trying to connect a small  1.5VDC up to 6VDC motor in series or parallel to three pager vibrators .5V to 3VDC and two LED lights connected in parallel  to be powered by a usb plug.  For some reason, the small 1.5VDC up to 6VDC motor doesn't seem to be working. I tried connecting power directly to this motor and it still would not turn.  I thought the motor was burned out, so I tried to swap it with an three identical new motors and couldn't get any of them to run.  The pager vibrators and LED light up when connected to motor in series but not in parallel.  The larger motor however still does not seem to be getting enough power to turn.   I previously had the motor running on a single AA battery and can't figure out why it is not getting enough power with the five volt usb power.  I also have a small potentiometer hooked into the circuit to make the motors variable.  I set it to pass the full power through the circuit.  Is it necessary to add more power to this motor?  Also, is there a way to add power to this motor without risking sending too much voltage to USB via a battery?  I am a novice at electronics.

Note:  Adding power with a battery would be ok... but it must turn on and off motors by power turning on and off of USB. 

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mpaudel (author)2011-03-02

hello guys ,
I want to use the dc motor rating 12 volts and 20 Amp in my robot . Any one could suggest ,please for this ,How it is possible or if it is not please give me another Idea too.
I will be wating for the kind suggestions

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lemonie (author)2010-02-07

If they're in parallel, some are going to take more power than others. In series, current will be limited too much for at least one of them, and potentiometers are not the way to vary speed.
This is a not a good way of powering things from from USB - consider taking a separate supply for the big motor or not using USB at at. Spare MOLEX connector inside?

L

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DarkRubyMoon (author)lemonie2010-02-07

I don't have much room for components in what I am making.  I know a potentiometer is not ideal, but it seems to be working for what I need it to do.  It doesn't seem to be overheating.  Is there any issues with using it I am unaware of? 

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lemonie (author)DarkRubyMoon2010-02-07

Molex is the usual plug for internal disk-drives - 5 & 12V.
Potentiometers do have a tendency to burn with not a great amount of current, it might not have happened yet but it is a risk.
I'm not familiar with switching the USB 5V on and off, how do you do it?

L

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DarkRubyMoon (author)lemonie2010-02-07

It took me a lot of research to find out how to turn on and off a USB ports power.  Normally, a usb ports power is constant, and there is no way to control it via the computer.  It  requires a special circuit board that plugs into the usb port along with a driver and a program.  I am using the motor-bee circuit board available at http://www.pc-control.co.uk/motorbee_info.htm  which has a modifiable software program .  There are other similar boards available, though this seemed to be the cheapest and simplest I could find.

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lemonie (author)DarkRubyMoon2010-02-07

You don't need the USB though, you could use a different power supply.
Thanks for the link - it interests me.


L

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DarkRubyMoon (author)lemonie2010-02-07

I could use a different power supply, but it must be activated by the power turning on from the usb... am not sure how to do this without risking too much power returning to the computer as I am a novice.  The power supply must be small... little room in the device for external power.  It would seem it should be possible to generate enough power to run the motor in burst perhaps with a capacitor or by some other means.  The usb connection however is essential for other reasons and is not optional.

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lemonie (author)DarkRubyMoon2010-02-07

I'm a bit confused - I thought you were controlling the on off with the motor-bee. If you aren't, can you tell me how you're switching the USB on and off without the motor-bee?
Yes, you could store charge in a capacitor, but get a big one.

L

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DarkRubyMoon (author)lemonie2010-02-07

Yes, I will be controlling the power on and off with the motor-bee, but I am planning to make the connections to the motor-bee female usb plugs.  In this way, I can unplug a device from the motor-bee to swap for another usb device.  In effect, I plan to turn the motor-bee circuit board into a usb hub with the ability to switch on and off any usb device plugged into it.  In this way I can re-use the motor-bee for future project experiments.  (I'm being cheap :)  If I add power via the motor-bee circuit, I'd have to make it so I can switch on or off the extra power to the individual usb connections which is an option... but I want to be able to simply plug this into any standard usb plug and have it still work minus the computer control. 

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lemonie (author)DarkRubyMoon2010-02-09

Ah right, I get you now. You might be better not running this off the USB, it's been designed to a standard, which may not be the best for your purposes.

