I partially stopped the motor and saw the current draw rise to 1A.
How is this even possible, I thought usb could only supply 500mA.
That is probably a minimum specification so manufacturers of
No, 500mA is the maximum for USB according to the USB specification (versions 1 and 2, anyway, not sure about USB3).
QuoteThat is probably a minimum specification so manufacturers ofNo, 500mA is the maximum for USB according to the USB specification (versions 1 and 2, anyway, not sure about USB3).USB spec says a device can have 100mA for "free", and can negotiate with the host for up to 500mA. In practice, many hosts will supply 500mA without negotiation. There are also other deviations from that spec, such as the Macs that provide 1A or more for charging iPads.Powering a motor directly from an output on the arduino will kill the processor - maybe one output pin, maybe the whole IC. The maximum for a single pin is 40mA (that's on the original ATmega8, newer may be a bit higher but similar).Keep trying to drive a motor from an output pin and you will kill your arduino, if you haven't already.-j
QuoteI partially stopped the motor and saw the current draw rise to 1A.Placing drag on the motor causes the current to rise toward the stall level. Thus if the motor coil has 5ohm resistance, a 1amp current is quite possible.USB standard requires 500 milliamp supply. An externally powered hub can provide more. I hope you are not directly powering with your laptop usb. You do not want to conduct a 'smoke test' on your pc
Probably better stated as "it depends".http://en.wikipedia.org/wiki/Universal_Serial_Bus
What is wrong with powering it via a laptop usb? please explain
The arduino was powered using a desktop computer, not the motherboard but the case
QuoteProbably better stated as "it depends".http://en.wikipedia.org/wiki/Universal_Serial_BusI guess wikipedia trumps the official USB specification. :|
Hello,I have my arduino powered via usb and have connected this motor https://www.sparkfun.com/products/10171? to the 5V pin on the arduino directly.I have a 1n4001 diode connected across the motor. No load current I find to be: 210-230mAI partially stopped the motor and saw the current draw rise to 1A.THIS IS MADNESS!!!How is this even possible, I thought usb could only supply 500mA.
looks like your offcial USB specification is totally optional. Post your official USB specification link.
1.2 Objective of the Specification This document defines an industry-standard USB. The specification describes the bus attributes, the protocol definition, types of transactions, bus management, and the programming interface required to design and build systems and peripherals that are compliant with this standard.
This section describes the USB power distribution specification.
The power source and sink requirements of different device classes can be simplified with the introduction of the concept of a unit load. A unit load is defined to be 100 mA. The number of unit loads a device can draw is an absolute maximum
A device may be either low-power at one unit load or high-power, consuming up to five unit loads. All devices default to low-power. The transition to high-power is under software control. It is the responsibility of software to ensure adequate power is available before allowing devices to consume high-power.