Arduino bug

[WalterMo]

Hello,
I think the most often used microcomputer on this forum is the Arduino Duemilanove. Now I found a bug on it.
Normally (or formerly) they have used the MOSFET NDT2955 to switch off the 5V comming via the USB-port if the Arduino is powered by Vin:
http://dailylearningnotes.blogspot.com/ ... ffect.html

and here the total circuit diagram of the board:
http://arduino.cc/en/uploads/Main/ardui ... ematic.pdf

But now I notice that I cannot boot my PC when the Arduino is connected and additionally supplied by Vin. The reason is that they don't still use the NDT2955 but a transistor which is labeled 340A.
Maybe it is the MOSFET FDN340. And this item is connected through all the time and the 5V, produced on board, disturb the PC.
Looking on the datasheets of both MOSFETs I found a serious difference regarding the gate threshold voltage.
I think not all new Arduinos will have a 340A and show this behaviour. Up to now I know of 5 items, all bought at Watterott.
So please be careful for your motherboard if you have a 340A on the Arduino.

Walter

[Bongobat]

Hi Walter,

I looked for a number on my Duemilanove from Pololu but could not find any markings. I have not had any trouble but I do not normally start the computer with the Vin energized.

However,I always disliked that input voltage detect feature because I power my small red 5mw laser off of the onboard 5V regulator and I do not want it ever coming from the computer's USB. If we do not ever need the the USB power can we just cut the USBVCC trace to the NDT2995/340A on the arduino? Would this solve both problems?

Greg

EDIT: Couldn't you also cut the 5V line from the USB cable instead and not have to cut any traces on the Arduino?

[WalterMo]

Hi Greg,
Your transistor surface is really sheer? Also if using a magnifying glass?

You can make a simple test if you want to check its function: Disconnect the USB cable and supply the Arduino externally. Now measure the voltage at the „golden“ fuse (labeling 500H) nearby the MOSFET. The voltage must be 0V and not 5V. 0V means that the MOSFET breaks the 5V circuit correctly.

Cutting the 5V line from USB isn't good because if we now connect the board to a PC and we forget an external supply it might happen that the signals from the PC could cause trouble in the ICs on the board.

What I am now doing is first to boot the computer and then to connect the Arduino. In so doing only very small equalizing currents are flowing between both 5Volts. But I also intend to contact Watterott. It is a general problem which must be solved by Arduino.

Walter

P.S. In the meantime I have started a discussion on the Arduino forum.

[Bongobat]

Hi Walter,

Your transistor surface is really sheer? Also if using a magnifying glass?

Yes, I looked very hard but I did not see anything.

I performed the test you describe and I do see 5V at the fuse with the USB unplugged.

Cutting the 5V line from USB isn't good because if we now connect the board to a PC and we forget an external supply it might happen that the signals from the PC could cause trouble in the ICs on the board.

I guess it is a matter of which is worse for the computer? What kind of damage can those signals cause in the ICs of the arduino board? I saw that Khalid wrote that he may have damaged his mother board and I would rather the arduino get damaged rather than an expensive motherboard in case of accidentally starting the system up the wrong way.

Thanks for finding this hopefully they can fix it soon.

BTW Can you post a link to your bug report on the arduino forums?

Greg

[WalterMo]

Hi Greg,
I am very carefully since I had lost two EasyDriver boards by damaging their direction input. At that time I had made a test setup and had connected them to the Arduino outputs. But I had not supplied the EasyDrivers with power.
Now they are still motor drivers, but without the possibility to change the direction. Up to now I don't exactly know what the real cause of damage was, perhaps only because a 30cm wire was connected and works as an antenna for electrostatics. Since that I always put 10k resistors from the inputs to ground. To lose an EasyDriver is bad, to lose an Arduino is worse, but to lose a motherboard is something like a MCA.

Here is the link to the Arduino forums:
http://www.arduino.cc/cgi-bin/yabb2/YaB ... 1284034373

Today I have informed Watterott. We will see.

Walter

[Ordibble Plop]

'Nice' find Walter

I don't really understand much in the Arduino forum thread, so could you briefly explain what impact this has for your 'Simple Laser Scanner' circuit for those with affected Arduinos. Is there a process one should go through (e.g. order of connection) to ensure safe use?

How many Arduinos are affected - if it is a common issue, would not Arduinos or computers be dieing all over the world?

Also, I saw you mention a better system in the Arduino forum thread with USB synchronicity - I wondered if this been documented on these forums yet or whether you are clearing this Arduino problem first?

[WalterMo]

Hi Dave,

There is no problem to use affected Arduinos with my 'Simple Laser Scanner'. Simply do the following:
1.) Disconnect an external power supply if you upload the software via USB.
2.) Then, for normal scanning, disconnect the USB cable and plug the power supply.

It would be interesting to know what kind of MOSFET is on your board. So please take a look on it. If you can read something of '2955' all should be ok and the above mentioned precautions are not necessary.

Since the Arduino is an open source hardware, I think it will be produced at different places. And if e.g. the original MOSFET NDT2955 is not available or they can find a replacement which is a few cent cheaper, they probably use it. And the reseller will order from the cheapest manufacturer. I myself have boards with the NDT2955 and with 340A. Gunter mentioned also a 340A. Greg told us of an unnamed item. You see, not everywhere where Arduino is printed on, is a fine Arduino within.

Yes, another system which can also be used for the planeless scanning is nearly ready. But because I am not the one and only developer I cannot say when it will be published here. Please appreciate this decision. Sometimes economic interests are also important on our globe.

Walter

[Ordibble Plop]

Thanks for your reply Walter.

The mosfet on my Arduino duemilanove is labelled with "DJ45AK" and then with "2955" underneath. It also has what looks like an italicized "F" before the DJ45AK. I guess I don't need to worry then . I bought it quite a while ago from an official Sparkfun distributor in New Zealand.

I look forward to the release of your planeless system and would be more than happy to pay for it, though if it is hardware coming from Germany I'm afraid I will likely not get it. For some reason the cost of postage from Germany to New Zealand is the most expensive I have seen and sadly ends up making purchases prohibitive.

Dave

[Sven]

Hi,
my Arduino has a "340 f" transistor... Is it a "bad one" like "340A"?

Sven

[WalterMo]

Yes Sven, it is a „bad one“.
But for good measure, measure the voltage at the golden fuse, just below the transistor.

Walter

[milz]

heho

did you own a AT168 or AT328 version ?
i have the at328 serialno N1965 sold as new version in the shop
and there is a DK06AA2955 seems a mosfet 2955 but not A340
around there ...

mfg milz

[WalterMo]

Hi milz,

I mean the AT328 which is now since more than one year on the Duemilanove available. Where have you bought your boards?

Walter

[milz]

Hi milz,

I mean the AT328 which is now since more than one year on the Duemilanove available. Where have you bought your boards?

Walter

from watterott http://www.watterott.com/de/Arduino-Duemilanove

mfg milz

[Sven]

Yes Sven, it is a „bad one“.
But for good measure, measure the voltage at the golden fuse, just below the transistor.
Walter

I have connected only the external 9V power supply and measured at the +5V pin of the USB port, and there are 5V.
(Also I have connected a 100 Ohm resistor as 50mA load, and the 5V dropped only to 4.9V.)
So my "340 f" transistor really does not cut off the 5V.
Good to know. I'll have to be careful when connecting the PC.
Sven

[WalterMo]

@ milz: I had forgotten to ask: What voltage is at the fuse when USB is unplugged?