L

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DarkRubyMoon (author)lemonie2010-02-07

I am planning to plug this device into a motor-bee circuit board that will turn on and off the power to the usb to turn on and off the device... so a separate power supply is only possible if it can be turned on and off by powering on and off the usb... not sure how to do this.  I don't know what a Molex connector is.

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steveastrouk (author)2010-02-06

A standard, uncontrolled USB connection will only supply 100mA - that's probably not enough for your load.   You're probably stuck.

Steve

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I forgot to mention, the large motor does not have to run continuously, though it would be nice if it did.  What if I used a solar engine circuit to run the larger motor such that it runs when it gets enough power?

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What's the AIM ? Why do you want to use USB power in the first place ?

Steve

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A computer controlled vibration device activated by games and such.  It will be connected to a motor-bee control board that can turn on and off power to the usb power devices.  The motor-bee board itself does allow increasing power, but i want to be able to use the card for other applications, and so a easy usb disconnect is perfect.   I don't have a problem with adding power to it... so long as it turns on and off by power turning on and off to the usb port.  I also want to keep its size down... so a big battery isn't ideal.  I want to keep it usb because I plan to operate it using a netbook, and don't feel like going through a parallel or serial port which is no longer supported on newer computers.  USB is ideal because it is so universal and easy to work with...it just doesn't have much power.  If I can add some power with a 9 volt battery, yet keep activation by power on and off from the usb power, this would be fine.  The key is that the power on and off of usb turns on and off the motors.

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How do you turn USB power on and off with program control ? 

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It took me a lot of research to find out how to turn on and off a USB ports power.  Normally, a usb ports power is constant, and there is no way to control it via the computer.  It  requires a special circuit board that plugs into the usb port along with a driver and a program.  I am using the motor-bee circuit board available at http://www.pc-control.co.uk/motorbee_info.htm  which has a modifiable software program .  There are other similar boards available, though this seemed to be the cheapest and simplest I could find.

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Forget USB as a source of power then - try measuring the current draw of your load, off a good 5V supply NOT the USB port. Once you know the draw in mA, you'll be in a better position to decide what to do next.

The motorbee page you refer to itself uses an external supply - that's the only way this is going to work.

Steve

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I'd like to avoid using external supply if possible on the Motor-bee circuit as I plan to make the devices plugged into it swappable with standard usb devices... so that is a last resort as  I don't want to have to buy a new card for every project.  I plan to make the connection to the motor-bee a female usb plug... that way I can just unplug it and swap it with some standard usb device like an LED lamp or something.  I wouldn't mind adding power to the device... perhaps some relay switch that turns on when there is usb current?  What about an Easter solar circuit https://www.instructables.com/id/The-Easter-Solar-Engine/ ?  Can I use this without risking damage to my usb port?  I'm just not sure how to activate the additional power source via the usb power turning on and off... and adding power to the motor-bee would make the card unusable for standard usb devices.

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Measure what you need. Then we can think about it. Until then, its useless guess work.

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milsorgen (author)steveastrouk2010-02-06

 It's my understanding you should be able to pull 500mA.

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NachoMahma (author)milsorgen2010-02-06

.  You are correct (per USB specs), but, either way, it's not enough. The 100mA is what the USB specs refer to as a "unit load" and each port will handle 5 unit loads. In USB 3, unit load will be raised to 150mA.

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steveastrouk (author)NachoMahma2010-02-07

Am I not right that you can't pull higher currents without negotiating for it though ? 

Yes, you MIGHT be able to have 500mA, if the other ports on the hub aren't maxed out, but unless you handle the ennumeration etc, you ain't getting the juice.

Steve

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NachoMahma (author)steveastrouk2010-02-07

.  Perhaps I misunderstood the specs.
.  I doubt that even 500mA is going to be enough. ;)

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steveastrouk (author)NachoMahma2010-02-07

Perhaps I misunderstood the specs ! I don't dabble inside USB specs at all.

Steve

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DarkRubyMoon (author)2010-02-07

Just want to say thank you to everyone for your post and help.  Rather than saying thank you for each post... Thank you everyone! 

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