Hello,
I'm looking for methods to be able to make a USB device as user friendly as possible so I'd like some methods for protection is from voltage spikes, over current, other 5V voltage inputs(reverse voltage probably the better) and anything else I might not know that could harm the electronics from both sides.
TVS diodes can protect against spikes.
A polyfuse, then a diode reversed after it across the supply can protect against false polarity.
But a search using those terms in the forum will show other ideas.
Its standard for USB ports to use a chip to manage the power output from the port on a motherboard,
USB hub etc - it has the job of protecting the motherboard from over-current and ESD, and of course USB
connectors only fit one way so polarity reversal is impossible.
A USB device only has to avoid pushing back nasty voltages and spikes and draw sensible max currents
to play nicely - so I'm wondering what scenarios you have in mind that might need extra precautions?
Powering inductive loads comes to mind as a possible.
Silicon Chip magazine just published an extensive article on USB protection. It would be worth paying them a few bucks to download the article online. It will save you a lot of time and money buying the wrong parts.
6v6gt:
TVS diodes can protect against spikes.
A polyfuse, then a diode reversed after it across the supply can protect against false polarity.
But a search using those terms in the forum will show other ideas.
Sounds good about the TVS diode between where should I connect it and which should I get?
And how'd you mount the diode? wouldn't it create a too high of a voltage drop if you put it in series?
Here is an example:
In this case a 10 Ohm resistor is wired in series with the load (described as an energy absorbing resistor).
The TVS diode is wired reversed across the power rails after the resistor.
For your application you want a unidirectional TVS diode rated at 5 volt stand off voltage.
I asked a similar question on Stack Exchange some time ago:
There is no method to protect against destructive fantasy :-)).
If you do not believe me, let a kid alone in a room with whatever protected device (safety warning here!) for one hour.
+++
What power source do you plan to use?
One capacitor (tens microF) on source can help reduce spikes at the connection moment.
Diodes can protect against reverse polarity (voltage drop applies). But the same protection you can achieve by whatever non-symmetrical connector (one that can not allow, by its shape, a reversed coupling).
But an USB connector can be mounted only one way, so the risk of reverse polarity is low in my opinion.