PC Protection
- Thread starter richuk
- Start date
So you must be using a USB-Serial adaptor.
Most, if not all, PCs will have a limiter to limit the current from the USB. I don't know how accurate or fast it is.
I would guess the USB adaptor will give some protection against project cock-ups, unless you cockup severely. I've yet to hear of a disaster.
You can get isolated USB adaptors. They aren't cheap. Unless you can find some cheap anonymous lump off Ebay - but then would you trust it? Because, for sure, if it didn't work you won't get any backup. (Or sympathy from me
)
If you want something good then you will have to open your wallet.
Most, if not all, PCs will have a limiter to limit the current from the USB. I don't know how accurate or fast it is.
I would guess the USB adaptor will give some protection against project cock-ups, unless you cockup severely. I've yet to hear of a disaster.
You can get isolated USB adaptors. They aren't cheap. Unless you can find some cheap anonymous lump off Ebay - but then would you trust it? Because, for sure, if it didn't work you won't get any backup. (Or sympathy from me
)If you want something good then you will have to open your wallet.
No worries
The PICAXE is not able to directly communicate with a PC USB port and therefore requires an RS-232 serial adaptor. The RS-232 standard is pretty tolerant of short circuits and over/reverse voltages. However, in the unlikely event that you did manage to damage the adaptor it would still probably protect the PC USB port.
The PICAXE is not able to directly communicate with a PC USB port and therefore requires an RS-232 serial adaptor. The RS-232 standard is pretty tolerant of short circuits and over/reverse voltages. However, in the unlikely event that you did manage to damage the adaptor it would still probably protect the PC USB port.
Blue Eagle
Member
I dont how relevant this is but i stood on a pendrive on the front of my PC, bent it and the usb ports (luckily it was in the top port and both of them shifted down, rather than the bottom where the pendrive might have snapped completely)
A message popped up in windows saying something along the lines of "usb power error" or something similar. But both the pendrive and usb port still work so no real damage was caused (cept for a rather bent pendrive lol)
A message popped up in windows saying something along the lines of "usb power error" or something similar. But both the pendrive and usb port still work so no real damage was caused (cept for a rather bent pendrive lol)
Thanks for your help.
I also used a Microchip PIC programmer and I was just concerned if wiring mistakes (that do happen hehe) could potentially damage your PC as it’s not the cheapest thing to replace.
Ideally optical isolation would give peace of mind E.g: http://www.bb-europe.com/product.asp?SKU=UISOHUB4
Maybe a wireless USB hub would be a good idea because the most you could damage would be the hub itself: http://catalog.belkin.com/IWCatProductPage.process?Product_Id=398632
Or even a typical USB hub with current protection E.g: http://catalog.belkin.com/IWCatProductPage.process?Product_Id=279201
Is this concern worth bothering with because it seems that most USB ports have good protection?
Cheers
I also used a Microchip PIC programmer and I was just concerned if wiring mistakes (that do happen hehe
) could potentially damage your PC as it’s not the cheapest thing to replace. Ideally optical isolation would give peace of mind E.g: http://www.bb-europe.com/product.asp?SKU=UISOHUB4
Maybe a wireless USB hub would be a good idea because the most you could damage would be the hub itself: http://catalog.belkin.com/IWCatProductPage.process?Product_Id=398632
Or even a typical USB hub with current protection E.g: http://catalog.belkin.com/IWCatProductPage.process?Product_Id=279201
Is this concern worth bothering with because it seems that most USB ports have good protection?
Cheers
The PICAXE USB download cable has an FTDI chip in it ( FT232RQ ). Not sure how RS232C compliant that is or what current limiting and wrong-voltage protection it has but the two I/O lines are protected by 100R in series.
That's at least one chip which needs to be destroyed before you can destroy the PC's USB port and it has only limited connection to the PICAXE board. Power for the PICAXE is not taken from the USB port.
For extra protection you could get a PCI USB Card and always connect via that. You'd have to destroy the USB download cable chip and PCI USB Card before you would damage the PC motherboard itself. Add a hub and that's a chain of three you have to destroy. You could add a hub to what you already have.
This is the theory anyway. Ultimately, any mistake could be catastrophic enough to cause a cascade of damage though most aren't.
Perhaps the best thing to do is power the PICAXE board through a current limited PSU. That way the minimum amount of current will surge into the PC and will limit the potential for damage.
That's at least one chip which needs to be destroyed before you can destroy the PC's USB port and it has only limited connection to the PICAXE board. Power for the PICAXE is not taken from the USB port.
For extra protection you could get a PCI USB Card and always connect via that. You'd have to destroy the USB download cable chip and PCI USB Card before you would damage the PC motherboard itself. Add a hub and that's a chain of three you have to destroy. You could add a hub to what you already have.
This is the theory anyway. Ultimately, any mistake could be catastrophic enough to cause a cascade of damage though most aren't.
Perhaps the best thing to do is power the PICAXE board through a current limited PSU. That way the minimum amount of current will surge into the PC and will limit the potential for damage.
Well, it's up to you isn't it.
You can get slightly cheaper isolators, e.g.
http://www.impulse-corp.co.uk/display_product.asp?id=479
I'm sure there are more but there's little point posting them all.
And if you screw up with a normal one (assuming you aren't fiddling with high voltages) you'll probably just pop your adaptor.
I use USB PIC prgrammers. One is a standalone and the other is on an eval board. I have made numerous 'mistakes' on the eval board resulting in the USB shutting down temporarily. (Including popping several PICs due to careless wiring but don't tell anyone) . No harm to PC thankfully. The on-board current limiting did it's job, however I don't suppose for one moment it was designed for people to connect 24V up to it.
Nothing is indestructible except Captain Scarlet. So if you do something REALLY stupid then the buck stops with you.
And like hippy says, and I have said it at least a zillion times, get a QUALITY (=expensive) Bench PSU with variable current setting.
For prototyping at the early stages I would NOT use the USB supply for my circuit.
A lot of this depends on your experience/skill/knowledge/care/patience.
I have yet to hear of anyone damaging the USB or Serial interfaces on their PCs. Maybe they have and are just too embarrassed to confess.
You can get slightly cheaper isolators, e.g.
http://www.impulse-corp.co.uk/display_product.asp?id=479
I'm sure there are more but there's little point posting them all.
And if you screw up with a normal one (assuming you aren't fiddling with high voltages) you'll probably just pop your adaptor.
I use USB PIC prgrammers. One is a standalone and the other is on an eval board. I have made numerous 'mistakes' on the eval board resulting in the USB shutting down temporarily. (Including popping several PICs due to careless wiring but don't tell anyone) . No harm to PC thankfully. The on-board current limiting did it's job, however I don't suppose for one moment it was designed for people to connect 24V up to it.
Nothing is indestructible except Captain Scarlet. So if you do something REALLY stupid then the buck stops with you.
And like hippy says, and I have said it at least a zillion times, get a QUALITY (=expensive) Bench PSU with variable current setting.
For prototyping at the early stages I would NOT use the USB supply for my circuit.
A lot of this depends on your experience/skill/knowledge/care/patience.
I have yet to hear of anyone damaging the USB or Serial interfaces on their PCs. Maybe they have and are just too embarrassed to confess.
Yeah, unless you actually make your own connections to the USB wires you aren't going to be in any danger of damaging it. The Picaxe programming lead doesn't supply any power.
There is only one wire that has a direct connection and that's the ground wire. You'd need to be putting mains supply on the wrong side of a transformer or something equally as dangerous to be able to damage the PC via the ground wire.
Evan
There is only one wire that has a direct connection and that's the ground wire. You'd need to be putting mains supply on the wrong side of a transformer or something equally as dangerous to be able to damage the PC via the ground wire.
Evan
Mycroft2152
Senior Member
Another level of protection to add a 4 port USB Hub between the pc and the cable.
There are powered versions availible, which could also be used to power your picaxe circuits without impacting your pc.
Myc
There are powered versions availible, which could also be used to power your picaxe circuits without impacting your pc.
Myc
Re Dippy "I have yet to hear of anyone damaging the USB or Serial interfaces on their PCs. Maybe they have and are just too embarrassed to confess."
This is the great thing about RS232. It is a strange standard in that it uses -12 and+12V. But the great thing is that you can feed any voltage from -12 to +12V back up a line and not zap the PC. You can also short lines out. And you can send volts back up the line when the PC is off. The RS232 system is designed to be *robust*.
USB is also pretty robust - eg the current is measured and as pointed out above, you can short out pins and the PC can flag this as an error.
So PC => USB => RS232 is even more robust.
Of course, Manuka would also say that you should start by powering your picaxe with batteries. That is even more unlikely to cause problems, as the batteries will be well under 12V or -12V and are also limited with short circuit current.
In fact, if you were to randomly connect wires from RS232 to a picaxe board, you are much more likely to zap the picaxe with -12V than the picaxe will zap the PC.
If you really want proper protection and you are not just downloading things, but also using picaxe to communicate to a PC, use Max232 chips on the picaxe side. Then the comms are PC <=> USB <=> RS232 <=> max 232 <=> picaxe. That is ultra robust. Probably overkill really!
This is the great thing about RS232. It is a strange standard in that it uses -12 and+12V. But the great thing is that you can feed any voltage from -12 to +12V back up a line and not zap the PC. You can also short lines out. And you can send volts back up the line when the PC is off. The RS232 system is designed to be *robust*.
USB is also pretty robust - eg the current is measured and as pointed out above, you can short out pins and the PC can flag this as an error.
So PC => USB => RS232 is even more robust.
Of course, Manuka would also say that you should start by powering your picaxe with batteries. That is even more unlikely to cause problems, as the batteries will be well under 12V or -12V and are also limited with short circuit current.
In fact, if you were to randomly connect wires from RS232 to a picaxe board, you are much more likely to zap the picaxe with -12V than the picaxe will zap the PC.
If you really want proper protection and you are not just downloading things, but also using picaxe to communicate to a PC, use Max232 chips on the picaxe side. Then the comms are PC <=> USB <=> RS232 <=> max 232 <=> picaxe. That is ultra robust. Probably overkill really!